THURSDAY, May 27, 2004 (HealthDayNews) -- Chinese women have significantly lower rates of endometrial cancer compared with U.S. women, and soy may be the reason why, new research suggests.
Eating soy regularly reduced the risk of endometrial cancer by 30 percent to 40 percent among the women studied in Shanghai, according to a report in the May 29 issue of the British Medical Journal.
The protective effect of soy was particularly significant among obese women, who are at high risk for endometrial cancer.
"One reason for the fewer cases of endometrial cancer in Asian women compared with Western women is diet," said lead researcher Dr. Xiao Ou Shu, a professor of medicine from Vanderbilt University.
Soy foods may be protective because they are rich in isoflavones, which act like estrogen in the body but are not as potent as natural estrogen. They also contain high amounts of dietary fiber. Women who have high levels of estrogen-like isoflavones may be protected from endometrial cancer, Shu said.
Shu and her colleagues collected data on 832 Chinese women in Shanghai diagnosed with endometrial cancer between 1997 and 2001 and compared them with 846 healthy Chinese women.
The researchers measured the amount of soy foods eaten over five years and the women's current body weight.
The researchers found that women who ate soy regularly significantly reduced their risk for endometrial cancer by as much as 40 percent. Obese women saw the greatest reduction in risk, Shu said.
Shu added, however, that because the number of women in the study was small, further research in a larger population is needed to confirm this finding.
More people in the United States are eating soy foods, Shu said. And the American Heart Association recommends soy to protect against heart disease.
Dr. Stephen C. Rubin, chief of the division of gynecologic oncology at the University of Pennsylvania Health System, commented, "It's an interesting study, but not at all surprising."
However, he added, "there is not enough evidence on the subject at present to recommend to women that they increase soy intake as a means of decreasing the risk of endometrial cancer."
Endometrial cancer is an increasing problem in this country, primarily because of the epidemic of obesity -- obese women have higher levels of natural estrogen, which can increase the risk of endometrial cancer, Rubin said.
"Weight reduction is a much better strategy than increased soy intake to reduce the risk of the disease. Losing 20 to 30 pounds, for instance, would provide much more protection against endometrial cancer than a high soy intake," he said.
Dr. Debbie Saslow, director of breast and gynecologic cancers at the American Cancer Society, added, "This study has some value, but does not provide a definitive answer."
Because women in China eat more soy than most women in the United States, she said, "It is hard to look at this study from the perspective of women in the U.S. who wonder if they should do something differently to avoid this type of cancer."
However, Saslow added this is the fourth study that has reached the same conclusion. "They all show that women who have a high intake of tofu and other soy products tend to have a lower risk of endometrial cancer compared with women with a lower soy intake."
To reduce the risk of endometrial cancer, Saslow recommends healthy eating, maintaining a healthy weight and exercising. "I don't think women should start eating tofu four times a day, but if they want to increase the amount of soy food, it probably won't hurt," she said.
However, she cautioned, women who have had breast or endometrial cancer should avoid too much soy, because it may increase their estrogen levels causing estrogen-sensitive cancer cells to become active.
The U.S. Food and Drug Administration can tell you more about soy.