Any reduction in risk as a result of changing one's diet is very exciting. It may be that by sticking to a low-fat diet, the women also were able to make other healthy choices that helped to reduce their breast cancer risk. These other lifestyle and dietary changes might include eating more fruits and vegetables and losing weight.
And maybe by eating less fatty red meat or dairy products, the women on the low-fat diet limited their exposure to hormones or pesticides. There is a concern about the safety of eating red meat and dairy products because of possible high levels of hormones or pesticides from some sources, which may increase risk.
It would be interesting to know if the women on the low-fat diet were less likely to smoke and drink alcohol, and were more likely to exercise. These factors could also influence the risk of cancer coming back.
We all know how hard it is to stay on a low-fat diet month after month, year after year. The women in this study who followed this diet probably had to work very hard to stick with the plan. They didn't have to do it alone, however. A big part of this study was getting regular, intensive, one-on-one expert dietary advice and encouragement from dietitians. And given what we know about the power of support groups, it's possible that being coached in itself had a positive impact on the risk of recurrence.
Another clinical trial, known as the Women's Healthy Eating and Living Well study, is examining whether a low-fat, plant-based diet might help reduce the risk of breast cancer coming back in women with stage I, II or IIIA cancer. By looking at the women's whole diet, researchers hope to learn more about how combinations of food can affect the risk of cancer recurrence. When those results become available, breastcancer.org will report them to you.
Talk to your doctor if you would like to reduce the amount of fat in your diet. You may also want to visit a registered dietitian who specializes in working with cancer patients. You can search for a registered dietitian in your area on the American Dietetic Association website. You may also want to look at the American Cancer Society's recommendations for nutrition and physical activity.
And stay tuned to Breastcancer.org for more news on nutrition and breast cancer, including more definitive information from this study. Perhaps the results of the study will change after a longer follow-up time.
In the upcoming months, breastcancer.org will launch a new section on nutrition that will give you the most up-to-date information on the topic. The new section will also offer suggestions on how to lose weight that you may have gained as a result of treatment.
Reviewed study: "Low-Fat Diet May Reduce Risk of Recurrence" by R.T. Chlebowski et al., American Society of Clinical Oncology Annual Meeting, May 2005, Abstract #10
Is this for me? If you're a post-menopausal woman and have breast cancer and want to learn about how your diet may influence the risk of the cancer coming back, you might want to read this article.
Background and importance of the study: Researchers have suspected that reducing the amount of fat in your diet might reduce the risk of breast cancer coming back (recurrence). But earlier studies have not found any conclusive evidence of this.
Studying the relationship between diet and breast cancer is complicated. That's because someone who is able to stick to a low-fat diet is also likely to make other healthy choices that could also lower breast cancer risk. Here are two examples:
The study reviewed here is called the Women's Intervention Nutrition Study and is funded by the National Cancer Institute and The Breast Cancer Research Foundation. Researchers wanted to know if being on a low-fat diet would reduce the risk of cancer coming back in post-menopausal women with a personal history of breast cancer. Fat made up about 25% of daily calories in the low-fat diet. In comparison, on an average diet you get between 30% and 50% of daily calories from fat.
Study design: The study took place at 37 sites in the United States and included 2,437 post-menopausal women with early-stage (non-metastatic) breast cancer. All the women had had surgery—either mastectomy or lumpectomy plus radiation. The women were between 48 and 79 years old.
After they had surgery:
Researchers put the women into two groups:
The women were placed into the two groups at random, but they were similar in terms of:
The researchers followed the women for about five years to see how many of them were free of cancer and how many had the cancer return.
Results: After about five years, the researchers found that women on the low-fat diet ate an average of 33 grams of fat per day, while the other women ate an average of 51 grams of fat per day.
The cancer came back in 9.8% of the women on the low-fat diet and in 12.4% of the women on the normal diet. This means that the low-fat diet was associated with a 2.6% "absolute risk reduction"—12.4% minus 9.8%. The "relative risk reduction" was 24% (because the absolute risk reduction of 2.6% is about one quarter of the 9.8% result).
Women with estrogen-receptor-negative cancer—about one in five, in this study—seemed to benefit the most. These women had a 42% lower relative risk of recurrence if they ate low-fat diets. For the women who were estrogen-receptor-POSITIVE, being on a low-fat diet did not have statistically significant results, which means the risk reduction could have happened by chance alone. The benefit of the low-fat diet in this study appeared to be limited to women with estrogen-receptor-negative breast cancers.
Conclusions: The researchers concluded that a low-fat diet may reduce the risk of breast cancer coming back in post-menopausal women.
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