Flawed research methods may mask a link between dietary fat and breast cancer

Contrary to published reports, researchers from the UK believe there is an association between high dietary fat intake and breast cancer. It just hasn’t come to light because past studies have been imprecise.

The problem is that food frequency questionnaires (FFQs) are “prone to measurement error,” Dr. Sheila Bingham, deputy director of the MRC Dunn Human Nutrition Unit in Cambridge, and colleagues suggest in the July 19th issue of The Lancet. “The degree of error associated with FFQs is considerably larger than previously estimated, which could account for the negative findings of cohort studies of diet and cancer,” they write. The UK team looked at the relation between breast cancer risk and fat intake using both a FFQ and the more detailed 7-day food diary in roughly 13,000 women between 1993 and 1997. By the year 2000, 168 incident breast cancer cases had occurred. The team matched each case patient to four healthy controls. “With food-diary estimates, the fifth quintile of saturated-fat consumption was associated with a two-fold rise in breast cancer risk compared with the first quintile,” they report. However, no association between fat intake and breast cancer was evident based on the FFQ. According to Dr. Bingham and colleagues, these “preliminary findings suggest that use of the food diary can detect relations between diet and cancer risk within a relatively homogeneous population.” The food diary, they add, “is more expensive to code for conversion into nutrients than the FFQ, but we have shown that its use is acceptable and feasible in large cohort studies.” (Source: Lancet 2003;362:212-214: Reuters Health: July 17, 2003: Oncolink)