Researchers studied 2,400 post-menopausal women who had been successfully treated for breast cancer, and monitored their condition for five years. The women had all previously received standard treatments for their cancer, including surgery, hormone therapy, chemotherapy or radiation therapy.
One group of women was asked to consume less than 33 grams of fat per day � 20 percent of their total calorie intake. The control group ate a standard diet of approximately 51 grams of fat per day, or 30 percent of their total daily calories. After five years, the relapse rate among those who had eaten the low-fat diet was 9.8 percent, compared with 12.4 percent for the control group � in other words, a 20 percent lower risk. The difference was statistically significant, said researchers.
When the researchers divided the breast-cancer cases depending on whether or not the tumors contained receptors for estrogen hormones, a different pattern emerged. Among those with estrogen-receptor-negative tumors, women who ate the low-fat diet had a 41 percent lower risk of recurrence. Preliminary results suggested that this difference became even more drastic when the observation period was extended past five years. Among those with estrogen-receptor-positive tumors, however, a low-fat diet produced no statistically significant difference in relapse risk.
The study could not determine the cause for the correlation between reduced fat intake and reduced risk.
Prior studies have shown a correlation between obesity and breast cancer risk, such that gaining 22 pounds can increase person's risk of contracting breast cancer by 18 percent.
The recurrence study � called the Women's Intervention Nutrition Study � was funded by the American Institute of Cancer Research.
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