Is soy the cause of your man boobs?

Is soy the cause of your man boobs?

While perfectly fine on women, most men do not want enlarged breasts, often referred to as man boobs.  The medical term for this condition is gynecomastia and is when a male may have an overdevelopment of breast tissue of either one or both breasts. From newborns, boys going through puberty to older men, gynecomastia can affect any male as a result of normal changes in hormone levels, though other causes may also exist.

However, an oft referenced food some believe to be the cause of male “manneries,” is foods containing soy. Does soy hold the answer for some men with larger breasts and what does the science say about it?

Why is soy blamed for man boobs?

The reason foods containing soy – soymilk, soybeans, tofu, edamame, and tempeh – have been blamed for the cause of enlarged male breasts, is due to their content of phytoestrogens also known as isoflavones. These substances in soy foods are often called “plant estrogens.”  Seeing the word “estrogen,” has led individuals to believe soy to mimic the estrogen in females, which triggers the development of various sex characteristics, including growth of breast tissue.

A 2008 study in the journal Endocrine Practice, highlighted a case in which a man developed gynecomastia due to a high intake of soy products.  This man had unexplained breast growth, hair loss on his arms and erectile dysfunction.  After various doctors were unable to find the root cause of his symptoms, it was finally established that he had up to 8 times the normal levels of estrogen in his body – even higher than women.  But, it was also discovered he had been excessively consuming up to 3 quarts or 12 cups of soy milk a day. 

Once the man discontinued drinking soy milk, he had a significant reduction in the size of his breast tissue.

Soy does not increase male breast tissue

What many people may not realize is that phytoestrogens are also found in many other foods besides soy products.  Other foods which also contain phytoestrogens include apples, lentils, beer, beans, coffee, and carrots.

If regular consumption of soy products resulted in male breast development, it would be plausible to expect a surge of Asian men to have this condition.  People living in Asian countries have a higher intake of soy foods on a regular basis than other parts of the world.  Yet, this is not the case.  A 2010 study in the journal Fertility and Sterility by a researcher at Loma Linda University School of Public Health, found that isoflavones (phytoestrogens), do not exert feminizing effects on men at intake levels equal to and even considerably higher than are typical for Asian males. The study went on to conclude that the average Asian diet includes a higher proportion of soy in their diet compared to Western countries like the U.S., yet there is no “man-boob” epidemic sweeping through Asia.

After this study, many more studies also did not find a correlation between eating soy and the development of male breasts or other feminine features.

In conclusion

As with any recommendation regarding food intake, research shows that moderate soy intake does not lead to male breast enlargement.  Men can safely consume soy foods as they are a high quality plant source of protein, perfect for enlarging muscles with no worries of developing enlarged man boobs.