Soy Products Do Not Make You Healthy

Commercial milk products have been linked to a number of disease conditions including allergies, asthma, arthritis, diabetes, auto immune diseases, childhood anemia, heart disease and cancer. Many have turned to soy products as substitutes for dairy products. A popular booklet describes soy foods as ” . . . uniformly high in protein but low in calories, carbohydrates and fats, entirely devoid of cholesterol, high in vitamins, easy to digest, tasty and wonderfully versatile in the kitchen, [which] positions them as irresistible new food staples for the evolving American (and also many other countries) diet. ¹. . . with each mouth watering soy food dish,” says the author, “comes a balanced, adequate and sustainable nutritional package.” ²

Leaving aside the question of whether products like tofu and soy milk are really “mouthwatering” and “irresistible,” those charged with providing nutritious meals for their families should carefully examine claims that newly introduced soybean products provide an easily digested and complete nutritional package, one that adequately replaces dairy products like milk, butter and cheese, which have, after all, provided nourishment for our generations.

History of the Bean

Soybeans come to us from the Orient. During the Chou Dynasty (1134 – 246 BC) the soybean was designated one of the five sacred grains, along with barley, wheat, millet and rice. However, the pictograph for the soybean, which dates from earlier times, indicates that it was not first used as a food; for whereas the pictographs for the other four grains show the seed and stem structure of the plant, the pictograph for the soybean emphasizes the root structure. Agricultural literature of the period speaks frequently of the soybean and its use in crop rotation. Apparently the soy plant was initially used as a method of fixing nitrogen.³ soybean did not serve as a food until the discovery of fermentation techniques, sometime during the Chou Dynasty. Thus the first soy foods were fermented products like tempeh, natto, miso and shoyu (soy or tamari sauce). At a later date, possibly in the 2nd century B.C., Chinese scientists discovered that a puree of cooked soybeans could be precipitated with calcium sulfate or magnesium sulfate (plaster of Paris or Epsom salts) to make a smooth pale curd – tofu or bean curd. The use of fermented and precipitated soy products soon spread to other parts of the Orient, notably Japan and Indonesia. Although the highly flavored fermented products have elicited greater interest among scientists and epicures, it is the bland precipitated products that are most frequently used, accounting for approximately 90% of the processed soybeans consumed in Asia today.4 The increased reliance on bean curd as a source of protein, which occurred between 700 A.D. and the present time, has not necessarily been a beneficial change for the populations of the Orient and Southeast Asia.

Fit for Human Consumption?

The Chinese did not eat the soybean as they did other pulses (legumes) such as the lentil because the soybean contains large quantities of a number of harmful substances. First among them are potent enzyme inhibitors which block the action of trypsin and other enzymes needed for protein digestion. These “antinutrients” are not completely deactivated during ordinary cooking and can produce serious gastric distress, reduced protein digestion and chronic deficiencies in amino acid uptake. In test animals, diets high in trypsin inhibitors cause enlargement and pathological conditions of the pancreas, including cancer. The soybean also contains hemaglutinin, a clot promoting substance that causes red blood cells to clump together. Trypsin inhibitors and hemaglutinin have been rightly labeled “growth depressant substances.” They are deactivated during the process of fermentation. In precipitated products, enzyme inhibitors concentrate in the soaking liquid rather than in the curd. Thus in tofu and bean curd, these enzyme inhibitors are reduced in quantity, but not completely eliminated.

Soybeans are also high in phytic acid or phytates. This is an organic acid, present in the bran or hulls of all seeds, which blocks the uptake of essential minerals-calcium, magnesium, iron and especially zinc-in the intestinal tract. Although not a household word, phytates have been extensively studied. Scientists are in general agreement that grain and legume based diets high in phytates contribute to widespread mineral deficiencies in third world countries.⁵ Analysis shows that calcium, magnesium, iron and zinc are present in the plant foods eaten in these areas, but the high phytate content of soy and rice based diets prevents their absorption. The soybean has a higher phytate content than any other grain or legume that has been studied.⁶ Furthermore, it seems to be highly resistant to many phytate reducing techniques such as long, slow cooking.⁷ Only a long period of fermentation will significantly reduce the phytate content of soybeans. Thus fermented products such as tempeh and miso provide nourishment that is easily assimilated, but the nutritional value of tofu and bean curd, both high in phytates, is questionable.

