Scientific Advisory Board
- Alan Rogol, MD, PhD»
- Ian Rowland, PhD»
- Donna Kritz-Silverstein, PhD»
- Mark Messina, PhD, MS»
- Mary Hardy, MD»
- David Jenkins, MD, DSc, PhD»
Silk®s Nutrition Team
Answered Questions
- Are fermented soyfoods nutritionally superior to unfermented soyfoods?»
- How much soy protein is recommended for daily consumption?»
- What is the status of the Food and Drug Administration (FDA) soy heart health claim?»
- What exactly makes soy heart-healthy?»
- Is soy protein a complete protein?»
- How can consumers determine how much soy protein is in a food?»
- Is there an FDA recommendation for daily isoflavone intake?»
- Is soymilk recommended for infants?»
- Are soyfoods recommended for toddlers and older children?»
- Do isoflavone supplements provide the same benefits as eating soyfoods?»
- Does soy increase the risk of breast cancer?»
- Is it possible to consume too much soy protein?»
- Is the use of soyfoods associated with gastrointestinal disturbances?»
- Does consuming soy affect hormone levels?»
- What is the relationship between soy and thyroid function?»
- Is it possible that soy could have negative health effects on men?»
- What is the relationship between soy intake and prostate cancer?»
- Is soy infant formula safe?»
- Could avoiding soy impact the thyroid function of a person with Hashimoto’s disease?»
- Are soyfoods safe for breast cancer survivors to consume?»
ANSWERED QUESTIONS
What exactly makes soy heart-healthy?
Answered by Mark Messina, PhD, MS - October 1, 2010
Soyfoods potentially reduce risk of heart disease through three separate mechanisms. First and most obvious, most soyfoods are low in saturated fat and high in polyunsaturated fat.1 Therefore, when substituted for common dietary protein sources in the Western diet (which tend to be high in saturated fat), soyfoods may help reduce blood cholesterol levels.2 Importantly, recent research shows that to most effectively reduce risk of heart disease, saturated fat should be replaced with polyunsaturated fat in the diet.3,4 Soyfoods are ideal for this purpose.
Second, soy protein itself directly lowers blood cholesterol levels. In 1999, the U.S. Food and Drug Administration approved a health claim for soyfoods and coronary heart disease based on the cholesterol-lowering effects of soy protein.5 Comprehensive statistical analyses of the scientific literature show that on average, soy protein lowers LDL cholesterol about 4%.6,7 Each one percent reduction in cholesterol lowers coronary heart disease risk at least 2%.8,9 Therefore, when the cholesterol-lowering effects of soy protein are combined with the reduction in cholesterol due to displacing higher-saturated fat foods in the diet, the overall reduction in coronary heart disease risk can be at least 10%.
Finally, there is intriguing evidence suggesting that soyfoods may reduce risk of heart disease via mechanisms independent of their effects on blood cholesterol. Studies of Asian people show higher soyfood consumers are often more than 50% less likely to have heart disease.10 This protective effect is far beyond that which could be attributed to cholesterol reduction alone. Thus, the evidence suggests even people with normal cholesterol levels can reduce their heart disease risk by eating more soy.
Exactly how and why soy provides such impressive heart health benefits is not yet fully understood. Some studies suggest soy directly improves the health of the arteries11 and lowers blood pressure,12 but more research is needed in these areas. In the meantime, the research to date clearly demonstrates that soyfoods are an excellent choice for heart health.
Featured Expert
Dr. Messina is the co-owner of Nutrition Matters, Inc., a nutrition consulting company, an adjunct associate professor at Loma Linda University, and the Executive Director of the Soy Nutrition Institute. Full bio >>
References
1. 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.
2. Wu Z, Rodgers RP, Marshall AG. Characterization of vegetable oils: detailed compositional fingerprints derived from electrospray ionization fourier transform ion cyclotron resonance mass spectrometry. J Agric Food Chem. 2004;52:5322-8.
3. Mozaffarian D, Micha R, Wallace S. Effects on coronary heart disease of increasing polyunsaturated fat in place of saturated fat: a systematic review and meta-analysis of randomized controlled trials. PLoS Med. 2010;7:e1000252.
4. Jakobsen MU, O’Reilly EJ, Heitmann BL, Pereira MA, Balter K, Fraser GE, Goldbourt U, Hallmans G, Knekt P, et al. Major types of dietary fat and risk of coronary heart disease: a pooled analysis of 11 cohort studies. Am J Clin Nutr. 2009;89:1425-32.
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. Sacks FM, Lichtenstein A, Van Horn L, Harris W, Kris-Etherton P, Winston M. Soy protein, isoflavones, and cardiovascular health: an American Heart Association Science Advisory for professionals from the Nutrition Committee. Circulation. 2006;113:1034-44.
7. Zhan S, Ho SC. Meta-analysis of the effects of soy protein containing isoflavones on the lipid profile. Am J Clin Nutr. 2005;81:397-408.
8. Law MR, Wald NJ, Thompson SG. By how much and how quickly does reduction in serum cholesterol concentration lower risk of ischaemic heart disease? BMJ. 1994;308:367-72.
9. Law MR, Wald NJ, Wu T, Hackshaw A, Bailey A. Systematic underestimation of association between serum cholesterol concentration and ischaemic heart disease in observational studies: data from the BUPA study. BMJ. 1994;308:363-6.
10. Messina M, Lane B. Soy protein, soybean isoflavones, and coronary heart disease risk: Where do we stand? Future Lipidology. 2007;2:55-74.
11. Li SH, Liu XX, Bai YY, Wang XJ, Sun K, Chen JZ, Hui RT. Effect of oral isoflavone supplementation on vascular endothelial function in postmenopausal women: a meta-analysis of randomized placebo-controlled trials. Am J Clin Nutr. 2010;91:480-6.
12. Hooper L, Kroon PA, Rimm EB, Cohn JS, Harvey I, Le Cornu KA, Ryder JJ, Hall WL, Cassidy A. Flavonoids, flavonoid-rich foods, and cardiovascular risk: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2008;88:38-50.