While fermented soy products,  such as traditional tempeh (tempe), contain protein, vitamins, anti-carcinogenic substances and important fatty acids, they can under no circumstances be called nutritionally complete. Like all pulses, the soybean lacks vital sulfur-containing amino acids cystine and methionine. These are usually supplied by rice and other grains in areas where the soybean is traditionally consumed. Soy should never be considered as a substitute for animal products like meat or milk.Claims that fermented soy products like tempeh can be relied on as a source of vitamin B12, necessary for healthy blood and nervous system, have not been supported by scientific research.²⁷

Finally, soybeans do not supply all-important fat soluble vitamins D and preformed A (retinol) which act as catalysts for the proper absorption and utilization of all minerals and water soluble vitamins in the diet. These “fat soluble activators” are found only in certain animal foods such as organ meats, butter, eggs, fish and shellfish. Carotenes from plant foods and exposure to sunlight are not sufficient to supply the body’s requirements for vitamins A and D.²⁸ Soy products often replace animal products in third world countries where intake of B12and fat soluble A and D are already low. Soy products actually increase requirements for vitamins B12 and D.²⁹

Are soy products easy to digest, as claimed? Fermented soy products probably are; but unfermented products with their cargo of phytates, enzyme inhibitors, rancid fatty acids and altered proteins most certainly are not. Pet food manufacturers promote soy free dog and cat food as “highly digestible”.

Only Fermented Soy Products Are Safe

To summarize, traditional fermented soy products such as miso, natto and tempeh-which are usually made with organically grown soybeans-have a long history of use that is generally beneficial when combined with other elements of the Oriental diet including rice, sea foods, fish broth, organ meats and fermented vegetables. The value of precipitated soybean products is problematical, especially when they form the major source of protein in the diet. Modern soy products including soy milks and ersatz meat and dairy products made from soy protein isolate and textured vegetable protein are new to the diet and pose a number of serious problems.

Another Look at Milk

What then about dairy products? A few studies have linked modern commercial milk products with serious diseases such as cancer, diabetes and arthritis; but natural milk products have a long history of conferring good health in many parts of the globe. Dr. Weston Price, a pioneer in the science of nutrition, studied isolated population groups during the 1930’s. He found that milk products were the principal food of many supremely healthy populations including isolated villagers in the Swiss Alps, the Masai and related tribes in Africa, and Arabic peoples in the Middle East.³⁰

Of the three areas in the world noted for the longevity of the local population -the Caucasus Mountains in Russia, the village of Vilcabamba in Ecuador and the land of the Hunza in northern India- all three use whole milk products. The people of Hunza and Kashmir consume whole fermented goat milk products; inhabitants of Vilcabamba consume raw cows milk which they usually separate into cream cheese and whey; and the centenarians of the Caucasus Mountains eat whole milk yogurt and other dairy products.

Milk products form the backbone of the Hindu diet, with clarified butter (ghee) and fermented curds eaten with every meal. “The cows are our friends, they give food, they give strength, they likewise give a good complexion and happiness,” said Gautama Buddha. While the Japanese have the longest life span of the civilized world on a diet containing few milk products, the Swiss are a close second in the longevity stakes with a diet just loaded with rich milk products like butter, cream and cheese. Tied for third and fourth are the Austrians and the Greeks. Both these populations consume whole milk products, especially cheese. Milk products are even found in some parts of the Orient, from water buffalo milk in Southeast Asia to cows milk in northern China. The longest living man in the West was Old Par, an English peasant who labored in the fields until his death at 152 years. His diet consisted almost entirely of raw goat milk products-milk, cheese and whey.³¹

Processing Is the Problem

The path that transforms healthy milk products into allergens and carcinogens begins with modern feeding methods that substitute high-protein, soy-based feeds for fresh green grass; and breeding methods to produce cows with abnormally large pituitary glands so that they produce three times more milk than the old fashioned scrub cow. These cows need antibiotics to keep them well. Their milk is then pasteurized so that all valuable enzymes are destroyed-lactase for the assimilation of lactose; galactase for the assimilation of galactose; phosphatase for the assimilation of calcium. Literally dozens of precious enzymes are destroyed in the pasteurization process. Without them milk is very difficult to digest. The human pancreas is not always able to produce these enzymes; overstress of the pancreas can lead to diabetes and other diseases.³²

Non-fat dried milk is added to 1% and 2% milk. Unlike the cholesterol in fresh milk, which plays a variety of health promoting roles, the cholesterol in nonfat dried milk is oxidized and it is this rancid cholesterol that promotes heart disease. Like all spray dried products, non-fat dried milk has a high nitrite content. Non-fat dried milk and sweetened condensed milk are the principal dairy products in third world countries; use of ultra high temperature pasteurized milk is widespread in Europe.

