On World Health Day, Take a Closer Look at Reasons to Add Soyfoods to Your Diet

By Mark Messina

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World Health Day 2021—sponsored by the World Health Organization (WHO) on April 7 each year—highlights WHO’s commitment to building a fairer, healthier world. Worldwide, the COVID-19 pandemic has pushed more people into poverty and food insecurity and has exposed health inequities. 

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A healthy diet is essential for good health. Widely available and affordable soyfoods fit in with the goals of making healthier lifestyles possible for a greater number of people. Soybeans provide excellent quality protein. In addition, compared to other beans, soybeans offer low carbohydrate content, provide beneficial unsaturated fat, and consuming soyfoods may contribute to the reduced risk of several chronic diseases.

Traditional Asian soyfoods have been consumed for centuries and have become quite popular in Western countries over the past several decades as increasing numbers of people adopt diets that are more plant-based.  But so much has been written about soy over the past many years, it is easy to be confused about just why nutritionists recommend adding it to your diet.

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Soy is a legume or, to use more common nomenclature, a bean. Beans are a vastly underutilized source of protein in many parts of the world including the United States.1  The soybean does differ from other beans like pinto beans and black beans, however. Most beans are comprised primarily of carbohydrate; not so for soybeans, as they are low in this macronutrient.2,3 

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The low carbohydrate content of soybeans and soyfoods like tofu make them a good addition to the diet of people with diabetes who are restricting their carbohydrate intake.4 Furthermore, much of the carbohydrate in soybeans is comprised of sugars called oligosaccharides. These sugars increase the number of health-promoting bacteria in the intestine.5

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In contrast to carbohydrate, soybeans are higher in fat than other beans. The fat in soybeans is mostly unsaturated, the type of fat that lowers blood cholesterol levels. The American Heart Association recommends soyfoods for the heart-healthy fat they provide.6 

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Soybeans are also higher in protein, but more importantly, the quality of soy protein is superior to the quality of all other plant proteins and similar to the quality of animal protein.7 That is one reason that foods like tofu, soymilk, and edamame (green soybeans) are so prized by vegetarians. The quality of a protein is determined by how well the protein is digested into its constituent amino acids (the building blocks of protein) and how well the pattern of amino acids in a protein matches our biological requirement for those amino acids. 

 

Recent research shows that soy protein promotes gains in muscle mass and strength to the same extent as animal protein in individuals engaged in resistance exercise training.8

While the protein, fat and carbohydrate content of soybeans is reason enough to add soy to your diet, there is an even more intriguing reason. An impressive body of research suggests that consuming soyfoods reduces the risk of several chronic diseases. For example, soy may reduce risk of heart disease, not only because of the healthy fat it provides, but because soy protein directly lowers blood cholesterol levels.9

 

The US Food and Drug Administration formally recognized the cholesterol-lowering effects of soy protein more than 20 years.10 

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While the heart benefits of soy have attracted attention, those benefits pale in comparison to the interest in the role of soy in reducing risk of developing breast cancer.  Although there may be many reasons for the historically low incidence rates of breast cancer in Asia, much research points to soy being one of those reasons, especially if it is consumed during childhood and/or during the teenage years.11,12 And the reason that soyfoods may be protective against breast cancer is because they are uniquely rich sources of isoflavones.

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Isoflavones are often referred to as phytoestrogens or plant estrogens. These compounds share some of the same properties as the hormone estrogen, but also differ from estrogen in multiple ways. Isoflavones have been shown to alleviate hot flashes in menopausal women.13 For those women who have bothersome hot flashes but do not want to use hormone therapy, isoflavones are a good choice. Evidence suggests about two servings of traditional soyfoods daily is sufficient to reduce hot flashes by at least 50 percent.

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The isoflavones in soybeans are also the reason that soy may help to prevent cognitive impairment14 and bone loss15 that occurs with aging. Like the case for hot flashes, two servings of traditional soyfoods appear to be sufficient to derive these proposed benefits.

Finally, some of the confusion about soyfoods is because despite their many desirable nutritional attributes, some reports, mostly based on research in animals, suggest that in some people, soy could have harmful effects. 

 

However, a just-published comprehensive technical review to evaluate these concerns, that included hundreds of studies and was written by 10 leading experts, should give considerable comfort to anyone questioning the safety of soy. Apart from soy allergy, which is relatively uncommon, this team of experts concluded there was no substantial evidence indicating soyfoods exert harmful effects in anyone.16

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Fortunately, the vast array of soyfoods, from the traditional soyfoods to the modern soyfoods like soy burgers and soy yogurt, make adding soyfoods to the diet easier than ever.

 

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Meta Description: On World Health Day, the Soyfoods Council shares information about soyfoods contributing to healthier lifestyles.

 

1. Semba RD, Ramsing R, Rahman N, et al. Legumes as a sustainable source of protein in human diets. Global Food Security. 2021;28:100520.

2. Messina MJ. Legumes and soybeans: overview of their nutritional profiles and health effects. Am J Clin Nutr. 1999;70:439S-50S.

3. Messina V. Nutritional and health benefits of dried beans. Am J Clin Nutr. 2014;100 Suppl 1:437S-42S.

4. Feinman RD, Pogozelski WK, Astrup A, et al. Dietary carbohydrate restriction as the first approach in diabetes management: critical review and evidence base. Nutrition. 2015;31:1-13.

5. Hata Y, Yamamoto M, Nakajima K. Effects of soybean oligosaccharides on human digestive organs: estimate of fifty percent effective dose and maximum non-effective dose based on diarrhea. Journal of clinical biochemistry and nutrition. 1991;10:135-44.

6. Sacks FM, Lichtenstein A, Van Horn L, et al. Soy protein, isoflavones, and cardiovascular health: an American Heart Association Science Advisory for professionals from the Nutrition Committee. Circulation. 2006;113:1034-44.

7. Hughes GJ, Ryan DJ, Mukherjea R, et al. Protein digestibility-corrected amino acid scores (PDCAAS) for soy protein isolates and concentrate: Criteria for evaluation. J Agric Food Chemistry. 2011;59:12707-12.

8. Messina M, Lynch H, Dickinson JM, et al. 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. International journal of sport nutrition and exercise metabolism. 2018;28:674-85.

9. Blanco Mejia S, Messina M, Li SS, et al. A meta-analysis of 46 studies identified by the FDA demonstrates that soy protein decreases circulating LDL and total cholesterol concentrations in adults. J Nutr. 2019;149:968-81.

10. Food labeling: health claims; soy protein and coronary heart disease. Food and Drug Administration, HHS. Final rule. Fed Regist. 1999;64:57700-33.

11. Messina M, Hilakivi-Clarke L. Early intake appears to be the key to the proposed protective effects of soy intake against breast cancer. Nutr Cancer. 2009;61:792-8.

12. Messina M, Wu AH. Perspectives on the soy-breast cancer relation. Am J Clin Nutr. 2009;89:1673S-9S.

13. Taku K, Melby MK, Kronenberg F, et al. Extracted or synthesized soybean isoflavones reduce menopausal hot flash frequency and severity: systematic review and meta-analysis of randomized controlled trials. Menopause. 2012;19:776-90.

14. Cui C, Birru RL, Snitz BE, et al. Effects of soy isoflavones on cognitive function: a systematic review and meta-analysis of randomized controlled trials. Nutr Rev. 2020;78:134-44.

15. Sansai K, Na Takuathung M, Khatsri R, et al. Effects of isoflavone interventions on bone mineral density in postmenopausal women: a systematic review and meta-analysis of randomized controlled trials. Osteoporos Int. 2020;31:1853-64.

16. 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. 2021:1-57.

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