A recent surge in evidence from an array of sources highlights the nutritional and health attributes of soy protein for men. These sources include newly published research, the recently released 2020-2025 Dietary Guidelines for Americans and an authorized FDA health claim.
Nutrition scientists increasingly recognize the importance of maintaining muscle mass and strength throughout life. Consuming sufficient dietary protein helps to achieve this goal, but some have questioned whether or not the type of protein matters. In response, researchers statistically analyzed the results of 9 clinical studies involving men engaged in resistance exercise training.1 According to the findings, supplementation with soy protein led to gains in muscle mass and strength to the same degree as supplementation with animal protein (including whey protein which is often considered to be the gold standard protein for building muscle).
“Despite a persisting belief among some people that those involved in resistance exercise training need to consume animal protein to reach optimum results, our work found that soy protein performs just as well,” said Heidi Lynch, PhD, RDN, associate professor of kinesiology, Point Loma Nazarene University, and one of the authors of the analysis. “The results confirm that supplementing with soy protein leads to similar gains in strength and lean body mass as whey protein.”
Experts recommend that individuals trying to bulk up consume about twice as much protein as sedentary individuals (1.6 g/kg body weight or about 0.7 g/lb). Older individuals may also need more protein than younger people. A recently published study from China found that simply adding an additional 16 grams of protein daily maintained or increased muscle mass and strength and the physical performance of older men and women with low lean mass, even though they were not participating in strength building exercises and were consuming the recommended amount of protein at the start of the study.2 Again in this study, soy protein performed as well as whey protein.
In most studies that have examined the impact of protein supplementation, the participants are consuming an omnivorous diet, a diet that includes both plant and animal sources of protein. An exception is a study conducted at the University of Sao Paulo and published earlier this year that compared the effects of adding soy protein to the diet of vegans with adding whey protein to the diet of omnivores.3 After 12 weeks of resistance exercise training, those consuming the vegan-soy diet experienced gains in muscle mass and strength similar to those consuming the omnivore-whey protein diet.
Soy protein is a good choice for men wanting to bulk up and it may directly lower blood cholesterol levels; however, some men may be reluctant to consume soyfoods because of misguided concerns that plant estrogens (isoflavones) in soybeans cause unwanted effects. Recent research puts those concerns to rest. In 2021, a statistical analysis of 41 clinical trials involving nearly 2,000 men, found that neither soy protein nor isoflavones had any impact on testosterone or estrogen levels.4
“Time and time again, research has shown that soy protein is a great choice for your health and won’t negatively impact your hormone levels,” Jim White, RDN, American College of Sports Medicine Exercise Physiologist, owner of Jim White Fitness & Nutrition Studios said. “With so much misinformation circulating, it is imperative that we look to credible sources such as these studies.”
These hormone findings concur with the conclusions of a comprehensive technical review of the safety of soyfoods and isoflavones that was published in March of this year.5 In addition to hormone levels, this review examined other outcomes specific to men, such as sperm and semen parameters and gynecomastia (breast enlargement in men). Soy received a clean bill of health.
Important to note, the U.S. Food and Drug Administration (FDA) authorized a health claim in 1999 stating, “25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.” Additionally, while evaluating the evidence in support of the cholesterol-lowering effects of soy protein, the FDA also rejected concerns about the safety of soy.
Finally, in the 2020-2025 Dietary Guidelines for Americans soyfoods received several important mentions.6 For example, tofu and tempeh, and soy protein powders were specifically included in the protein category. Fortified soymilk and soy yogurt were the only plant-based dairy alternatives considered by the guidelines to be nutritionally appropriate substitutes for milk and yogurt.
Soyfoods provide high quality protein in varying amounts: tofu (6-13 g protein/3 oz), tempeh (11-17 g protein/3 oz), edamame (9-11 g/0.5 cup), soymilk (7-8 g/1 cup), soy nutrition bar (6-14 g/1 bar), and soy-based burger (9-16 g/1 patty).7 An abundance of research, FDA soy protein heart health claim, and inclusion of soy in the Dietary Guidelines demonstrate that soy is a healthful, nutritious choice for men (and women) of all ages.
The Soy Nutrition Institute is a scientific organization dedicated to research on soy and health. Established in 2004, the organization includes a scientific advisory board and research and health professionals from soy-related companies and organizations including the United Soybean Board, IFF, ADM, Cargill, Kellogg, Danone North America, Medifast, Impossible Foods, Herbalife, Soylent, House Foods America, Benson Hill, LIVEKINDLY, the Agricultural Utilization Resource Institute (AURI), the United States Soybean Export Council, American Soybean Association’s World Initiative for Soy in Human Health, and the Soyfoods Council.
For more information about the Soy Nutrition Institute, visit www.thesoynutritioninstitute.com.
- Messina, M., Lynch, H., Dickinson, J. M., Reed, K. E. No difference between the effects of supplementing with soy protein versus animal protein on gains in muscle mass and strength in response to resistance exercise. Int J Sport Nutr Exerc Metab. 2018; 28(6), 674-685. doi:10.1123/ijsnem.2018-0071
- Li C, Meng H, Wu S, et al. Daily supplementation with whey, soy, or whey-soy blended protein for 6 months maintained lean muscle mass and physical performance in older adults with low lean mass [published online ahead of print, 2021 Feb 18]. J Acad Nutr Diet. 2021;S2212-2672(21)00006-X. doi:10.1016/j.jand.2021.01.006
- Hevia-Larraín V, Gualano B, Longobardi I, et al. High-protein plant-based diet versus a protein-matched omnivorous diet to support resistance training adaptations: A comparison between habitual vegans and omnivores [published online ahead of print, 2021 Feb 18]. Sports Med. 2021. doi:10.1007/s40279-021-01434-9
- Reed KE, Camargo J, Hamilton-Reeves J, et al. Neither soy nor isoflavone intake affects male reproductive hormones: An expanded and updated meta-analysis of clinical studies. Reprod Toxicol. 2021;100:60-7.
- Messina M, Mejia SB, Cassidy A, et al. Neither soyfoods nor isoflavones warrant classification as endocrine disruptors: a technical review of the observational and clinical data. Crit Rev Food Sci Nutr. 2021.
- S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th Edition. December 2020. Available at DietaryGuidelines.gov.
- USDA Food Composition Databases, https://ndb.nal.usda.gov/ndb/search.