Adding fiber-rich fruit, vegetables, and whole grains (all foods naturally low in fat) and decreasing total fat intake to 20% of calories may protect against ovarian cancer, reports new research involving nearly 50,000 women.*
No Quick Fix
The results also affirmed that when it comes to disease prevention, there is no quick fix. In the first four years of the eight-year study, the women in the healthy low-fat diet group and those in the typical American diet group had cancer rates that were comparable. But in the next four years, the low-fat diet group cut their risk of ovarian cancer by 40% compared to the other group.
“This report provides evidence for a reduced risk of ovarian cancer as a result of the low-fat dietary pattern intervention, along with suggestive evidence for a reduction in total invasive cancer,” concluded lead author Dr. Ross L. Prentice and colleagues at the Fred Hutchinson Cancer Research Center in Seattle, Washington.
Gold Standard
Previous research, mostly population studies, tended to support a link between low-fat, high-fiber diets and reduced risk of ovarian cancer. This new study is the first to use the gold standard of scientific inquiry, a randomized controlled trial, to investigate the effects of a healthier diet on ovarian cancer occurrence.
In the trial, part of the Women’s Health Initiative Dietary Modification Randomized Controlled Trial, nearly 20,000 women were randomly assigned to the healthy diet group, and nearly 30,000 were told to continue eating their normal American-style diet, high in fat and refined, processed foods.
The women in the healthy diet group were asked to reduce their fat intake to 20% or less of their overall calorie intake, as well as eat at least five servings of fruits and vegetables a day and at least six servings of whole grains.
At recruitment, all the women were postmenopausal and aged 50 to 79 years.
40% Reduction In Ovarian Cancer Rates
In the second half of the eight-year study, the typical American diet group had a rate of 64 cases of ovarian cancer per 1,000 persons per year while the healthy diet group ended up with 38 cases per 1,000 persons, a 40% reduction in cancer rates.
Moreover, the women in the healthy diet group who had the highest fat intake before the trial, averaging about 38% calories from fat, saw the greatest reduction in risk, which was “perhaps the strongest data in favor of an intervention effect,” noted the authors.
The American Cancer Society estimates that 22, 430 American women will be diagnosed with ovarian cancer this year; 15,280 will die of it.
Long-term healthy dietary changes could significantly reduce these cancer rates, asserts cancer researcher Dr. Prentice. "The bottom line is that doctors should encourage their postmenopausal patients to adopt a low-fat diet, which may reduce their risk of ovarian cancer. Such a diet may also reduce the risk of breast cancer and other malignancies."
* Journal of the National Cancer Institute, 2007; 99: 1534.
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