10 Sep Ask an RD: Can eating soy cause man boobs?
I’ve been hearing a lot of peripheral talk recently about soy and the danger of man boobies.
This culminated on a recent trip to NS when myself, my mother, and my sister (Dad doesn’t talk much), discussed “the dangers of soy” and the threat of man boobs.
Always happy to call bullshit, I realized I had to get to the bottom of this once and for all.
Our friend, Dr. Pamela Fergusson, RD was happy to speak with me on the matter.
Dr.Pam, can soy cause man-boobs?
Man boobs or gynecomastia is swelling of the breast tissue in boys or men. This is caused by an imbalance between the hormones testosterone and estrogen. Soy products frequently get the blame for causing gynecomastia, but is there any scientific evidence for that claim? Read on!
When does gynecomastia happen?
There are three periods of life when gynecomastia is common.
Newborns: More than half of newborn babies have enlarged breasts from their mother’s estrogen. This will usually fade 1-2 weeks after birth
Puberty: Hormones are in flux during puberty. Males produce both estrogen and testosterone and during puberty, these hormones may get out of balance temporarily and boys can develop breasts. In most cases, the breasts will go away without treatment, but it can take from six months to two years for that to happen (!)
Adults: Gynecomastia affects men as well, peaking between ages 50-59 when one in four men have enlarged breasts. In many cases, this will resolve on its own, especially with some lifestyle changes. But men also commonly have plastic surgery to remove excess breast tissue.
What causes gynecomastia in adults?
Alcohol: Alcohol, particularly hoppy beers like IPAs, contain phytoestrogens. These are more potent than those found in soy, and much more likely to be a cause of gynecomastia in moderate to heavy drinkers. Alcohol can also inhibit testosterone production.
Medications: Many types of medications including some antianxiety and antidepressant meds, some heart meds and ulcer treatments can cause enlarged breasts in men.
Drugs: Anabolic steroids, marijuana, and heroin have all been implicated in the development of excess breast tissue in men, but the evidence is scant.
Health conditions: Hyperthyroidism, cancer, kidney or liver failure and malnutrition can all contribute to gynecomastia
Obesity: Increased body weight can stimulate estrogen production in men, and increased body fat will also contribute to larger breasts.
Aging: Breast tissue, in men and in women, tends to sag as we age.
Herbal products: tea tree oil and lavender oil have been associated with hormone disruption and breast tissue enlargement in boys
What about soy?
A 2010 systematic review of the evidence showed that there is no evidence that moderate or even high consumption of soy causes feminizing effects in men (read more here).
There was no increase in estrogen production or decrease in testosterone production in men who ate soy products.
Asian men have a high intake of soy and do not experience an increased incidence of gynecomastia.
That is great news, because tofu, edamame, and tempeh are delicious and so nutritious too. People looking for plant-based sources of protein can’t do much better than soy; a ¼ block of tofu contains 9 grams of protein, and a cup of edamame contains 17 grams.
I always recommend that people chose whole food sources of soy, like tofu, edamame, and tempeh more often, and keep your consumption of more processed soy burgers and protein powders and bars to a minimum.
But don’t worry guys! Enjoy your soy. You won’t be shopping for a sports bra.
Thank you, Pamela, for helping clear that up!
Seems like a good night for some tofu burgers.
See you at the next meal!