A case-control study of diet and benign proliferative epithelial disorders of the breast.

Benign proliferative epithelial disorders (BPED) of the breast are conditions which, although not proven precursors of breast cancer, are strongly associated with increased risk of this disease. In a case-control study conducted in Adelaide, South Australia, we investigated the association between dietary factors and risk of BPED. The study involved 383 cases of biopsy-confirmed BPED, 192 controls whose biopsy did not show epithelial proliferation, and 383 unbiopsied community controls matched to cases on age and area of residence. When cases were compared with community controls, there was little variation in the risk of BPED across levels of daily intake of energy, protein, and fat, but there was some suggestion of inverse associations with daily intake of retinol, beta-carotene, and fiber; in contrast, with biopsy controls as the comparison group, risk of BPED increased with increasing energy and fat intake but varied little with retinol, beta-carotene, and fiber intake. The results of this study provide additional evidence against roles for dietary energy and fat intake in the etiology of breast cancer. However, further studies of diet and BPED should be conducted in populations surveyed cross-sectionally for breast changes, in an attempt to limit or avoid the selection and misclassification biases to which studies of putative precursor lesions are susceptible.