We are a vegetable eating animal
Wild humans eat lots of vegetables
Who said thats a 'vegetable'?
Tubers, bulbs, and other storage organs
Wild African and Asian vegetables
Wild African and Asian tubers, roots, rhizomes, bulbs and corms in an aquatic environment
Wild African and Asian tubers, roots, rhizomes, bulbs and corms in a woodland and riverine savannah environment
Wild African and Asian tubers, roots, rhizomes, bulbs and corms in temperate & subtropic shoreline and upland environments
Plant toxins - our evolutionary adaptation to them
Domesticated versus wild veggies
Essential protectants in vegetables
Antioxidants in vegetables
Folic acid
Vitamin C
Vitamin A and Beta-carotene
Fiber
Links and further reading

Summary: Humans evolved from ancestral apes, and our genes are still reflect a vegetation and small animal eating past. Evolving in Africa and then Asia, we ate a huge range of leaves, buds, flower buds, stems, gums, roots, tubers, and even pollen.
The number of plant families we used as food was very much greater than the restricted range we eat today. Wild foods were carefully selected to avoid the plants or parts of plants with bitter and unpleasant taste, which likely contained toxic compounds. Today's plants are more palatable, and yet paradoxically, we eat very few plants as part of our daily diet.
The major contribution of plants to human health has always been thought to be the large amounts of vitamin A, the folic acid vitamin, and the vitamin C they contained; as well as a good amount of some minerals.
It is becoming more and more obvious that there are many plant chemicals that act together to protect the human body from the onset of cancers and heart disease, and that vitamin supplements can be helpful, but are not as useful as the whole plant.
Very little is known about the health benefits or toxicity of the wide range of plants we ate in the course of our evolution. After millions of years, they are now eliminated from our diet.
The small number of plants we do eat are being increasingly well studied, so we know a lot about their vitamin content and antioxidant and health protective effects.
The most powerfully protective domesticated vegetables that we are likely to eat are spinach, garlic, broccoli, brussels sprouts, carrots, sweet potato, red pepper, winter squash, and frozen peas - more or less in that order. These are outstanding vegetables, but every vegetable is an important contributor to well being.
While tubers and roots are an important slow burning energy food, vegetables are responsible for more subtle feelings of daily well-being, and for protection from long term degenerative disease. It is certain that Western people in particular are paying a heavy price - in any terms - for their cultural alienation from a primal and essential natural food.

NOTE: THIS WEB PAGE PRINTS OUT AS ABOUT 27 PRINTER PAGES

Why do we eat vegetables?

This is a question that would never be asked of fruit. Fruit is sweet. We love sweet things. We love to eat fruit. But vegetables can be bitter, and apart from carrots and sweet potatoes, they are generally not sweet.

How is it, then, that we came to eat vegetables? Partly, it is 'hardwired' into us. For good body efficiency reasons.

Basically, we are an evolutionary line from a group of mammals that, from about 65 million years ago until around 50 million years ago were small insectivores, but which evolved to fill  tree top vegetable-matter (foliage, fruit, tree seeds, or mixed vegetation based diets) eating niches, while still eating insects whenever we could (chimpanzees , orang-utans, gorillas, gibbons, and the siamang - all apes - eat insects).

Gorillas probably branched out earlier from the ape human ancestral line and so their life way gives us fewer insights into our ancestry (they probably went their separate way around 8 million years ago). Mountain gorillas, in particular, are primarily foliage eaters, consuming large amounts of pithy stems, buds, leaves and shoots. These foods are low in energy density, and gorillas have to eat a lot of plant material to meet their energy needs. They are now fairly specialized vegetation eaters.

Chimps, which have more recently diverged from our ancestral line (generally estimated at around 4.5 million years ago), are more likely to reflect at least some of our ancestral food preferences. Chimps don't seem to tolerate grossly fibrous food as well as gorillas. They chew leaves into a "wadge', and press the wadge against their teeth to extract the juicy parts, then spit out the fibrous residue. Chimps prefer insects and meat where it is available in their environment, but in their (primarily)  forest environment it is not commonly available. Succulent piths - carefully peeled of the tough exterior - blossoms, fruit, shoots, and leaves are the mainstay (around 95%) of their diet, with insects, eggs, and monkey meat opportunistically thrown in as and when available.

Even limited omnivory is a conservative adaptive trait, and even in the great apes, which have put 'all their eggs in one evolutionary basket', so to speak, retain the ability and desire to eat insects (and eggs!).

We eat vegetables because, while we intensively exploit ground based and shoreline animal protein and fats, we share massive amounts of our genetic profile with our related plant food subsisting apes (some scientists assert the genetic similarities are so overwhelmingly great that chimpanzees, the ape genetically 'closest' to us, ought to be classified as a species of human), and we are therefore genetically 'programmed' to exploit plant food as part of the primate omnivorous capabilities.

Even by the Australopithecine stage in our evolutionary line, we lacked the kind of molar configuration to deal with very pithy vegetation. But we did have the kind of jaw form that could do a lot of chewing on moderately firm and fibrous foods - such as lizards, locusts, baby birds, and plant 'underground storage organs' -  tubers, roots, corms, bulbs - soft new stems, immature flower buds, fleshy leaf bases, tender new shoots, tree seeds (once opened with rocks), fungi, and acacia gums. The microscopic wear marks on Australopithecus afarensis front teeth are very similar to those on baboon front teeth - suggestive of an intake of similar highly selected, nutrient dense shoots, bulbs, and leaves.

Our gut has become overall shorter, but with an increase in the proportion devoted to the small intestine (where high nutrient foods such as meat are dealt to and absorbed) in order to be able to handle the higher nutrient density foods of seashore and hunt. The price of a shorter gut is less efficient digestion of plant materials, as there is not enough room for the necessary micro flora to help break it down (the female of our species is said to have a longer gut than men. It is an interesting speculation whether this is an evolutionary adaptation to eating more vegetable foods than men, and whether this explains the difference in 'intestinal gas production' between men and women -women have more vegetable efficient guts).

Because we have taken omnivory far further than any other related animal, and can live quite well on an almost exclusive meat and fat diet if we had to, does not mean that we can forever abandon eating plants. Plants are 'powerhouses' of many and complex 'life enhancing compounds', and we almost instinctively 'know' that we need them. If our sense of taste hasn't been completely dulled and distorted by the cultural forces of our urban 'fad' diet, we sometimes feel a craving for 'bitter herbs', and seek them out. There may be the distant echo of instinctive 'self medication', or perhaps, 'self biochemical regulation' in this feeling.

Vegetables are an important - perhaps key - part of our 'generalist' evolutionary niche, in that the reliable carbohydrate source of bulbs and roots (and certain seeds) acted as insurance against failure in the high value but much more uncertain hunt. On top of this, humans need far more energy to fuel our brains than any other primate - around 300 kcal when at rest, and it has to be in the form of glucose, because that is the fuel the brain runs on. This energy requirement can be met relatively easily with some roots and tubers, depending on the carbohydrate content of the particular species. In some respects, we should perhaps consider roots and tubers as a major food item, in a separate class to leafy greens, shoots, buds, and flowers.                    TOP
 
All hunter gatherers eat veggies

"Their groups were small because the desert gives food sparingly,  and often each family lived apart from other tribal members most of the year.  The women did much of the work of food gathering -- except for meat...the Indians couldn't make a good living from the desert alone. They lived around the edges; they haunted the lakes for wildfowl, eggs, tules, cattails, and yellow water lilies."
- commentary of an observer of the Paiute tribespeople of the North American deserts, from earlier this century.

Weeds - dock, tarweek, mustard, lamb's quarter.
Water plants -- yellow pond lily, rushes, sedges, tules.
Trees -- sugar pine, Pinus lambertiana. Edible half inch long seed, sweet but rather laxative gum exudes from injured branches.

Food from Leaves and Young Shoots
Dock, ? Rumex hymenosepalus - The bitter succulent leaves were roasted on hot ash beds. (Young leaves of some species are more edible, and even used to be cultivated as a vegetable in Europe.  A native African dock, 'Abyssinian spinach', R. abyssinicus has been domesticated.)
Camas, Camassia sp. - a bulbous plant of damp places, marshes and lake edges. Altho' they are edible raw, the bulbs were usually baked (on ashes, in an earth oven), or cooked and dried and the flour extracted. (Not to be confused with the very similar 'death camas', Zygadenus venenosus. No doubt the Indians people didn't confuse them, as they only gathered them in the flowering season, when they could distinguish between the two...urban westerners need to be extremely cautious in areas outside their life experience. Don't eat what you don't 'know' is safe!). Murderous tribal wars were fought over this resource.
Sedge, ?  Scirpus sp. -  grows in damp and marshy places by lakes. The young shoots are edible.
Cattail, Typha latifolia - water margin plant, the young shoots ('Cossack asparagus') are edible from spring onward, as are the immature flower heads, and later, the pollen.
Reed, ? Phragmites communis, a plant of damp places and lake shores
Mint, Mentha sp.
Wild parsnip, ?Phellopterus montanus
False dandelion, Pyrrhopappus catolianus. The roots are also edible in Autumn.
Mushrooms - various species. Puffballs, in particular were valued by many West coast tribes, and were dried for later use.
Pigweek, Amaranthus palmerii and A. retroflexus - the young leaves are very mild.
Watercress, Nasturtium officinale - introduced from Europe
Shepherd's purse, Capsella bursa-pastoris - A small, common weed. The whole plant is edible.
Lamb's quarter, Chenopodium album - An introduced annual, grows to seven feet. The leaves are quite mild.
Dandelion, Taraxacum officinale - the leaves are bitter, but edible,  Young leaves are used raw.
Mustard, Brassica campestris - the lower leaves, or very young plants, which are least hot, are eaten.
Fireweek, Erechthites (Senecio) hierarcifolia - a thistle like plant.
Wild lettuce, Mimulus guttatus - a low growing plant found on wet ground, the leaves are like a somewhat bitter watercress.
Peppergrass, Lepidium freemontii - A small land cress with 'hot' tasting leaves
Mallow, ? pimple mallow, C. pedata of Western USA.
Wood sorrel, Usually, Oxalis sp. ? Oxalis tuberosa, or O. enneaphylla. (Oxalis species leaves and bulbs were once commonly eaten wherever in the world they were found - Africa has around 130 indigenous species - in spite of their oxalic acid content.)
Plantain, Plantago sp.
Solomon's seal, ?Polygonatum giganteum - the very young shoots of the related European P. officinale were used like asparagus; perhaps the Paiute used P. gigantuem the same way. (The rhizomatous roots of P. giganteum are also starchy, and were used by the Ainu people of Northern Japan as a food source. P. giganteum grows in both Asia and America)
Purslane, Probably Portulacca oleracea, a sour tasting introduced annual weed with succulent crisp textured leaves; possibly Portulacca retusa, known to be used by tribes in the Southwest as a vegetable, or Calandrinia sp. - adapted to dry western parts of USA. Or maybe even Lewisia rediviva, a purslane more commonly known as 'bitter root', altho' it is usually harvested for its very nourishing flour (in spite of its common name!), rather than as a vegetable.
Bracken fern, Pteridium aquilinum - the very young shoots ('fiddle heads') are eaten raw or cooked, when they taste like somewhat bitter asparagus.
Bulrush, Typha latifolia. - see below
Sow thistle, Sonchus sp. - very young leaves are edible.
Chickweek, Stellaria media - a common small annual plant with vaguely cabbage tasting leaves.
Pennycress, ?Thlapsii sp, a relative of 'shepherd's purse', Capsella bursa-pastoris.
nettle, ?Urtica sp. - in other countries, fresh nettle tops are regarded as a very nutritious spring 'spinach', usually used in soup.
Wild violet. Viola sp., possibly V. palmata, or V. papailionacea - While viola flowers, at least, have been used in food in Medieval time, the roots are poisonous - except the mucilaginous roots of V. palmata. The basal leaves of
V. papailionacea  are still collected for greens today. They are quite extraordinarily rich in vitamin A.

