Some studies indicate that soy is a superfood while others have linked it to health problems. Why has research yielded such conflicting results?
Many of the studies supporting soy’s health benefits have taken place in Asian countries where people eat more fermented soy products (miso, tempeh, etc.). Those in Europe and North America tend to consume unfermented and highly processed soy products, many of which contain trans fats and artificial additives, and to eat soy protein in larger quantities, so health outcomes are bound to differ.
Soy is considered a health food for a number of reasons. One cup of cooked soybeans provides as much complete protein as 100 grams of cooked meat, but without the cholesterol. Soy contains good fats, including omega-3 fatty acids, so it supports heart health, and studies suggest that soy consumption may reduce the risk of breast, uterine, and prostate cancer.
However, in the United States, soy represents a $4 billion industry, and there are powerful forces with a stake in promoting its health benefits and suppressing information about its health risks. In addition to the fact that most soy, with the exception of organic, is genetically modified, soy formulas may negatively impact infant development.
Soy can block the absorption of certain minerals due to its phytate content (phytates are reduced by fermenting). Research suggests that high consumption of tofu (an unfermented soy product) may increase the risk of cognitive decline in old age.
Soy is among the foods most likely to provoke allergic reactions, and is often consumed in processed foods that contain trans fats and harmful additives. Some people have also expressed concerns that soy consumption might lower testosterone levels in men, but the findings of a large meta-analysis conducted by Hamilton-Reeves et al. (2010) disproved this theory.
Overall, the research suggests that fermented organic soy, consumed in moderation, can be considered a health food, whereas unfermented soy products have both positive and negative health impacts.
Dieticians of Canada, “What Are the Health Benefits of Soy,” 1 September 2010.
Hamilton-Reeves et al., “Clinical Studies Show No Effects of Soy Protein or Isoflavones on Reproductive Hormones in Men: Results of a Meta-Analysis,” Fertility and Sterility 94(3): 997–1007, 2010.
Terrain, M.V., “The Dark Side of Soy,” Utne Reader, July/August, 2007.
White et al., “Brain Aging and Midlife Tofu Consumption,” Journal of the American College of Nutrition, 19(2): 242–255, 2009.
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