While there are many well-documented advantages of a vegetarian diet, it is also true that a vegetarian diet must be done skilfully and with knowledge of how to provide complete nutrition for the body. If one eats a well-balanced and well-cooked diet of fresh and whole foods and avoids fats and refined sugars, most nutritional requirements will easily be met. There are a few nutrients which are likely to be deficient in vegetarians, however, especially in those vegetarians who are in transition from a meat-based diet. The purpose of this chapter is to discuss three of these common pitfalls: iron, zinc, and B_l2.

Iron

An appreciation of the importance of iron in the diet goes back further than perhaps that of any other mineral. The ancients thought of it as a carrier, and it was identified with the planet Mars, perhaps because of the distinctive redness of Mars. Iron has a tendency to take up oxygen readily, changing its colour to red. This is the basis for its function in the blood, where it is the carrier of oxygen to the tissues of the body.

Iron's tendency to take up oxygen comes from its curious ability to change valences—it can have either two or three electrical charges. This means it can, by altering itself from one state to the other, take up or let go of an extra oxygen atom. Because of this ability, iron is the centre of the body's oxygen transport system, which is based on hemoglobin. Hemoglobin is a giant complex molecule which contains, like a tiny jewel in the centre of each of its four basic components, a single atom of iron. This iron in the centre of the hemoglobin molecule accepts the oxygen and as it does so develops the bright red colour which differentiates oxygenated blood from the dark red or bluish blood of the veins.

Anemia, which is a relative lack of red blood cells, usually shows up as tiredness, fatigue, paleness, and a tendency to dizziness on standing. Although many other substances besides iron are also necessary to build red blood cells, iron deficiency is one of the most common causes of anemia.

Many nutritionists are concerned that vegetarians may be at special risk for iron-deficiency anemia. These fears are not unfounded; in fact a number of cases of such anemia have been reported among vegetarians. Although iron has been shown by surveys to be low in diets of many populations, some groups within any population are at particular risk. These include infants, because of the low iron content of milk; children and adolescents, because of their rapid growth; and women during their reproductive years, both because of blood losses during menstruation and because of the demands of pregnancy. For such persons, moving toward a vegetarian diet requires special attention to the issue of iron.

There is no question that red meat, such as beef, is richer in iron than many other foods. (See table below.) Yet it is also clear that many plant foods, such as beans and green leafy vegetables, may equal or surpass red meat in iron content.

^{* Cooked in own broth until water evaporates ( not drained ).}

^{Sources : Truesdell et al: Nutrients in Vegetarian Foods.
U.S. Dept of Agriculture: Nutritive value of American Foods.
Davidson et al: Human Nutrition and Dietetics.}

The problem is in the different absorption rates of iron from meat versus iron from plant foods. Half or more of the iron in muscle meats such as beef is of a sort that nutritionists refer to as "heme" iron. It is found in hemoglobin, the molecule in blood that turns red on picking up oxygen, and in myoglobin, the pigment that makes muscle tissues red. Heme iron, in the form of iron-containing fragments of the hemoglobin and myoglobin molecules, crosses the intestinal wall intact. This seems both to accelerate the absorption of the iron and to protect it from being picked up by and bound to substances in the diet which form compounds with iron. For this reason heme iron is absorbed at a rate of from 25% to 35% of what is ingested.

By contrast, iron absorption from plant foods usually runs in the 2% to 10 range. Certain iron-binding substances in plant foods, such as the fiber in fruits and vegetables, the phytates of grains, or the oxalic acid in spinach, have been observed to bind iron, and are thus thought to carry it out of the body, preventing the absorption of much of what is present.