Food from Roots and Tubers
Wild onion, ?Allium validum - 'swamp onion'. - there are many species of wild onion, most have small bulbs, and are found in a variety of habitats, depending on the species.
Mariposa lily, Calochortus sp. - 'Indian potato'.- a wide ranging genus with corms that can be eaten raw or cooked. They can also be dried and pounded into flour.
Camas, Camassia sp. - a bulbous plant of damp places, marshes and lake edges. The bulbs were baked, or cooked and dried and the flour extracted.
Bitterroot, ?Lewisia rediviva, see above
Cous, Pastinacea cous - a close relative of the parsnip, P. sativa
Ipo (squaw root) cattail -? Typha sp.
Brodiaea, a pretty flowering 'bulb', most species of which are edible. They produce their edible corms in a wide range of habitats, according to the species.
Yellow bell, ? species
Primrose, ?Primula sp. In Europe the leaves and flowers of 'cowslip', P. veris, have a history of use as salad greens. Which species - if it is a Primula - that was used by the Paiute, I have no idea.
Water parsley, Oenanthe sarmentosa - the black tubers are said to have a 'cream-like taste'. The leaves and stems are also edible, tasting a bit like celery. Some similar looking species are poisonous.
Balsam root (Oregon Sunflower), ? possibly a species of sunflower, Helianthus. Many sunflower species have edible roots.
Wocus (water lily) N. advena - the roots are starchy, and can be baked, grilled, pounded for flour, or stored whole for winter use ("hundreds of bushels" were stored for winter time by west coast tribespeople, according to a note written by a European observer in 1855). The seeds are also edible.
*  italicized notes are mine

The list was compiled by a European. A tribespersons list would certainly have been more detailed than this. The identification of the botanical names is mine, and is based on the common english name, which may be misleading. The notes in italics are also mine.

This is simply an illustration of the general principle that we ate everything in the environment. There is always a hierarchy of preference, of course, but in general, there was probably not a great deal of freedom to choose. Some environments are very difficult to make a living from -as we have seen - maybe they are dry, or very cold, for example. The richest pickings are at the margin of two different ecosystems, such as forest edge abutting a lake or shoreline. When times were hard, we turned to our least preferred vegetables-

"Although the lichens were not regarded as common foods, in emergencies many types were eaten. They were scraped from rocks or trees and eaten raw or boiled with fat. To remove the bitter taste, some tribes washed them in water mixed with the ashes of a campfire."
M.A. Weiner, 'Earth Medicine-Earth Foods'.

What are 'vegetables'?

1. buds, flower buds, leaves, shoots

A vegetable is basically any part of a plant that can be eaten. Plants, naturally, are not too keen on being eaten, and have devised various methods of dissuading us from eating them. This aspect is discussed further on. Luckily, humans are smarter than plants, and we have discovered many ways to get past plants chemical defenses.

As a result, we have been able to eat many different parts of selected plants - flowers, flower buds (globe artichoke), leaves (lettuce), leaf buds (Brussels sprouts), shoots (asparagus), shoot buds (cabbage), stems (celtuce), flower stem (broccoli), pollen (bulrush), immature seed pods (green beans), fruit (chayote) , immature seeds (broad bean). We have also eaten gums (from acacia trees), sea algae (seaweed), and lichen.

If it's a plant, palatable and non-poisonous (at least, not medium term nonpoisonous), it's been food for humans. Guaranteed.

The fact we eat such a small range of vegetables is a matter of luck, culture, and inertia; not because "these plants are vegetables because I can get them at the supermarket, therefore only plants I can buy at the supermarket are vegetables".

2. tubers, bulbs, and other storage organs

Tubers are the major fall back carbohydrate source, and are 'not' veggies

You can live without greens for a long term - although there are long term consequences for fitness - but we must have fuel to burn for daily activity. No matter what fiber, vitamins and minerals may be in tubers, particularly starchy tubers, their main importance is as a fuel for daily life. It is in this respect that they perhaps ought to be thought of more as seeds are thought of - as a mainstay of life. Seeds are more nutritionally dense than tubers, especially oily seeds, and protein rich legume seeds. Even so, combined with even relatively small amounts of protein from lizards, locusts, mollusks, and other relatively easily collected animal food, they are a viable primary food for long periods, and as a bridge between preferred, nutritionally dense tree seed, legume, meat, fat, marrow, and internal organ foods.

For example, in Africa the residual Tanzanian hunter gathers (the Hazda) live in a "game-rich habitat", and yet average only one large game animal every thirty days devoted to the hunt. Plant food is the mainstay that fills the gap (women, mothers and grandmothers in the main, do the work of collecting sustenance for the whole family ...), especially in the dry season, when children can't find enough of their own food. (Only adults are strong enough to dig up deeply buried tubers. Perhaps this explains kids fixation with 'buried treasure, aarr, aarr!')

 "underground storage organs occur at higher biomass in drier sites because they store food and/or water during periods of climatic stress (Andersen 1987). In Tanzanian savanna woodland, for example, Vincent (1984) found densities of edible tubers averaging 40,000 kg per km2, compared with only 100 kg per km2 found by Hladik and Hladik (1990) in a rain forest of the Central African Republic. (Even at a density of 100 kg per km2, Hladik and Hladik considered them sufficiently abundant to support a human population.)"
Richard Wrangham et al 'The raw and the stolen: Cooking and the ecology of human origins'

The same principal of 'plant underground storage organ bridging' ('PUSOB') no doubt applied to Eurasian areas; especially during our evolutionary history when Europe and Asia went through markedly colder, drier and more climatically extreme periods. These were the conditions Homo erectus had to contend with when it radiated out of Africa. And H. erectus' teeth wear patterns are not unlike pigs - an underground root finder, as any pig owner will tell you.(And fungi - don't forget truffles).

The following brief notes are just a few of the plants we probably ate in the course of our evolution and radiation out of Africa and into Asia and Europe.

African and Asian veggie sources in the wild over evolution

Vegetables
Today we eat an astonishingly narrow range of vegetables if we compare the local produce department with what scientists and historical observers have recorded as being eaten by tribespeople in Africa. One writer lists 83 plants known to be used as vegetables in Zimbabwe; another records forty different leaves used as greens; in one small part of South Africa more than 120 plants were used as vegetables. In more extreme marginal environments the options are much fewer; yet one observer lists 18 plants used by the San of the arid areas of Namibia and Botswana.

Much of the knowledge of what 'can' and 'can't' be eaten was passed from mother to daughter and child to child (children live in a 'knowledge' subculture passed by word of mouth eternally); our keen sense of taste also alerted us to potentially dangerous chemicals in the plant. Then as now, we selected the youngest, least bitter parts, and the youngest plants. Most of the detailed knowledge about the wild vegetables we evolved with in Africa has now been lost, because we are no longer gatherer hunters, and we don't need these mental encyclopedias any more. One of the very best records of what knowledge remains is 'Food from the Veldt', the source for much of the data in this essay, and required reading for anyone interested in nutrition and the human animal (details below).

 "...the flowers heads of this plant, which thrives abundantly near the seashore, furnish a kind of culinary vegetable which somewhat resembles asparagus and is known as Hottentots' cabbage. When stewed and properly prepared they make no contemptible dish'
-L. Pappe, in 'Silva Capensis', 1862, referring to Trachyandra revoluta, a strap leafed perennial of the lily family in South Africa. The italics are mine.

Some of the vegetable matter we almost certainly ate for countless millennia in the course of our evolution we now never eat. For example, the gum exuded from the injured bark of some species African acacia (the common leguminous tree of the Savannah and open woodlands), such as the very common and very widespread 'karroo thorn', Acacia karroo, was eaten in late summer, particularly by children (it has a sweetish taste).  The gum is apparently very nutritious, and can sustain life for days in the absence of other food (180 grams/6 and a half ounces, has enough calories to meet an adults energy needs for a day). The young leaflets of some acacia species were also eaten by some tribespeople. Small amounts of 'gum arabic', acacia gum, are used as thickeners in some industrial foods, but that is as close as we get to eating this ancient ancestral legume product.

The young shoots of trees are very rarely eaten in the West, yet some are highly nutritious. An Ethiopian tree, Moringa stenopetala, has leaves that are very nutrituious, edible flowers, edible pods, edible seeds, and the bark can be used as a 'hot' condiment (it is a close relative of the the Indian drumstick tree, M. oleifera, with one of the highest calcium levels and highest vitamin C level of any tropical vegetable, beside being the source of a very stable edible oil- Ben oil - and with antibiotic properties in the seed). In South East Asia young shoots of a small evergreen tree, Gnetum gnemon are regularly eaten, as are the immature flowers. They are quite nutritious, with 100 grams providing 104 calories, and being about 7% protein, around 19% carbohydrate, 11% fiber, and providing excellent vitamins and minerals - 1,680 I.U.. vitamin A, 121 mg vitamin C, and 44 mg of calcium. There are several species of Gnetum in tropical  West Africa. Once the human is out of its natural environment, the options close out. But new ones come in...

One of the more surprising group of plants that clearly have been part of our diet ever since we evolved in Africa are the members of the family Asclepiadaceae. Several plants of the genus Asclepias provide food for the caterpillar of the monarch butterfly. Birds don't eat the caterpillar because the caterpillars concentrate within their body bitter chemicals from the milky sap of the Asclepias plants they browse on. Even altho' there are poisonous Asclepiadaceous species, indigenous people have used various parts of various species within this genus - raw leaves, cooked leaves, raw root, cooked root, raw stem, raw fruit, cooked fruit, varying with the particular genus and species. The various species in this family are spread over a wide range of environments, and are often quite common. The West African tuber-bearing species can be eaten raw or roasted, and one, the 'fikongo', Brachystelma bingere, is still popular in parts of Nigeria. It is interesting that when humans relatively recently radiated into North America, they immediately used the native american Asclepias species the monarch caterpillars feed on as a food source! Yes, the 'swan plant' A. tuberosa, was harvested for its edible tuberous roots! In Asia, we found other members of the Asclepiadaceae we could eat - several creepers of the genus Telosma provide, variously, edible flowers, leaves, immature fruit, and roots.

However, accepting the principle that we ate all edible parts of all plants, it would take several books worth to mention all the plants we ate or probably ate over our evolutionary history in Africa and Eurasia. We will take a brief look at a few of the tiny number of domesticated plants that now constitute ( an insufficient!) part of our present day rather odd - compared to our natural evolutionary determined -industrial diet.

