Intake of selected foods and nutrients and breast cancer risk: an age- and menopause-specific analysis

The relationship between selected foods and nutrients and breast cancer risk was investigated in strata of age and menopausal status using data from a case-control study on breast cancer conducted between June 1991 and April 1994 in six Italian areas. Cases were 2,569 women with histologically confirmed incident breast cancer admitted to the major teaching and general hospitals of the study areas; controls were 2,588 women with no history of cancer admitted to hospitals in the same catchment area as cases for acute, nonneoplastic, nongynecological conditions unrelated to hormonal or digestive tract diseases or to long-term modifications of diet. Dietary habits were investigated using a validated food frequency questionnaire, including 78 foods or food groups. Among food groups, bread was directly and significantly related to breast cancer risk in older women and, consequently, in postmenopause, whereas the protection conferred by fish consumption was stronger in postmenopause and that exerted by raw vegetables was stronger in premenopause. Among nutrients, unsaturated fatty acids were inversely related to breast cancer risk, the association being stronger in postmenopausal and elderly women. The pattern was similar for total fats. For starch, available carbohydrates, and total proteins, no heterogeneity emerged across strata of age and menopausal status. Among micronutrients, protection diminished with increasing age for beta-carotene and calcium, whereas no heterogeneity emerged for vitamin E. Thus this age-specific analysis of the largest investigation to date on diet and breast cancer did not show any consistent pattern of breast cancer risk in relation to selected dietary factors across strata of age and menopausal status.