GENERAL INFORMATION: Soy refers to many products derived from the soybean. Soybeans have played an integral part in Asian culture, both as a food and as a medicine for many centuries. Soybeans are best known in the West for their protein content, but increasingly, soyfoods are being recognized as having potential roles in the prevention and treatment of chronic diseases most notably cancer and heart disease (1). The two most important dietary supplements derived from soybeans are isolated soy proteins and extracts which contain a high amount of compounds called isoflavones. Isoflavones have been well studied for health benefits most closely tied to cardiovascular health (see research below).
HEART PROTECTION: The Department of Medicine at the Helsinki University Central Hospital in Finland showed dietary supplementation with soy-derived isoflavones helps to inhibit the harmful effects of LDL ("bad" cholesterol) (2). The National Heart & Lung Institute of London demonstrated through study that phytoestrogens such as soy induce relaxation of coronary arteries and may contribute to potential long-term cardiovascular protection (3). The Wake Forest University School of Medicine in North Carolina reviewed soy and found it to favorably influence coronary artery reactivity. They also concluded that soy helps to inhibit the progression of atherosclerosis (a form of arteriosclerosis in which plaque containing cholesterol and lipids is deposited on the inner walls of the arteries) (4). Yet another group at Wake Forest found dietary soy protein to improve arterial dilation in postmenopausal women (5). The Department of Human Nutrition at Laval University in Quebec experimented with soy protein beverage and found it to induce significant reductions in LDL cholesterol while increasing the beneficial HDL cholesterol (6). The Department of Food Science and Nutrition at the University of Minnesota concluded through studies that soy isoflavones significantly improve the lipid profile across the menstrual cycle in premenopausal women (7). Finally, the Children's Nutrition Research Department at the US Department of Agriculture reports a soy-protein diet associates with a statistically significant decrease in the plasma concentrations of LDL cholesterol (8).
REFERENCES:
(1) Messina M. Modern applications for an ancient bean: soybeans and the prevention and treatment of chronic disease. J Nutr. 1995 Mar; 125(3 Suppl):567S-569S.
(2) Tikkanen MJ, Adlercreutz H. Dietary soy-derived isoflavone phytoestrogens. Could they have a role in coronary heart disease protection? Biochem Pharmacol. 2000 Jul 1; 60(1):1-5.
(3) Figtree GA, Griffiths H, Lu YQ, Webb CM, MacLeod K, Collins P. Plant-derived estrogens relax coronary arteries in vitro by a calcium antagonistic mechanism. J Am Coll Cardiol. 2000 Jun; 35(7):1977-85.
(4) Clarkson TB, Anthony MS. Phytoestrogens and coronary heart disease. Baillieres Clin Endocrinol Metab. 1998 Dec;12(4):589-604.
(5) Clarkson TB. Soy, soy phytoestrogens and cardiovascular disease. J Nutr. 2002 Mar; 132(3):566S-569S.
(6) Jacques H, Laurin D, Moorjani S, Steinke FH, Gagne C, Brun D, Lupien PJ. Influence of diets containing cow's milk or soy protein beverage on plasma lipids in children with familial hypercholesterolemia. J Am Coll Nutr. 1992 Jun;11 Suppl:69S-73S.
(7) Merz-Demlov BE, Duncan AM, Wangen KE, Xu X, Carr TP, Phipps WR, Kurzer MS. Soy isoflavones improve plasma lipids in normocholesterolemic, premenopausal women. Am J Clin Nutr. 2000 Jun;71(6):1462-9.
(8) Wong WW, Smith EO, Stuff JE, Hachey DL, Heird WC, Pownell HJ. Cholesterol-lowering effect of soy protein in normocholesterolemic and hypercholesterolemic men. Am J Clin Nutr. 1998 Dec; 68(6 Suppl):1385S-1389S.
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