Background. Actinic keratoses are premalignant lesions and are a sensitive and important manifestation of sun-induced skin damage. Studies in animals have shown that dietary fat influences the incidence of sun-induced skin cancer, but the effect of diet on the incidence of actinic keratosis in humans is not known. Methods. We randomly assigned 76 patients with non- melanoma skin cancer either to continue their usual diet (control group) or to eat a diet with 20 percent of total caloric intake as fat (dietary- intervention group). For 24 months, the patients were examined for the presence of new actinic keratoses by physicians unaware of their assigned diets. Results. At base line, the mean (±SD) percentage of caloric intake as fat was 40±4 percent in the control group and 39±3 percent in the dietary- intervention group. After 4 months of dietary therapy the percentage of calories as fat had decreased to 21 percent in the dietary-intervention group, and it remained below this level throughout the 24-month study period. The percentage of calories as fat in the control group did not fall below 36 percent at any time. The cumulative number of new actinic keratoses per patient from months 4 through 24 was 10±13 in the control group and 3±7 in the dietary-intervention group (P = 0.001). Conclusions. In patients with a history of nonmelanoma skin cancer, a low-fat diet reduces the incidence of actinic keratosis.
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