FRIDAY, Jan. 25, 2013 (HealthDay News) -- Eating plenty of fruits and vegetables may lower women's risk for a tough-to-treat form of breast cancer, but it does not reduce their odds of getting breast cancer overall, a new study finds.
Specifically, the new study found lower rates of what's known as "estrogen receptor-negative breast cancer" among women who ate high amounts of fruits and vegetables.
These tumors -- which do not respond to circulating estrogen -- account for 15 percent to 20 percent of breast cancers, and have a lower survival rate than other types of breast cancer.
According to a team led by Seungyoun Jung, formerly at the department of nutrition at the Harvard School of Public Health, previous research has suggested that consuming higher amounts of fruits and vegetables might lower breast cancer risk, but there haven't been enough data to prove it.
In their new investigation, Jung's team analyzed data from 20 prior studies of women who were followed for a maximum of 11 to 20 years.
They found a statistically significant link between higher fruit and vegetable consumption and a lower risk for estrogen receptor-negative breast cancer, but not with a lower risk of estrogen receptor-positive breast cancers (those that do respond to estrogen) or for breast cancer overall.
The lower risk for estrogen receptor-negative breast cancer was mostly associated with higher intake of vegetables, Jung's team noted in a journal news release.
Two breast cancer experts responded to the findings with caution, noting that a cause-and-effect relationship is far from certain.
"It is plausible that estrogen receptor-negative breast cancer is influenced by nutritional factors," said Dr. Paolo Boffetta, director of the Institute for Translation Epidemiology at the Mount Sinai Medical Center, in New York City.
"However, eating fruits and vegetables is closely tied to environmental factors and healthy lifestyle, such as weight control, physical activity and other healthy eating habits," he noted. "Since these are so closely tied together, it is difficult to disentangle the specific effect of fruits and vegetables."
And Dr. Stephanie Bernik, chief of surgical oncology at Lenox Hill Hospital in New York City, agreed.
"The study fails to control for some bias that may occur when observing the two populations," she said. "Perhaps the women that eat well also exercise, drink little alcohol, don't smoke and eat less animal fats overall."
Still, living healthily is always a good idea, and "the study does add some evidence that a healthy lifestyle can perhaps help decrease the risk of breast cancer," Bernik said.
The study was published Jan. 24 in the Journal of the National Cancer Institute.
The American Cancer Society has more about breast cancer.