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Health Management Fresno, California (CA) - Saint Agnes Medical Center

 

Soy

Definition

Humans have been eating soy beans for almost 5000 years. The soybean is high in protein. The quality of protein from soy is equals that of protein from animal foods.

Function

Soy in your diet can lower cholesterol. Many research studies support this claim. The U.S. Food and Drug Administration (FDA) agrees that 25 grams per day of soy protein may reduce the risk of heart disease. Health benefits of soy products may be due to their high levels of polyunsaturated fats, fiber, minerals, vitamins, and low saturated fat content.

Isoflavones that occur naturally in soy product may play a part in preventing some hormone-related cancers. Examples include breast cancer, endometrial cancer, and prostate cancer. However, the role of isoflavones in prevention or treatment of cancer is not certain at this time. Using isoflavone supplements in food or pills is not recommended for this purpose. However, these supplements may ease menopause symptoms such as hot flashes.

Food Sources

Not all soy protein products contain the same amount of protein. The following list ranks the protein content of some common soy foods. Highest protein items are at the top of the list.

  • Soy protein isolate (added to many soy food products, including soy sausage patties and soybean burgers)
  • Soy flour
  • Whole soybeans
  • Tofu

To find out about protein content in a soy-based food:

  • Check the Nutrition Facts label to see the percentage of soy protein.
  • Also look at the list of ingredients. If a product contains isolated soy protein (or soy protein isolate), the protein content should be fairly high.
  • Some products also list how many grams of soy protein are in one serving of the product.

Note: There's a difference between soy supplements in the form of tablets or capsules and soy protein products. Most soy supplements are made of concentrated soy isoflavones. These substances may help relieve symptoms of menopause. However, there is not enough evidence to support soy isoflavones for other health purposes, such as lowering cholesterol.

Side Effects

People who are not allergic to soy do not have serious side effects from eating these foods. Mild side effects may include stomach aches, constipation, and diarrhea.

Soybeans also contain a natural substance called purine. Large amounts of purines can make gout worse. Persons with gout should not eat a lot of soy products.

Recommendations

In adults, 25 grams per day of soy protein may reduce the risk of heart disease.

Soy foods and soy-based infant formula are often used for children. No studies have shown whether isolated soy protein or isoflavone supplements are useful or safe for this group. Therefore, isolated soy products are not recommended for children at this time.

References

Food Labeling: Health Claims; Soy Protein and Coronary Heart Disease. Federal Register: (Volume 64, Number 206); 1999. p.57699-57733.

Taku K, Melby MK, Kronenberg F, Kurzer MS, Messina M. Extracted or synthesized soybean isoflavones reduce menopausal hot flash frequency and severity: systematic review and meta-analysis of randomized controlled trials. Menopause. 2012 Jul;19(7):776-790.

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 Feb 21;113(7):1034-44. Epub 2006 Jan 17.

Hasler CM. Position of the American Dietetic Association: Functional foods. J Am Diet Assoc. 2004;104(5): 814-26.

Nedrow A, et al. Complementary and alternative therapies for the management of menopause-related symptoms: a systematic evidence review. Arch Intern Med. 2006 Jul 24;166(14):1453-65.


Review Date: 4/30/2013
Reviewed By: Alison Evert, MS, RD, CDE, Nutritionist, University of Washington Medical Center Diabetes Care Center, Seattle, Washington. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.
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