Copyright © 2006 American Heart Association. All rights reserved. Print ISSN: 0009-7322. Online
Circulation is published by the American Heart Association. 7272 Greenville Avenue, Dallas, TX
2006;113;1034-1044; originally published online Jan 17, 2006;
Kris-Etherton, Mary Winston and for the American Heart Association Nutrition
Frank M. Sacks, Alice Lichtenstein, Linda Van Horn, William Harris, Penny
Association Science Advisory for Professionals From the Nutrition Committee
Soy Protein, Isoflavones, and Cardiovascular Health: An American Heart
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Soy Protein, Isoflavones, and Cardiovascular Health
An American Heart Association Science Advisory for Professionals
From the Nutrition Committee
Frank M. Sacks, MD; Alice Lichtenstein, DSc; Linda Van Horn, PhD, RD; William Harris, PhD;
Penny Kris-Etherton, PhD; Mary Winston, EdD;
for the American Heart Association Nutrition Committee
Abstract—Soy protein and isoflavones (phytoestrogens) have gained considerable attention for their potential role in
improving risk factors for cardiovascular disease. This scientific advisory assesses the more recent work published on
soy protein and its component isoflavones. In the majority of 22 randomized trials, isolated soy protein with isoflavones,
as compared with milk or other proteins, decreased LDL cholesterol concentrations; the average effect was ?3%. This
reduction is very small relative to the large amount of soy protein tested in these studies, averaging 50 g, about half the
usual total daily protein intake. No significant effects on HDL cholesterol, triglycerides, lipoprotein(a), or blood pressure
were evident. Among 19 studies of soy isoflavones, the average effect on LDL cholesterol and other lipid risk factors
was nil. Soy protein and isoflavones have not been shown to lessen vasomotor symptoms of menopause, and results are
mixed with regard to soy’s ability to slow postmenopausal bone loss. The efficacy and safety of soy isoflavones for
preventing or treating cancer of the breast, endometrium, and prostate are not established; evidence from clinical trials
is meager and cautionary with regard to a possible adverse effect. For this reason, use of isoflavone supplements in food
or pills is not recommended. Thus, earlier research indicating that soy protein has clinically important favorable effects
as compared with other proteins has not been confirmed. In contrast, many soy products should be beneficial to
cardiovascular and overall health because of their high content of polyunsaturated fats, fiber, vitamins, and minerals and
low content of saturated fat. (Circulation. 2006;113:1034-1044.)
Key Words: AHA Scientific Statements ? cardiovascular diseases ? soybean proteins ? isoflavones ? cholesterol
disease (CVD). In October 1999, the US Food and Drug
Administration (FDA) approved labeling for foods containing
soy protein as protective against coronary heart disease.1The
FDA based this decision on clinical studies showing that at
least 25 g of soy protein per day lowered total and LDL
cholesterol. The FDA requires for the claim that a serving
contain at least 6.25 g of soy protein, 25% of the necessary
daily amount (25 g), with the expectation that foods contain-
ing soy protein would be eaten at least 4 times per day. The
FDA also stated that “the evidence did not support a signif-
icant role for soy isoflavones in cholesterol-lowering effects
of soy protein.”1
In 2000, the American Heart Association (AHA) Nutrition
Committee released a scientific advisory on soy protein and
oy protein has gained considerable attention for its
potential role in improving risk factors for cardiovascular
CVD.2At that time, the conclusion was that “it is prudent to
recommend including soy protein foods in a diet low in
saturated fat and cholesterol.” Since then, many well-
controlled studies on soy protein and soy-derived isoflavones
substantially added to the knowledge base. For this reason,
the AHA Nutrition Committee decided to reevaluate the
evidence on soy protein and CVD and update its scientific
advisory. Thus, this scientific advisory assesses the more
recent work published on soy protein and its component
isoflavones. The focus is on blood LDL cholesterol because it
is by far the most studied risk factor for CVD, is the primary
criterion on which the National Cholesterol Education Pro-
gram estimates risk and recommends therapy,3and forms the
basis for the FDA-approved health claim. In this advisory, we
also consider the effects of soy protein and isoflavones on
several other CVD risk factors: HDL cholesterol, triglycer-
The American Heart Association makes every effort to avoid any actual or potential conflicts of interest that may arise as a result of an outside
relationship or a personal, professional, or business interest of a member of the writing panel. Specifically, all members of the writing group are required
to complete and submit a Disclosure Questionnaire showing all such relationships that might be perceived as real or potential conflicts of interest.
This statement was approved by the American Heart Association Science Advisory and Coordinating Committee on August 10, 2005. A single reprint
is available by calling 800-242-8721 (US only) or writing the American Heart Association, Public Information, 7272 Greenville Ave, Dallas, TX
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Expert peer review of AHA Scientific Statements is conducted at the AHA National Center. For more on AHA statements and guidelines development,
© 2006 American Heart Association, Inc.
Circulation is available at http://www.circulationaha.orgDOI: 10.1161/CIRCULATIONAHA.106.171052
AHA Science Advisory
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