The original asparagus that our species evolved alongside is Asparagus laricinis, a somewhat spiny bush of South and South West Africa. The young shoot is eaten, and is still considered by some to be superior in flavor to the domesticated asparagus, A. officianalis. Many of the wild species of asparagus are eminently edible, from the 'white asparagus', A. allus that grows on the high plateaus of North Africa, to a species in Southern Europe, A. acutifolius. And of course we ate the wild seaside asparagus, A. officianalis maritima, native to Europe's Atlantic and Mediterranean coastline, and the possible progenitor of today's supermarket asparagus.

It wasn't really until we left Southern and Eastern Africa and moved around the Mediterranean shoreline that we came into contact with the seaside plant, Brassica oleracea subsp oleracea, which is the ancestors of the cabbage, cauliflower and broccoli. But that is still half a million years or more. A long time to be a cabbage head. There is some linguistic evidence which suggests it was the young stems that were eaten. Several other Southern European and Mediterranean shoreline species were also probably harvested - B. insularis (also found in North Africa), B. macrocarpa, B. rupestris, and several others.

Brassicas are hardy, cold and salt tolerant plants, and therefore well suited to eventual domestication. But what about the more tender leafed lettuce, you ask?

Lettuce is derived from the wild Latuca serriola, widespread in North African and throughout Eurasia. The wild form is a annual plant of open woodlands and clearings, and forms a narrow leafed ground hugging rosette over winter, expanding into a stalk taller than the average person in summer. The leaves contain a very bitter milky latex, and no doubt the only young leaves were collected, as a winter green. Another species, L. indica, native to East Asia, is a perennial plant whose leaves are eaten either cooked or raw. Young plants and young leaves of biennial plants were the target in temperate areas. After that long winter, we craved for our tender 'spring greens'. Now, of course, we have different cravings...

Humans seem to like 'umbelliferous' biennial herbs ('Apiaceae' plant family). These plants form a strong root one year, and send up a flower head made up up one or many umbrella shaped flower heads. Typical examples are carrots, parsnips, fennel, cumin, and celery. They are just about all strong smelling plants, and some 'umbellifers', such as hemlock, are not just strong smelling, they are deadly.

However, we have had a long evolutionary association with this plant family. In Southern Africa the leaves and young shoots of a very common grassland plant of this family, Peucedanum magalismontanum, are eaten in some quantity by the indigenous people, mainly in the spring and summer wet season. All the several species of the genus Alepidea in Southern Africa provide good greens when the young leaves are selected. Only A. amatymbica is too bitterly aromatic to be used at all.

While we didn't encounter the parsnip, Pastinaca sativa, until we radiated out into Central and Southern Europe, a related species with a "turnip- or parsnip-like root" [1] page 85 , Annesorrhiza capensis, has been eaten since time immemorial in the Southern tip of Africa.

Green beans are in the genus Phaseolus, and come from South America. Why did we take to them with such enthusiasm? Because we have a long evolutionary history of eating legume pods (particularly some African acacias, such as A. luederitzii, and Bauhinia sp. pods in Asia), and the vegetative parts of legumes in general. The leaves of the cow pea, Vigna unguiculata, widespread in Southern Africa, are eaten by tribepeople, and sometimes in what can only be described as heroic quantities, even although they can be quite bitter. Further brief notes on legumes in Africa are on the seed and bean page. 'Green bean-like' legumes are well spread beyond Africa. For example, the Lablab bean, Lablab purpureus subsp. uncinatus, is native to the Indian subcontinent. This climbing short live perennial 'bean' has a seed pod which is eaten when immature,  leaves (unusually high in protein - up to 28% in some varieties) which are edible, edible flowers, and seeds which are edible if they are ground first (or cooked for a very long time).

No salad would be complete without tomato. But they are also a South American fruit. Africa and Eurasia doesn't have an equivalent, even although numerous members of its family the Solanaceae, have provided edible leaves and berries in the African and Asian environment since the faint beginnings of the evolution of the human species. The leaves of 'Ethiopian nightshade', Solanum aethiopicum, are eaten by indigenous people as a vegetable, and the immature fruit are cooked and eaten as well.
S. macrocarpon is used the same way. Another native African solanum, 'gilo', S. aethiopicum ssp. gilo, also has immature fruit that are cooked as a vegetable. When we migrated into Asia, we would have been comforted to find a Solanum, the yellow berried nightshade, S. xanthocarpum, that we could use in the same way as our native African species.

Perhaps the nearest we ever came to having an African tomato is the fruit of the 'olive tomato', S. aethiopicum 'Gilo' group, (synonym S. olivare) native to tropical West Africa, and eaten by the peoples of the region.

Solanums protect their leaves with acrid and poisonous chemicals to greater or lesser degree, depending on the species. But, as with all plants, just because we evolved alongside these plants over an unimaginably long period of time doesn't mean we have evolved an ability to survive the more toxic species, or that we can eat the plant at the stage when they are potent with damaging or irritating chemicals. Evolution has given us elegant sensory discrimination, and culture to pass on what has been learned, without each generation having to experiment with the safety of each plant anew.                                                                TOP

Tubers, roots, rhizomes, bulbs and corms

"During several years of living in the bush of southern and central Africa I ate very little food that was not cooked on an open fire, outside on the ground...corms and bulbs dug up in the veld with a sharpened stick or oryx horn were also simply thrown in the hot ashes to cook"
-John Seymour, describing his life in sub-saharan Africa prior to World War 2.

1. In an aquatic environment

Trapa natans, T. natans var. bispinosa (Roxb.) 'Water chestnut'
This vigorous water plant lives in shallow waters throughout Africa, Europe and Asia, right up into the Russian far East, although it is at its most abundant only in the warmest parts. Small, two horned fruit ripen in the leaf axils, and fall to the bottom if not collected. The seed inside can be eaten raw, boiled, roasted, or dried and ground into flour. It is sometimes called the 'water chestnut'. It fits nicely into the round of seasonal water food collection in Southern Africa; as the swamps and small lakes drop in level over winter it becomes easy to search out the 'nuts' in the mud. Until recently, at least, this underwater fruit (technically a nut) was a winter time staple of some of the river tribes of Southern Africa; as it keeps well, a particularly useful food item.

This is an enormously productive plant where conditions suit it. An estimated annual harvest of between four and five million kilograms (approximately 4,000-5,000 tons) is taken from Wular lake, Kashmir. The lakeside population of around 30,000 humans live almost entirely on this food for five months of the year.

Archaeological evidence shows water chestnuts were used by prehistoric lake dwellers in Switzerland. This familiar and rich resource was doubtless exploited heavily as ancestral humans migrated through river valleys, across deltas and along lake shorelines on our radiation out of Africa.

From time to time, as climate changed in the distant past, rainfall patterns changed, lakes filled with sediment, and temperatures dropped. Water chestnuts and water lilies declined and then disappeared, and their place was taken by sedges (Cyperaceae family) and bulrushes (Typha sp.), which are well adapted to cooler temperatures.

Typha sp. 'Bulrush'
 Bulrushes ('cattails') in general are plants of marshes, swamps, shallow waters, and wet ground. They are about as tall as an adult, and one form of the most common species,  T. latifolia forma capensis, is common in marshlands throughout south west Africa. The species itself, T. latifolia, is widespread in North Africa, and the whole of Eurasia. In many parts of Europe it is regarded as a weed. The bulrush is a very valuable plant. The root (rhizome) that grows in the mud is full of starch (about 30%) by autumn. Native people everywhere collect the approximately 30cm/12 inch long roots, dry them, and pound them to release the starch, which can then be formed into cakes, flat bread, porridge, or whatever (the roots also contain a small amount-about 8% - of protein). The new spring sprouts from the roots are eaten raw, baked or boiled. Young green flower stalks can also be eaten, raw or cooked, and are said to have a flavor "suggestive of olives and artichokes" (Ferdinand et al, 1958). The bright yellow pollen itself is highly nutritious - it contains about 19% protein, about 18% carbohydrates, mainly sugars such as glucose and fructose. The pollen has about 1% fats, and while I have not seen an analysis of the pollens fatty acid constituents, the fat component of the actual seed when it forms is predominantly linolenic acid, an 'omega-3 fatty acid, and glycerides. Which may perhaps be suggestive of a good omega-3 content in the pollen. Tribespeople in Asia, America and the Maori people of New Zealand have been recorded as using the pollen to make pollen cakes or 'bread'. Pima tribespeople of Southwest USA used to make a 'mini earth oven' and bake a pollen and water paste (on leaves, over hot ash, more hot ash on top, then earth sealed to steam/bake). The result was a kind of sweet 'biscuit'.
The plant as a whole is "said to be rich in vitamin B1, B2, and C", but I have seen no analysis.

Beyond being a valuable autumn/winter carbohydrate source, and a good protein source in Spring, bulrushes are, like the water chestnut (Trapa.), both enormously productive (estimates of whole plant mass vary from  6 to 20 metric tonnes per hectare/approx 3 to 10 tons per acre per year) and widespread throughout tropical to cool temperate environments. As with water chestnuts, we have probably eaten bulrushes throughout the greater part of our evolutionary history.

The river beds of coastal South Africa and Botswana's Okavango swamp both support dense stands of  a bulrush-like semi aquatic plant, Prionum serratum, whose masses of roots have good supplies of carbohydrate that, like bulrush rhizomes,  can be separated from the fiber by pounding. The fresh young rootlets - before they are too fibrous - are also a good vegetable in themselves.

Eleocharis tuberosa 'Chinese water chestnut'
When Homo erectus left Africa and radiated into Southern China and South East Asia (probably at least a million years ago), it would have found, and no doubt enjoyed, this crunchy aquatic root. And when H. sapiens dispersed out of Africa and displaced (no doubt with extreme crunchy munchy prejudice) H. erectus, we too, will have put Chinese water Chestnuts on the dinner mat.

Eleocharis is a kind of rush with one and a half metre long slender stems. The edible part is the under-mud corm (a corm is a bulb-like storage root). As it's name suggests, the crisp white flesh is sweet and vaguely nutty tasting, with chestnut being the best, but not especially accurate, approximation for the flavor. It is good either raw or cooked. A related species, E. platiginea (sphacelata), was eaten by Australian 'Ab-original' people.

Phragmites autralis (communis) 'ditch reed', 'water grass'
This grass is common in marshes and watery places in Africa and Eurasia, whether tropical or temperate. The roots are edible, as are the seeds (although the yield is presumably poor, given the sparse references to it's use by indigenous people).

Nymphaea caerulea 'blue water lily'
This water lily occurs in lakes, pools, ponds and the slower reaches of rivers throughout Southern Africa. The tubers were collected and dried for later use by !Kung bushmen; and some of the Zulu people of South Africa historically collected the tubers in the plants winter dormant season when water levels were lower. In fact, the water lily tubers were a winter/spring staple for these people, and they cooked and ate them as westerners do potatoes (they don't have to be cooked - some tribespeople in Zimbabwe eat them raw). The edible seeds provide a late summer bonus - in crocodile and hippo free areas...

