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The Benefits, Risks, and Uncertainties of Soy for Lower Blood Cholesterol by Skye Schulte, MS, MPH

Soy, a type of legume, can be found in many products. On the grocery store shelves, you will see soy milk, tofu, protein bars, veggie burgers, and many other options. Are you interested in adding soy to your diet? Are there health benefits? Find out if soy is a good option for you.

Soy and Cholesterol Levels

Some studies have found that substituting soy protein for high-fat meats and other foods may slightly reduce LDL "bad" cholesterol levels. Since high cholesterol puts you at an increased risk of developing heart disease, the Food and Drug Administration (FDA) allows a "heart healthy" label on foods that contain 6.25 grams (g) of soy protein. But, researchers do not know the exact components of soy that may lead to these benefits. And some experts are debating if this label is deserved at all.

Soy Safety Issues

While soy is considered safe for most people, there are some health concerns if you have certain conditions, such as:

Impaired thyroid function—Soy may affect the thyroid gland, but research had produced conflicting results. In general, if you have problems with your thyroid gland, it is a good idea to avoid eating large amounts of soy.
Lowe testosterone levels—One study found that soy may decrease testosterone levels in men. This could potentially cause problems with infertility or erectile dyfunction.
Problems with absorbing certain nutrients—Soy could reduce how well your body absorbs zinc, iron, and calcium.

If you are concerned about any of these safety issues, talk to your doctor before adding soy to your diet.

Ways to Get More Soy Into Your Diet

Here are some tips on substituting soy protein for meats and other protein sources in your diet:

Hide it:
- Mash a cake of tofu and use it in place of ricotta cheese in your lasagna.
- Mix textured vegetable protein into hamburgers and seasoned meat dishes like tacos, chili, and casseroles.
- Add cubes of fried, seasoned tofu to salads.
Try Asian cuisine.—Japanese, Chinese, Thai, and Vietnamese foods often contain flavorful soy options, including tofu, tempeh, and edamame (green soy beans). Edamame is eaten cold and salted. Tofu and tempeh can be stir-fried, steamed, or added to soups.
Use supplements and soy protein powders.—Try mixing soy protein powders into smoothies or mashed potatoes.
Soy nuts, flavored with salt and spices, make a delicious snack.
Use soymilk in cereal.

Major Food Sources

Soy Food	Serving size	Soy content (grams)	Isoflavones (milligrams)
Soybeans, cooked	½ cup	9-11	40-50
Soy milk (regular)	1 cup	7	10
Soy milk (fortified)	1 cup	10	43
Textured soy protein	¼ cup	11	33
Isolated soy protein	½ ounce	11	27
Tofu	½ cup	10	25
Meat alternatives (soy crumbles)	½ cup	11	8.5

RESOURCES:

American Heart Association http://www.americanheart.org/
National Heart, Lung, and Blood Institute http://www.nhlbi.nih.gov/

CANADIAN RESOURCES:

Dietitians of Canada http://www.dietitians.ca/
Health Canada http://hc-sc.gc.ca/

References:

Anderson JW, Johnstone BM, Cooke-Newell ME. Meta-analysis of the effects of soy protein intake on serum lipids. New Engl J of Med . 1995;333:276-281.
Columbia University. Go Ask Alice: What are the benefits of soy? Columbia University website. Available at: http://www.goaskalice.columbia.edu/2445.html. Updated November 2011. Accessed July 12, 2012.
Hypercholesterolemia. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/. Updated May 17, 2012. Accessed July 12, 2012.
Harland JL, Carr TA. Does a practical daily intake of ~25 g soy protein significantly lower cholesterol?—A meta-analysis of recent studies. J of Nutr. 2004;134(5):1267S (Poster Abstract).
Indiana Soybean Board. The US Soyfoods Directory. Stevens & Associates, Inc. Indianapolis, IN; 2002.
Mackey R, Ekangaki A, Eden JA. The effects of soy protein in women and men with elevated plasma lipids. Biofactors . 2000;12:251-257.
Rosell MS, Appleby PN, Spencer EA, Key TJ. Soy intake and blood cholesterol concentrations: a cross-sectional study of 1033 pre- and postmenopausal women in the oxford arm of the European Prospective Investigation into Cancer and Nutrition. American J of Clin Nutr . 2004;80(5):1391-1396.
Hedelin M, Klint A, et al. Dietary phytoestrogen, serum enterolactone and risk of prostate cancer: the cancer prostate Sweden study (Sweden). Cancer Causes Control. 2006;17(2):169-180.
Sacks FM, Lichtenstein A, Van Horn L, Harris W, Kris-Etherton P, Winston M; American Heart Association Nutrition Committee. Soy protein, isoflavones, and cardiovascular health: an American Heart Association Science Advisory for professionals from the Nutrition Committee. Circulation. 2006;113(7):1034-44.
Soy. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscohost.com/healthLibrary/. Updated August 2011. Accessed July 12, 2012.
12/17/2009 DynaMed's Systematic Literature Surveillance DynaMed's Systematic Literature Surveillance: Shu XO, Zheng Y, Cai H, et al. Soy food intake and breast cancer survival. JAMA. 2009;302:2437-2443.

Last reviewed July 2012 by Brian Randall, MD

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