Caffeine ingestion and breast cancer. A negative correlation.

The potential association of breast cancer and caffeine intake was examined using international aggregate data. Death rates from breast cancer were correlated with caffeine ingestion from tea and coffee sources in 44 countries. By using multiple regression analysis, the authors demonstrated that 85% of the international variation in breast cancer rates is associated with variations in fat intake. When this is accounted for, the partial correlation of breast cancer rates with caffeine intake is negative (and significant at P less than 0.05). When the data are weighted by populations in each country, the negative partial correlation of caffeine with breast cancer disappears, but the strong positive association with fat intake remains unchanged. Although there have been suggestions that caffeine exacerbates fibrocystic disease of the breast and may be a causal factor in breast cancer, data from this study do not support a positive association between caffeine intake and subsequent development of breast cancer.