Cutting Fat May Reduce Ovarian Cancer Risk

Oct. 9, 2007 — -- Good news for postmenopausal women on healthy diets: A low-fat diet may also lower the risk of developing ovarian cancer.

In a randomized controlled study following 48,835 postmenopausal women over an average of eight years, those who ate a low-fat diet -- more whole grains, fruits and vegetables -- showed a lower risk of developing ovarian cancer in the last four years of the study.

The lower risk, however, was not apparent when all eight years of the study were taken into account -- suggesting that any benefits of such a diet against ovarian cancer required adherence to the healthy regimen.

The study appears in the current issue of the Journal of the National Cancer Institute.

Lead author Ross Prentice, interim director of the public health sciences division of the Fred Hutchinson Cancer Research Center in Seattle, views this as a promising finding. Unlike shorter, less rigorous and less expensive previous studies, this, he said, is "quite an unusual study [because] it is a randomized trial" in which women were followed for a longer period of time.

"The women whose intake is comparatively high in fat content -- 35 percent of calories from fat -- and who make the biggest reduction in fat content in their diet exemplify the strongest reduction in ovarian cancer risk."

The findings could potentially benefit thousands of postmenopausal women who are attempting to take strides in the prevention of this deadly cancer.

Dr. Brent DuBeshter, director of gynecologic oncology at the University of Rochester Medical Center, agrees. "Because there is no early detection method for ovarian cancer and it is difficult to treat, any proven preventive measure, including dietary intervention, is important."

But skeptics remain. Dr. Tim Byers, professor of the department of preventive medicine and biometrics and deputy director of the University of Colorado Cancer Center, said, "I am not convinced. There were many changes in the diet of these women."

Still, Byers agrees with the study's authors on the point that changing the diets of postmenopausal women with the worst diets -- those who initially ate more fat, fewer fruits and vegetables, and were overweight -- could have considerable advantages, suggesting that modest dietary change later in life might nevertheless offer some surprising health benefits.

Mike Cummings, chair of the department of health behavior at Roswell Park Cancer Institute in Buffalo, is also skeptical. He notes that a previous trial, known as the WHEL trial, which was published in the Journal of the American Medical Association this year, "found no impact of dietary modification on recurrence of breast cancer.

"The take-home message for me is that small changes in diet appear not to make much difference," Cummings said.

Cummings believes that although the analysis comprising the last four years of the study is interesting, it probably has little practical impact.

"I'm sure there are some people who may gain a slight benefit from dietary changes, but how will you identify who will benefit and who won't?" he asked.

In addition, Cummings said he feels that the U.S. population may not be ready to make massive dietary changes -- such as adopting a vegan diet, for example -- to alter their risk.

Four Years: the Magic Number?

The fact remains, however, that for the last four years of the study, the women who ate a low-fat diet incorporating more whole grains, fruits and vegetables did indeed have a lower risk of developing ovarian cancer.

Prentice notes, "It takes some time for dietary change to express itself in chronic disease." And although we do not yet understand the biological mechanisms, he suggests that hormones may play a role.

Byers also stresses the importance of hormones, adding that a better understanding of the hormonal factors affected by dietary change might offer a clue.

And the fact that the apparent drop in ovarian cancer risk took four years to manifest suggests such changes take time to kick in.

"I wouldn't expect a low-fat dietary intervention to have an immediate impact on the risk of ovarian cancer," DuBeshter said. "Any dietary intervention would take time to have an impact. The findings of this study bear this out."

Byers cautions, however, that although a low-fat diet may take time to have effect, "this could also be just the play of chance."

As such, Byers said he prefers to focus more on the bigger picture of the study, which showed no significant effects of the low-fat diet.

"The time-related patterns are interesting and hopeful, but thin ice," he added.

Compounding this possibility is the fact that ovarian cancer is a relatively rare disease -- a point that Prentice himself acknowledges.

"This is an important but rare disease," Byers concurred. "That it was observed to be rare in this study is not surprising."

DuBeshter, however, feels that "the low risk of ovarian cancer wasn't a factor in this study's results, since the statistical analysis was carefully done."

Precautions for Pre- and Postmenopausal Women?

For young women who hope to reduce their ovarian cancer risk, DuBeshter recommends a few preventive measures.

"Use oral contraceptives for up to five years," he suggested. "This has been shown to reduce the risk of ovarian cancer by 50 percent.

"Alternatively, for women with a family history of ovarian or breast cancer, genetic counseling and testing may be warranted," he added.

Similarly, Byers emphasizes that if women's concerns stem from a family history of ovarian cancer, they should seek counseling about their possible genetic risk.

Dietitian Denise Snyder, clinical trials manager at Duke University School of Nursing in Durham, N.C., said, "We do need to keep in mind that just because someone does follow a low-fat diet, it does not mean that they won't get ovarian cancer."

But still, she added, "Following a low-fat diet may reduce their risk of developing ovarian cancer."

Indeed, as Snyder points out, the study is yet another that supports the American Cancer Society guidelines for the population on cancer prevention.

In addition, she encourages women to maintain a healthy weight, engage in regular physical activity, and limit their alcohol intake to one drink per day.

Study author Prentice also cautions that this is not a magic bullet in the prevention of ovarian cancer in postmenopausal women.

"This is just one dietary maneuver of several in postmenopausal women," he said.