Women's Health: A Low-Fat Diet May Protect Against Breast Cancer After All
Women treated for breast cancer may be able to lessen the odds of a recurrence by cutting fat from their diets, according to a new, large study. The findings come as good news to researchers, because a far larger study released earlier this year found such a slight difference in risk in women trimming the fat that it might have been due to chance alone.
In this study, researchers assigned more than 2,400 women who had been treated for early stage breast cancer to one of two groups. Some were given an individual target of daily grams of fat consumed, counseling from dieticians, and a low-fat eating plan. The other women simply met with a dietician and got general written nutritional guidelines. The women were followed for an average of five years.
The women assigned to low-fat diets successfully cut back to an average of about 33 grams per day, compared with about 51 in the control group. (Both groups started at about 57 grams of fat per day.) In the earlier study, women on the low-fat diet weren't able to reduce fat as much as they were supposed to, thus putting the findings into question. "People actually followed the diet," says Larry Norton, breast cancer chief at Memorial Sloan-Kettering Cancer Center in New York. (He's also affiliated with a not-for-profit breast cancer group that funded a small part of the study, known as the Women's Intervention Nutrition Study, most of which was funded by the National Cancer Institute.)
The women who stuck to the diet saw a 24 percent lower risk of a recurrence of cancer than the others. That is, after about five years, breast cancer had recurred in 9.8 percent of the group, compared with 12.4 percent of those eating as they pleased. Women with a particular type of breast cancer that isn't fueled by estrogen and thus isn't treatable with drugs like tamoxifen, saw the biggest reduction in risk: a 42 percent drop in the odds of recurrence. (That finding was unexpected and needs confirmation with further studies.)
The women on the low-fat diet also lost weight, which may have been a factor; they were 6 pounds lighter on average than the women on the regular diet by the end of the study. So the question is, was it the lesser amount of fat in the diet that explains the results or the fact that they lost body fat? "It's hard to tease out, but who cares?" says Norton. Whatever the cause, the results should immediately be applied to breast cancer survivors, he says.
The study was released at the San Antonio Breast Cancer Symposium and will appear in the Journal of the National Cancer Institute (which is independent from the NCI). At the same conference, other researchers reported that new breast cancer cases declined by 7 percent in 2003, and that cases of cancer fueled by estrogen dropped 15 percent. They hypothesized that the widespread abandonment of hormone replacement therapy the year before stopped small tumors from progressing by starving them of estrogen.