Quality Dairy Products Are Available

Public health officials and the National Dairy Council have worked together in this country to make it very difficult to obtain wholesome fresh raw dairy products. Nevertheless, they can be found with a little effort. In some states you can buy raw milk directly from farmers. Whole pasteurized non-homogenized milk from cows raised on organic feed is now available in many gourmet shops and health food stores. It can be cultured to restore enzyme content, at least partially.³³ Cultured buttermilk is often more easily digested than regular milk; it is an excellent product to use in baking.

Many shops now carry whole cream, that is merely pasteurized (not ultra pasteurized like most commercial cream): diluted with water it is delicious on cereal and a good substitute for those allergic to milk. Traditionally made creme fraiche (European style sour cream) also has a high enzyme content. Fresh, organic yogurt made from whole milk according to traditional methods is also now available, as well as organic raw cheese. Many imported cheeses are raw (look for the words “milk” or “fresh milk” on the label) and are of very high quality.

Butter Is a Healthy Food

Organic, cultured butter is available in many stores. It has restored enzymes and a high vitamin A content. Contrary to widely held opinion, there is no evidence that butter contributes to heart disease or cancer. At the turn of the century, butter consumption in America was 18 pounds per person per year. Today it is a mere five pounds. As butter consumption has plummeted, cancer and heart disease have risen dramatically. The real blame for this increase points squarely at hydrogenated butter substitutes—margarine and shortening.³⁴ Butter contains many nutrients that protect us against disease. Those with severe allergies to milk products can still eat clarified butter (ghee) and enjoy its good taste and numerous nutritional benefits.

In countries that traditionally produce milk, adults favor fermented products such as yogurt, clabber, buttermilk and soft and hard cheeses. These are easier to digest because of enhanced enzyme content. But fresh whole milk is easily digested by most children and is an appropriate food up to the age of three or four. A child’s toleration for milk will be much greater if it is raw. If you have property in the country, consider raising scrub cows or goats in order to provide fresh raw milk for your children, grandchildren, nieces and nephews-there is no greater gift you can give them than the healthy start conferred by fresh whole raw milk.

Homemade Formula Best for Babies

Neither milk-based nor soy-based infant commercial formulas can be recommended for optimal development of the infant. Mothers who cannot breast feed, for whatever reason, should prepare homemade formula based on whole milk for their babies. The rare child allergic to whole milk formula should be given a whole foods meat-based formula, not one made of soy protein isolate. Time invested in preparing homemade formula will be well rewarded with the joys of conferring robust good health on your children.

Consumer Beware!

To summarize, there may be some beneficial factors in soy foods prepared according to traditional fermentation methods. In the Orient these are eaten in small amounts as condiments, and not as a replacement for animal foods. Highly processed soy protein isolates and textured vegetable protein have little in common with traditional soy products. They might be compared to plastic processed cheese slices, which have nothing in common with traditionally processed whole milk natural cheeses.
Promotion of modern, industrially processed soy products should be viewed with skepticism. This is a huge and powerful industry.

References:

27. Scheer, James F., Health Freedom News, March 1991, p.7.

28.  Jennings, I.W., Vitamins in Endocrine Metabolism, Charles C. Thomas, Springfield, IL, 1970, pp.39-57,84-85.

29.  Smith, Op. Cit., pp. 184-188.
30.  Price, Weston A., D.D.S., Nutrition and Physical Degeneration, Keats Publishing, New Canaan, CT, 1945.

31.  McLaughlin, Terence, A Diet of Tripe, David & Charles, London 1978, p. 36.

32.  Pariza, Michael W., “Newly recognized anti-carcinogenic fatty acid identification and quantification in natural and processed cheeses”, Journal Agricultural and Food Chemistry, Jan/Feb 1989 v. 37 (1) pp. 75-81.

33.  Piima powder, for culturing fresh milk, may be ordered by sending a check or money order for $5.00 to Piima, PO Box 2614, La Mesa, CA 91943-2614.

