A study published in the Journal of the National Cancer Institute shows that eating a diet high in fat may increase the risk for three common types of breast cancer.
In a large European study evaluating 337,327 women in 10 countries over 11 years, researchers found that women who ate the most saturated fat were about 30% more likely to develop breast cancer than those who ate the least.
In the study, women answered questions about their fat intake and other habits that could affect risk, including smoking, pregnancy history, and their body mass index. To correct for measurement errors in the diet questionnaire, the researchers interviewed a random sample of 8% of the women, asking for a 24-hr dietary recall. After an average follow up of 11.5 years, 10,062 women were diagnosed with breast cancer.
The researchers found that a high intake of total fat and saturated fat was linked to an increased risk of breast cancer subtypes known as estrogen receptor-positive (ER-positive) and progesterone receptor-positive (PR-positive). High-fat diets also were tied to a raised risk of developing HER2-negative breast cancer. Cancers that are ER- or PR-positive grow in response to those hormones. Cancers that are HER2-negative have tested negative for the presence of a protein, HER2, which promotes cancer cell growth.
Women in the group eating the most saturated fat averaged 48 g/day, compared to 15 g/day in the group eating the least.