When precipitated soy products are consumed with meat, the mineral blocking effects of the phytates are reduced.⁸ The Japanese traditionally eat tofu as part of a mineral-rich fish broth. Vegetarians who consume tofu and bean curd as a substitute for meat and dairy products risk severe mineral deficiencies. The results of calcium, magnesium and iron deficiency are well known, those of zinc are less so.  Zinc is called the intelligence mineral because it is needed for optimal development and functioning of the brain and nervous system. It plays a role in protein synthesis and collagen formation; it is involved in the blood sugar control mechanism and thus protects against diabetes; it is needed for a healthy reproductive system. Zinc is a key component in numerous vital enzymes and plays a role in the immune system. Phytates found in soy products interfere with zinc absorption more completely than with other minerals.⁹ Literature extolling soy products tends to minimize the role of zinc in human physiology, and to gloss over the deleterious effect of diets high in phytic acid.

Milk drinking is given as the reason second generation Japanese in America grow taller than their native ancestors. Some investigators postulate that the reduced phytate content of the American diet—whatever may be its other deficiencies-is the true explanation, pointing out that Asian and Oriental children who do not get enough meat and fish products to counteract the effects of a high phytate diet, frequently suffer rickets, stunting and other growth problems.¹⁰ The current climate of medical opinion in America has cast a cloud of disapproval on tallness. Parents would do well to ask their six-year-old boys whether they would prefer to be six-foot-one or five-foot-seven when they grow up, before substituting tofu for eggs, meat and dairy products.

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REFERENCES

1. Leviton, Richard, Tofu, Tempeh, Miso and Other Soyfoods: The “Food of the Future” -How to Enjoy Its Spectacular Health Benefits, Keats Publishing, Inc, New Canaan, CT, 1982, p. 12.
2. Ibid. p. 2.
3. Katz Solomon H., “Food and Biocultural Evolution: A Model for the Investigation of Modern Nutritional Problems”, Nutritional Anthropology, Alan R. Liss Inc., 1987 p. 50.
4. Ibid. p. 49.
5. Van-Rensburg, et. al. “Nutritional status of African populations predisposed to esophageal cancer”, Nutr-Cancer, V.4, 1983, pp. 206-216; Moser, P.B. et. al., “Copper, iron, zinc and selenium dietary intake and status of Nepalese lactating women and their breast-fed infants”, Am-J-Clin-Nutr, v.47, Apr 1988, pp.729-734; Harland, B.F., et. al., “Nutritional status and phytate: zinc and phytate X calcium: zinc dietary molar ratios of lacto-ovo-vegetarian Trappist monks: 10 years later”, J-Am-Diet-Assoc., v. 88, Dec 1988, pp. 1562-1566.
6. El Tiney, A.H., “Proximate Composition and Mineral and Phytate Contents of Legumes Grown in Sudan”, Journal of Food Composition and Analysis, v. 2, 1989, pp. 67-78.
7. Ologhobo, A.D., et. al., “Distribution of phosphorus and phytate in some Nigerian varieties of legumes and some effects of processing”, J-Food-Sci, v.49 (1), Jan/Feb 1984, pp. 199-201.
8. Sandstrom, B. et. al., “Effect of protein level and protein source on zinc absorption in humans”, J-Nutr, v. 119 (1), Jan 1989, pp. 48-53; Tait, Susan, et. al., “The availability of minerals in food, with particular reference to iron”, J-R-Soc-Health, v. 103 (2), April 1983, pp. 74-77.
9. Phytate reduction of zinc absorption has been demonstrated in numerous studies; results are summarized in Leviton, Op. Cit, pp. 14-15.
10. Mellanby, Edward, “Experimental rickets: The effect of cereals and their interaction with other factors of diet and environment in producing rickets:”, Medical Research Council, v.93, Mar 1925, pp. 2-65; Wills, M.R., et. al., “Phytic Acid and Nutritional Rickets in Immigrants”, The Lancet, April 8,1972, pp. 771-773.