University of Virginia Health System

Ovarian Cancer Odds Lowered with Fiber, Low-Fat Diet

Older women who stick to a low-fat, high-fiber diet could cut their odds for ovarian cancer, according to a report in the Journal of the National Cancer Institute.

Those who saw the greatest benefit from the low-fat diet were women who had originally eaten a relatively high-fat diet, the researchers add.

On average, the women had managed to add one serving of fruits or vegetables to their daily diet by end of the six-year follow-up. They had also reduced their daily fat consumption by about 8 percent.

The findings support "the idea that lifestyle changes can be made with intensive help," says Dr. Robert Morgan, section head of medical gynecologic oncology at the City of Hope Cancer Center. He was not involved in the study.

Morgan says many of his patients ask him about ways they can reduce their cancer risk through diet and exercise. But he says he's found that "it's difficult to change habits, especially if they are longstanding."

Long-Term Adherence to Diet a Plus

According to Morgan, women have a 2 percent lifetime risk of getting ovarian cancer, so the relatively small benefit effect shown over the course of this study should be magnified during a lifetime.

Besides helping curb cancer, a low-fat, high-fiber diet would also help reduce the risk of other chronic diseases, such as heart disease.

The new multi-center study was led by Dr. Ross Prentice of the Fred Hutchinson Cancer Research Center. The findings come on the heels of a similar study released by the same group in April.

That study found that increased consumption of fruits and vegetables helps reduce the risk of head and neck cancers.

The same team has also shown that low-fat diets cut the odds of breast and colorectal cancers. Prior to the publication of this analysis, the impact of particular diets on ovarian cancer was unknown.

In the study, Prentice's team recruited almost 50,000 postmenopausal women between the ages of 50 and 79. Almost 20,000 of those women were randomly assigned to eat a low-fat diet in which fat intake totaled less than 20 percent of daily calories.

They also ate at least five servings of fruits and vegetables a day and at least six servings of whole grains.

The women received 18 diet-support group sessions in the first year to help keep them on track, and quarterly maintenance meetings during the following years.

The researchers then monitored the women's rates of ovarian and endometrial malignancies during the next eight years.

The result: ovarian cancer rates were roughly similar for women during the first four years of the study, regardless of their diet.

But by the end of more than eight years of follow-up, a clear trend emerged, with women on the healthier diet having a 40 percent reduction in ovarian cancer incidence.

There was no such effect on the risk of endometrial cancer, however, the researchers add. That was surprising, explains Morgan, because some experts theorize that fat increases estrogen levels in the body, which may boost the risk for both ovarian and endometrial cancer.

Previous reports have indicated that low-fat diets lower circulating estrogen, says Morgan, so he expected to see a similar effect for both tumor types.

Women looking to duplicate the diet in their own lives should follow the Food Pyramid guidelines set out by the U.S. Department of Agriculture, says Morgan.

But he adds that one of the components that made this study so unique was the intense dietary counseling and support the women received.

According to Prentice, the diet was developed especially for this research and does not follow any contemporary "popular" diets.

"In particular, the Women's Health Initiative intervention did not have a goal of restricting energy [calorie] consumption, though participating intervention group women did lose some weight. Nor was there an attempt to reduce carbohydrates," says Prentice. "On the contrary, most of the reduced dietary fat was replaced by complex carbohydrates."

Reduction in Obesity with Low-Fat Food

The potential link between dietary fat and cancer is not fully understood, he adds.

During the study, Prentice says the researchers did note lower levels of estradiol - an estrogen hormone produced by the ovaries - in the blood of dieting women. Estradiol is an important risk factor for cancer among women, he notes.

"This or other circulating hormones could have a stimulatory effect on epithelial [blood vessel] tissue in the ovary or breast, possibly including effects on cells in yet undiagnosed cancers," says Prentice.

"The evidence for reductions in ovarian and breast cancer is strongest among women whose usual [prior] diet was relatively high in fat (e.g., more than 35 percent of calories) who made a comparatively large fat reduction if assigned to the low-fat diet group," he adds.

There is an increasing amount of evidence linking healthier diets and exercise to lower cancer risk.

But Prentice says he would like to see more basic science research focused on the ways in which these lifestyle changes affect the biochemical mechanisms that drive cancer.

Physicians Develop Detection Guidelines

In other recent news about ovarian cancer, the Gynecologic Cancer Foundation and the Society of Gynecologic Oncologists have agreed on a set of symptoms that can be signs of early ovarian cancer.

"We want people to know it's not the silent killer," says Dr. Linda Duska, a member of the National Ovarian Cancer Coalition medical advisory board and a gynecologic oncologist at Massachusetts General Hospital Cancer Center.

The screening test developed late last year involves an extensive checklist of symptoms and their frequency. It picked up 56.7 percent of early-stage ovarian cancer cases and 80 percent of late-stage ovarian cancer cases.

The test also produced a 10 percent to 13 percent false-positive rate. The test searches for many of the symptoms agreed upon by cancer experts as indicative of ovarian cancer.

The symptoms of ovarian cancer can be subtle and hard to assess, because they often mimic common digestive and gastrointestinal disorders.

They include persistent swelling, bloating, pressure or pain in the abdomen, gastrointestinal upset, difficulty eating or feeling full quickly and the frequent or urgent need to urinate.

Because these symptoms are so common, women should be careful not to assume the worst, Duska says.

To learn more about ovarian cancer or other women's health topics, visit www.uvahealth.com.

Always consult your physician for more information.