Other water lilies

The young roots and shoots of the Asian 'prickly water lily', Euryale ferox, are edible, although not very nice (the seeds are the most valued part, as they can be ground into an acceptable flour). But most important are the water lilies of the genus Nelumbo. The sacred lotus, N. nucifera, grows throughout South and Southeast Asia, and, originally, in North Africa. The young leaves are used as vegetables, the seeds are eaten both raw and cooked (the edible seeds are available in Chinese grocery stores in the West), and the very large starchy rhizome is eaten raw, roasted, boiled, or the starch extracted and used as a flour to make flat breads, 'cakes', or as a thickener. The roots and seeds of both the white Egyptian lotus, N. lotus, and the blue Egyptian lotus, N. caerulea, are still eaten by indigenous people.
As we expanded into Europe, we ate the seeds and roots of the 'yellow water lily' (Nuphar luteum), the roots of Nymphaea alba, the white' water lily', amongst other aquatic and semi-aquatic plants.

The warmer waters of Africa don't just grow starchy tubers and seeds; a water plant called 'Cape asparagus', Aponogeton diastychum, has a flower stalk (as its name suggests) that tastes somewhere between asparagus and spinach. But Asian members of this genus do have edible tubers, and particularly desirable tubers. The tubers of the Indian A. monostachyum "are said to be as good as potatoes"[2] and the tubers of several other Asian species in this genus have been described as 'excellent'[2].                                                                                                                                                                      TOP

2. In a woodland and riverine savannah environment

The number of roots and tubers that hunter gatherer and indigenous tribespeople have been recorded as eating is so large that only a relative few will be mentioned here.

The principle is that, as gather hunters, we were able to use every available food source in whatever environment we were in, or had moved into. Any edible root or tuber was exploited. Roots and tubers that our taste buds indicated were toxic either weren't eaten, or were de-toxified by grinding and steeping in water, or by heat, or both. Our African and Eurasian ancestors ate a vast range of plant underground storage organs that makes our Western food choice of potatoes, sweet potatoes, carrots, onions and parsnips look like some crazy minimalist 'fad' diet. Which in many ways, it demonstrably is.

One of the most useful starchy roots of dry woodland and some coastal areas of  both west equatorial and South Africa is the 'native potato', Plectranthus esculentus. This tall perennial has long, narrow tubers that store well, or are fairly readily available when needed. The taste seems to vary with local populations, sometimes being described as having a taste "similar to sweet potatoes", "similar to parsnips but are an acquired taste being rather bitter", "well liked by blacks and Europeans" and "said to be also eaten raw".[1] pages 245, 246. Several other Southern African Plectranthus species are also edible, with one at least regarded as a delicacy in its winter season.

In the extremely arid parts of Namibia,  5-10 tubers of Walleria nutans, a small arid land plant,  made a filling and satisfying meal for the indigenous Bushmen families. These golf ball sized tubers would be lightly baked in the ashes of a fire, and are said to taste like boiled potatoes. They can be successfully stored for three months.

Quite a few of the corms, bulbs and tubers our evolving ancestors ate in Southern Africa are known to us only as ornamental garden plants. The genus Babiana is named from the Dutch 'babanier', which means baboon, because the corms of these pretty little flowering plants of Southern Africa are a regular food of foraging baboons. Babiana hypogea is recorded as being eaten by indigenous tribespeople, and a thick rhizomatous rooted Babiana, the 'baboon root', B. plicata was also eaten by human residents of the South African Cape. The domesticated 'Gladiolus' flower was perhaps better known by our distant ancestors as a feast for the stomach, not the eye. Roasted corms of the 'edible sword lily', Gladiolus edulis, are said to taste like chestnuts, the 'spiky sword lily', G. spicatus, was eaten in tropical Africa, and in East Africa the 'Zambezi sword lily', G. zambesiaticus, was a food resource for some of the local tribes.

Pelargonium rapaveum is a dry land pelagonium with a thick underground tuber, an adaptation to it's seasonally arid environment. A writer from earlier this century reported that it was roasted in ashes by the peoples of the Bokkesveld. Young leaves and buds of other pelargonium species are eaten raw as a vegetable.

In the more desert like arid climate areas plants survive the dry by storing nutrients and moisture in storage roots -sometimes very large- deep underground. These underground food and water stores were one of the keys to survival in these more unforgiving marginal habitats. It may be that in the course of human evolution one of the periodic climate changes may have made for a much more extensive arid area, with a much lower carrying capacity for a human population.

The ability to dig for, and live on, tubers such as those of the Morama bean (Tylosema esculentum) may have been one of the deciding factors in preventing the unwitnessed extinction of the human species. This legume produces a large to very large tuber, which, when eaten young (at about 1kg in weight) is slightly sweet and pleasant (luckily for it, it is unpalatable when older). The plant is highly adaptable to variable rainfall levels, and is present in Southern Africa from Botswana south, as well as in South West Africa. Its astonishingly nutrient density has already been mentioned.

Ethiopia and the Red sea shoreline are both areas where evidence of human evolution has been found. So it is almost certain that we have evolved eating the large succulent roots of Ethiopian asparagus, Asparagus abyssinicus, which is endemic to both areas. It may be that Homo erectus feasted on oysters (stone tools have been found embedded in ancient fossil coral reefs in the region) and asparagus at some times of year....mmmm, oysters and asparagus again...                                                 TOP

3. Seashore, natural meadow, woodland and foothill environment; temperate, warm temperate and subtropical

The move out of Africa was a move into different climatic conditions, seasonality, and plant ecosystem. As always, we ate all roots that weren't too fibrous or small, and all leaves, buds and stems that weren't too bitter. While in Southern Africa bulbs evolved as a mechanism to survive the dry season, for the most part, in the more temperate areas bulbs evolved to survive the cold winter. Fleshy roots were a mechanism for plants to build up a good store of of plant food in one year (often in the form of sugars rather than complex starches), and send up a large and robust flower and seed stem the next. A bit like accumulating rocket fuel in one season for next seasons supreme effort of launch off. Carrots, parsnips, and various other obscure roots which have never been domesticated (caraway roots, Carum carvi; earth nut, Bunium bulbocastanum; the North African 'talruda'
B. incrassatum, and many others) follow this pattern.

Wild carrots, Daucus carota, usually have white roots, but some wild carrots in Afghanistan have red or purple roots, due to anthocyanins and other phytochemicals (including lycopene, found also in tomatoes and other fruits). Carotene is a pigment naturally present at low levels in wild carrots, and this slight presence was amplified thru' selection for orange color in the seventeenth century, and the then predominant purple (and yellow, derived from the purple) domestic varieties faded from favor.

Some temperate plants, such as Europe's lesser celandine, Ranunculus ficaria, were starchy, and provided a useful energy source, albeit the bulbs are small. Lesser celandine also provides tender new leaves for spring salads. A relative, the 'Arctic crowfoot', R. pallasii, fills the same dietary spot for Eskimo peoples in the more extreme cold of Alaska.

While we evolved alongside numerous edible bulbs of the Liliaceae family that are present in Africa, and some, especially bulbs of the genus Dipcadi, are superficially 'onion-like', there don't appear to be any members of the genus Allium, to which the domesticated onion (and garlic) belongs, in Africa. (Although the small bulbs of the fairly widespread 'wild onion', Ornithogalum tenuifolium both looks and tastes like the ordinary onion). But the story changes as we radiate out of Africa into Eurasia and South Asia. Here ran into numerous wild Allium species, tasting like the Ornithogalum we left behind.  And from some of these species, the domesticated onion, garlic, and leek arose.

One of the more widespread onion relatives is giant garlic, Allium scorodroprasum, a bulbous plant something between an onion and a leek. This plant has a wide distribution across Eurasia, and would have been one of the first Alliums we encountered as we came out of Africa and radiated into the Mediterranean and into Central Asia.

Also in Asia are 'Chinese chives', A. tuberosum, valued mainly for their leaves and edible flowers, and A. chinense in the mountains of central China. Oriental, or elephant garlic, A. ampeloprasum,  is a large cloved, extremely mild form of garlic, if it can be considered garlic at all, and possibly the ancestor of leeks. It is a native of East Asia. Garlic itself, A. cepa, is unknown in the wild, but it is thought it may have derived from a species (A. longicuspis) found in the foothills of Central Asia.

Although Allium bulbs are not a great energy source - unlike some of the more starchy tubers and roots - there must be something about them that the human species likes, because we have been eating them for half a million years or more...and they still give us gas! fut, fut....

Liliaceous bulbs may have been a good food source in Africa, but I haven't seen any reference to edible members of the actual genus Lilium there. But once we move out of Africa into Eurasia, we find many edible lilies. The most widespread is Lilium martagon, growing throughout Eurasia. The bulb can be roasted, or dried for future use. This species grows as far as Siberia, and other edible species, such as L. dauricum, L. spectabile, and L. tenuifolium, are well adapted to to these colder climates. They may have been an important factor in helping tide humans over times of food shortage as we radiated into colder climate areas. In subtropical Southern China, Lilium brownii fed us, in western China L. davidii, and in Northern China L. leichtlinii and L. maculatum.

The number of plants that live in Eurasia that have edible roots, rhizomes, corms or bulbs is quite substantial. The range of  edible roots in only one particular climatic and ecological environment has already been illustrated above, with the notes on the food plants of the North American Paiute tribespeople. This range is not unique to that environment, or to the North American continent. It is to greater or lesser degree typical of most parts of the world, including Eurasia.                                             TOP

Plants have compounds to discourage eating

Plants weren't 'put here' for our benefit. They are as likely to be 'harmful' (a humancentric view!) as 'useful' . Obviously, plants don't 'want' to be eaten, so various bitter, acrid, soapy, or toxic compounds are sequestered in the leaves and stems to dissuade browsers. Primates have learned over the course of evolution to become finely tuned to the times in a plants life cycle when they are most palatable.

Baboons, for instance, are highly selective about what they eat. A study of their eating pattern found that the vegetation in the study area was changing almost every two weeks, with different fruits and pods ripening, new plants flowering, or sprouting. But invariably, the researchers found that the baboons would highly selectively only feed on the the most nutritious part of the most nutritious plants.

The human animal was no less tuned into the seasonal environment. The particular advantage we had - and still have - is that we are able to use 'culture' as a tool to pass on techniques to exploit plant food resources that would otherwise be unavailable to us. We do this by removing some of the unpleasant compounds in the plant.

A variety of techniques are used by indigenous people to reduce or eliminate the bitter or acrid components that are common in leaves and roots (our first technique, of course, is to select only those plants naturally low in such unpleasant compounds).

The simplest technique is to choose only the youngest and fastest growing plants, and, if necessary, only the youngest leaves of the young plant, which are least likely to have a build up of bitter and unpleasant compounds. The African 'sow thistle', Sonchus integrifolius has, like other members of the genus, a bitter latex or 'milk' in the stems and leaf veins, but young plants are palatable, if still somewhat bitter.

The Maori people of New Zealand eat the related 'Puha', S. oleraceus, an introduced weed native to North Africa and Eurasia. The very youngest and tenderest plants are cooked, but as the plant ages it is necessary to bruise the leaves and stems, and then wash them to remove the latex before cooking. The older the plant becomes, the more processing is required.