34.  Enig, Mary, Ph.D., “Trans Fatty Acids-An Update”, Nutrition Quarterly, v.17 (4), Nov 4, 1993, pp.79-93.

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1. Soy Products Do Not Make You Healthy (part II)
2. Soy Products Do Not Make You Healthy
3. Being Vegetarian: Is It Good or Bad for You?

The truth is, however, that most of us are unlikely to adopt traditional soy products as their principal food. Tofu, bean curd and tempeh (tempe) have a disagreeable texture and are too bland for the Western palate; pungent and musty miso and natto lose out in taste tests; only soy sauce enjoys widespread popularity as a condiment. The soy industry has therefore looked for other ways to market the superabundance of soybeans now grown in the United States and around the world.

Large scale cultivation of the soybean in the United States began only after the Second World War, and quickly rose to 140 billion pounds per year. Most of the crop is made into animal feed and soy oil for hydrogenated fats- margarine and shortening. During the past 20 years, the industry has concentrated on finding markets for the byproducts of soy oil manufacture, including soy “lecithin“, made from the oil sludge, and soy protein products, made from defatted soy flakes, a challenge that has involved overcoming consumer resistance to soy products, generally considered tasteless “poverty foods”. “The quickest way to gain product acceptability in the less affluent society,” said a soy industry spokesman, ” … is to have the product consumed on its own merit in a more affluent society.”¹¹ Hence the proliferation of soy products resembling traditional American foods-soy milk for cows milk, soy baby formula, soy yogurt, soy ice cream, soy cheese, soy flour for baking and textured soy protein as meat substitutes, usually promoted as high protein, low-fat, no cholesterol “healthfoods” to the upscale consumer increasingly concerned about his health. The growth of vegetarianism among the more affluent classes has greatly accelerated the acceptability and use of these ersatz products. Unfortunately they pose numerous dangers.

Processing Denatures and Dangers Remain

The production of soy milk is relatively simple. In order to remove as much of the trypsin inhibitor content as possible, the beans are first soaked in an alkaline solution. The pureed solution is then heated to about 115 degrees C in a pressure cooker. This method destroys most (but not all) of the anti-nutrients but has the unhappy side effect of so denaturing the proteins that they become very difficult to digest and much reduced in effectiveness.¹² The phytate content remains in soy milk to block the uptake of essential minerals. In addition, the alkaline soaking solution produces a carcinogen, lysinealine, and reduces the cystine content, which is already low in the soybean.¹³ Lacking cystine, the entire protein complex of the soybean becomes useless unless the diet is fortified with cystine-rich meat, eggs, or dairy products, an unlikely occurrence as the typical soy milk consumer drinks the awful stuff because he wants to avoid meat, eggs and dairy products.

Most soy products that imitate traditional American food items, including baby formulas and some brands of soy milk, are made with soy protein isolate, that is the soy protein isolated from the carbohydrate and fatty acid components that naturally occur in the bean. Soy beans are first ground and subjected to high-temperature and solvent extraction processes to remove the oils. The resultant defatted meal is then mixed with an alkaline solution and sugars in a separation process to remove fiber. Then it is precipitated and separated using an acid wash. Finally the resultant curds are neutralized in an alkaline solution and spray dried at high temperatures to produce high protein powder. This is a highly refined product in which both vitamin and protein quality are compromised-but some trypsin inhibitors remain, even after such extreme refining! Trypsin inhibitor content of soy protein isolate can vary as much as 5-fold.¹⁴ In rats, even low level trypsin inhibitor soy protein isolate feeding results in reduced weight gain compared to controls.¹⁵ Soy product producers are not required to state trypsin inhibitor content on labels, nor even to meet minimum standards, and the public, trained to avoid dietary cholesterol, a substance vital for normal growth and metabolism, has never heard of the potent anti-nutrients found in cholesterol-free soy products.