Happily, however, recent studies have taught us more about the subtleties of iron absorption from non-meat foods. Contrary to earlier opinions, new work has shown that oxalates and most of the fiber in fruits and vegetables, when taken in moderate amounts, do not interfere with iron absorption in the living body, though some of them may bind iron in the test tube. Phytates, indigestible substances especially concentrated in the bran layer of whole grains, remain controversial. It has been shown in the case of calcium that the intestine can develop the ability to break down phytates, thus freeing the mineral bound by them. Current research has not yet demonstrated conclusively whether the intestine can develop the ability to break down the phytate which binds iron, but is true that other components of bran such as its phosphates, do seem to inhibit iron absorption.

However, the effects of one previously suspected inhibitor have definitely been confirmed: that of tea. Black tea is a very potent obstacle to the assimilation of iron. This effect comes from the tannic acid in the tea, which combines with the iron to form an insoluble compound. For this reasons tea probably should not be taken along with meals, although it is possible that some of the traditional additives such as mink or lemon may neutralize the tannic acid and reduce its interference with iron absorption.

Boosting Available Vegetarian Iron

One of the most interesting and important discoveries about iron is that its absorption from grains and legumes can be greatly enhanced by the presence of ascorbic acid (vitamin C). Vitamin C is plentiful in such foods as tomatoes, green peppers, turmeric, and lemons. A recent report states: "The effect of ascorbic acid on non-heme iron absorption has been tested in a number of dietary settings and in every case has been shown to be profound. It plays a particularly critical role in diets in which lithe or no meat is present. Non-heme iron absorption in one study was quadrupled by including in the meal enough vegetables to provide 65 milligrams of vitamin C. This amount is exceeded by a cup of broccoli or half a green pepper.

Green leafy vegetables, which are often high in both iron and vitamin C, can be exceptionally good sources of dietary iron. Favourite non-meat recipes in many parts of the world make generous use of ingredients rich in vitamin C, such as tomatoes, green peppers, or hot chillies. This is especially true of bean dishes, and it is interesting to discover that legumes such as lentils, beans and peas have recently been recognized as being particularly rich in iron. The potential use of ascorbic acid to facilitate the assimilation of such iron makes it a valuable source of this mineral for the vegetarian. Lactic acid (in yogurt) has been thought to play a similar role, but other acids probably don't.

Vitamin C Content of Foods Often Used in Vegetarian Meals

Source : Nutritive value of American Foods.

There are other tricks for boosting the iron available in non-meat foods. For example, it has been shown that the iron from pots and skillets can add significantly to absorbable iron in the diet. It is leached from the inside of the pot and combines with the food. Available iron in food can be increased by 100% to 400- when it is prepared in iron cookware. This effect might even be excessive when very acidic dishes, such as concentrated tomato sauce, are prepared in iron cookware. In that case, the inside of the cooking utensil will lose its shiny surface and the food will become darkened and develop an unpleasant metallic taste. Regular consumption of such food could eventually lead to iron overload. Although a certain amount of iron from cooking utensils is helpful, too much can cause iron to accumulate in tissues and cause illness. Very little iron is carried over into the food when non-acidic dishes are cooked in ironware, especially if some cooking fat is present. Thus, an appropriate rule of thumb for a vegetarian would be to cook about half his food, (an assortment of dishes, but not very acidic ones) in iron pots and pans. A heavy iron skillet with beans, peppers and tomatoes simmering away may be appetizing in part because of the satisfaction of iron that it suggests. Minerals often compete with one another for absorption. Foods very high in calcium can interfere with the absorption of other minerals, such as zinc. Too much milk, which is high in calcium and low in iron, can block iron intake.