Some plants can have the bitter or dangerous parts removed by leaching in running water. There are half a dozen or so edible 'yams', genus Dioscorea, in Central and Southern Africa. They are found in a variety of ecosystems in Southern Africa, for example; from dry savvanah forests, scrublands, and forest clearings, to moist forests. Other edible species are also in West and East Africa, and throughout Eurasia and South East Asia. There are even two edible species in Southern China that grow in the mountains up to about the 7,000 foot mark.

A few are 'sweet', having effectively no toxic compounds, and are quite palatable to most people; most others have a variety of chemicals, which, if not leached out, can, at the least, make you nauseous, and at the worst, cause paralysis of the lower limbs and other nasty effects. But once well leached and cooked are usually fine. Others have to be soaked with ashes before they are leached. Unsurprisingly, these more dangerous species of Dioscorea are well down the hierarchy of preferred foods.

Some vegetables are soaked, then boiled. If older leaves are a bit tough - for example Vigna leaves - ash (an alkaline substance) is added to the water to tenderize them. They are sometimes left in the sun to reduce the bitterness.

And fire itself is a useful tool for de-naturing some chemicals, making an otherwise unpleasant food palatable.

One of the reasons we eat so many different species of vegetable in the wild is that we have to stop eating a given species of  plant when it becomes older and unpalatable. In other words, we were forced to eat widely. Extremely productive, non bitter plants that had spring, summer, and winter harvests and were enormously productive - particularly bulrushes, Typha sp.- were very much the exception, not the rule.

What is surprising is that we eaten of so wide a range of plant families with bitter, unpleasantly 'sharp', and probably slightly toxic chemical constituents throughout the course of our long evolution.

One of the more intriguing aspects of our relationship to plants is the idea of some foods being 'medicine'. As one scientist observes-

 "Several chemicals that have been shown to be carcinogens at high doses in rodents have also been shown to be
     anticarcinogens in other animal models at lower doses, e.g., limonene, caffeic acid, dioxin, indole carbinol.
     Therefore, the dose and context of a chemical exposure may be critical."  (my emphasis)

The old adage about there being 'a fine line between pharmacology and toxicology' applies. Wild living humans had an extensive knowledge of the 'medicinal' qualities of plants. Some were minor foods, some were 'medicinal', and sometimes the line may have been blurred. But no doubt there was an acute awareness of the dangers of certain plants at certain stages of growth, when it was 'safe' to eat them, and which were never safe. After all, the penalty for being wrong ranges from acute abdominal distress to death.

The most heavily consumed tuber in modern times is the potato, Solanum tuberosum. While we have encountered members of the solanum family all through our evolutionary history, we can't say we have become 'immune' to some of their damaging self protective chemicals, such as the toxic 'solanine' in potatoes. Very high doses, such as are found in green potatoes - and especially green potatoes with skin damage - can be fatal. But, again, we are 'tuned in' to soapy and bitter and acrid substances. They are unpleasant. By the time we have leached them in water, denatured them with heat, then the small amounts of toxins left can be dealt to by our liver. It is a testament to our discriminatory powers that only 30 people are recorded as having died from eating green potatoes in this century. No doubt both desperate circumstances and youthful carelessness played a part in many of these deaths. Human, the learning animal, has also learnt, during domestication, to select and re-select plant with lesser amounts of toxin than occur naturally. We can do it. Other animals can't.                                                                                         TOP

Modern selective breeding - are domesticated plants 'better', 'worse', or essentially no different?

In the wild, selective breeding tends to happen in reverse - at least from the human point of view. All animals tend to favor the most pleasant and palatable of plants (even grazing animals like cattle and sheep are quite selective), and so these individuals in the plant population tend to be eliminated from the breeding stock. The most unpalatable individuals tend to be left to pass on their 'unpleasant eating' genes. That, of course, is evolution at work.

With the evolution of culture, part of which is agri-culture, we very quickly learned to 'keep the best' for replanting. Suddenly, selective pressure was thrown into reverse (from the plants 'point of view') and only those plants with the least amount of nasty, bitter, or toxic chemicals survived to pass on their genes.

So while our liver, our organ of detoxification, had to be able to some degree deal with a very wide array of low doses of toxic plant chemicals in its evolutionary journey, it now finds itself on a permanent holiday (or it would if not for alcohol and 'never in our evolution encountered' man made environmental chemicals). Modern selections of the few plants we eat generally have much lower concentrations of unpleasant plant chemicals than the wild forms.

This is a tremendous advantage, because we can now eat far more vegetative material than our ancestors and still not reach the level of possibly toxic plant chemicals intake that our ancestors livers would have been daily challenged with. The great irony is that most Westerners actually now eat only a fraction of the amount of vegetable matter we ate as a wild living animal (not the number of kinds, altho' this is also true, but probably irrelevant).

However, lowering the amount of  'bitter principals' in the plants we have happened to domesticate can be taken too far. Part of the chemical composition of Brussels sprouts, for example, is a chemical called 'sinigrin', whose breakdown product is 'allyl isothiocyanate', and causes the rather strong smell of sprouts. Which is bad. The allyl isothiocyanate has been shown to destroy pre-cancerous cells colon cells - scientists suspect that occasional meals of brussels sprouts exert a powerful anti colon cancer effect. Which is good. Scientists are interested in breeding sprouts with lower levels of sinigrin so they are not so bitter, and so more people eat them. But is that good or bad?

In some cases, protective chemicals can be enhanced without enhancing bitterness and unpalatability at the same time. For example, another isothiocyanate is 'sulphoraphane', which also has powerful anti-cancer effect (by stimulating the body's 'phase II enzymes' to block the cancer). Fortunately, sulphoraphane doesn't cause an unpleasant taste, so it is a candidate for 'ramping up' for its protective effect. Broccoli is an excellent source of sulphoraphane, but the amount present varies with the particular variety. The variety 'Trixie', for example, has 150 micromoles per gram of plant, whereas 'Emperor' has about 70 micromoles per gram of plant. By going back to the wild seaside cabbages our distant ancestors ate, scientists hope to find and introduce genes for higher sulphoraphane content. (Broccoli is a derived form of the wild sea cabbage.) Recently (year 2000), they have succeeded. A wild Sicilian Brassica species has been crossed with broccoli to develop breeding lines with up to 100 times the sulphoraphane content of existing broccoli varieties, and with unchanged palatabilty!

At days end, modern vegetables are more palatable, less woody, have lower oxalic acid, and in general, are pleasanter to eat. On the other side of the ledger, some vegetables, such as cabbage, are not as deep green as their wild precursors, may have reduced amounts of protective chemicals, and suffer loss of nutrients in storage - but that is a different issue. Only cauliflower can be fairly said to be inferior to its wild progenitor. The white 'curd' contains only a few micrograms of vitamin A - a big difference from the ancestral cabbage. But plant breeding can change this. Recently a cauliflower has been bred with orange heads, and good amounts of beta - carotene. What humans have done, can be undone.

We may have a dramatically reduced inventory of species to eat, but we have a dramatic increase in availability year round, and some of our domesticates are absolutely outstanding in their nutritional and protective profile.

It is actually difficult to compare the nutritional profile of very recent  industrial, domesticated vegetation and the other, wild vegetation we evolved with and once ate. The reason is that very few analyses have been done on our evolutionary diet, because we have abandoned it in large degree. And because we no longer (or very rarely) eat these plants, there is little point in studying them.

Certainly, when fresh samples (uncooked) of leaves of wild plants are analyzed for vitamin A and C, there are good results-

                                                                                 Vitamin A/100gms          Vitamin C/100 gms

Spinach, fresh leaves (uncooked) for comparison             6,715 IU                              28

Blue Violet, Viola papilionacea                                          15,000 IU                             130
Goosefoot, Chenopodium album                                       14,000 IU                             130
Ground Ivy, Glechoma hederacea                                     14,000 IU                               44
Garlic mustard Sisymbrium alliaria                                    12,000 IU                             190
Ox eye daisy, Chrysanthemum leucanthemum                  12,000 IU                               23
Moringa tree, Moringa oleifera*                                        11,500 IU                             134
Plantain, Plantago major                                                   10,000 IU                               19
Shepherd's purse, Capsella bursa-pastoris                           5,000 IU                               91
Judas tree, Cercis canadensis                                                  -                                        75
Overground plant, Portulaca oleracea                                 6,100 IU                                26

Adapted from  'Ascorbic Acid and Vitamin A Content of Edible Wild Plants of Ohio and Kentucky'.
*From CRC Handbook of Tropical Food Crops by Franklin W. Martin. 1984

But again, we have to look at palatability. Its easy enough to eat 100 grams of spinach, but not so easy to eat 100 grams of plantain. And a lot also depends on the stage of growth of the wild plant - younger equals more palatable. And, younger plants often have a higher concentration of vitamins. For example, the basal leaves of the Blue Violet, Viola papilionacea, have 15,000 IU of vitamin A and 130mg/100 grams vitamin C in a mature plant; but in early spring, when they are tender and more palatable, they have 20,000 IU of vitamin A and double the vitamin C content!.

Domesticated plants are always presented at their maximum palatability, so they are likely to be at their most nutrient rich at the point of sale; albeit storage does reduce the levels somewhat. Fresh is definitely best, but canned and frozen is powerfully good as well. The trend to 'bump up' both the protective phytochemicals and the vitamin content of vegetables through breeding is a fairly small one, but it will probably continue. Even without 'beefing up', it is crystal clear that eating vegetables is vital to long term well being and prevention of disease.                                                                                                                         TOP

Benefits of veggie eating

The more science studies even the very few vegetables that western humans do eat -let alone the huge array of vegetables that we actually evolved with, of which most researchers are entirely ignorant - the more evidence we find that they are essential to preventing disease and maintaining a state of well being. The more researchers look, the more they find. The antioxidant levels in some edible but wild species may greatly exceed our domesticated stars-

"Although wild edible plants of the western Sahel and other parts of sub-Saharan Africa are consumed to some extent at all times of the year, greater amounts are consumed when cereal harvests are insufficient to support the populations living in these areas. The purpose of this study was to use a recently reported Trolox-based assay to measure the total antioxidant capacity of aqueous extracts of 17 plants that we gathered from southern Niger. The antioxidant contents of the aqueous extracts were compared to those of spinach and potato. Of the 17 plants, 11 had a greater antioxidant content than spinach and 14 had a greater antioxidant content than potato. The leaves of Tapinanthus globiferus had the greatest antioxidant content, and the fruit of Parinari macrophylla had the lowest. In general, leaves contained more antioxidants than either fruits or seeds. The total antioxidant capacity of the aqueous was relatively high, indicating that the wild plants of the western Sahel may contain substantial amounts of water-soluble flavonoid glycosides, which are potent antioxidants and have been shown to have anticancer properties."
-Cook J A, VanderJagt D J, Dasgupta A, Mounkaila G, Glew R S, Blackwell W and Glew R H .1998. 'Use of the Trolox assay to estimate the antioxidant content of seventeen edible wild plants of Niger'. Life Sciences, 63(2): 106-110

 While we could just take pills with protective phytochemicals in them, it is quite likely that the wide variety of chemicals in plants interact to produce a greater health benefit than adding up the health benefit of each identifiable chemical would indicate.

