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Soy: What Every Man Needs to Know

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Though soy is commonly touted as a great addition to a healthy diet, some evidence suggests going overboard could result in some negative side effects for men. (Man boobs, anyone?) But fret not, soy enthusiasts! Studies suggest gulping down a glass of soy milk or munching on that edamame — in moderation — likely doesn't have feminizing effects for men [1].

Soyz II Men — Why It Matters

Graphic by Jordan Shakeshaft

Native to Southeast Asia, the soybean has long been promoted for its high protein content and numerous other health benefits. Soy’s cancer-prevention properties stem from isoflavones, plant estrogens that mimic the estrogen produced in humans. But while researchers have expressed concern that consuming these estrogens might lower testosterone levels, decrease sperm count, or even contribute to male breast formation, studies suggest moderate quantities of soy do not significantly affect hormone levels in men [2] [3]. But watch out, swimmers (not you, Phelps)! Although sperm motility and speed go unaffected, higher consumption of soy products has been associated with lower sperm concentration and slight hormonal changes in men, though not at a level that would dramatically affect fertility [4] [5].

Besides supposedly being suitable for consumption by even the manliest of men, soy has been linked to lower cholesterol levels and blood pressure, osteoporosis prevention, and a reduced risk of prostate cancer [6]. Soy bueno!

Tofu Or Not Tofu — The Answer/Debate

Soy-rry naysayers, looks like men can consume soy (in moderation) without worrying about their cup size. But before replacing that moo-juice with soy milk, be aware that very high consumption of soy products (the equivalent of more than three quarts of soymilk per day) could lead to increased estrogen levels in the body and hence some feminizing effects [7]. And while more research is needed to determine the extent of such side effects — which likely differ among individuals — limiting intake of soy-heavy foods to no more than a few servings per day should keep men in the clear [5].

So don’t worry about that daily soy latte, but maybe refrain from ordering one every hour.

The Takeaway

 

  In moderate quantities, soy does not create feminine qualities in men and can even help protect against prostate cancer.

Works Cited

  1. Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence. Messina, M. Department of Nutrition, School of Public Health, Loma Linda University, Loma Linda, California. Fertility and Sterility. 2010 May 1; 93(7):2095-104.
  2. Hormonal effects of soy in premenopausal women and men. Kurzer, MS. Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN. The Journal of Nutrition. 2002 Mar; 132(3):570S-573S
  3. Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence. Messina, M. Department of Nutrition, School of Public Health, Loma Linda University, Loma Linda, California. Fertility and Sterility. 2010 May 1; 93(7):2095-104.
  4. Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic. Chavarro, JE., Toth, TL., Sadio, SM., et al. Department of Nutrition, Harvard School of Public Health, Boston, MA. Human Reproduction. 2008 Nov; 23(11):2584-90.
  5. Soy, phyto-oestrogens and male reproductive function: a review. Cederroth, C.R., Auger, J., Zimmermann, C., et al. Department of Genetic Medicine and Development, University of Geneva Medical School. International Journal of Andrology. 2010 Apr;33(2):304-16. Epub 2009 Nov 16.
  6. Effect of soymilk consumption on serum estrogen and androgen concentrations in Japanese men. Nagata, C., Takatsuka, N., Shimizu, H., et al. Department of Public Health, Gifu University School of Medicine, Japan. Cancer Epidemiology, Biomarkers and Prevention. 2001 Mar; 10(3):179-84
  7. An unusual case of gynecomastia associated with soy product consumption. Martinez, J., Lewi, JE. Department of Medicine, Brooke Army Medical Center, Fort Sam Houston, Texas. Endocrine Practice: Official Journal of the American College of Endocrinology and the American Association of Clinical Endocrinologists. 2008 May-Jun; 14(4):415-8.
  8. Soy, phyto-oestrogens and male reproductive function: a review. Cederroth, C.R., Auger, J., Zimmermann, C., et al. Department of Genetic Medicine and Development, University of Geneva Medical School. International Journal of Andrology. 2010 Apr;33(2):304-16. Epub 2009 Nov 16.