Soy Facts

CLINICAL RESEARCH

Heart Health

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Heart disease remains the leading cause of death for both men and women in the United States.1 Dietary choices have a significant impact on heart disease risk, and soyfoods can be an important component of a heart-healthy diet. It is well-established that soy protein directly lowers LDL cholesterol levels. Soyfoods are often low in saturated fat and high in polyunsaturated fats, potentially further reducing cholesterol when they are used to replace animal protein sources. Soy also contains naturally occurring omega-3 ALA fatty acids which have been studied for their impact on heart health.

References: 1. Heart Disease and Stroke Statistics 2010 Update: A report from the American Heart Association, Circulation. 2010; 121: e46-e214.

Soy & Blood Pressure

Coronary heart disease (CHD) includes a number of risk factors. One of the most important is elevated blood pressure. A recent study presented by researchers from Wake Forest University found that the systolic blood pressure (top number) of people consuming the most soy isoflavones was 5 points (mm Hg) lower than that of people who consumed diets low in isoflavones.1 The effects were especially pronounced in African Americans. Isoflavones are naturally-occurring plant compounds that are found in especially high amounts in soybeans and traditional soyfoods such as soymilk.

Soyfoods can make important contributions to heart-healthy diets. They provide high-quality protein and, in contrast to more traditional sources of protein in Western diets, they are low in saturated fat, high in polyunsaturated fat, and cholesterol free.2,3 When soyfoods are substituted for animal products, blood cholesterol levels may be reduced.4 In addition, soy protein directly lowers LDL blood cholesterol. This benefit of soy protein was formally recognized by the U.S. Food and Drug Administration in 1999 when it approved a health claim for soyfoods and coronary heart disease.5

The results from the Wake Forest study by itself do not allow definitive conclusions to be drawn. However, they are consistent with previously published research. To this point, a recently published statistical analysis that included 27 clinical (human intervention) studies found that on average, soy lowered blood pressure about 2 ½ points.6

More research into the effects of soy on blood pressure is needed. Given all the advantages of soyfoods, people concerned about reducing their risk of heart disease may want to consider adding soyfoods to their diets.

References
1. Richardson S, Smith C, Burke L, Xia Z, Shikany JM, Steffen L, Rodriguez CJ. Dietary isoflavone intake is associated with lower systolic blood pressure: the Coronary Artery Risk Development in Young Adults (CARDIA) Study (Abstract). Am College Cardiol Annual Meeting. 2012.
2. Hughes GJ, Ryan DJ, Mukherjea R, Schasteen CS. Protein digestibility-corrected amino acid scores (PDCAAS) for soy protein isolates and concentrate: Criteria for evaluation. J Agric Food Chem. 2011; 59: 12707-12.
3. Slavin M, Kenworthy W, Yu LL. Antioxidant properties, phytochemical composition, and antiproliferative activity of Maryland-grown soybeans with colored seed coats. J Agric Food Chem. 2009; 57: 11174-85.
4. Jenkins DJ, Mirrahimi A, Srichaikul K, Berryman CE, Wang L, Carleton A, Abdulnour S, Sievenpiper JL, Kendall CW, et al. Soy protein reduces serum cholesterol by both intrinsic and food displacement mechanisms. J Nutr. 2010; 140: 2302S-2311S.
5. Food labeling: health claims; soy protein and coronary heart disease. Food and Drug Administration, HHS. Final rule. Fed Regist. 1999; 64: 57700-33.
6. Dong JY, Tong X, Wu ZW, Xun PC, He K, Qin LQ. Effect of soya protein on blood pressure: a meta-analysis of randomised controlled trials. Br J Nutr. 2011; 106: 317-26.

Research suggests a portfolio diet including soy may be more effective at lowering cholesterol than a low saturated fat diet.

A study showed adults with high cholesterol who followed a “portfolio diet” of cholesterol-lowering foods including soyfoods like soymilk and soy meat alternatives, oats, nuts and plant sterols, lowered LDL cholesterol by 13.8% compared with a decrease of only 3% in those that followed a standard low saturated fat diet. 1

Link to study

References:
1.Jenkins DJ et al. Effect of a Dietary Portfolio of Cholesterol-Lowering Foods Given at 2 Levels of Intensity of Dietary
Advice on Serum Lipids in Hyperlipidemia Epidemiology of soy exposures and breast cancer risk. JAMA 2011; 306(8): 831-839.

Research suggests soy may lower cholesterol in as little as four weeks.

One study compared cholesterol levels between those who drank soymilk and those who drank 1% dairy milk as part of an overall sensible diet. In only four weeks, the soymilk group showed a 5% reduction in LDL cholesterol—a statistically significant advantage over those who consumed dairy milk.1

Link to Study

References:
1. Gardner CD, Messina M, Kiazand A, Morris JL, Franke AA. Effect of two types of soy milk and dairy milk on plasma lipids in hypercholesterolemic adults: a randomized trial. J Am Coll Nutr. 2007 Dec;26(6):669-77.

Research suggests soy reduces LDL cholesterol by 3% to 5%.

This level of reduction is significant, particularly from a public health perspective, since every 1% reduction in LDL reduces the risk of cardiovascular disease by 2%—5%.1

In a meta-analysis of 23 studies, soy protein was shown to reduce total cholesterol, LDL cholesterol (by 5.25%) and trigylcerides, and to modestly increase HDL levels.2 Other similar meta-analyses have reported LDL reductions of 3% and 4%.3,4

Link to study

References:
1. Law M, Wald NJ, Thompson SG. By how much and how quickly does reduction in serum cholesterol concentration lower risk of ischemic heart disease? BMJ. 1994; 308: 367-72.
2. Zhan S, Ho SC. Meta-analysis of the effects of soy protein containing isoflavones on the lipid profile. Am J Clin Nutr. 2005 Feb;81(2):397-408.
3. Sacks FM, Lichtenstein A, Van Horn L, Harris W, Kris-Etherton P, Winston M. Soy protein, isoflavones, and cardiovascular health: an AHA Science Advisory for professionals from the Nutrition Committee. Circulation. 2006; 113: 1034-1044.
4. Weggemans RM, Trautwein EA. Relation between soy-associated isoflavones and LDL and HDL cholesterol concentrations in humans: a meta-analysis. Eur J Clin Nutr. 2003: 57: 940-946.