Eating large quantities of red meat and high-fat dairy foods is associated with an increased risk of breast cancer, concludes a prospective study, one of the first to support the theory.
The findings came from an analysis of the relation between dietary fat intake and breast cancer risk among premenopausal women, rather than postmenopausal as often used before. Breast cancer usually appears after menopause but factors from a woman's early lifestyle may be important.
The researchers from Brigham and Women's Hospital and Harvard Medical School studied more than 90,000 women, aged 26 to 46 years at baseline, from the Nurses Health study to assess fat intake using a food-frequency questionnaire at baseline in 1991 and again in 1995. In the group of 714 women who developed breast cancer, those in the highest quintile of fat intake were 33 per cent more likely to develop the disease than those in the lowest quintile.
The increase was associated with intake of animal fat but not vegetable fat, added the team. Women with highest risk of breast cancer consumed on average 23 per cent of their calories from animal fat, against only 12 per cent in the lowest risk group.
It has long been suspected that diet is closely related to risk for breast cancer. The much lower quantity of animal fats in the Asian diet is thought to offer an explanation for Asian women's lower incidence of breast cancer.