While for years it has been hypothesized that meat consumption is associated with breast cancer, a new study from Brigham and Women's Hospital (BWH) provides compelling evidence that diets high in animal protein may not be significantly associated with breast cancer risk. This finding is the latest result from the landmark BWH-based Nurses' Health Study. It was published in the International Journal of Cancer.

"Overall, we observed that there was no difference in risk of breast cancer, comparing women who consumed the highest and lowest amounts of several types of meat," said Michelle Holmes, MD, DrPH, of BWH, lead author of the study.

Several international comparisons have associated intake of meat with higher breast cancer rates and mortality. However, other differences between countries, such as reproductive patterns and exercise, could possibly explain the variations in breast cancer risk. This most recent finding may pave the way for a better understanding of the dietary issues surrounding breast cancer, Holmes said.

According to the National Cancer Institute, up to 35 percent of cancers are related to dietary habits. Unlike nutritional choices, breast cancer is largely influenced by reproductive factors and risk factors women can't control, such as family history.

After following 88,647 women for 18 years, the largest and longest individual study of its kind to date, Holmes and her co-investigators found no evidence that intake of meat during mid-life and later was associated with risk of breast cancer. Similarly, the data showed no reduced risk among women who were vegetarians. In fact, vegetarians had a slightly increased-though not statistically significant-risk of breast cancer. The results did not change when controlling for a variety of factors including mammogram screening, multivitamin use, food preparation and sugar intake.

"Contrary to popular belief, we found no positive association between risk of breast cancer and meat consumption," said Holmes, also of Harvard Medical School. "Although more research is required, this finding may bring us one step closer toward defining what dietary habits, if any, are helpful in lowering breast cancer risk."

SOURCES:
International Journal of Cancer, online edition, January 9, 2003
Brigham and Women's Hospital (http://www.bwh.partners.org)