Soy consumption among men has been a debated topic due to estrogen-like compounds called isoflavones that are present in soy proteins. Rodent studies reveal that soy isoflavone consumption may have an effect on male hormones and reproductive development. However, effects of soy on rodents may not be applicable to humans. Soy's effects on humans show mixed results.
Background
Soy is a protein food derived from soybeans, and is the only high-quality complete protein present in plant-based foods, according to the Office of Minority Health. Soy is a common food source for vegetarian and vegan men, and is an ingredient in many sports supplement protein drinks. Soy consumption may also help lower your LDL cholesterol levels, according to the Center for Complimentary and Alternative Medicine.
Rodent Studies
Results from some rodent studies show that soy consumption among rodent neonates can affect reproductive development. One study published in a 2010 edition of "Biology of Reproduction" found that perinatal exposure of soy isoflavones to male rats may affect testis function. However, a 2010 review article published in "Fertility and Sterility" notes that animal studies are not necessarily applicable to humans because of differences in soy isoflavone metabolism.
Effects on Testosterone
Due to soy's estrogen-like components, soy's effects on testosterone levels in men is also the focus of human studies. A 2010 article reviewing recent research, published in "Fertility and Sterility," found that consumption of isoflavone-rich soy products or isoflavone supplements does not affect free testosterone, total testosterone, sperm or circulating estrogen levels. Another 2010 review article published in "Fertility and Sterility" found that consuming soy foods or isoflavone supplements did not significantly affect bioavailable testosterone concentrations in men.
Effect on Thyroid
Men with a condition called hypothyroidism don't have enough natural thyroid hormone circulating in their body. Prescription synthetic thyroid hormone is a common treatment for hypothyroidism. According to the American Thyroid Association, soy can inhibit full absorption of prescription synthetic thyroid hormone.
References
- Center for Complimentary and Alternative Medicine; Soy; July 2010
- Department of Health and Human Services Office of Minority Health: Key to Nutrition: A Diversified Portfolio; October 2006
- "Biology of Reproduction"; Developmental exposures of male rats to soy isoflavones impact Leydig cell differentiation; J.D. Sherrill et al.; June 2010
- "Fertility and Sterility"; Soybean Isoflavone Exposure Does Not Have Feminizing Effects on Men: A Critical Examination of the Clinical Evidence; M Messina; May 2010
- "Fertility and Sterility"; Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis; J.M. Hamilton-Reeves et al.; August 2010
- American Thyroid Association; Thyroid Hormone Treatment; 2008
