What is the first thing that comes to your mind when you think of soy? Probably one of the many forms in which it is consumed: tofu, soymilk, tempeh, edamame, and so on. Soy-based foods are popular, and not without reason: soy has multiple health benefits for both men and women.

Soy is a great source of high-quality protein, and soyfoods are generally low in saturated fat. Soybeans also contain fiber, calcium, iron, omega-3 fat, and other essential vitamins and minerals. Additionally, according to a meta-analysis published in the International Journal of Sports Nutrition and Exercise Metabolism, supplementing your resistance exercise training with soy protein can lead to increases in muscle mass and strength to the same extent as supplementation with animal protein.

There is a growing body of research to support the many health benefits of soy. However, some men still have reservations about consuming it. Those reservations might be based on two misconceptions that I want to address.

Soy Does Not Raise Estrogen or Lower Testosterone Levels in Men

Misconceptions concerning soyfoods stem from the fact that soy is a uniquely rich source of isoflavones, which are naturally occurring plant chemicals classified as phytoestrogens. Phytoestrogens are plant components found in several different types of food but the amounts in soy are much greater than other foods. However, despite being classified as plant estrogens, soybean isoflavones differ at both the molecular and clinical levels from the human hormone estrogen.

The origin of the concern about hormone disruption has a lot to do with two case reports each describing individual men who experience hormonal disturbances that allegedly occurred as a result of consuming soy foods. But – and this is important to note – each of the men described in these reports consumed extremely high amounts of soy foods, about nine times the amount of isoflavones typically consumed by older men in Japan, a country for which soy is a traditional component of the diet.

Too much of any food may lead to health problems. Furthermore, the soy intake of these two men occurred in the context of nutrient-deficient diets since most of their calories were derived from one food.

In contrast to these two case reports, extensive clinical data show that neither soy foods nor isoflavones affect testosterone and estrogen levels in men. This is true even when intake greatly exceeds typical Japanese intake.

Each serving of a minimally processed soy food (1 cup soymilk or ½ tofu or edamame) provides about 25 mg of isoflavones or 3.5 mg isoflavones per gram of protein. Generally, more refined soy products such as isolated soy protein have much lower isoflavone concentrations.

Soy Does Not Increase the Risk for Developing Prostate Cancer

This question is also rooted in the isoflavones/estrogen confusion. However, the very opposite might be true: research indicates soy may reduce the risk of prostate cancer in men. This is important information since prostate cancer is the second most commonly occurring cancer in men worldwide.

In a recent review of 30 observational studies, high soy consumption was linked to a significantly lower risk of developing the disease. Interest in the role that soy may play in reducing the risk of developing prostate cancer dates back three decades. In part, the initial focus on prostate cancer can be attributed to the historically lower prostate cancer mortality rates in Asian, soy food-consuming countries.

For example, per every 100,000 men in Japan, Korea, and China, prostate cancer incidence rates are 26.6, 22.4, and 12.0 respectively. By contrast, in the U.S., prostate cancer rates for blacks and non-Hispanic whites are 178.8 and 112.3 respectively.

Make Soy Part of Your Healthy Diet

Soy foods can play an important role in the diets of men by providing high-quality protein and healthy fat. Soy protein also supports normal blood cholesterol levels and is a good choice of high-quality, plant-based protein for those wanting to increase muscle mass.

The research overall indicates that soyfoods can be safely incorporated into the diets of essentially all healthy individuals except for those allergic to soy protein, which is relatively uncommon. The key is to incorporate soy as part of your nutrient-dense overall healthful diet.

Mark Messina

Mark MessinaPhD – Nutrition Matters Inc.

Dr. Messina is the co-owner of Nutrition Matters Inc., a nutrition consulting company, an adjunct associate professor at Loma Linda University in California, and the Executive Director of the Soy Nutrition Institute. For the past 30 years, Dr. Messina has devoted his time to the study of the health effects of soyfoods and soybean isoflavones. He writes extensively on these subjects, having published more than 100 articles and book chapters for health professionals. Dr. Messina is the chairperson of the editorial advisory board and writes a regular column for The Soy Connection, a quarterly newsletter that reaches over 250,000 health professionals. Dr. Messina has organized 10 international conferences on soyfoods and has given over 650 presentations to health professionals and has presented in 54 countries. He is also the co-author of three books along with his wife, Virginia Messina, MPH, RD, two on vegetarian diets and one on soyfoods.