Researchers who have studied the iron levels of long-term vegetarians have demonstrated that iron and hemoglobin levels were within normal levels. These researchers termed the results "surprising", and suggested that the vegetarians had somehow adapted their diet in such a way as to enable them to increase their efficiency of iron absorption. It seems reasonable to postulate that long-term vegetarians can handle the iron in plant foods differently from persons accustomed to mixed meat and vegetable diets. In any case, it seems clear that one need not become iron deficient on a meat-free diet. Following are the main points to remember in obtaining optimum dietary iron:

1. The well-planned vegetarian diet (based on whole grains, beans and green vegetables) has as much iron as the average meat-based diet but it is less readily absorbed.
2. Absorption can be increased (up to five-fold), by including in the meals, fruits and vegetables rich in vitamin C.
3. The iron content of the diet can be doubled, tripled or quadrupled by using iron pots and skillets.
4. Diets or supplements excessively high in tea (or tannic acid), protein, calcium, phosphorus or fiber can interfere with iron absorption.

ZINC

Zinc is a trace mineral which is important for the health of the skin and perhaps the lining of the arteries. Veterinarians found that animals whose feed contained inadequate amounts of zinc developed red and cracked skin with loss of hair or wool, as well as other problems. In humans, zinc supplementation is a well-documented, effective treatment for acne.

Zinc is found in dramatically high concentrations in the prostate gland and semen, and we now know that adequate levels of zinc are required for the proper functioning of the sexual organs of the male. Zinc deficiencies have also been found in children who had a history of poor appetite and failure to gain in height and weight. One of the symptoms noticed among boys in one study was a loss of sense of taste. Loss of taste is important, since it tends to decrease appetite and the enjoyment of food, and this leads to further malnutrition and failure to grow properly. In every case, the sense of taste was restored by taking zinc, and other health improvements were dramatic.

Meat, poultry and fish are by far the richest sources of zinc. Although some vegetable foods contain substantial amounts of it, fibre and phytates appear to carry much of it out of the body. Phytates are phosphorus compounds found in most plant foods but especially in whole grains, beans, and peas. They have the property of combining with minerals, especially calcium, iron, and zinc, to form insoluble compounds which are carried out in the stool. Though other minerals are well absorbed from plant foods, zinc—like iron or calcium—seems more problematic, and nutritionists have expressed concern over the availability of zinc in the vegetarian diet.

There are recent research studies that indicate this concern may well be justified. For example, when a group of students were put on a vegetarian diet for three weeks, their tissue levels of zinc dropped and they responded to physiological tests in a way that suggested they had developed a mild zinc deficiency.

But three weeks isn't long. As mentioned, we know that in the case of other minerals such as calcium, some adaptation to the presence of fibre and phytates occurs and that, over time, absorption improves. So the research team looked next at a group of 79 persons that had been vegetarian for a year or longer. They found that their body levels of zinc were also low,- despite the fact that they had been vegetarian for a longer period of time.

This is different from other minerals, where adaptation seems to take place and phytates and fibre seem to lose their tendency to interfere with mineral absorption. Why would zinc be different? The answer may lie in the fact that the enzyme that is developed to break down phytates—intestinal phytase—is itself zinc dependent. Zinc is needed for the manufacture of phytase, and when zinc is deficient the enzyme cannot be produced in adequate amounts. So a vicious circle ensues: less phytase means more phytate to interfere with the absorption of zinc, which in turn results in more severe zinc depletion and still less phytase.

Therefore, once a zinc deficiency is established, it would appear that it would be difficult to climb out of it—even with adequate zinc intake was long as one's diet is rich in whole grains, which contain so much phytic acid. Once phytase production has been started, and zinc can be released from phytate and absorbed, handling a vegetarian diet is possible. But if a person's zinc stores are depleted during the transition phase, he won't be able to increase his output of phytase and adjust to the new diet. For such reasons, zinc supplements may be necessary during the time when one is changing over to a vegetarian diet.

Though the transition period is always tricky and is a time when developing a zinc deficiency is especially likely, this risk is even higher if one starts out with a borderline zinc deficiency. There is evidence, such as low zinc levels in patients with retarded wound-healing, indicating that a significant percentage of the general, non-vegetarian population suffers from marginal zinc status. Girls and young women seem to have substandard intakes most often, though men and boys, who tend to eat more animal foods, may become deficient despite their larger intakes since the normal development and functioning of the male reproductive system requires a substantial intake of zinc. This is thought to be why it is mostly boys who have been found to be undersize as a result of zinc deficiency. In adult males, zinc deficiency can contribute to sterility and impotence.