The studies pile up one after the other, almost ad nauseum. We can't be surprised that a good part of the answer is to eat as evolution has fit us to eat - eating vegetation of all kinds, and not just selecting those we find most palatable. Hunger was ever present in our evolutionary past, and we had much less chance to 'pick and chose'. Especially women and children, who were likely to be the last fed, or may well have had to find a good portion of their own food, as well as extra for 'the boys'.

Anyway, here is but a sampling of the often 'reductionist' studies on the health benefits of vegetables, and/or the risks we take by not eating them-

• After reviewing 156 studies of fruit and vegetable intake and its relationship to cancer risk, a University of California scientist determined that 128 of these studies supported the protective effect of beta-carotene-rich foods.[4]

• "Many large-scale studies have shown that folic acid plays a significant role in prevention of neural tube defects, such as spina bifida, which occur when a  segment of the spinal nerve cord grows outside the bony spiny column."

• While previous studies have been designed in such a way that they have unwittingly created the false perception that you would have to eat many kilograms of raw garlic to gain sufficient of the active phytochemical 'diallyl disulfide' to have an anti-cancer effect, a recent study shows that eating as little as half a clove of raw garlic, or if it is cooked, about four and a half cloves, may gain you meaningful protection against bowel cancer. The diallyl disulfide in these modest intakes of garlic were shown to induce the production of protective enzymes by between 20% and 60%.

• Australia's Center for Research in Vascular Biology has shown that garlic inhibits the build-up of heart disease causing 'plaque' on artery walls.

• " Japanese scientists working with cultured cells suggest that at least some of the carotenoids (such as the beta-carotene in carrots) fight cancer cells by effectively putting malignant cells to sleep and suppressing the expression of a gene that might otherwise promote tumor growth". - Science News.

• "The antioxidant potential of Beta-carotene and lutein, carotenoids with or without pro vitamin A activity, respectively, was evaluated using the human liver cell line HepG2.[ and then exposed to a chemical oxidant] Carotenoid-loaded cells were partially or completely protected against oxidant-induced changes in lipid peroxidation, LDH release and amino acid and deoxyglucose transport. These data demonstrate that Beta-carotene and lutein or their metabolites protect HepG2 cells against oxidant-induced damage and that the  protective effect is independent of pro vitamin A activity."

• Lutein, a carotenoid with antioxidant properties has been shown to inhibit the growth of mammary tumors in experimental mice.

• A USDA study found a low carotene diet (few fruit and vegetables) compromised immune function in otherwise healthy female humans.

• A University of Nebraska study showed that that the blood cholesterol levels of rabbits on a high cholesterol diet could be pushed down by giving beta-carotene.

• Japanese scientists have shown in animal studies that the carotenoid lycopene apparently normalizes the immune function in animals with experimentally induced tumors.

• Rats fed a diet that included the rat-sized equivalent of a large spinach salad showed that as they approached rat old age, their memory for maze solving was better than non-spinach eaters, and they had better movement control. This is thought to be the result of the spinach (and by extension other greens) "retarding age-related central nervous system and cognitive behavioral deficits", according to the researchers.

• A high blood level of the amino acid homocysteine is believed to be a strong risk factor for heart disease. "Extensive research has shown that heart disease and stroke patients often have levels that are 50  to 100 per cent higher [than the normal10-12mmol/L)... Homocysteine levels increase with age and are usually higher in men. High homocysteine levels are believed to be caused by low levels of  folic acid and vitamin B12 ...High homocysteine levels can be normalized by supplementation with vitamins B6, B12 and folic acid..." Geriatrics, April 1999

• The study of 34 middle-aged women found that brief periods of stress increased blood levels of homocysteine, an amino acid byproduct of the breakdown of animal protein that is normally broken down in the bloodstream by folic acid and the B vitamins . “People who have deficiencies in folic acid and the B vitamins have higher sustained levels of  homocysteine and are at increased risk for cardiovascular disease”  -Dr. C. Stoney, Ohio University.

• Naturally occurring flavenoids in vegetables (and fruits) have been shown to 'spare' the bodies vitamin E. Flavenoids are suspected to act as antioxidants and consequently reduce the 'consumption' of vitamin E in protecting cell membranes.

• The natural plant chemical 'lycopene' when present in the bloodstream has been shown to protect low density lipoproteins (LDL) from oxidation, the oxidised ('rancid') form of this lipoprotein being suspected as a major cause of arterial artery disease.

• In a randomized prospective clinical trial, 15 milligrams of Lycopene as a pure tomato extract was administered for 3 weeks prior to surgery to remove the prostate gland due to localized cancer. After surgery, the lycopene group proved to have smaller tumors that showed signs of regression and decreased malignancy.

• Epidemiological studies have shown an association between the consumption of tomato products and decreased risk of prostate cancer. However, the studies to date that have shown protective effects are said to have been flawed in that they did not control for total vegetable consumption. Vegetables in general are protective against prostate cancer, and 5 studies on the protective effect of tomato lycopene have found no protective effect against prostate cancer.

• Eating three servings of vegetables a day can cut a man's risk of prostate cancer nearly in half,  the strongest effect being for cruciferous vegetables (broccoli, cabbage, cauliflower, brussels sprouts, mustard). Journal of the National Cancer

Institute Jan 5, 2000.

 "The bottom line is that if you eat a lot of vegetables, you can cut your risk of prostate cancer by about 45
 percent," says Alan Kristal, Dr.P.H., co-investigator of the study. "And, if some of those vegetables are from the
 cruciferous family, like broccoli and cabbage, you may reduce your risk even further. At any given level of total vegetable consumption, as the percent of cruciferous vegetables increased, the prostate-cancer risk decreased"
 

• An analysis of 72 studies looking at the association between consuming tomatoes and tomato based products concluded that " high consumers of tomatoes and tomato products are at substantially decreased risk of numerous cancers, although probably not all cancers." The data are most convincing for cancers of the prostate gland, lung and stomach, and weaker but suggestive of protective against pancreatic, colorectal, oesophageal, oral, breast and cervical cancers.

• Mouse studies have shown that lutein in the diet helps protect against formation of lesions in the aorta.

• A  study by researchers at Cambridge University in 1996 found the level of lutein and other carotenoids in the blood of people in Toulouse, France, was higher than that of people in in Belfast, Ireland. Toulouse has a low rate of heart disease. Belfast has one of the highest rates of heart disease in the world.

• A study from the University of Wisconsin-Madison on two 'isoprenoids', from a group of around 22,000 naturally occurring plant chemicals derived from mevalonic acid, demonstrates they inhibit three types of human cancer cell lines - at least, in the laboratory. The importance is that they do this at concentrations obtainable by following a diet that includes plenty of vegetables and fruit. That is, a diet natural to the human animal. One of the compounds, beta-ionone,  is related structurally to beta carotene, and is widely found in vegetables and fruit. Beta-ionone was shown to suppress the growth of laboratory cell lines for human leukemia, breast cancer, and human colon cancer. "Our studies showed that cancer cells were more sensitive to these compounds than normal cells and that the two compounds had a stronger effect when combined than we would have expected from the action of either alone. These compounds act as a group to inhibit cancer growth with some enhancing the effectiveness of others. Our findings strengthen the idea that a diet rich in plants is beneficial because of the large array of plant compounds rather than the  singular action of one kind of plant or one compound in plants." - Charles Elson, nutritional scientist, University of Wisconsin-Madison.

• A  test, known as 'oxygen radical absorbance capacity', or ORAC, measures the ability of a given food to 'scavenge' and neutralize damaging free radicals free radicals in the body. A USDA study at Tufts University tested the effect of doubling the intake of fruit and vegetables normally consumed by a group of  men and women, between ages 20 to 80. Although the test subjects had already been eating five plus serving of fruit and vegetables a day, in line with 'government' recommendations, doubling the intake to ten servings resulted in the blood levels of antioxidant, as determined by the ORAC test, also almost doubling.

• Women given 280 grams/10 ounces of fresh, raw spinach pushed their ORAC score higher than when they took a massive 1.250 grams (1,250 mgs) of vitamin C (a powerful antioxidant).

• Vegetables held retain stronger bones. Vegetables and fruits  have been shown to decrease the amount of calcium excreted in the urine. Vegetables and fruit as as an 'alkaline buffer' neutralizing acids produced when fish and meat are digested. These acids would otherwise tend to increase the amount of calcium lost in the urine -sufficient fruit and vegetables consumption neutralizes this effect. [Appel et al. 1997].                                                                           TOP

Antioxidants in vegetables
As you can see, vegetables contain compounds that are valuable antioxidants and protectants.

Chief among these are the carotenoids. There are over 600 carotenoids in plants and in some animals (pink salmon is pink because of the the carotenoid 'astaxanthin' it contains). Only some - mainly beta-carotene- are precursors to vitamin A production by the body. The carotenoids not destined to be converted to vitamin A and unconverted beta-carotene are present in our tissues in very small amounts. The main carotenoids in human tissues eating a western diet are beta-carotene, alpha-carotene, lycopene, lutein, zeaxanthin, and beta-cryptoxanthin.

Lycopene has the greatest antioxidant properties,  beta-carotene and cryptoxanthin has the next greatest activity, then lutein and zeaxanthin.

One very useful measure of the protective antioxidant potential of a vegetable or fruit is to measure its ability to absorb damaging oxygen radicals. These free radicals are implicated in aging, especially memory loss and loss of co-ordination, and degenerative diseases. This does not measure the activity of specific protective phytochemicals that may use other biochemical pathways to inhibit tumors or protect blood vessel walls, for example. It does give us a way to measure one element of the relative health 'usefulness' of a vegetable, without having to understand which natural plant chemical, or combination of chemicals acting together, are responsible for the effect.

From the measurements of various vegetables so far, scientists estimate that a single serving of fresh or freshly cooked vegetables has, on average, 300 to 400 'ORAC units'. But some specific vegetables-such as garlic and kale-have particularly high antioxidant levels. A single garlic clove, which weighs around 5 grams, has around 100 ORAC units - a massive contribution in a small package (it is interesting to note the annual garlic consumption per person in the USA is 900 grams/2 pounds, where in Asia it is supposedly more like 23kg/50 pound per person - about 12 cloves a day!). But even a small - 30 gram (about 1 ounce) - serving of carrots, much lower on the ORAC scale, just about matches a clove of garlic for oxygen radical absorbance capacity.

