For years data on the relationship between dietary fat and breast cancer have left scientists and the public puzzled, but the latest study from Brigham and Women’s Hospital (BWH) provides more compelling evidence for young women to replace their intake of animal fats with vegetable fats. In contrast to earlier work in this area, the researchers looked specifically at the diets of women during their premenopausal years. The study, published in the July 16 issue of the Journal of the National Cancer Institute, found that diets high in animal fats – not vegetable fats – may influence a woman’s risk of breast cancer.
“Overall, we observed that there was a higher risk of breast cancer among women who ate foods rich in animal fat, such as red meat, cheese, ice cream, and butter during their 20s, 30s, and 40s,” said Eunyoung Cho, BWH researcher and instructor in medicine at Harvard Medical School.
In the past, several international comparisons have suggested that the Western diet, higher in animal fat, may be associated with higher rates of breast cancer. However, the most current literature disputes this claim. A recent pooled analysis, combining data from 13 different studies, found no apparent link. Cho said her investigation may point to a possible explanation for the discrepancies: the age at which women are consuming foods high in animal fats.
“Considering the causes of this disease vary depending on menopausal status, the relation between dietary fat intake and breast cancer risk may be different in younger women, a group that hasn’t been studied previously,” noted Cho.
According to the World Health Organization, more than 1.2 million people will be diagnosed with breast cancer this year. It is the second leading cause of cancer deaths in women today.
Among the 90,655 women who were studied – ages 26 to 46 when enrolled – the researchers documented and confirmed 714 cases of invasive breast cancer over eight years. When comparing women who consumed the greatest levels of fat to those women in the lowest fat intake category, the research team found that diets highest in animal fats were associated with a 33 percent greater risk of breast cancer. The correlation was strongest for red meat and high-fat dairy foods. The researchers documented no strong association between total fat intake, polyunsaturated fats, and vegetable fat and the risk of breast cancer.
“In an area of breast cancer research that has yielded often starkly different findings, we have illustrated that there may be stronger support for lowering overall animal fat intake, especially during a woman’s early adult life,” said Cho. “We have long known that replacing animal fats with nonhydrogenated vegetable oils will reduce risk of heart disease. Now, more women may be more encouraged to adopt a healthy diet earlier to prevent breast cancer.”