Zinc nutrition for pregnant and nursing women is of serious concern, since the infant must draw its supply of zinc from the mother. Materrial zinc deprivation in experimental animals has produced offspring with learning disabilities and abnormalities in the chemistry and structure of the brain, especially that part that is related to emotions. (In view of this it is interesting that some cases of schizophrenia seem to clear dramatically when given zinc.) There is also evidence that zinc deficiency during pregnancy can lead to later impairment of immune function.

Low zinc later in life may also lead to a number of symptoms of immune deficiency as well as impairment of the capacity to heal quickly. Inadequate tissue repair has been suspected of playing a role in the earliest stages of the development of atherosclerosis, where failure to properly heal some form of injury to the arterial lining may set the stage for plaque formation.

Getting Enough Zinc

If one does decide to take zinc supplements while adjusting to a vegetarian diet, 15 to 20 milligrams a day should be sufficient, since the recommended daily intake is only 15. Since absorption is only partial on any diet, this amount would not be excessive, especially when fibre and phytate levels are substantial.

In fact, zinc is one of the nutrients with the largest margin of safety. One would have to take vvell over 100 milligrams a day to cause any toxicity. Unfortunately, some physicians and laypersons recommend 135 milligrams per day for treatment of acne, much higher than what is necessary or desirable.

Even at moderate doses zinc can compete with copper for absorption or utilization. Since vegetarian diets tend to be relatively rich in copper, this is not likely to be a problem. However, zinc can also interfere with selenium utilization, and though selenium, too, is generally ample in vegetarian diets, zinc doses should be kept at reasonable levels for this reason.

Besides milk and eggs, the non-meat foods richest in zinc are beans, tofu, seeds, nuts, and hard cheeses. If these foods are taken in the diet and the fibre intake is kept moderate, zinc should not be a problem. Those in transition, and pregnant or nursing women should consider supplementation. Because of its role in the sense of taste, it is a happy coincidence that those in need of zinc generally find its taste agreeable, and those who have adequate levels find the taste unpleasant. This has led to a simple taste test for deficiency. Other signs of zinc deficiency are: white spots on nails, slow wound healing, poor resistance to infections and acne.

Vitamin B₁₂

Vitamin B_l2 is unique in many ways. First of all, it is the vitamin which is needed by the body in the tiniest amounts. Only a few thousands of a milligram (3 or 4 micrograms) per day are necessary to prevent the symptoms of deficiency. Even more important for vegetarians is the fact that vitamin B_l2 is the only vitamin which is not found in strictly vegetarian diets, e.g. those without dairy products. Vitamin Bl2 is present in milk, eggs, and meat, and is manufactured by many bacteria and yeasts. Any food which is strictly of plant origin, not ferrnented, and free of all bacteria and insects, will be found to contain no vitamin B_l2

In cultures where food is grown organically and processed little or not at all, deficiencies of vitamin B_l2 are uncommon, even when there is no meat, milk, eggs or other animal food in the diet. This is thought to be due to the fact that organically grown foods will often contain traces of bacteria from the soil or even tiny bits of insects which are difficult to see or remove completely. These alone may be enough to provide the extremely small doses of vitamin B_l2that are necessary. When foods are grown with the use of pesticides, however, insects and bacteria are likely to have been thoroughly exterminated, and the processing of food to make it suitable for long storage or shelf-life will be even more likely to remove any traces of vitamin B_l2. Thus vegans who eat processed foods are at increased risk.

It is often said that a vegetarian diet can supply everything except vitamin B_l2. Physicians and nutritionists are trained to caution those who are eliminating all animal foods about the grave consequences of B_l2 deficiency and to advise them that, at the very least, B_l2 supplements should be taken. This concern is understandable. Pernicious anemia, the disease connected with insufficient body stores of vitamin B_l2, is a serious disease.

