Understanding Soy Foods: Possible Benefits of Eating Soy Foods

Many people are including soy foods in their diets because of their reputed health benefits:

• Epidemiology studies have found that people who have more soy in their diet have lower risk for cancers, including cancer of the breast, colon, and prostate.¹
• Soy protein reduces cholesterol, enhances coronary artery function, and reduces other heart disease risk factors.^{2, 3, 4}
• Soy foods have a favorable effect on bone mineral density. The isoflavones contained in soy foods may improve bone retention, and replacing animal protein with soy protein in the diet reduces the amount of calcium lost in the urine.^{5, 6}

In Asia, where tofu, soymilk, and other soy products are commonly consumed, cancer and heart disease are much more rare than in the United States and Europe, and longevity is greater. However, it is important to remember that the apparent benefits of soy consumption seen in epidemiological studies may be caused by people replacing unhealthy foods—such as meat, chicken, dairy, and eggs—with plant–protein sources like soy. Simply adding soy to a diet focused on animal products is unlikely to bring the same benefits.

References:
1. Badger T, Ronis M, Simmen R, Simmen F. Soy Protein Isolate and Protection Against Cancer  Journal of the American College of Nutrition, Vol. 24, No. 2, 146S–149S (2005)
2. Anderson JW, Johnstone BM, Cook–Newell ME. Meta–analysis of the effects of soy protein intake on serum lipids. N Engl J Med. 1995 Aug 3;333(5):276–82.
3. Nestel PJ, Yamashita T, Sasahara T, Pomeroy S, Dart A, Komesaroff P, Owen A, Abbey M. Soy isoflavones improve systemic arterial compliance but not plasma lipids in menopausal and perimenopausal women. Arterioscler Thromb Vasc Biol. 1997 Dec;17(12):3392–8.
4. Squadrito F, Altavilla D, Morabito N, Crisafulli A, D'Anna R, Corrado F, Ruggeri P, Campo GM, Calapai G, Caputi AP, Squadrito G. The effect of the phytoestrogen genistein on plasma nitric oxide concentrations, endothelin–1 levels and endothelium dependent vasodilation in postmenopausal women. Atherosclerosis. 2002 Aug;163(2):339–47.
5. Ho SC, Chan SG, Yi Q, Wong E, Leung PC. Soy intake and the maintenance of peak bone mass in Hong Kong Chinese women. J Bone Miner Res. 2001 Jul;16(7):1363–9.
6. Spence LA et al: Effects of Soy isoflavones on calcium metabolism in postmenopausal women. J Nutr 132: 581S,2002.