Soy can play an important role in the diet for men. A number of reputable studies have examined soy and men’s health, and there is no clinical data suggesting soy consumption negatively affects sperm quality or quantity. Three clinical trials have examined soy consumption and sperm quality and quantity, and all showed no effect.1,2,3 The trials also showed no relationship between soy consumption and men’s reproductive hormone levels.
Myth: Consuming soy causes feminizing effects in men.
Claims that soy exerts feminizing or estrogenic effects in men are not supported by science. Clinical studies show conclusively that neither soyfoods nor isoflavones affect testosterone or estrogen levels or sperm quality or quantity.4
1. Messina M, Watanabe S, Setchell KD. Report on the 8th International Symposium on the Role of Soy in Health Promotion and Chronic Disease Prevention and Treatment. J Nutr 2009 Apr;139:796S-802S.
2. Mitchell JH, Cawood E, Kinniburgh D, Provan A, Collins AR, Irvine DS. Effect of a phytoestrogen food supplement on reproductive health in normal males. Clin Sci (Lond) 2001 Jun;100:613-8.
3. Beaton LK, McVeigh BL, Dillingham BL, Lampe JW, Duncan AM. Soy protein isolates of varying isoflavone content do not adversely affect semen quality in healthy young men. Fertil Steril 2009 Oct 9.
4. Messina M. Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence. Fertil Steril 2010;93:2095-104.