In the early stages of the illness there are numbness and tingling of the hands and feet with a loss of sensation. Blood tests done on such patients reveal low hemoglobin levels and large, pale, red bloods cells. Gradually a lack of motor coordination develops. These symptoms are now known to be due to an in ability to synthesize myelin, the fatty sheath that insulates nerve fibres. As a result, the nerves to the limbs degenerate. If allowed to proceed unchecked, the deterioration progresses into the spinal cord and ultimately to the brain. Moodiness, poor memory, and confusion give way gradually to delusions, hallucinations, and overt psychosis. For vitamin B_l2to be absorbed, the stomach wall must secrete a substance called intrinsic factor, which combines with the B_l2, forming a complex that can then be taken up by the lower end of the small intestine. Patients with pernicious anemia were found to lack intrinsic factor because of the destruction of stomach wall cells. Thus B_l2, even when present in the diet in ample quantities, cannot be absorbed.

When originally described, the disease was observed to occur sporadically in most populations without regard to dietary practices. It was not considered to result from inadequate dietary intake of vitamin B_l2. Indeed there was no reason to assume that the disease had anything to do with the amount of vitamin B_l2 consumed, since amounts many times than ordinarily needed are of no use without intrinsic factor.

Nevertheless, because it has long been known that vitamin B_l2 is absent from foods that are strictly of plant origin, when nutritionists and dieticians began to encounter growing numbers of strict vegetarians, they were alarmed. While vegetarians who used dairy products were generally thought to be on safe ground, vegans, who take no foods of animal origin, were a different matter. A diet with no B_l2) it was felt, was sure to produce vitamin B_l2 deficiency and ultimately pernicious anemia.

Dietary Deficiency of B_l2: Myth or Reality ?

In the 1960s and 1970s a large number of case reports in medical journals seemed to fulfill this dire prophecy: "Subacute combined degeneration of the spinal cord in a vegan", "Megaloblastic anemia in an adult vegan," and so on. Nutrition manuals warned of the danger of developing pernicious anemia from an inadequate intake of vitamin B_l2. But despite the ominous tone of such case reports, surveys of groups of vegans reported with some surprise that most of the subjects they studied seemed quite well, with no signs of anemia or neurological degeneration. The occurrence of symptoms was, at most, rare. one might expect, after all, to find some cases of the disease in any population.

Were the cases of pernicious anemia that were reported merely persons with the disease who happened to be vegans, or were these cases caused by the all-plant diet? Of course, vegans argued the former in their magazines and newsletters, while nutritionists argued the latter in their books and scientific journals. As is usual with such debates, the ardour of the controversy yielded little in the way of illumination.

Nevertheless, by the beginning of the 1980s there was enough published literature to make evident some of the oversights that had led to premature conclusions: many of the diagnoses of inadequate vitamin B_l2 in the diet had been hastily made. For example, problems that can interfere with absorption, such as a lack of intrinsic factor, had not been ruled out as causes of the low body level of B_l2. To establish firmly that a person is suffering from a dietary deficiency of vitamin B_l2, certain criteria must be met.

A critical review of reports published up to 1980 on vegans showed that none of them met all these criteria. In each case, other explanations were possible, including deficiency of intrinsic factor, iron deficiency anemia, and neurological problems from other causes. In fact, in many of the published case reports, the authors noted that these alternative explanations seemed the most likely. Yet the cumulative weight of the first impressions created by numbers of such scientific papers is persuasive in itself and has tended to support the view not only that dietary deficiency of vitamin B_l2 is an actuality, but that it is common among vegetarians who use no animal foods. Despite this prevailing impression, in point of fact there is little incontrovertible evidence that a diet low in B_l2 can, in and of itself, cause problems.