Garlic, Allium sativum (note:100 grams of garlic is about 20 cloves!!).....2,000
Kale, Brassica oleracea var. acephala..................................................1,800
Spinach, Spinachia oleracea..................................................................1,300
Brussels sprouts, B. oleracea var. gemmifera........................................1,000
Alfalfa sprouted seeds (sprouts), Medicago sativa.....................................950
Broccoli, B. oleracea var. italica...............................................................900
Beet, Beta vulgaris...................................................................................850
Red Pepper, Capsicum annuum...............................................................700
Onion, Allium cepa...................................................................................500
Sweetcorn, Zea mays................................................................................450
Eggplant, Solanum melongena..................................................................400
Frozen peas, Pisum sativum.....................................................................400
Potato, Solanum tuberosum.....................................................................300
Sweet potato, Ipoemea batatas................................................................300
Cabbage, B. oleracea var. capitata...........................................................300
Lettuce, leaf, Latuca sativa.......................................................................250
Carrot, Daucus carota..............................................................................200
Green bean, Phaseolus vulgaris................................................................200
Tomato, Lycopersicon lycopersicon..........................................................200
Yellow squash ?courgette type ?Cucurbita pepo.......................................150
Lettuce, iceberg/crisphead.........................................................................100
Celery, Apium graveolens........................................................................100
Cucumber, Cucumis sativus.....................................................................100
Adapted from [6]

There are other phytochemicals with helpful effects. The cancer cell destroying properties of allyl isothiocyanate in brussels sprouts has already been mentioned. As usual, the more we look, the more we find. But most of us have heard that vegetables 'are good for you' because of the vitamins and minerals they contain.                                                                                  TOP

Vitamins & minerals
Vegetables are important to get enough vitamins for health. They are particularly important as a source of  vitamin A, vitamin C, and folate (folic acid, folacin). These three are the 'biggies', but most vegetables are a 'good' source of thiamine (B1), potatoes and green leafy vegetables are rated a 'good' source of riboflavin (B2), and potatoes, broccoli, cauliflower and tomatoes are a 'good' source of pantothenic acid (B5). Pyridoxine (B6) is important in brain function, immune system function, and as a precursor to several important hormones. All the brassicas are rated a 'good' source, as are potatoes, spinach, peas, carrots, watercress, and onions. Many vegetables contain small but useful amounts of vitamin E. Vegetables are generally very good sources of most minerals (with the exception of iron). Tubers and roots as an energy source aside, it is the protective phytochemicals and the vital vitamin C, vitamin A, and folic acid content that make vegetables essential to human well-being. Vegetables are genrally a good source of calcium, and green beans, in particular are a good source. There are differences between green bean varieties - the variety 'Hystle' has nearly double the amount of calcium as the variety 'Labrador'. It is likely that scientists will work to breed enhanced mineral and vitamin content in the future.

Folic acid
The word 'folate' is derived from the latin 'folium', a leaf - a pretty good clue to its high concentration in green leafy vegetables.

Many nutritionists believe that folate deficiency is one of the most common deficiencies in the West. Deficiencies in pregnant women have been linked to particular forms of birth defects. This is because folate is involved in enabling normal cell multiplication for growth and development. Folate deficiency means red blood cell production is reduced, resulting in fatigue; white blood cell production is slowed, making us more susceptible to infection; in fact many tissues are affected to greater or lesser degree when folate is lacking. Even highly conservative government nutritional advisors have become concerned enough to allow folic acid 'enrichment' of the isolated carbohydrate extracted from whole grass seeds ('white flour'). Folate is water soluble, and reduces in amount in storage.

Folate is stored by the body, so you have to wonder why deficiency could arise at all.

The answer is partly that folate is water soluble, and can be thrown out when vegetables are boiled-raw cabbage 90 micrograms per 100 grams, boiled cabbage 35 micrograms per 100 grams.

Add to that the losses in storage, and the fact that folate is damaged to some degree by heat.

But the real answer can be gleaned from the following list of folate rich foods.

The richest sources [1] are:
wheat germ...................330 micrograms/100 grams
raw endive ...................330 micrograms/100 grams
bran flakes ...................260 micrograms/100 grams
liver .............................240 micrograms/100 grams
watercress ...................200 micrograms/100 grams

Spinach .......................115 micrograms/100 grams
parsley ........................116 micrograms/100 grams
Broccoli ......................110 micrograms/100 grams
Swiss chard/Silverbeet....92 micrograms/100 grams
raw cabbage ..................90 micrograms/100 grams
brussels sprouts..............87 micrograms/100 grams
(cooked) frozen peas .....78 micrograms/100 grams

How many have you eaten recently? Most of us will have eaten none or very little of the very richest folate sources (200 micrograms upwards). Most of us probably eat  two or three of the relatively rich foods, such as broccoli or raw cabbage, most days. (Or do we? A nutritional epidemiologist at the University of California tells us that "today, fewer than 9 percent of Americans eat the recommended five daily servings of fruits and vegetables". This figure would be typical for most Western countries outside continental Europe.)

If we list the vegetables that we are actually likely to eat at least 100 grams of, then our 'rich list' is:
watercress...................200 micrograms/100 grams
spinach........................115 micrograms/100 grams
broccoli.......................110 micrograms/100 grams
Swiss chard/Silverbeet ..92 micrograms/100 grams
raw cabbage..................90 micrograms/100 grams
(cooked) frozen peas.....78 micrograms/100 grams

If we marry this data with the ORAC (oxygen radical absorbance capacity) data, we get, im my opinion, this 'stellar' list*:

spinach
broccoli
frozen peas (cooked)

* there is no ORAC data for watercress or Swiss chard, so this list is not entirely accurate. Watercress is a cruciferous plant, and is likely to score high in an ORAC list. Swiss Chard is botanically beetroot, which scores high in ORAC and may also score high in an ORAC list (altho' the red anthocyanins in beetroot root may be the determining factor).

The Recommended daily intake of about 200mcg for an older child and adult will be met by half a cup of cooked fresh spinach
(130 mcg), an orange (37mcg), and half an avocado (33 mcg) eaten during the course of a day.

Probably the commonest green, lettuce, has variable amounts of folate. According to the USDA reference data, half a cup of lettuce has about 15 mcg if it is the rather pallid but very crisp 'iceberg' type, 20 mcg if it is the soft boston/bibb/butterhead type, and a surprisingly small 14 mcg for half a cup of shredded dark green leaf lettuce. (Iceberg lettuce has a very low ORAC score, where leaf lettuce has double the ORAC score, but is still low.) But given that lettuce is so frequently eaten, it makes a contribution greater than it's fairly modest folate content would suggest.

Pregnant and lactating women are advised by nutritionists to make sure they take in twice this amount. It is hard to see how these women could be achieve the minimum RDA without either eating heroic amounts of spinach, frozen peas, and broccoli; or eating about a cup of raw peanuts; or eat 200 grams/ 7 ounces of liver every day...or a combination of these three high folate foods.                                                                                                                                                                              TOP

Vitamin C

We lost the ability to synthesize our own vitamin C early in our evolutionary history. While there is almost no information on the vitamin C content of the plant foods we ate in the course of our evolution, there is some data for the domesticated versions of the small range of plants we eat in the industrial west. We are able to store vitamin C in our bodies for around 3 months - just long enough to see us through the dry season, or the winter in temperate climates - with small top-ups from tubers and dried fruits, of course. In sub tropical and tropical areas, young palatable vegetation is pretty much always available, so storage is not such an issue.

     Figures are for half a cup, unless stated otherwise
Red ripe sweet pepper (one, medium size)......................226 mg
Broccoli, cooked..............................................................58 mg.
Brussel sprouts.................................................................48 mg

Sweet potato, baked........................................................25 mg
Cabbage, shredded, raw..................................................16 mg
Watercress, chopped.......................................................15 mg
Potato, baked, one medium..............................................12 mg
Green pea, frozen, boiled....................................................8 mg
Spinach, boiled...................................................................8 mg
Cowpea (Vigna unguiculata) chopped, boiled leaf tips......5 mg.
Lettuce, looseleaf, shredded...............................................5 mg
Lettuce, butterhead............................................................3 mg
Carrot, slices, boiled..........................................................2  mg

red ripe sweet pepper
broccoli
Brussels sprouts
sweet potato

The other major contribution that vegetables make is vitamin A; or rather, the building blocks from which your body can construct vitamin A. Plants are full of natural pigments called carotenoids, generically referred to as vitamin A.                    TOP

Vitamin A
is a loosely used term for retinol and beta-carotene. Retinol  'is' vitamin A, and is obtained from fish liver oils, liver, eggs, and butter and cheese. Very large amounts of retinol are potentially toxic. Vitamin A is concentrated in the liver of all animals, and the very highest concentrations are in the livers of carnivorous animals. Eating polar bear liver is definitely not advised. Eating cows liver definitely is advised.

Carotenes in general, and beta-carotene the most common, are obtained from plant foods. Beta-carotene is a precursor of vitamin A (its sometimes called 'pro-vitamin A'). Beta-carotene is converted to vitamin A by the body. Because the rate at which beta-carotene is converted to vitamin A in the body is known, most often vitamin A content of foods is quoted as 'actual' vitamin A (retinol) - generally the number of micrograms per 100 gram sample - and the micrograms of  beta-carotene are converted into International Units of vitamin A (by multiplying mcg of beta-carotene by 1.6).  Beta-carotene is non toxic under most circumstances. In fact, the body has a mechanism whereby it can regulate the absorption of carotenes (although absorption is generally rather low anyway - maybe around the 15-35% range). For raw carrots, for example, only around 1% of the carotene present in the carrot ends up being absorbed. This rises - variably - to maybe 19% when the carrot is cooked. In spite of the fairly low rate of conversion, carrots alone provide 30% of the vitamin A in the USA diet. This is a marker of both how few kinds of vegetables we westerners eat, and how influential cultural practices are - as either gateways, or barriers to health. Even how a food is prepared, or how it is cooked influences its vitamin A value.

Fats in a meal improve the conversion of beta carotene to the fat soluble vitamin A. The amount of beta carotene converted to vitamin A varies -the more finely chewed, or grated, the greater the availability. Moderate cooking increases the availability, as it helps break down the cell walls of the vegetable. Repeated cooking at higher temperatures destroys some of the vitamin A. And having adequate vitamin E - often inadequate in Western 'techno food' -  seems essential to efficient conversion.

So vegetables lightly cooked in olive oil, for example, seem a very good way to maximize the amount of available beta carotene in your diet.

Luckily, your liver can 'stock up' and store vitamin A (which is why carnivorous animals accumulate such large amounts); in fact the human liver can store up to six months supply.

There are a number of carotenoids in plants, usually contributing to the yellow, orange, or red coloration of the tissues, amongst other things. Pumpkin is an outstanding source of carotenoids - it is said to have over 500 kinds of carotenoids, and the cooked pulp has as much beta carotene as cooked carrot (curiously, a cup of boiled pumpkin rates way lower in the USDA nutritional database, at 2,650 IU. This might perhaps be a difference in varieties - some 'pumpkin', Cucurbita maxima, varieties have much deeper flesh color than others.)

Vitamin A is an important anti-oxidant, vital for healthy skin and cell membranes, and important for the function of the immune system, amongst other things. But regardless of whether they are converted to vitamin A or not, carotenoids protect cells against oxidative damage.

There is a definite co-relation between intake of beta carotene derived from vegetable and fruit and lower risk of cancer.

Vegetables are one of the most important sources of beta carotene (the best fruit are mangoes, with 3,894 IU per 100 gram serving;  melons, with 3224 IU per 100 grams; and apricots with 914 IU per fruit), not least for their inexpensiveness and everyday availability and use.

The recommended daily allowance of beta-carotene for an adult is 3,200 IU, with the 'optimum' intake for well being considered to be 8,000 IU.

