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 issures 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 reproductivefactors and risk factors women can't control, such as family history. It is the most common form of cancer in women and the second leading cause of cancer deaths in women today.
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 midlife and later was associated with risk of breast cancer. Similarly, the data showed no reduced risk amoung 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."