![]() #Tofu protein update#According to a comprehensive update of soy research by the nutrition committee of the American Heart Association (AHA) published in 2000, eating 50 grams of soy per day lowered LDL by only about 3%. However, a number of studies since have tempered that finding. In response to this finding, in 1999 the Food and Drug Administration (FDA) allowed companies to claim that diets low in saturated fat and cholesterol that also contain soy “may reduce the risk of heart disease.” Such reductions, if sustained over time, could mean a greater than 20% lower risk of heart attack, stroke, or other forms of cardiovascular disease. A 1995 meta-analysis of 38 controlled clinical trials showed that eating approximately 50 grams of soy protein a day (no small amount as this translates to 1½ pounds of tofu or eight 8-ounce glasses of soy milk!) in place of animal protein reduced harmful LDL cholesterol by 12.9 percent. ![]() Soy protein took center stage after research showed that it might lower levels of harmful cholesterol. Some believe that fermenting soy improves its digestibility and absorption in the body, as this process partially breaks down soy’s sugar and protein molecules. Fermented means that the soy food has been cultured with beneficial bacteria, yeast, or mold. Soy foods are also classified as fermented or unfermented (see table with examples, below). Unlike some plant proteins, soy protein is considered a complete protein, containing all nine essential amino acids that the body cannot make which must be obtained from the diet. Thus, there are many factors that make it difficult to construct blanket statements about the health effects of soy.Īside from their isoflavone content, soy foods are rich in nutrients including B vitamins, fiber, potassium, magnesium, and high-quality protein. What type of soy is being studied: Whole soy foods such as tofu and soybeans, processed versions like soy protein powders, or soy-based veggie burgers? Fermented or unfermented soy foods? If supplements are used, do they contain isoflavones or soy protein? Also, women with breast cancer are classified into hormone type-either hormone positive (ER+/PR+) or hormone negative (ER-/PR-) breast cancer-and these tumors respond differently to estrogens. In this context soy may act like an anti-estrogen, but among postmenopausal women soy may act more like an estrogen. Premenopausal women have much higher circulating levels of estradiol-the major form of estrogen in the human body-than postmenopausal women. Because soy can have estrogenic properties, its effects can vary depending on the existing level of hormones in the body. Is it being examined in a study with animals or humans? Soy may be metabolized differently in animals, so the outcomes of animal studies may not be applicable to humans. ![]() Soy isoflavones and soy protein appear to have different actions in the body based on the following factors: The two major soy isoflavones are called genistein and daidzein. Soy isoflavones can bind to estrogen receptors in the body and cause either weak estrogenic or anti-estrogenic activity. Soy is unique in that it contains a high concentration of isoflavones, a type of plant estrogen (phytoestrogen) that is similar in function to human estrogen but with much weaker effects. Part of the uncertainty is due to the intricacy of soy’s effects on the body. However, due to contrary research that suggests possible negative effects of soy in certain situations, there has been a hesitancy to wholeheartedly promote soy. As a species within the legume family, nutrition scientists often label soy as a food with potential for significant health benefits. Whether published in a popular press article or a well-designed clinical study, some debate about soy remains. ![]() Soy is exalted as a health food by some, with claims of taming hot flashes, warding off osteoporosis, and protecting against hormonal cancers like breast and prostate.Īt the same time, soy is shunned by others for fear that it may cause breast cancer, thyroid problems, and dementia, though these claims have not been substantiated. Soy is a nutrient-dense source of protein that can safely be consumed several times a week, and probably more often, and is likely to provide health benefits-especially when eaten as an alternative to red and processed meat. Results of recent population studies suggest that soy has either a beneficial or neutral effect on various health conditions. Studies may seem to present conflicting conclusions about soy, but this is largely due to the wide variation in how soy is studied. The Takeaway: Soy is a unique food that is widely studied for its estrogenic and anti-estrogenic effects on the body. ![]()
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