Food intake, dietary patterns, and actinic keratoses of the skin: a longitudinal study.

Background: Actinic keratoses (AKs) are premalignant actinic tumors of the skin. Evaluation of the role of diet in their development is lacking.
Objective: The objective was to determine whether intake of certain food groups or dietary patterns retard the occurrence of AKs over a 4.5-y period.
Design: In a community-based study of skin cancer in Queensland, Australia, food intake of 1119 adults was assessed in 1992, 1994, and 1996 by using a validated food-frequency questionnaire. Dermatologists counted prevalent AKs during full-body skin examinations in 1992 and 1996. The relative ratio (RR) of AK counts in 1996 relative to 1992 was compared across increasing intakes of 26 food groups, and for 3 dietary patterns identified by principal components analysis, with the use of generalized linear models with negative binomial distribution, allowing for repeated measures. All analyses were adjusted for confounding factors, including skin color and sun exposure indexes.
Results: AK acquisition decreased by 28% (RR: 0.72; 95% CI: 0.55, 0.95) among the highest consumers of oily fish (average of one serving every 5 d) compared with those with minimal intake. Similarly, the rate of acquisition of AKs was reduced by 27% (RR: 0.73; 95% CI: 0.54, 0.99) in those with the highest consumption of wine (average of half a glass a day in this study population). There was no consistent association of dietary pattern with AK acquisition.
Conclusion: Moderate intake of oily fish and of wine may decrease the acquisition of AKs and thus complement sun protection measures in the control of actinic skin tumors.