The soybean plant is an annual native to southeastern Asia that grows to approximately 5 feet.1 It has white or lilac flowers, pods that are yellow, green, brown, or black, and beans (seeds) that are 4-8 mm (0.16 to 0.31 inch) in diameter. Soy was first domesticated in China in the 11th century BCE and grows well in subtropical climates. The major world producers are the United States, Brazil, Argentina, and China. Soy protein is a derivative of the soybean obtained through processing. Different soy protein products have varying amounts of protein.1
Soybeans have been used as a source of protein and as medicine in Asia for centuries.2 Soybeans were used in several food products that are traditionally Japanese. These include soy milk, tempeh, tofu, miso, natto, and soy sauce.1 Tempeh, miso, and natto are all made from the fermentation of the soybean.1 Soy protein products have been important to nutrition in the United States since the 1960s when they were incorporated into cereals as a protein supplement. Soy protein is one of the few sources of protein that is vegetable based. Unlike animal protein, soy protein is comparatively low in cholesterol and fat. Soy protein has been used in both food and industrial products, such as baby food, breakfast cereals, meat substitutes, cleaning compounds, plastics, textiles, and cosmetics.2
Studies suggest that soy may reduce coronary heart disease risk.3,4 Research suggests that it may also improve bone health by increasing bone density and reducing bone loss.5,6,7,8 Soy protein can lower cholesterol9 and, in 1999, the US Food and Drug Administration (FDA) approved a health claim for the cardiovascular benefits of foods containing at least 6.25 grams of soy protein with limited fat and salt content.10 In a review of 19 clinical trials testing the usefulness of soy for relieving menopausal symptoms, the authors report that soy is modestly effective for women experiencing five or more hot flashes per day.11
The production of soybeans in the United States doubled from 1987 to 1997.12 Soybean oil makes up eighty percent of the vegetable oil used in the United States.12
1 Vaughan JG, Judd PA. The Oxford Book of Health Foods. New York: Oxford University Press, 2003.
2 Soy Protein Council. Protein Quality and Human Nutrition, 1986. Available at: http://www.spcouncil.org/SoyProtein.pdf. Accessed December 3, 2004.
3 Squadrito F, Altavilla D, Morabito N, Crisafulli A, D’Anna R, Corrado F, et al. The effect of the phytoestrogen genistein on plasma nitric oxide concentrations, endothelin-1 levels and endothelium dependent vasodilation in in postmenopausal women. Atherosclerosis. 2002;163:339-347.
4 Nestel PJ, Yamashita T, Sasahara T, Pomeroy S, Dart A, Komesaroff P, et al. Soy isoflavones improve systemic artherial compliance but not plasma lipids in menopausal and perimenopausal women. Arteroscler Thromb Vasc Biol. 1997;17:3392-3398.
5 Arjmandi BH. The role of phytoestrogens in the prevention and treatment of osteoporosis in ovarian hormone deficiency. J Am Coll Nutr. 2001;20:398S-402S.
6 Alekel DL, Germain AS, Peterson CT, Hanson KB, Stewart JW, Toda T. Isoflavone-rich soy protein isolate attenuates bone loss in the lumbar spine of perimenopausal women. Am J Clin Nutr. 2000;72:844-852.
7 Morabito N Crisafulli A, Vergara C, Gaudio A, Lasco A, Frisina N, et al. Effects of genistein and hormone-replacement therapy on bone loss in early postmenopausal women: a randomized double-blind placebo-controlled study. J Bone Miner Res. 2002;17:1904-1912.
8 Potter SM, Baum JA, Teng H, Stillman RJ, Shay NF, Erdman JW Jr. Soy protein and isoflavones: their effects on blood lipids and bone density in postmenopausal women. Am J Clin Nutr. 1998;68:1375S-1379S.
9 Anderson JW, Johnstone BM, Cook-Newell ME. Meta-analysis of the effects of soy protein intake on serum lipids. N Engl J Med. 1995:333:276-282.
10 FDA Talk Paper. FDA Approves New Health Claim for Soy Protein and Coronary Heart Disease. Available at: http://www.cfsan.fda.gov/~lrd/tpsoypr2.html. Accessed May 6, 2005.
11 Messina M, Hughes C. Efficacy of soyfoods and soybean isoflavone supplements for alleviating menopausal symptoms is positively related to initial hot flush frequency. J Med Food. 2003;6:1-11.
12 Bailey B. Soy Story: The Politics Behind the Boneless Protein. Center for Ethics and Toxics. Available at: http://www.cetos.org/articles/soystory.html. Accessed November 29, 2004.