Dietary antioxidant supplements and risk of keratinocyte cancers in women: a prospective cohort study

Purpose Experimental studies suggested that antioxidants could protect against skin carcinomas. However, epidemiological studies on antioxidant supplement use in relation to basal-cell carcinoma (BCC) and squamous-cell carcinoma (SCC) risks yielded inconsistent findings, and few prospective studies have been conducted to date. We aimed to investigate the associations between antioxidant supplement intake and keratinocyte cancer (KC) risk. Methods E3N is an ongoing prospective cohort initiated in 1990 and involving 98,995 French women aged 40–65 years at recruitment. Intakes of dietary antioxidants were estimated via a validated dietary questionnaire in 1993 and self-reported antioxidant supplement use was collected in 1995. We used Cox models to compute hazard ratios (HRs) and 95% confidence intervals (CIs) adjusted for age and skin cancer risk factors. Results Over 1995–2014, 2426 BCC and 451 SCC cases were diagnosed among 63,063 women. We found positive relationships between vitamin A supplement use and KC risk (HR = 1.37, 95% CI 1.15–1.62), particularly with BCC (HR = 1.40, 95% CI 1.17–1.69); and between vitamin E supplement use and risks of both BCC (HR = 1.21, 95% CI 1.03–1.52) and SCC (HR = 1.43, 95% CI 1.03–1.99). Intake of beta-carotene supplements was associated with an increased SCC risk (HR = 1.59, 95% CI 1.00–2.54). Vitamin C supplement use was not associated with KC risk. We found similar results when considering total antioxidant intake. Conclusions Intakes of vitamin A or E supplements were associated with an increased KC risk in women. Further studies with information on doses and duration of supplement use and the ability to examine their underlying mechanisms are needed.