Women who followed an obese diet rich in fruits, vegetables and grains had a lower risk of dying for breast cancer than those on a fatter diet, according to results from a major new study released Wednesday.
The conclusions of the latest analysis of the federally funded women's health initiative provide the first randomized clinical trial with evidence that diet can reduce the risk of postmenopausal women dying from breast cancer, the researchers said. Previous observational studies – which do not measure cause and effect – have had inconsistent results.
The results "are exciting and empowering the patient," says Elisa Port, head of breast surgery at Mount Sinai Health System, who was not involved in the study. "This is a wake-up call for women – there is something they can do instead of just waiting for the shoe to release."
The trial involved more than 48,000 women who did not have breast cancer when they entered the study at 40 centers across the United States. From 1993 to 1998, women were randomly assigned either to follow their regular diet, where fat accounted for 32 percent of the daily calories on average or to try to reduce fat intake to 20 percent of calories while consuming daily servings of vegetables, fruits and cereals .
The dietary intervention group lacked the target, they managed to reduce their fat consumption to about 24.5 percent and then "drive up to about 29 percent," according to senior study author Rowan Chlebowski of the Los Angeles Biomedical Research Institute at the Harbor-UCLA Medical Center. The members of the group lost 3 percent of their body weight on average. Still, women in the group that developed breast cancer had a lower risk of death than women who followed their usual diets and developed the disease.
Chlebowski said the study showed that women could improve their health by making modest changes in what and how much they eat. "This is diet moderation, it's not like eating twigs and branches," he said. "That's what people eat, say 20 years ago, before you could get 900 calories in a candy bar."
The diet intervention lasted for 8.5 years and included several sessions with nutritionists. The latest analysis represents a follow-up up to nearly 20 years.
Breast cancer experts generally praised the study but expressed some reservations. For one thing, the study was designed not to determine whether a low-fat diet gave a death benefit, but whether such a diet could reduce the risk of developing breast cancer in the first place.
Previously released data showed that the diet did not result in it in any statistically significant way. In addition, breast cancer experts noted that mortality gave up 20 years to emerge. Some also said that it was not clear which dietary component was responsible for the benefit – reduced fat or added fruits, vegetables and barley?
The study authors said dietary modification grew up using a diet similar to one called DASH – for dietary habits to stop hypertension – designed to prevent or treat high blood pressure.
The new study "adds more evidence of dietary impact but I wouldn't trust recommending a particular diet to a patient, considering that people react differently to different diets, depending on their biology," says Neil Iyengar. a medical oncologist at Memorial Sloan Kettering Cancer Center. "I tell patients if they eat more herbal foods, less red meat, lower alcohol and maintain a healthy weight, they may have a reduced risk of recurrent breast cancer or death."
The study did not look at the influence of diet on the risk of recurrent breast cancer. A separate study examines whether weight loss achieved by lowering calories and increasing physical activity leads to a reduction in the risk of relapse. The study, called Breast Cancer Weight Loss Study, or BWEL, is led by the Dana-Farber Cancer Institute.
The study comes as more evidence gathering about the relationship between obesity or obesity and a number of cancers. Being overweight and overweight – long associated with heart disease and diabetes – has been associated in recent years with an increased risk of at least 13 types of cancer, including gastrointestinal, pancreas, colorectal and liver malignancies, as well as postmenopausal breast cancer.
The study will be presented in the coming weeks at the annual meeting of the American Society of Clinical Oncology in Chicago.