FACT or MYTH: Soy causes “feminizing” effects in Men

You may have heard about soy foods in the news, including claims that accuse soy consumption as the causation for breast development among males. So, what’s the truth on soy?

First and foremost, we must ask the question, what is soy? 

Soy, or soybeans, are legumes which include beans, lentils, peas and peanuts. Soy can be found in various forms such as soymilk and soy cheese, and is most commonly used in the manufacturing of vegetarian and vegan products. Soy is a popular source of protein among this population because vegetarians and vegans do not consume meat products and are otherwise often lacking in protein.

The Myth:

Do soy and soy products cause feminization in men?phyto-what

It has been noted that high doses of phytoestrogens have been shown to impair male rats’ ability to produce offspring, but the same effect has yet to be proven among male humans. Since many of the concerns related to soy come from studies in rats and mice, it’s crucial to recognize that rodents metabolize soy isoflavones much differently than humans, essentially making these studies inapplicable.

Individual cases of sex hormone changes among men consuming soy foods has been reported. But, these men were consuming extreme amounts of soy (3 quarts of soymilk per day, in one case!), and the effects were reversed when the soy intake was discontinued. A 2010 review in Fertility and Sterility concluded that “neither isoflavone supplements nor isoflavone-rich soy affect total or free testosterone levels” and that there’s “essentially no evidence from nine identified clinical studies that isoflavone exposure affects circulating estrogen levels in men.”

The Truth:

The is no scientific link between the consumption of soy and the development of enlarged breasts in the male population.

lean green protein machineSoy beans and soy food products have been given a bad rap for causing breast development in men. There is no scientific evidence that soy foods cause any type of feminizing effects in men. According to multiple research studies, phytoestrogens are similar in structure to estrogen but they do not impact testosterone or estrogen levels in men. Soy foods serve as an excellent source of complete protein and nutrients with no cholesterol and very little saturated fat. Soy protein is considered a high-quality protein, which is key for performance in active and athletic men because it contains all of the necessary amino acids for muscle building and repair.


For additional information on soy, visit Soyfoods Assocaition of North America at http://www.soyfoods.org





Academy of Nutrition and Dietetics . (2013, January ). Eat Right. Retrieved from Eat Right : http://www.eatright.org/resource/food/nutrition/vegetarian-and-special-diets/vegetarian-glossary-of-terms

Mary L. Gavin, M. (2015, September ). Kids Health. Retrieved from Kids Health: http://kidshealth.org/en/teens/soy.html

Soyfoods Association of North America . (2017). Soyfoods. Retrieved from Soyfoods: http://www.soyfoods.org/good-for-you/soy-facts/lower-the-risk-of-heart-disease-prostate-cancer


By, Christina Ezak

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s