Eating Less Fat Found to Ward Off New Breast Tumors
By Rob Stein
Washington Post Staff Writer
Tuesday, May 17, 2005
Breast cancer patients can cut the chances their tumors will come back by adopting low-fat diets, according to the first study to produce direct evidence that a lifestyle change can fend off any type of malignancy.
The study of more than 2,400 middle-aged and elderly women found that those who reduced the fat in their diets after undergoing standard treatment for early breast cancer were significantly less likely to have recurrence in the next five years, researchers said yesterday.
The findings indicate that low-fat diets, which are also being tested to protect women against getting breast cancer in the first place, could become a standard weapon for fighting the disease -- the most common cancer among women.
"Many breast cancer survivors are looking for things they can do to improve their chances," said Rowan T. Chlebowski of the Harbor-UCLA Medical Center in Los Angeles, who led the study. "Now we have evidence women can play a role in the management of their disease."
The study provides the most powerful support yet for the idea that people can reduce their risk of developing cancer by lifestyle changes such as eating better and exercising more, experts said. Previous research has suggested that might be the case, but the new study is the first to show a benefit in a large number of patients from carefully changing a single behavior -- other than quitting smoking.
"For the first time, we have scientific data about what patients can do for themselves as a lifestyle change that can significantly improve their chances," said Charles Balch of the American Society of Clinical Oncology, which is sponsoring the meeting in Orlando where the findings were announced.
Although Chlebowski and other experts said the findings need to be confirmed, they added that breast cancer patients might consider reducing their fat intake in the meantime since that could have other health benefits as well.
"I think women, with their physicians, can consider taking this step along with their standard care," said Peter Greenwald, director of the National Cancer Institute's division of cancer prevention.
Some experts and patient advocates, however, were concerned that the findings could create the impression that people have more control over whether they get cancer or suffer recurrences than they do, perhaps prompting feelings of guilt and blame.
"People should not take this study as an indication that if someone with breast cancer had just done this, they wouldn't have cancer," said Barbara Brenner of Breast Cancer Action, a patient advocacy group.
The findings come from the Women's Intervention Nutrition Study, a federally funded study of early-stage breast cancer patients ages 48 to 79 in 37 states that began in 1994. For the study, 975 post-menopausal women who had undergone standard surgery, radiation, chemotherapy and sometimes hormone treatment then went through eight weeks of nutritional counseling about how to cut fat from their diet. An additional 1,462 similar women received counseling for how to eat a well-balanced diet but no specific guidance about reducing fat intake.
On average, the women who received the low-fat diet counseling reduced fat from 29 percent to 20 percent of their daily caloric intake, whereas the women in the other group did not significantly lower fat consumption. The women on the low-fat diet consumed about 33.3 grams of fat a day, while women in the other group ate about 51.3 grams.
After an average of five years, 96 women on the low-fat diet -- 9.8 percent -- had had a recurrence of cancer, compared with 181 -- 12.4 percent -- of those on a standard diet. That amounted to a 24 percent reduction in risk on the low-fat diet.
Surprisingly, the risk reduction was even greater for women whose cancers were not sensitive to the hormone estrogen. Their risk fell by about 42 percent. That finding was especially encouraging because those women have no other way to reduce the risk of a recurrence. Women whose cancers are sensitive to estrogen can take hormone-blocking drugs such as tamoxifen, which lowers their risk by about the same amount.
Chlebowski noted that the diet tested in the study was designed to be practical for most people.
"It doesn't require eliminating meat from the diet or any drastic steps. It's mostly just substituting one food for another -- like eating cereal in the morning instead of a sweet roll for breakfast, cutting back on butter on bread and reducing portion sizes," he said in a telephone interview.
Researchers are uncertain why low-fat diets might reduce the risk of recurrence, but reducing fat in the diet may cut the amount of the hormone insulin in the blood, Chlebowski said. In addition to controlling blood sugar levels, insulin may also promote cancer growth.
Other researchers questioned whether the study adequately accounted for other changes that may have played a role, such as whether the women on the low-fat diets lost weight, ate more fruits and vegetables, exercised more or reduced their overall caloric intake.
Chlebowski acknowledged that the women in the study who cut their fat intake lost about four pounds on average, and probably consumed more fruits and vegetables. But they did not increase their exercise significantly or sharply reduce overall caloric intake, he said.
"The point is, if you do this intervention, this is the result you apparently get," Chlebowski said. "So in that way the exact mechanism isn't important."