Danger of eating soy
Absorption and Metabolism of Soy Isoflavones—from Food to Dietary Supplements and Adults to Infants
It has been known since 1931 that soybeans contain relatively high concentrations of isoflavones (Walz 1931); genistein glycoside was first isolated from soybeans almost 60 years ago (Walter 1941). An appreciation of the hormonal potency of isoflavones became apparent with the recognition in the mid-1940s that an infertility syndrome in sheep was caused by the ingestion of clover containing high levels of the related isoflavonesformononetin and biochaninA (Bennetts et al. 1946). These two methoxylatedisoflavones were metabolized by intestinal bacteria to equol, a unique mammalian isoflavone that shows much greater affinity for binding to estrogen receptors than do the clover-derived isoflavones. The importance of intestinal bacteria for the absorption and metabolism of isoflavones in animals was thus established. There was little clinical or nutritional interest shown in phytoestrogens until the chance discovery of equol in human urine and the recognition that when soy foods were consumed, the levels of isoflavones in urine and blood far exceeded those of endogenous estrogens (Axelson et al. 1984, Setchell et al. 1984). These observations led to the hypothesis that phytoestrogens would be biologically active at these concentrations, conferring health benefits that could explain the relatively low incidence of hormone-dependent diseases in countries in which soy is a dietary staple (Setchell et al. 1984).
Soy: Too Good to be True
Here at the Gerson Institute, we feel the positive aspects of the soybean are overshadowed by their potential for harm. Soybeans in fact contain a large number of dangerous substances. One among them is phytic acid, also called phytates. This organic acid is present in the bran or hulls of all seeds and legumes, but none have the high level of phytates that soybeans do. These acids block the body?s uptake of essential minerals like calcium, magnesium, iron and especially zinc. Adding to the high-phytate problem, soybeans are very resistant to phytate reducing techniques, such as long, slow cooking.
Soybeans also contain potent enzyme inhibitors. These inhibitors block uptake of trypsin and other enzymes that the body needs for protein digestion. Normal cooking does not deactivate these harmful "antinutrients," that can cause serious gastric distress, reduced protein digestion and can lead to chronic deficiencies in amino acid uptake.
Beyond these, soybeans also contain hemagglutinin, a clot promoting substance that causes red blood cells to clump together. These clustered blood cells are unable to properly absorb oxygen for distribution to the body's tissues, and cannot help in maintaining good cardiac health. Hemagglutinin and trypsin inhibitors are both "growth depressant" substances. Although the act of fermenting soybeans does deactivate both trypsin inhibitors and hemagglutinin, precipitation and cooking do not. Even though these enzyme inhibitors are reduced in levels within precipitated soy products like tofu, they are not altogether eliminated.
Only after a long period of fermentation (as in the creation of miso or tempeh) are the phytate and "antinutrient" levels of soybeans reduced, making their nourishment available to the human digestive system. The high levels of harmful substances remaining in precipitated soy products leave their nutritional value questionable at best, and in the least, potentially harmful.