Newsletter 90, Winter 2006
A Lowfat Diet May Help Protect Breast Cancer Survivors
A recent study suggests that breast cancer survivors may reduce their risk of recurrence by following a lowfat diet. Dr. Rowan Chlebowski, who led the study, describes how to interpret the results of this clinical trial.
One of the first diet-cancer topics scientists ever explored was the possible link between breast cancer and fat. Some studies have indicated that adult overweight and obesity may raise breast cancer risk. Others suggest that eating a diet high in saturated fat from animal proteins, such as red meat and high-fat dairy products, could raise a womanÕs risk for breast cancer.
Last spring, results from a study called the Women's Intervention Nutrition Study (WINS) found that, for post-menopausal women who had been treated for breast cancer, a lowfat diet significantly reduced recurrence of the disease.
According to study leader Dr. Rowan T. Chlebowski, of the Los Angeles Biomedical Research Institute, Harbor-UCLA Medical Center, the results are encouraging.
"I think the results generated so much media publicity because they contradict the concept that only drugs are the answer," he says. "It's reassuring to the public to think they can do something about preventing disease by eating a healthy diet."
Eating Realistically Is Key
The randomized study included more than 2,400 postmenopausal women who had been treated for breast cancer. All had received standard therapies - surgery followed by radiation, chemotherapy, hormone therapy, or some combination of these treatments.
Half the women were asked to cut their dietary fat to 20 percent of total calories each day (33 grams of total fat). The other half followed a standard diet (51 grams of fat). Five years later, breast cancer had recurred in 9.8 percent of the women on the lowfat diet, compared with 12.4 percent of the women on the standard diet.
Gretchen Moore of California was in the lowfat diet group that was instructed on how to eat less fat. She says the individual guidance, as well as support she received at group meetings every few months, helped keep her on track. She also kept a daily food diary of her portion sizes, fat grams and when she ate. She says it got tiresome sometimes - but she stuck with it.
"The hardest part was eating away from home," she recalls. "Portions are so large at restaurants. And when I go to someone's house, I don't want to tell them I'm not going to eat their food. Instead, I just eat a small portion if it has a lot of calories." She sometimes eats an apple before going out for a meal so she will be less hungry.
Gretchen is now a 10-year survivor with no recurrence and considers herself lucky. "It doesn't take a lot of money to eat right," she says. "Just leave all the processed foods alone and eat fresh foods that are low in fat. It's not hard to eliminate fat if you do it that way."
Unexpected Hormone-Related Findings
It is not known whether the apparent reduction of risk from cancer recurrence was due to the lowfat diet itself or to the greater weight loss that occurred, Dr. Chlebowski notes. Women on the lowfat diet lost an average of 4 pounds each compared to the other group - a small but statistically significant amount.
One possibility is that reducing fat in the diet might have cut the amount of the hormone insulin produced in the body. A couple of studies have shown that women with higher insulin levels had a greater risk of breast cancer recurrence than women with lower levels, Chlebowski said, but this theory needs further study before any general conclusions can be reached.
A separate, unexpected outcome from WINS is that women on the lowfat diet whose breast cancer was not sensitive to the hormone estrogen (i.e., estrogen receptor-negative breast cancer) achieved a 41 percent reduction in their risk of cancer recurrence. Women who do have breast cancer that is influenced by estrogen can take estrogen inhibitors to lower their risk. But the fact that there is aneffect on ER-negative breast cancer gives hope to women with that type of cancer.
"This finding makes the WINS results much more exciting," Dr. Chlebowski says. "It means there is a mechanism involved that is not mediated by estrogen."
Whether eating a lowfat diet may prevent breast cancer from developing in the first place was not addressed by WINS. But results due out in 2006 from the Women's Health Initiative, which examines dietary modifications similar to WINS, should provide some answers, Dr. Chlebowski notes.
Meanwhile, until results from WINS and other studies are confirmed by more research, the best advice appears to be AICR's long-standing recommendation to eat a diet that is 2/3 (or more) plant foods and 1/3 (or less) lean meat and low-fat dairy products, and to choose healthy fats, such as olive oil, instead of saturated fats like butter. All active news articles