Vitamin B₁₂ Vegan Sources

If it's true that a purely dietary deficiency of B_l2 occurs rarely, if at all, the question is, Why? How could it be that vegans, who consistently consume no B_I2-containing foods at all, might be perfectly healthy, with adequate tissue levels of the vitamin?

At least part of the answer to this question becomes apparent when we look at the origin of vitamin B_l2. Though it is found in animal foods, it is not manufactured by animal cells. It must be absorbed from their food by most animals, as it must be by humans. All B_l2 is made by bacteria. Ruminants, such as cows, do quite well, because bacteria in an accessory stomach, or rumen, produce B_l2 as they break down the fibre of the animal's food. But bacteria aren't just in cows' stomachs; they're practically everywhere. Researchers studying B₁₂ have complained that it is necessary to carefully clean all instruments to get meaningful measurements of Bl2 -since even tap water can contain substantial amounts. ("Substantial amounts" in the sense that they can approach the range of what is needed in the human diet.)

It is for this reason that some batches of beans, bean sprouts, comfrey leaves, turnip greens, peanuts, lettuce, fermented soybeans, and whole wheat have been reported to contain significant amounts of B_l2—while other batches of the same foods have been found to have none at all. The presence of bacteria on such foods is incidental; that is, the presence or absence of the vitamin will depend on whether the plants were fertilized with manure or not, how well they were washed and with what, and so forth. So as sources of B_l2 any one of such foods must be considered unreliable, though on any average day several of them might happen to bring along some small but significant amounts of the vitamin.

What's more, bacteria also grow on and in the body. In fact, it has been estimated that the microorganisms between the teeth and gums, around and in the crevices of the tonsils, in the folds at the base of the tongue, and in the upper respiratory passages will make up to half a microgram of B₁₂ a day. This is at least half of the minimum requirement, though some nutritionists think this quantity may be all that is needed for most people. Official recommended intakes by the World Health Organization and the Food and Nutrition Board provide for generous margins of safety, and up the level to as high as 3 or 4 micrograms for adults, but it is unlikely that it is necessary or even useful to consume such large amounts. An egg or a cup of milk will contain 1 microgram of vitamin B_l2 (see table below).

B₁₂ Content of Common Foods

* See p. 168

Sources : Goodman and Gillman : Pharmacological Basis of Therapeutics. U.S Dept. of Agriculture : Vitamin B₁₂ in Foods. Shurtleff : Sources of B₁₂

Other Complications in Vitamin B₁₂ absorption

There are countless bacteria in the human intestinal tract, too. Whether or not they make a contribution to the B_l2 needs of their human host is the subject of another long-standing controversy. Early studies on the bacterial flora of the gut focused on the colon, where the bulk of the intestinal microorganisms are found. Although producers of B_l2 were found there, there was a controversy around whether this would pass through the wall of the large intestine. More refined research techniques revealed that a smaller but still substantial community of bacteria inhabits the small intestine. Recent studies have demonstrated that these organisms do produce vitamin B_l2 and that they do so high enough in the intestinal tract to allow it to combine with intrinsic factor before it reaches the lower end of the small intestine, where the vitamin is absorbed.

Another complication is that some bacteria will compete with their host for dietary B₁₂ without contributing significant quantities in return. They can even deplete body stores, since Bl2 is constantly being secreted with the bile. Ordinarily much of this B_l2 is reabsorbed as the bile passes through the intestinal tract; but occasionally an unfriendly population of bacteria with an inclination for robbing their host of vitamins will prevent reabsorption. It's also known that B₁₂ absorption is more thorough when intake is lower. In other words, the meat-eater who consumes 10 micrograms of vitamin B_l2 in a day will absorb only 16% of it, while the vegan who takes in a mere fraction of that will absorb 70%. All of these factors add up to a rather delicate balance, which can be disturbed by any major disruption, such as migration to a different culture, or the use of antibiotic medications. Other important factors:

1. Excess fat or protein. Too much in the diet can increase vitamin B_l2 needs.
2. Highly processed foods. Whereas boiling milk for two to five minutes only decreased its B12 content by 30%, sterilization in sealed containers for 13 minutes caused a loss of 77%. Canned milk, for example, might be an inadequate source of vitamin B_l2.
3. Drugs, Tobacco, coffee, alcohol, and birth control pills have all been implicated in increasing one's need for B₁₂.
4. Pregnancy and nursing. Both pregnancy and nursing increase needs for vitamin B_l2. Low intake during nursing, for example, has resulted in breastmilk that is deficient even when the mother's levels remain normal, and has also resulted in symptoms such as apathy and retardation in the infant.
5. Chronic disease. Intestinal parasites, malaria, liver disease, chronic infections, and cancer will all disrupt normal mechanisms of B_l2 absorption and use, and increase needs.
6. Intestinal surgery. Removal of part of the stomach, where intrinsic factor is made and secreted, or removal of part of the lower small intestine, where it is absorbed, can drastically reduce uptake and may necessitate the use of injectable B_l2.
7. Use of megadoses of vitamin C, multiple vitamin/mineral preparations containing copper, and perhaps other food supplements such as spirulina (see below).

Vitamin B12, Mega C, and other supplements

Another ongoing controversy is that surrounding the effects of large doses of vitamin C on B_l2 availability. In 1974, one of the most respected authorities on vitamin B_l2 reported that mixing vitaniin C with vitamin B_l2 and incubating the combination in a way that would mimic digestion destroyed B₁₂. Both the population news media and the medical literature were quickly filled with warnings about the danger of vitamin C. Two years later, however, a different author observed that the original had been done using methods of B₁₂ measurement that were designed to test blood, not food. Since the B₁₂ in food is more tightly bound to protiens he concluded that the tests used had failed to pick it up. Using more apporopriate techniques, no destruction of B₁₂ was found. The researcher who had done the first study retaliated in 1978, demonstrating low blood levels of vitamin B₁₂ in patients who took 2 grams of vitamin C in a day and noting that another study had reported similar results.

Although the issue is still not completely resolved, it would appear that anyone taking more than 500 milligrams of vitamin C a day for a long period of time should have his or her vitamin B_l2 status monitored. An alternative that might provide some protection is to take vitamin C in high doses only for short periods of time, allowing intervals when it is stopped so that Bl2 stores can be replenished. A convenient regimen is one week on and one week off.

Other nutritional supplements can cause trouble, too. It is well established that vitamin B_l2 is destroyed by oxygen in the presence of vitamin C, vitamin B. (thiarnine), and copper ions. This may affect the B_l2 present in multivitamin preparations. It has been reported that 20% to 90% of the vitamin present in such supplements can be degraded to vitamin B1, analogues.

These are B_l2-like molecules that are similar enough to the real thing to replace it in metabolic reactions, but different enough to lack the effectiveness of the vitamin. Some of them can thus block the activity of the B_l2 that is present, preventing it from being used normally.

Spirulina, a dietary supplement widely acclaimed as an extraordinary source of B_l2, has also been found to contain many more B_l2 analogues than genuine B_l2—five to eight times as many. Whether or not these analogues are B_l2 antagonists and cause harm awaits investigation.

B_l2 as an oral supplement, when taken separately from other nutrients that can degrade it, such as vitamin C, copper, and thiamine, can be of help, however. It can be used by those with inadequate dietary B_l2 or when illness may increase one's needs beyond what is a normally adequate dietary intake. It can even be effective in those cases where absorption is impaired by a lack of intrinsic factor, since somewhere between 1% and 3% of vitamin B_l2 passes across the intestinal wall by simple diffusion. But much higher doses must be used when the normal mechanisms of fictive uptake are missing.