Half a cup (unless otherwise stated)  of-              contains this
                                                                               beta-carotene
pumpkin (? Cucurbita maxima), canned............ .......27,000 IU
sweet potatoes, Ipomea batatas*, baked...................20,000 IU
carrots, cooked..........................................................20,000 IU

spinach, fresh, boiled & drained....................................7,400 IU.
butternut pumpkin, cooked (C. moschata)....................7,000 IU
Red sweet pepper, one medium....................................6,800 IU
winter squash, "pumpkin", (Cucurbita maxima) ..........6,000 IU
beet greens, cooked.....................................................3,600 IU
swiss chard, cooked......................................................2,500IU
broccoli........................................................................1,000 IU
tomato, one medium........................................................760 IU
brussels sprouts, cooked.................................................560 IU
* there are both yellow and orange fleshed sweet potatoes - orange fleshed have much higher vitamin A.

sweet potato
carrot
spinach
pumpkin (canned)

Vegetables that are frozen or canned may still be important sources of vitamins and minerals. And they are cheaper. A study by the University of Illinois compared the nutrient value of fresh, frozen and canned produce using both the USDA's nutrient database and nutrition label claims. According to this study, in most cases the canned vegetables appeared to have nutritional values equivalent to the fresh and frozen form of the vegetable. Canned vs fresh asparagus are comparable for vitamin A and C,  and canned spinach, carrots and pumpkin exceeded the recommended daily intake (RDA) requirement for vitamin A. Canned, fresh cooked, and frozen carrots have comparable vitamin A. Canned spinach provides anywhere from 50%  to 160% of the RDA of vitamin A, depending on the brand, as well as about 15 mg of vitamin C. A serving of canned potatoes also has higher vitamin C than fresh - possibly because ascorbic acid may be added as an antioxidant in the canning process (to prevent the peeled potatoes browning when they are exposed to air).                                                                                                 TOP

Fiber
The remnant hunter-gatherers that have been studied typically eat more than 100 different species of fruits and vegetables over the course of a year. The roots, tubers, leaves, flowers, buds, corms, gums and bulbs were barely processed in many cases. The fiber content of the fruits and vegetables that hunter gathers ate is estimated at about 100 grams a day. Western nutritionists typically recommend 20 g to 30g, far below the amount we ate over the many millennia of our evolution. And most Western people would have a fiber intake even lower than that.

An analysis of the dietary fiber in 35 kinds of edible wild plant - the parts of the plant analyzed weren't revealed -  came up with 26.4% dietary fiber content (as a percentage of the dry weight). Of that, 21% is cellulose and hemicellulose, 3.1% was lignan, and 2.3% was pectins.

Send your corrections, comments, and feedback, please!  E-mail me at removethisspamtrapfirstcontact@naturalhub.com

More Information
Electronic reading
Tubers

Nelumbo sp.(lotus waterlily)  in Yamaguchi, M. 1990. Asian vegetables. p. 387-390. In: J. Janick and J.E. Simon (eds.), Advances in new crops. Timber Press, Portland, OR. Long eaten thru'out Asia, the yeilds of rhizome and nuts are discussed.
http://www.hort.purdue.edu/newcrop/proceedings1990/V1-387.html#ASIAN VEGETABLES

Other vegetative parts

Zizania latifolia (water bamboo stems)  in Yamaguchi, M. 1990. Asian vegetables. p. 387-390. In: J. Janick and J.E. Simon (eds.), Advances in new crops. Timber Press, Portland, OR.. Edible swollen stems of this aquatic grass.
http://www.hort.purdue.edu/newcrop/proceedings1990/V1-387.html#ASIAN VEGETABLES

Nutrients in vegetables
U.S. Department of Agriculture, Agricultural Research Service. Nutrient Data Laboratory 1998. 

[6] ORAC of common vegetables and fruits, research brief from the US Department of Agriculture Agriculture Research Service listing 10 common fruit and 10 common vegetables.
http://www.ars.usda.gov/is/np/fnrb/fnrb499.htm#Antioxidant [web page address]

Paper reading - Books-
These books are excellent, and if you are interested in human evolution, 'Food from the Veldt' is required reading.

[1]Fox, F.W. & Norwood Young, M.E. 'Food from the Veldt'
Delta Books, Johannesburg. 1982. ISBN 0 908387 32 6

[2] Lovelock, Yann  'The vegetable book: an unnatural history'.
Allen & Unwin, London. 1972  ISBN 0 04 581008 7

Olson, J.A. 1994. 'Vitamin A, retinoids, and carotenoids.' In: 'Modern Nutrition in Health and Disease' (Shils, M.E., Olson, J.A. & Shike, M., editors),  pages 287-307,
Lea & Febiger, Philadelphia. 1994 (8th edition)

Phillips, Roger & Rix, Martyn  'Vegetables'.
Pan Books, London 1993. ISBN 0 330 31594 3

Weiner, Michael A.  'Earth Medicine-Earth Foods'
Collier-Macmillan. New York London. 1972. Library of Congress Catalog Card 73-167802

Scientific papers, articles, reviews, reports, proceedings

Ames BN, Profet M, & Gold LS. 1990 'Nature's chemicals and synthetic chemicals: comparative toxicology'
Proceedings of the National Academy of Science USA, 1990 Oct, 87:19, pages 7782-6

[3]Birbeck, J.  NZ Nutrition Foundation, 1986 in article 'Folate: the forgotten vitamin'
New Zealand Commercial Grower, 1986 Jan/Mar: 39.
Note: the values are at variance with the 1998 USDA nutrient database, but whether this reflects better analytical techniques, differences between varieties, or, in the case of Swiss Chard, differences in inclusion/non inclusion of the white midrib, is uncertain.

[4]Block G et al. 1992 'Fruits, Vegetables and Cancer Prevention, A Review of the Epidemiological Evidence'.
Nutrition and Cancer 18(1): September 1992

Cao G, Sofic E, Prior RL. 1996. 'Antioxidant capacity of tea and common vegetables.'
J Agric Food Chem 1996; 44: pages 3426-3431.

de Candolle, A. 1989 [1883]. 'Origin of cultivated plants'.
Haffner, New York.

Golson, J. & P. J. Hughes 1980. 'The appearance of plant and animal domestication in New Guinea.'
Journal de la Societe des Oceanistes 36, 294-303.

Harlan, J. R. 1992. 'Indigenous African agriculture. In: The origins of agriculture: an international perspective.' C. W. Cowan & P. J. Watson (editors)
Smithsonian Institution Press, Washington & London.1992
.
Higham, C. F. W. & B. Maloney 1989. 'Coastal adaptation, sedentism, and domestication: a model for socio-economic intensification in prehistoric Southeast Asia.' In: 'Foraging and farming: the evolution of plant exploitation', D. R. Harris & G. C. Hillman (editors), pages 650-66
Unwin Hyman, London 1989.

Kajale, M. D. 1991. 'Current status of Indian palaeoethnobotany: introduced and indigenous food plants with a discussion of the historical and evolutionary development of Indian agriculture and agricultural systems in general'. In: 'New light on early farming: recent developments in palaeoethnobotany', Jane Renfrew (editor.), pages 155-90.
Edinburgh University Press, Edinburgh.1991

Kelsay, J. L. 1981. 'A review of research on effects of fiber intake on man.'
American Journal of Clinical Nutrition 31, pages 142-59.

Korhola, A.A. & Tikkanen, M.J. 1997. 'Evidence for the more recent occurrence of water chestnut (Trapa natans L.) in
Finland and its palaeoenvironmental implications'.
The Holocene 7, No.1, pages 39-44.

Liener, I. E. & M. L. Kakade 1969. 'Protease inhibitors.' In:' Toxic constituents of plant foodstuffs', I.E.Liener (editor.), pages 6-68.
Academic Press, London & New York 1969

Mangelsdorf, P. C., R. S. MacNeish & W. C. Galinat 1967. 'Prehistoric wild and cultivated maize'. In: 'The prehistory of the Tehuacan valley,' Vol. I. 'Environment and subsistence'. D. S. Byers (editor.), pages 178-200.
University of Texas Press,  Austin. 1967

Mehra, K. L. & Arora, R. K. 1985. 'Some observations on the domestication of plants in India.' In: 'Advances in Indo-Pacific prehistory', V.N. Misra & P. Bellwood (editors), pages 275-79.
Oxford-IBH, New Delhi. 1985

Noonan S C, Savage G P. 1999. 'Oxalate content of foods and its effect on humans.'
Asia Pacific Journal of Clinical Nutrition. 64-74, 1999.

Ross, A.B., Savage, G.P., Martin, R.J., Vanhanen, L. ?1999. 'Oxalates in Oca (New Zealand yam) (Oxalis Tuberosa Mol.).
Journal of Agriculture and Food Chemistry, 1999 (accepted).

Sowunmi, A. 1985. 'The beginnings of agriculture in West Africa: botanical evidence.'
Current Anthropology 26, pages 127-9.

Sporn, M.B., Roberts, A.B. & Goodman, D.S. (editors.) 1994. ' The Retinoids'.
Raven Press, New York .1994 (2nd edition).

Ungar, P. S. (In Press - as at 1998) 'Dental allometry, morphology and wear as evidence for diet in fossil primates.'
Evol. Anthropol.

Ungar, P. S., Kay, R. F., Teaford, M. F., & Walker, A. 1996. 'Dental evidence for diets of Miocene apes.'
American Journal of physical Anthropology. 1996 Suppl. 22:232-233.

van Zeist, W. & W. A. Casparie (editors) 1984. 'Plants and ancient man: studies in palaeoethnobotany.' :
A. A. Balkema, Rotterdam. 1984

Vincent, A. 1984. 'Plant foods in savanna environments: a preliminary report of tubers eaten by the Hadza of northern Tanzania.'
World Archaeology Volume 17. pages 131-148.

Richard W. Wrangham, James Holland Jones, Greg Laden, David Pilbeam, and NancyLou Conklin-Brittain 1999 'The Raw and the Stolen Cooking and the Ecology of Human Origins'
Current Anthropology Vol 40, Number 5, December 1999
[Review: an article hypothetically linking tuber eating as a key to explain elements of the human species behaviour via ancestral Homo erectus, in particular. Short on specifics of which plant species may have been eaten; provacative..]

Wang H, Cao G, Prior RL. 1997. 'Oxygen radical absorbing capacity of anthocyanins.'
J Agric Food Chem 1997; 45: pages 304-309.

[5] Zennie, Thomas M.  & Ogzewalla, C. Dwayne 1977 'Ascorbic Acid and Vitamin A Content of Edible Wild Plants of Ohio and Kentucky'.
Economic Botany Vol 31, pages 76-79

Zohary, D. & M. Hopf (editors) 1988. 'Domestication of plants in the Old World: the origin and spread of cultivated plants in West Asia, Europe and the Nile valley.'
Oxford University Press, Oxford. 1988.

Paper Reading on other elements of the 'evolutionarily congruent' diet-list of books & scientific papers to buy or find at the library (links to internet sources of the book or paper are included where available)

The author rejects any responsibility for any decisions about life, diet, or anything else other than his own. Any action you take after reading the material here is solely your responsibility - seek advice from others, read critically and widely, don't accept everything you read here. You have been warned! Question everything.

Form your own opinion on these matters after reading widely and consulting appropriate professional advice, including advice of medical practitioners and professional nutritionists.

Remember, there are many 'crackpot' sites on the Internet, and, although I don't believe this is one of them, it is only my opinion!