Soybeans and foods made from soy are rich in protein and nutrients. However, soy also contains high amounts of isoflavones, a chemical that may mimic estrogen in your body. Estrogen is a hormone normally associated with women, although men also produce smaller amounts of estrogen. As of 2011, no adverse effects of moderate soy consumption have been found in men.
Soy in Foods
You don't have to eat soybeans or edamame -- immature green soybeans -- to be eating soy. Soybean oil, flour, lecithin, protein and other soy products are used as ingredients in a wide range of foods. Tofu, miso, soy sauce and other Asian foods are fermented from soybeans. According to the Linus Pauling Institute, fermented products and whole, mature soybeans tend to be highest in isoflavones. Processed products, such as soy protein, can be high or low in isoflavones, depending on the method of processing.
Estrogen in Men
Estrogen plays many roles in men: regulating bone mineral density, controlling cholesterol and lipid levels in the blood, promoting sperm maturation and regulating gene expression. High levels of estrogen in men can lead to gynecomastia -- enlargement of breast tissue, water retention, female-pattern fat deposition and mood changes. High estrogen may also cause a decrease in testosterone, the male sex hormone.
Soy Isoflavone Effects
Soy isoflavones do not necessarily raise estrogen. Isoflavones slightly increase the effects of estrogens when estrogen levels are low. The effects of high estrogen levels are decreased by soy isoflavones. Of a similar structure to estrogen, isoflavones increase the rate that your body breaks down estrogen.
No research has shown that soy isoflavones can produce effects similar to pathologically high estrogen in men. A 2011 analysis of clinical data in the journal "Fertility and Sterility" found no effects of soy products or isoflavones on male sex hormones in men.
Bacteria in your digestive system and digestive enzymes process isoflavones before they are absorbed into your body. According to the Linus Pauling Institute, only one-third of people of Western ancestry process soy isoflavones into highly estrogenic forms.
Dietary Recommendations
Soy has been a dietary stable for many cultures with no significant report of health effects in men. Normal dietary intake of soy products is considered safe, although the Linus Pauling Institute recommends consuming less than 100 mg per day. Although no evidence has shown that soy raises the risk or severity of prostate cancer, men who have been diagnosed with it or are at risk should talk to their doctor about soy in their diet.
References
- Oregon State University: Linus Pauling Institute: Micronutrient Information Center: Soy Isoflavones
- "Fertility and Sterility"; Clinical Studies Show No Effects of Soy Protein or Isoflavones on Reproductive Hormones in Men: Results of a Meta-Analysis; Hamilton-Reeves et al.; 2010
- Endotext.com: Estrogens and Male Reproduction; Vincenzo et al.; October 20, 2009
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