Case-control study of malignant melanoma in Washington State. II. Diet, alcohol, and obesity.

Intakes of vitamin A, dietary antioxidants, and other dietary components were examined for their relation to the risk of malignant melanoma among 234 cases and 248 controls in three counties of western Washington State. Cases were drawn from persons diagnosed with melanoma between 1984 and 1987 and identified through a Seattle-Puget Sound cancer registry. Population controls were identified through random digit dialing and were randomly selected, stratified by age, sex, and county. Subjects completed a telephone interview and a mailed food frequency questionnaire asking for information on diet, demographic factors, and factors known to be associated with melanoma. Subjects were asked to estimate their food intake 7 years prior to diagnosis for cases and during a comparable time period for controls. Among data on 16 nutrients calculated from reported food intake, one significant finding emerged: Vitamin E obtained from food was inversely related to risk of melanoma (for highest quartile vs. lowest quartile, age-, education-, and energy intake-adjusted odds ratio (OR) = 0.34, 95% confidence interval (CI) 0.16-0.72; p for trend = 0.01). When intake of nutrients from food plus vitamin and mineral supplements was considered, zinc from food and supplements was associated with a decreased risk of melanoma (for highest quartile vs. lowest quartile, adjusted OR = 0.46, 95% CI 0.24-0.91; p for trend = 0.01). There was no evidence that vitamin A, preformed retinol, or carotenoids were associated with a decreased risk of melanoma or that alcohol or polyunsaturated fats were associated with an increased risk. Body mass index (weight (kg)/height (m)2) was significantly related to melanoma risk; cases were more obese than controls (for highest quartile vs. lowest quartile, age-, sex-, and education-adjusted OR = 1.90, 95% CI 1.10-3.27; p for trend = 0.02). These results provide limited support for the hypothesis that antioxidants such as vitamin E or cofactors in protection from oxidative damage such as zinc may be protective for melanoma, and they suggest that obesity should be measured in future studies of melanoma.