Like your favorite quirky cousin, soy is sometimes misunderstood. Discussions around the pros and cons of this widely-used protein source have surfaced as major talking points in recent years, with studies on both sides of the aisle generating serious buzz. The descriptions and vocabulary used in these articles can be just as confusing as the arguments themselves. Gyneco-what? Isoflave-who? But the key takeaway is that the “king of beans” has a lot of benefits, especially as an important part of a plant-based diet.

Bottom line is soy is high-quality protein. Sometimes it’s even called a “perfect” food.  Soy contains all nine essential amino acids, and scores a 1.0 on the PDCAAS (that’s protein digestibility corrected amino acid score, for short), making it the top performing plant-based protein.  Soybeans also contain fiber, calcium, iron, omega-3s and other essential vitamins and minerals, so it’s a great addition to a balanced diet. Consume it as the bean itself in edamame, soy nuts and tempeh, and also enjoy the benefits of soy from tofu, miso, soy milk and soy milk products like yogurt and cheese.

Given all its benefits, we wanted to clear the air and let science break down some common myths about this humble but mighty protein.

  1. Soy & estrogen. Soy contains weak phytoestrogens that are compounds that occur naturally in legumes like soybeans. So, what does that mean for your diet? Phytoestrogens are considered estrogen-like compounds, because they have a chemical structure similar – but not identical – to estrogen that is made by the body.  Isoflavones are the major phytoestrogens in soy, but they do not act the same way as the body’s natural estrogen. In fact, according to the Harvard T. H. Chan School of Public Health, phytoestrogens may actually block the action of estrogen in the body.
  2. Soy causes “manboobs.” This tale about gynecomastia (gyeno = female, mastia = breasts) surfaced as a result of a 2008 study that documented “feminizing” effects in a 60 year-old male who reportedly drank 3 quarts of soy milk daily. It was estimated that the subject was taking in more than seven times the amount of isoflavones typically consumed by older males in Japan and Shanghai (where soy intakes are higher than the worldwide average). While a single case report such as this one makes good headlines, it should not be used to draw conclusions. The report comes with the common-sense warning that consuming excessive amounts of anything may produce untoward effects.
  3. Soy lowers men’s testosterone levels. A meta-analysis of several key studies published in the journal Fertility and Sterility found that neither soy foods nor isoflavone supplements lower testosterone concentrations in men. The International Society for Sexual Medicine also confirms that soy intake does not raise or lower a man’s testosterone levels.

So enjoy your soy without worry! Moderation is the key to any balanced diet and soy can easily fit into of your overall nutrition plan.

Susan Bowerman

Susan BowermanM.S., R.D., CSSD, CSOWM, FAND – Sr. Director, Worldwide Nutrition Education and Training

Susan Bowerman is the senior director of Worldwide Nutrition Education and Training at Herbalife Nutrition. She also serves as a chairwoman of the Dietetic Advisory Board (DAB). As a registered dietitian, she educates distributors about our global nutrition philosophy and is responsible for developing nutrition education and training materials.

Bowerman earned a B.S. in Biology with distinction from the University of Colorado and an M.S. in Food Science and Nutrition from Colorado State University. She is a fellow of the Academy of Nutrition and Dietetics and holds two board certifications as a specialist in Sports Dietetics and in Obesity and Weight Management. When she is not busy teaching and writing, Susan enjoys spending time with her family, cooking and gardening. Her favorite Herbalife Nutrition products include Simply Probiotic and Herbalife Nutrition Formula 1 Healthy Meal Nutritional Shake Mix Banana Caramel.