Soy Formula Is Not the Answer

Soy protein isolate is the main ingredient of soy-based infant formulas. Along with trypsin inhibitors, these formulas have a high phytate content. Use of soy formula has caused zinc deficiency in infants.¹⁶ Aluminum content of soy formula is 10 times greater than milk based formula, and 100 times greater than unprocessed milk.¹⁷ Aluminum has a toxic effect on the kidneys of infants, and has been implicated as causing Alzheimer’s in adults. Soy milk formulas are often given to babies with milk allergy; but allergies to soy are almost as common as those to milk.¹⁸ Use of soy formula to treat infant diarrhea has had mixed results, some studies showing improvement with soy formula while others show none at all.¹⁹ Soy formulas lack cholesterol which is absolutely essential for the development of the brain and nervous system; they also lack lactose and galactose, which play an equally important role in the development of the nervous system. A number of other substances, which are unnecessary and of questionable safety, are added to soy formulas including carrageenan, guar gum, sodium hydroxide (caustic soda), potassium citrate monohydrate, tricalcium phosphate, dibasic magnesium phosphate trihydrate, BHA and BHT. Nitrosamines, which are potent carcinogens, are often found in soy protein foods, and are greatly increased during the high temperature drying process.²⁰ Not surprisingly, animal feeding studies show a lower weight gain for rats on soy formula than those on whole milk, high-lactose formula.²¹ Similar results have been observed in children on macrobiotic diets which include the use of soy milk and large amounts of whole grains. Children brought up on high-phytate diets tend to be thin and scrawny.²²

Fabricated Soy Foods

A final indignity to the original soy bean is high-temperature, high-pressure extrusion processing of soy protein isolate to produce textured vegetable protein. Numerous artificial flavorings, particularly MSG, are added to TVP products to mask their strong “beany” taste, and impart the flavor of meat. Soy protein isolate and textured vegetable protein are used extensively in school lunch programs, commercial baked goods, diet beverages and fast food products. They are heavily promoted in third world countries and form the basis of many food give-away programs. These soy products greatly inhibit zinc and iron absorption; in test animals they cause enlarged organs, particularly the pancreas and thyroid gland, and increased deposition of fatty acids in the liver.²³ Human feeding tests to determine the cholesterol lowering properties of soy protein isolate have not shown them to be effective.²⁴ Nevertheless, they are often promoted as having beneficial effects on cholesterol levels.

Cancer Preventing or Cancer Causing?

The food industry also touts soy products for their cancer preventing properties. Isoflavone aglycones are anticarcinogenic substances found in traditionally fermented soybean products. However, in non-fermented soy products such as tofu and soy milk, these isoflavones are present in an altered form, as beta-glycoside conjugates, which have no anti-carcinogenic effect.²⁵ Some researchers believe the rapid increase in liver and pancreatic cancer in Africa is due to the introduction of soy products there.²⁶

The fatty acid profile of the soybean includes large amounts of beneficial omega-3 fatty acids compared to other pulses (legumes); but these omega-3 fatty acids are particularly susceptible to rancidity when subjected to high pressures and temperatures. This is exactly what is required to remove oil from the bean, as soybean oil is particularly difficult to extract. Hexane or other solvents are always used to extract oil from soybeans, and traces remain in the commercial product.

(The Next Story)

References:

• 11. Coleman, Richard J., “Vegetable Protein-A Delayed Birth?”, J-Am-Oil-Chem-Soc, v. 52, Apr 1975, p. 238A.
• 12. Wallace, G.M., “Studies on the Processing and Properties of Soymilk”, J-Sci-Fd-Agric, v.22, Oct 1971, pp.526-535.
• 13. Berk, Zeki, “Technology of production of edible flours and protein products from soybeans”, FAO Agricultural Services Bulletin 97, Food and Agriculture Organization of the United Nations 1992, p. 85.
• 14. Rackis, J.J., et. al., “The USDA trypsin inhibitor study. I. Background, objectives and procedural details”, Qual-Plant-Foods-Hum-Nutr, v. 35 1985, p. 232.
• 15. Ibid.
• 16. Lonnerdal, B. et. al., “The effect of individual components of soy formula and cows’ milk formula on zinc bioavailability”, Am-Jour-Clin-Nutr, v. 40 Nov 1984, pp. 1064-1070.
• 17. Palmer, Gabrielle, “The Politics of Breastfeeding”, Pandora Press, London, 1993, p. 310.
• 18. Ganse, R. “Doctors still sleuthing cause of food allergies”, Sch-Foodserv J, v. 40 (4), May 1986, pp. 38-39.
• 19. Alarcon, P. et. al., “Clinical trial of home available, mixed diets versus a lactose-free soy-protein formula for the dietary management of acute childhood diarrhea”, J-Pediatr-Gastroenterol Nutr, v.12 (2), Feb 1991, pp.224-232
• 20. “Rackis”, Op. Cit., P. 225.
• 21. Dukakis, E.S., et. al., “Evaluating the nutritional quality of infant formula” Nutr-Res, v. 9 (1), Jan 1989, pp. 93-104.
• 22. “Lonnerdal”, Op. Cit.
• 23. Smith, Allan K. Ph.D. ed., Soybeans: Chemistry and Technology, Vol 1, Avi Publishing Company, Inc. Westport, CT, 1972, p. 183; Jenkins, M. Y., et. al., “Nutritional assessment of twelve protein foods/ingredients”, NutrRes, v. 9 (1), Jan 1989, pp. 83-92.
• 24. Wolfe, B.M., “Elevation of VLDL-cholesterol during substitution of soy protein for animal protein in diets of hypercholesterolemic Canadians”, Nutr-Rep-lnt, v. 32 (5), Nov 1985, pp.1057-1065.
• 25. Coward, L., et. al., “Genistein, daidzein and their beta-glycoside conjugates: Antitumor isoflavones in soybean food from American and Asian diets”, J-Agric-Food-Chem, v. 41 (11), Nov 1993, pp. 1961-1967.
• 26. Katz, Op. Cit.

