THURSDAY, Nov. 8, 2001 (HealthDayNews) -- Though foods high in plant-based estrogens, like soy, are believed to reduce the risk of breast cancer, a new study says you probably won't get that protection unless you're prepared to load your plate and dig in.
Compared with women in Asian countries, American women aren't consuming enough foods rich in plant estrogens, called phytoestrogens, to make a significant difference in breast health, say researchers at the Northern California Cancer Center.
"The traditional Asian diet contains about 15 to 30 milligrams per day of isoflavones [the major type of phytoestrogen found in soy]," says lead study author Pamela Horn-Ross, a research scientist. "Only 25 percent of [the women in our study] consumed more than 3 milligrams a day."
Phytoestrogens are weak, plant-based versions of the female hormone estrogen. Because they can mimic the effects of natural estrogen in the body, they can bind to estrogen receptors in certain tissues, including those in the breast, says Cindy Moore, director of nutrition therapy for Cleveland Clinic Foundation and spokeswoman for the American Dietetic Association.
Scientists believe this, in turn, blocks natural estrogens from reaching the same receptors and exerting their negative, cancer-causing effects, she says.
"Soy or other foods high in phytoestrogen can shift the type of estrogen from the kind predisposed to breast cancer to the type which protects against breast cancer," Moore says.
While a number of epidemiological studies have shown that consuming foods high in phytoestrogen can reduce beast cancer risks, most have involved Asian women, and most foods have been soy based.
Horn-Ross says the new study was designed to find out whether all phytoestrogen compounds have similar effects, and whether the amount that American women consume is enough to confer any anti-cancer benefits.
The research began with interviews of 1,326 black, Latino and white women, ages 35 to 79. All had been diagnosed with breast cancer between 1995 and 1998. Each was asked about how much and how frequently they ate various foods. The researchers then analyzed the food, looking for seven different phytoestrogens.
Their answers were compared with those of 1,657 healthy women selected from the general population.
None of seven different phytoestrogens was associated with any reduced risk of breast cancer in the amount the women consumed, the researchers say. Further, all three ethnic groups, and both pre- and post-menopausal women yielded similar findings. Details appear in a recent issue of the American Journal of Epidemiology.
Horn-Ross says the finding doesn't necessarily mean that phytoestrogens don't reduce the risk of breast cancer. Rather, she says the average of 3 grams a day consumed by the women in the study wasn't enough to have an effect.
"There was some reduction in breast cancer risks among those women using several of the soy-based foods, [but] because these foods are consumed relatively rarely in the non-Asian population, we weren't able to determine if the risk reduction was due to the soy or something else, such as dietary or lifestyle habits," Horn-Ross says.
What To Do
Experts say the take-home message here is that you'll likely need to eat more phytoestrogen-rich food than you probably consume now to get any protection.
However, increasing your intake to levels that other studies have shown might reduce cancer risks is not difficult.
If soy is your main source, for example, Moore says just 20 milligrams a day, or about 8 ounces of soy milk, may be all it takes to gain some protection from breast cancer. And, she says you might be getting even more bang for your soy buck in terms of overall health benefits.
"Soy has been shown to reduce risk of heart disease and osteoporosis and possibly prevent the accumulation of brain plaques that lead to Alzheimer's disease, in addition to the fact that it is a nutritious food in its many forms," Moore says.
However, she also cautions that soy is not recommended for women with a history of breast cancer, because it could antagonize the cancer cells, or for women taking hormone replacement therapy, because it could reduce effectiveness of the treatment.
To learn more about phytoestrogens, check information from Tulane University or Healthcare Reality Check, a Web site sponsored by the Georgia Council Against Health Fraud.
And for information on breast cancer, go to the Breast Cancer Awareness Network.
