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WASHINGTON — A diet extra heavy in fruit and vegetables was no better than one with the standard recommended amounts in preventing the recurrence of breast cancer, a study released on Tuesday found.
The study tracked 3,088 U.S. women. Half followed a diet with the widely recommended five daily servings of vegetables and fruit. The other half ate a diet doubling that intake.
Those who consumed twice the vegetables and fruit in a diet also high in fibre and low in fat were no less likely to avoid a recurrence of breast cancer or death than the women who followed the five-a-day diet.
The women, all of whom had been treated successfully for early-stage breast cancer, participated in the study from 1995 to 2000 at seven places in California, Texas, Arizona and Oregon. They were followed for between six and 11 years.
The findings, published in the Journal of the American Medical Association, come amid a debate among experts over the influence of diet on cancer.
The researchers called this the largest study of its kind to assess how diet affects breast cancer recurrence and said the results were quite definitive.
"I was surprised and disappointed," Marcia Stefanick of Stanford University in California, one of the researchers, said in a telephone interview. "I think we believed that by eating real food and nutrient-dense food, we were going to come up with a different outcome, but we didn't."
"I look at it the other way," said another of the researchers, John Pierce of the University of California, San Diego. "We're telling women they don't have to go overboard here. They can have a good quality of life without worrying about their dietary pattern all the time.
"What it says is there's a threshold effect," Dr. Pierce said, in which no more benefits are seen once a certain level of fruit and vegetable intake is reached.
About 17 per cent of the women in both groups had a recurrence of breast cancer. About 10 per cent in both groups died during the study, 80 per cent of them from breast cancer.
The researchers said they hoped women do not interpret the findings as suggesting diet does not matter when it comes to breast cancer.
They noted that the women who ate five servings a day of vegetables and fruit -- as recommended by the U.S. National Cancer Institute and the Agriculture Department -- consumed a diet far more healthful than many people.
They also noted that research has shown that such a diet, along with regular moderate exercise, can cut the risk of breast cancer survivors dying from a recurrence of the disease as well as conferring other health benefits.
The women in the group that doubled the daily intake were asked to cut dietary fat to 15 per cent to 20 per cent of total calories, eat five servings of vegetables, three servings of fruit, two 8-ounce (227-ml) glasses of vegetable juice and 30 grams of fibre a day. A serving size amounted to half a cup of chopped or shredded vegetables.
The researchers emphasized nutrient-dense vegetables like dark, leafy greens, sweet potatoes and carrots, and did not count vegetables such as iceberg lettuce and white potatoes.
The researchers said the study did not look at whether eating a diet high in vegetables, fruit and fibre and low in fat earlier in life would reduce the risk of ever getting breast cancer.