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1. Soy Products Do Not Make You Healthy (part III)
2. Soy Products Do Not Make You Healthy

The word vegetarian was first used in the 1840’s, although the practice of vegetarianism goes back thousands of years. People are influenced to follow this diet for a number of reasons – religious and moral, hygienic and physiological. Certain Hindu and Buddhist groups, Seventh-Day Adventist, and some Roman Catholic orders are among the religious group abstaining from meat. Some people feel that life is sacred to all living creatures and that it is ethically wrong to shorten the life-span of any animal to obtain food. Some vegetarians believe that the flesh of dead animals may harbor disease-causing bacteria and other impurities, and that no animals flesh can be as pure as plants grown by nature.

Nutritionally, a diet without meat, fish, or dairy products could be lacking  in protein, an essential nutrient for body-building and tissue repair. Great care must be taken in such a diet to emphasized foods rich in protein, such as  nuts and the seeds of legumes (peas, beans, lentils). It is also possible to buy specially prepared food supplements. In 1847 the Vegetarian Society was established in Manchester, England, the first group of this kind. In the early 20th century the International Vegetarian union was founded. It has affiliated societies through out the world.

Vegetarian Lack the Vital Vitamin B12

Vitamin B12 is found almost exclusively in animal foods such as:

• liver,
• kidney,
• meat,
• fish,
• shellfish,
• milk products,
• eggs

but the original source of B12 in nature is bacteria, the only creatures able to manufacture this vitamin. In humans and animals, these bacteria produce B12 in the colon; however, little if any is absorbed across the colon wall so we must get our B12 from animal foods. Bivalves such as clams, mussels and oysters contain high levels of B12 because they siphon large quantities of vitamin B12-synthesizing microorganisms from the sea.³ Production of B12 supplements involves fermentation procedures similar to those used for penicillin and other antibiotics.

Interestingly, while eggs contain B12, they also contain substances that block absorption,¹ a fact that leaves only milk as a good source of B12 for vegetarians. Some studies indicate that B12 is better absorbed from milk than from meat.² However, one source indicates that B12 in milk is destroyed by boiling.³ Analysis of B12 in pasteurized milk reveals only a 10 percent loss; however pasteurization deforms the milk proteins that aid in B12 absorption.⁴

Interestingly, some sources claim that fermentation of yoghurt from milk lowers B12 levels,⁵ although food tables indicate similar levels in commercial milk and yoghurt.

The vitamin B12 molecule is resistant to temperatures in excess of the boiling point, unless exposed to an alkaline medium. The molecule breaks down at 250^o C. Thus B12 is destroyed on the surface of grilled meat, but not in the interior. Eight percent of B12 in liver is lost by boiling for five minutes.⁶ Thus gentle braising or cooking steaks to rare or medium-rare best preserves B12 in meat.

Until recently, vegetarian and vegan literature claimed that certain plant foods could provide B12–seaweeds, fermented soybeans (tempeh ), spirulina, even unwashed vegetables that have been fertilized with manure. Proponents of vegetarianism pointed to inhabitants of India, who did not seem to exhibit signs of B12 deficiency in spite of very low levels of animal foods in the diet. Yet as early as 1974, an American study found that 92% of vegans, 64% of lactovegetarians, 47% of lacto-ovovegetarians and 20% of semi-vegetarians have blood levels below normal, that is, below the low range that marks the onset of pernicious anemia.⁷

Today, most vegetarian literature does warn about the very real possibility of depletion and recommends routine supplementation with B12. We now know that a source of B12 in the tropical, mostly vegetarian diet in India was insect excrement and parts in stored grains and legumes.⁸ These would have been an unavoidable feature of traditional diets in hot climates until the advent of modern sterilization and storage techniques.

