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Low-Fat Diet May Reduce Risk of Breast Cancer Returning (dateline May 26, 2005)

Breast cancer survivors who maintain a diet low in fat may reduce the risk that the disease will return, according to the results of a recent study funded by the U.S. government. In the study, there was a 24% reduction in breast cancer recurrence in women who reduced their consumption of dietary fat to 20% of their total calories per day compared to women who followed a standard diet (averaging about 40% of calories from fat daily). The risk reduction was even greater among women with so-called estrogen-receptor negative breast cancer, a type of breast cancer that has been traditionally more difficult to treat. The researchers say the study results suggest that post-menopausal breast cancer survivors may wish to consider low-fat diets to reduce their risk of breast cancer recurrence and lead more healthy lives.

The Women's Intervention Nutrition Study (WINS) was a large study that enrolled 2,437 women between 1994 and 2001 who had previously been treated for early-stage breast cancer with surgery and other appropriate therapies, such as chemotherapy. The goal of the study was to determine whether a low-fat diet could reduce the risk of breast cancer recurrence in post-menopausal breast cancer survivors.

In the study, the women were divided into two groups. The first group of women followed a standard diet and were not encouraged to change their diet. In this group, women consumed an average of 51 grams of fat per day, about 40 percent of their total daily caloric intake. The second group of women were asked to modify their diet to reduce their consumption of dietary fat to 20% of their total daily calories, or about 33 grams of fat per day. Each group met with nutrition counselors periodically and kept daily food diaries of what they ate. Most of the women in the study were not active and led relatively sedentary lifestyles.

After an average of five years follow-up, principal investigator Rowan T. Chlebowski, MD., PhD, of the Los Angeles Biomedical Research Institute in California and his colleagues found that breast cancer had returned in 9.8% of the women on the low-fat diet and 12.4% of those on the standard diet. This equaled a 24% risk reduction in the low-fat diet group. Furthermore, there was a 42% reduction in the risk of breast cancer recurrence among women who had estrogen-receptor negative breast cancer and maintained low-fat diets. Estrogen-receptor negative breast cancer occurs in approximately 20% of breast cancer patients. In these patients, the cancer does not depend on the hormone estrogen for survival. Thus, many therapies, such as the drug tamoxifen, are not as effective at treating the disease. Women in the low-fat diet group also lost an average of four pounds.

While the researchers call the study results promising, the National Cancer Institute emphasized that the results need confirmation in larger clinical trials. There may also have been limitations in the study that affected the results. For example, weight loss in the low-fat diet group, not the diet itself, may have contributed to the reduced breast cancer risk. In addition, some women had been treated with chemotherapy prior to joining the study, which may have affected their risk of breast cancer recurrence.

Nevertheless, maintaining a low-fat diet has been shown to have several health benefits, included a reduced risk of heart disease and other conditions. Therefore, it is logical that breast cancer survivors may wish to consider a low-fat diet to help maintain a healthier lifestyle.

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