Preventing breast cancer in postmenopausal women by achievable diet modification: a missed opportunity in public health policy.

The Diet Modification trial of the Women's Health Initiative studies was reported to be inconclusive as the overall risk reduction was not statistically significant at the 0.05 level. By our calculation, the trial's demonstrated risk reduction at average adherence to a simple diet modification translates into avoiding 7.3% invasive breast cancers in post-menopausal women in the USA. The trial also demonstrated a clear dose response between diet modification and risk reduction, meaning a higher percentage of breast cancers can be avoided among women whose diet modification was better than average. Yet, the DM trial findings as reported and interpreted in public sent the message to post-menopausal women that reducing the fat intake does not reduce the risk of breast cancer. Clearly, a valuable opportunity to affect public health policy was missed because the contextual significance and policy implications of the findings were ignored.