The question “Does soy cause man boobs?” comes up often in our practice. With so much misinformation online, it’s no surprise that men feel confused. Some blogs and forums warn against soy, claiming it leads to male breasts or even gynecomastia. But, what does science really say? Dr. Jacobs takes a closer look at separating the soy and gynecomastia myth from fact, providing evidence-based answers to all your “man boob” questions.
To help out our patients and others we talk with, we’ve written about this topic several times. (You can read about soy and other plants in our blog archives.) At the heart of the argument are compounds called phytoestrogens, or literally, “plant-based estrogens.” Many foods we consume regularly contain phytoestrogens, including a variety of fruits, vegetables, grains, herbs, and drinks.
A few years ago, we discovered a paper published at Tulane University that’s very helpful in understanding phytoestrogens. According to Tulane, these chemicals “mimic or interact with hormone signals in animals,” and “In general, phytoestrogens are weaker than the natural estrogen hormones (such as estradiol) found in humans and animals or the very potent synthetic estrogens used in birth control pills and other drugs.”
This is why headlines like “Does soy cause man breasts?” keep resurfacing. Because phytoestrogens can act a little like estrogen in the body, and because enlarged breasts can be triggered by hormonal imbalances, you can understand headlines like “Man Boobs from Hoppy Beer“. But these chemicals’ effects are weak compared to natural hormones, and research doesn’t support the myth that normal soy consumption causes gynecomastia.
The key to sorting out the real story is what Tulane has to say about the effect of phytoestrogens being weaker than natural and synthetic estrogen. So, can beer rich in hops cause man boobs? No, we think not, at least not in normal dosages.
Does marijuana cause moobs? So far, there’s no scientific proof. But there is plenty of anecdotal evidence that the phytoestrogens in marijuana can trigger breast growth in regular users, and most gynecomastia surgeons discourage consumption.
When it comes to soy and gynecomastia, moderation is key. Patients often ask whether foods like soy, lavender, or tea tree oil can cause male breasts. Our answer: occasional consumption is not linked to breast growth. Only extremely high daily intake might raise concern.
PubMed, a database of the National Institutes of Health, contains a case study of man boobs connected with soy from 2008. A man developed enlarged male breasts after drinking three quarts of soymilk daily, and the condition disappeared when he stopped.
Most studies about the topic, including a 2004 study in Italy which followed 34 children raised on soymilk, do not see a strong connection. In the 2004 study, researchers found that “none of the boys presented gynecomastia,” and concluded that long-term soymilk feeding does not cause hormonal disruptions.
The Tulane paper notes that phytoestrogens offer potential health benefits. Many foods rich in these compounds, such as soy, flax and sunflower seeds, some nuts, and many others, are thought to help women with some of the unwanted effects of menopause, like hot flashes and osteoporosis. It has also been suggested that phytoestrogens may play a role in protecting against cancer. More study is needed to prove these theories.
What shouldn’t get lost in a discussion of phytoestrogens are the benefits of the foods that contain them. Instead of fearing soy and male breasts, focus on variety and balance. A diet full of fruits, vegetables, nuts, and whole grains supports overall health. The phytoestrogens in these foods, when consumed as part of an ordinary diet, are considered safe and possibly beneficial.
Dr. Elliot Jacobs is one of the most experienced gyne specialists in the U.S.
Dr. Elliot William Jacobs is a board-certified aesthetic plastic surgeon who specializes in FTM top surgery, gynecomastia surgery, revision gynecomastia surgery and male breast reduction. He is a native of New York and has over 40 years of experience in his field. Dr. Jacobs is a highly respected and sought-after surgeon who is known for his skill, experience, and compassion. Whether you are interested in gynecomastia for the first time, or are looking to correct a gynecomastia you aren’t happy with, Dr. Jacobs can deliver amazing results.
DR. ELLIOT JACOBS M.D., F.A.C.S., F.I.C.S
July 8, 2025
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