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Soy

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This fact sheet provides basic information about soy—common names, usefulness and safety, and resources for more information.

 

Common Name:  soy

Latin Name: 
Glycine max

Background

  • This fact sheet focuses on the use of soy by adults for health purposes.
  • Soy, a plant in the pea family, has been common in Asian diets for thousands of years. Soy is also present in modern Western diets as a food and food ingredient.
  • Soy products are used for menopausal symptoms, bone health, improving memory, high blood pressure, and high cholesterol levels.
  • In addition to its food uses, soy is available in dietary supplements, in forms such as tablets, capsules, and powders. Soy supplements may contain soy protein, isoflavones (compounds that have effects in the body similar to those of the female hormone estrogen), or other soy components.

How Much Do We Know?

  • Although there have been many studies on soy products, there are still uncertainties about soy’s health effects.

What Have We Learned?

  • Consuming soy protein in place of other proteins may lower levels of LDL (“bad”) cholesterol to a small extent.
  • Soy isoflavone supplements may help to reduce the frequency and severity of menopausal hot flashes, but the effect may be small.
  • It’s uncertain whether soy supplements can relieve cognitive problems associated with menopause.
  • Current evidence suggests that soy isoflavone mixtures do not slow bone loss in Western women during or after menopause.
  • Diets containing soy protein may slightly reduce blood pressure.
  • There’s not enough scientific evidence to determine whether soy supplements are effective for any other health uses.
  • Current National Center for Complementary and Integrative Health (NCCIH)-funded studies on soy and its components are investigating a variety of topics, including stroke outcomes, anti-inflammatory effects, and effects on diabetes.

What Do We Know About Safety?

  • Except for people with soy allergies, soy is believed to be safe when consumed in normal dietary amounts. However, the safety of long-term use of high doses of soy extracts has not been established.
  • The most common side effects of soy are digestive upsets, such as stomach pain and diarrhea.
  • Long-term use of soy isoflavone supplements might increase the risk of endometrial hyperplasia (a thickening of the lining of the uterus that may lead to cancer). Soy foods do not appear to increase the risk of endometrial hyperplasia.
  • Current evidence indicates that it’s safe for women who have had breast cancer or who are at risk for breast cancer to eat soy foods. However, it’s uncertain whether soy isoflavone supplements are safe for these women.

Keep in Mind

  • Tell all your health care providers about any complementary or integrative health approaches you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care.

NCCIH Clearinghouse

The NCCIH Clearinghouse provides information on NCCIH and complementary and integrative health approaches, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.

Toll-free in the U.S.: 
1-888-644-6226
TTY (for deaf and hard-of-hearing callers): 
1-866-464-3615
E-mail: 

PubMed®

A service of the National Library of Medicine, PubMed® contains publication information and (in most cases) brief summaries of articles from scientific and medical journals. For guidance from NCCIH on using PubMed, see How To Find Information About Complementary Health Approaches on PubMed.

Office of Dietary Supplements (ODS), National Institutes of Health (NIH)

ODS seeks to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, supporting research, sharing research results, and educating the public. Its resources include publications (such as Dietary Supplements: What You Need to Know), fact sheets on a variety of specific supplement ingredients and products (such as vitamin D and multivitamin/mineral supplements), and the PubMed Dietary Supplement Subset.

E-mail: 

Key References

This publication is not copyrighted and is in the public domain. Duplication is encouraged.

NCCIH has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your primary health care provider. We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by NCCIH.
NCCIH Publication No.: 
D399
Updated: 
September 2016

This publication is not copyrighted and is in the public domain. Duplication is encouraged.


NCCIH has provided this material for your information. It is not intended to substitute for the medical expertise and advise of your primary health care provider. We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by NCCIH.


U.S. Department of Health & Human Services, National Institutes of Health, National Center for Complementary and Integrative Health

nccih.nih.gov

This page last modified December 01, 2016