TUESDAY, Jan. 11, 2005 (HealthDayNews) -- A survey of a quarter of a million European women found that eating fruits and vegetables did not protect against breast cancer.
The findings seem to fly in the face of previously published research.
"It was really surprising to me. I was kind of speechless," said Bridget Bennett, an oncology nutritionist at Beth Israel Cancer Center in New York City.
Dr. John Cole, section head of hematology/oncology at the Ochsner Clinic Foundation in New Orleans, added, "It certainly contradicts what many people have said and preached over the years."
But both Bennett and Cole pointed out that there are still numerous reasons to include plenty of fruits and vegetables in your diet.
"There's so much good information on fruits and vegetables in preventing other types of cancer, heart disease, diabetes, obesity," Bennett said. "We need to keep this in perspective."
The new findings appear in the Jan. 12 issue of the Journal of the American Medical Association.
Many previous studies had shown that eating fruits and vegetables decreased the risk of breast cancer. This made biological sense, the new study authors stated, because many fruits and vegetables have high amounts of fiber, antioxidant vitamins and minerals, and other compounds thought to protect against cancer.
The current study looked at 285,526 women, 25 to 70 years old, from eight European countries. Each participant was asked to complete a questionnaire on diet at the beginning of the study and then were followed for a median of 5.4 years.
"Our study is the largest on-going study on nutrition and cancer in Europe with a large variation in intake of fruit and vegetables," said two of the study authors, Dr. Petra Peeters and Carla van Gils of University Medical Center in Utrecht in the Netherlands. "Furthermore, this study is famous for its calibration study, by which we can measure the usual consumption more precisely."
During that follow-up period, 3,659 invasive breast cancer cases were reported, but there was no association between fruit and vegetable intake and risk for breast cancer. Nor were there any associations for six specific subgroups of vegetables. This lack of an association was seen in almost all the countries involved.
The authors did not rule out other possibilities. "We can not exclude the possibility that protective effects may be observed for the specific constituents or in specific subgroups of women, such as those with a family history of breast cancer or estrogen receptor positive breast tumours," Peeters and van Gils said.
One drawback to the study, which the authors acknowledged, was the relatively short follow-up period. "That's a fairly short follow-up time," Bennett said. "You see a positive effect when you do it for a long time."
Overall, though, the study was a strong one, Cole said. "To me, the take-home message is not that fruits and vegetables are bad for you in any way, shape or form, but that breast cancer is a very complicated process and that the role of fruits and vegetables in the prevention of breast cancer is one that certainly is not straightforward or easy to discern."
"Fruits and vegetables, by themselves, probably have a relatively limited impact, but we also have to keep in mind that any type of dietary measure is very difficult to look at," he continued. "I would certainly hope that this doesn't dissuade people from thinking fruits and vegetables are important."
As Peeters and van Gils noted, "Although the findings for fruit and vegetable consumption and breast cancer risk may be disappointing, there are indications that it may be protective for developing stomach cancer, esophageal cancer, head and neck tumors and possibly colorectal and lung tumors."
They added, "Furthermore, fruit and vegetable consumption has been shown to lower blood pressure and the risk of cardiovascular disease, therefore there are enough reasons to keep eating lots of fruit and vegetables."
The American Cancer Society has more on breast cancer.