Plant foods said to be sources of B12 actually contain B12 analogs (called cobamides)–substances that block the uptake of true B12 and increase the body’s need for the nutrient.⁹ A surprising source of cobamides is bacterial overgrowth in the small intestines, which can produce B12 analogs.¹⁰ The use of antibiotics, or a diet high in refined carbohydrates, can encourage the proliferation of bacterial overgrowth and lead to B12 deficiencies.

Yet another area for concern is multivitamin products! The late Victor Herbert, a noted B12 researcher, maintains that many multivitamin products contain spurious and even dangerous analogs of B12 possibly formed when crystalline B12 interacts with other nutrients in multivitamin products, such as vitamin C, iron and copper.¹¹

High levels of folic acid can accelerate neuropsychiatric complications in persons with B12 deficiency.¹² Since folic acid intakes of vegetarians tend to be high (from green vegetables and from grain products that have been fortified with folic acid), those following a vegetarian lifestyle may be at increased risk of neurological and psychological problems.

The body stores considerable B12 in the liver. Thus a delay of 5-10 years may separate the beginning of a vegetarian diet (or absorption problems) and the onset of deficiency symptoms. Interestingly, the body can recycle over 75 percent of the B12 it uses.¹³ Used B12 is excreted in bile and then reabsorbed in the small intestine by the same complex process described earlier. Some people have a more efficient recycling system than others and hence can go longer on a vegetarian diet without signs of deficiency. However, more B12 is excreted in the presence of high levels of fiber, a common feature of vegetarian diets.¹⁴

Vegan and vegetarian diets present a real danger for growing children because their stores are very low, especially if their mothers avoided animal foods during pregnancy and lactation. The scientific literature contains numerous case studies describing severe anemia, dramatic growth retardation, irritability and delays in the acquisition of motor skills in B12-deficient children from vegetarian families.

In a recent study, researchers assayed cognitive development in 72 young people raised on diets free of all animal products until at least the age of six and then on a diet containing milk and eggs. When compared with children who had eaten normal mixed diets (including meat) all their lives, they scored substantially lower on tests measuring spatial ability, short-term memory and “fluid intelligence,” that is, the capacity to solve complex problems, abstract thinking ability and the ability to learn.¹⁵

References:

1. Doscherholmen A and others. Proc Soc Exp Biol Med 1975 Sep;149(4):987-90; DoscherholmenA and others. Br J Haematol 1976 Jun;33(2):261-72
2. Tucker KL and others. Am J Clin Nutr 2000;71:514-522
3. www.vegsoc.org/info/b12.html
4. www.slowfood.com/img_sito/riviste/slow/EN/22/crudo.html.
5. Reddy KP and others. J Dairy Sci 1976 Feb;59(2)191-5.
6. Herbert V and Das KC. Folic acid and vitamin B12. In: Shils ME, Olson JA, Shike M, eds. Modern Nutrition in Health and Disease. 8th ed. Philadelphia, Lea & Febiger, 1994:402-25.
7. Dong A and Scott SC. Ann Nutr Metab 1982;26(4):209-16.
8. Nature’s Way 1979;10:20-30.
9. Herbert V. Am J Clin Nutr 1987;46:387-402.
10. Brandt LJ and others. Ann Intern M 1977 Nov;87(5):546-51.
11. Herbert V and Das KC. Folic acid and vitamin B12. In: Shils ME, Olson JA, Shike M, eds. Modern Nutrition in Health and Disease. 8th ed. Philadelphia, Lea & Febiger, 1994:402-25.
12. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, biotin, and choline. National Academy Press. Washington, DC 1998; Snow CF. Arch Intern Med 1999;159:1289-98.
13. Herbert V and Das KC. Folic acid and vitamin B12. In: Shils ME, Olson JA, Shike M, eds. Modern Nutrition in Health and Disease. 8th ed. Philadelphia, Lea & Febiger, 1994:402-25.
14. Cullen RW and Oace SM. J Nutr 1978 Apr;108(4):640-7.
15. Louwan MWJ and others. Am J Clin Nutr 2002 Sep;72:762.