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.
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
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
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.
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.
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.
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.
For More Information
“What’s in the Bottle? An Introduction to Dietary
“Herbal Supplements: Consider Safety, Too”
Toll-free in the U.S.: 1-888-644-6226
TTY (for deaf and
hard-of-hearing callers): 1-866-464-3615
E-mail: [email protected]
CAM on PubMed
Web site: nccam.nih.gov/camonpubmed/
NIH Office of Dietary Supplements
Web site: ods.od.nih.gov
NIH National Library of Medicine’s MedlinePlus
Soy Listing: www.nlm.nih.gov/medlineplus/druginfo/natural/patient-soy.html
Twin Sisters Are At High Risk of Early Menopause
(BlackDoctor.org) — Twin sisters face triple the odds of entering menopause prematurely compared to women who don’t have a twin, researchers report. “It’s a three-to-five-fold increase in risk of having menopause before the age of 40,” said study lead author Roger Gosden,
director of reproductive biology at Weill Cornell Medical College in New York City. However, he added, “We have to bear in mind that over 95 percent of women who are twins will still have menopause at the normal time. There shouldn’t be any general alarm.”
The study was published Wednesday in the Oct. 25 online edition of Human Reproduction.
Overall, about 1 percent of adult women have premature ovarian failure (POF), prompting menopause before the age of 40. Not only does this affect fertility, but it may also boost risks for cardiovascular disease and osteoporosis.
The mean age of menopause is 50 to 52 years.
Gosden had already published research on a twin who underwent POF at age 14. The woman’s twin, however, remained fertile and was able to donate ovarian tissue to her sister for a transplant.
“It was that study that stimulated us to do this big survey and to find out how common early menopause is in identical twins and how often there may be discordances,” Gosden explained.
There had already been hints in the medical literature that fraternal twins might be at higher risk of early ovarian failure. The current study confirmed that and added new information about identical twins.
In all, the researchers looked at 428 twin pairs from an Australian twin register and 404 from a British twin registry. These were compared to a control group of 3,483 Dutch women. Women who had undergone a hysterectomy were automatically excluded.
Rates of POF were similar in both registries and three-to-five times higher than the general population at ages 40 and 45. This was true of both fraternal and identical twins.
But in some cases, the twin pairs had very different ages of menopause, sometimes varying by as much as 20 years.
“The biggest mystery surrounds the identical twins because one would expect them to have similar menopause,” Gosden said. “That is true most of the time, but, in some cases, it’s extraordinarily early and may be different from the other twin.”
The reasons are unclear. However, Gosden said that scientists “know why identical twins [can be] very different in terms of their ovaries.”
“We do believe that the problem starts when the woman was actually a fetus, when the eggs were formed,” he continued. “We believe that the infertile sister doesn’t form a normal number of eggs, so she runs out of eggs earlier.”
“The ovary works like an hour glass with a fixed number of eggs,” Gosden explained. “When they’ve run out, the woman has menopause. We believe that the infertile twin has fewer eggs to begin with.”
Now Gosden is moving his research into the clinical stage.
“We’ve been receiving calls from twins where one has had an early menopause, and they’re interested in having a transplant from a fertile twin to an infertile twin to restore ovarian function,” Gosden said. So far, 10 patients have signed up, five of whom have already had transplants. All the transplants have been successful, and three women have become pregnant or delivered babies.
“One of the important things to take out of this study is that one twin could serve as an egg donor or donor of ovarian tissue in order to reverse early menopause for the other twin,” said Dr. Jennifer Wu, an obstetrician/gynecologist at Lenox Hill Hospital in New York
City. “We have so many advances these days in regard to fertility, so premature menopause is not the terrible thing it once was.”