Nutritional yeast is sometimes used as a dietary supplement to supply vitamin B_l2 by those who are consuming only vegetable foods. Not all nutritional or brewer's yeast, however, will furnish the vitamin. In order to contain B_l2, the medium on which such yeast is grown must contain it or it must be added during the final processing. If one wishes to use yeast as a source, one must read labels carefully to be sure that the yeast in question does indeed contain the vitamin, and in adequate amounts (at least 1 microgram in 1 tablespoon, since a tablespoonful is a maximal appropriate regular daily dose of yeast).

Thus with a little bit of care, vegetarians can have the best of both worlds—they can be certain of adequate nutrition, and avoid the atherosclerosis and cancer so common among meateaters. In addition, the transition to vegetarianism entails a transformation of consciousness as well.

The resources expended by those who are eating in a self-destructive way are not available for higher purposes such as creativity, self-development, and the exploration of the inner world. For us to progress to a new stage of development we must carefully examine our way of living and divest ourselves of those habits that are most limiting. A vegetarian diet which skilfillly includes all the necessary nutrients for human function appears more and more to be an evolutionary step that is inevitable.

REFERENCES

1. Monsen E.R. , Hallberg L., Layrisse M., etal: Estimation of available dietary iron. American Journal of Clinical Nutrition, 1978, 31: 134-41.
2. Cook J.D. . Noble N.L., Morsk T.A., et al: Effect of fibre on non-heme iron absorption. Gastroenterology, 1983, 85: 1354-58.
3. Walker A.R.P., Walker B.F.: Effect of wholemeal and white bread on iron absorption. British Medical Journal 19Z7, 2: 771-2.
4. Michaelsson, G. et al.: Effects of oral zinc and vitamin A in acne. Journal of the American Medical Association, 1977, 237: 401.
5. Prasad A .: Zinc deficiency in man. American Journal of Diseases of the Child. 1976, 130: 357-361.
6. Freeland-Graves J.H., Bodzy P. W., Eppright M.A.: Zinc status of vegetarians. Journal of the American Dietetic Association, 1980, 77: 655-61.
7. Sandstead H.H.: Zinc nutntion in the United States. American Journal of Clinical Nutrition, 1973, 26: 151-60.
8. Patterson K.Y., Holbrook J.T., Bodner J.E., et. al.: Zinc, copper, and manganese intake and balance for adults consuming self-selected diets. American Journal of Clinical Nutrition, 1984, 50s: 1397-1403.
9. Underwood E.J.: Trace Elements in Human and Animal Nutrition, 4th ed., New York: Academic Press, 1977, pp. 219-20.
10. Sandstead H.H., Evans G. W.: Zinc, in Present Knowledge in Nutrition, pp. 479-505.
11. Jathar V.S., Inamdar-Deshmukh A.B., Rege D.V., Satoskar R.S.: Vitamm B_l2 and Vegetarianism in India. Acta Haemotologia, 1975, 53: 90-97.
12. Ellis F.R., Montegriffo V.M.E.: Veganism: Clinical findings and investigations. American Journal of Clinical Nutrition, 1970, 23: 249-55.
13. Albert M.J., Mathan V.I., Baker S. T.: Vitatnin B_l2 synthesis by human small intestine bacteria. Nature, 1980, 283: 781-82.
14. Siddens R.C.: The experimental production of vitamin B_l2 deficiency in the baboon (Papio cynocephalus), a 2-year study. British Journat of Nutrition, 1974, 32: 219-28.
15. Herbert V., Jacob E.: Destruction of vitamin B_l2 by ascorbic acid. Journal of the American Medical Association, 1974, 230: 241-42.
16. Herbert V., Jacob E., Wong K., et. al.: Low serum vitamin B_l2 levels in patients receiving ascorbic acid in megadoses: Studies concerning the effect of ascorbate on radioisotope vitamin B_l2 assay. American Journal of Clinic Nutrition, 1978, 31: 253-58.