Soy
Keywords: soy, cholesterol, isoflavone, hot flashes,
menopause
 Soy © Steven Foster
Introduction
This fact sheet provides basic information about
soy—uses, potential side effects, and
resources for more information. Soy, a plant
in the pea family, has been common in Asian diets for thousands
of years. It is found in modern American diets as a food or
food additive. Soybeans, the high-protein
seeds of the soy plant, contain
isoflavones-compounds similar to the female hormone estrogen.
The following information highlights what is known about
soy when used by adults for health
purposes.
Common Names—soy
Latin Names—Glycine max
What It Is Used
For
People use soy products to prevent or treat a variety of health
conditions, including high cholesterol levels, menopausal
symptoms such as hot flashes, osteoporosis, memory problems,
high blood pressure, breast cancer, and prostate cancer.
How It Is Used
- Soy is available in dietary
supplements, in forms such as tablets and
capsules. Soy supplements may contain isoflavones or soy
protein or both.
- Soybeans can be cooked and eaten or used to make tofu,
soy milk, and other foods. Also, soy is sometimes used as
an additive in various processed foods, including baked
goods, cheese, and pasta.
What the Science
Says
- Research suggests that daily intake of soy protein may
slightly lower levels of LDL ("bad") cholesterol.
- Some studies suggest that soy isoflavone supplements
may reduce hot flashes in women after menopause.
However, the results have been inconsistent.
- There is not enough scientific evidence to determine
whether soy supplements are effective for any other health
uses.
- NCCAM is supporting ongoing studies of soy, including
its effects on women's arteries and bones after
menopause.
Side Effects and
Cautions
- Soy is considered safe for most people when used as a
food or when taken for short periods as a dietary
supplement.
- Minor stomach and bowel problems such as nausea,
bloating, and constipation are possible.
- Allergic reactions such as breathing problems and rash
can occur in rare cases.
- The safety of long-term use of soy isoflavones has not
been established. Evidence is mixed on whether using
isoflavone supplements, over time, can increase the risk of
endometrial hyperplasia (a thickening of the lining of the
uterus that can lead to cancer). Studies show no effect of
dietary soy on risk for endometrial hyperplasia.
- Soy's possible role in breast cancer risk is uncertain.
Until more is known about soy's effect on estrogen levels,
women who have or who are at increased risk of developing
breast cancer or other hormone-sensitive conditions (such
as ovarian or uterine cancer) should be particularly
careful about using soy and should discuss it with their
health care providers.
- Tell your health care providers about any complementary
and alternative practices you use. Give them a full picture
of what you do to manage your health. This will help ensure
coordinated and safe care.
Sources
- Balk E, Chung M, Chew P, et
al. Effects
of Soy on Health Outcomes. Evidence Report/Technology
Assessment no. 126.
Rockville
, MD: Agency for Healthcare Research and
Quality; 2005. AHRQ publication no.
05-E024-1.
- Low Dog T.
Menopause: a
review of botanical dietary
supplements.
American Journal
of Medicine. 2005;118(suppl
12B):98S–108S.
- Sacks FM, Lichtenstein A, Van Horn
L, et al.
Soy protein,
isoflavones, and cardiovascular health: an American Heart
Association Science Advisory for professionals from the
Nutrition Committee.
Circulation
.
2006;113(7):1034–1044.
- Soy. Natural Medicines Comprehensive
Database Web site. Accessed on January 2, 2007.
- Soy (Glycine max [L.] Merr.). Natural Standard
Database Web site. Accessed on January 2, 2007.
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