Background: The incidence of non-melanoma skin cancer (NMSC) in Britain has been increasing over the past 50 years. This has been attributed to increased sunlight exposure, but the increased exposure has not been quantified, and in any case, much of the increase in incidence has occurred in those parts of the body, mainly the head and neck, that have always been exposed to sunlight. There is evidence that increased dietary fat intake has increased the sensitivity of the skin to the carcinogenic potential of sunlight, particularly in causing squamous cell tumours.
Objectives: To test the hypothesis that increased dietary fat is a risk factor for NMSC.
Methods: The hypothesis was tested in a nested case-control study. The cohort was that recruited for the EPIC-Norfolk study, the cases (n = 123) were subjects with NMSC diagnosed since recruitment, and the controls (n = 247) were randomly selected from the same cohort. The effect of diet on the incidence of NMSC was assessed using conditional logistic regression.
Results: As there were so few cases (14) with squamous cell tumours they were excluded from the statistical analyses. Fat intake was not found to be a risk factor: the unadjusted odds ratio (OR) of basal cell cases vs. controls was estimated as 0.860/(25.5 g total fat daily) with 95% confidence interval (CI) (0.663, 1.116), P = 0.25. Exploratory analyses of diet components and food groups found a protective effect of increased vitamin E consumption: unadjusted OR of basal cell cases vs. controls was 0.731/(3.06 mg vitamin E daily), 95% CI (0.564, 0.948), P = 0.015. Adjusted analyses gave broadly similar results.
Conclusions: The potentiating factor remains unknown: if dietary fat has any effect on NMSC, it is not apparent when basal cell tumours are considered. There was no evidence of a generalized healthy eating effect. A substantial protective effect was found in exploratory analyses for the fat soluble antioxidant vitamin E.