Estimated intake of vitamin D and its interaction with vitamin A on lung cancer risk among smokers

Abstract

Data are very limited on vitamin D and lung cancer prevention in high-risk populations. The authors investigated whether estimated vitamin D intake was associated with lung cancer risk and whether effect modification by vitamin A existed among current/former heavy smokers and workers with occupational exposure to asbestos. A case-cohort study selected 749 incident lung cancers and 679 noncases from the Carotene and Retinol Efficacy Trial (CARET), 1988-2005. The active intervention was supplementation of 30 mg β-carotene + 25,000 IU retinyl palmitate/day. Baseline total intake including both diet (from food frequency questionnaire) and personal supplements (from brand names linked to the labeled potencies) was assessed. Hazard ratios (HRs) were estimated by Cox proportional hazard models. No significant association of total vitamin D intake with lung cancer was observed overall. However, total vitamin D intake ≥600 versus <200 IU/day was associated with a lower risk of non-small cell lung cancer among former smokers [HR = 0.36, 95% confidence interval (CI) = 0.13-0.96]. Total vitamin D intake ≥400 versus <400 IU/day was associated with a lower risk of total lung cancer among participants who received the CARET active intervention (HR = 0.56, 95% CI = 0.32-0.99) and among those who had total vitamin A intake ≥1,500 μg/day retinol activity equivalent (RAE; HR = 0.46, 95% CI = 0.23-0.91). The beneficial associations were attenuated among those who did not receive the CARET active intervention or who had total vitamin A intake <1,500 μg/day RAE (p-interaction = 0.02 for current smokers). Our observation suggests that vitamin A may assist vitamin D in preventing lung cancer among smokers. What's new? Data are limited on vitamin D and lung cancer prevention in high-risk populations. Vitamin A (retinol) plays important roles in cell growth, cell differentiation, and the vitamin D signaling axis, and it is unknown whether high-dose vitamin A assists or counteracts association of vitamin D with lung cancer among smokers. This study demonstrated inverse associations of estimated vitamin D intake with lung cancer risk among smokers ingesting higher levels of vitamin A or receiving high-dose retinol+β- carotene supplementation. This is the first study investigating the role of vitamin A in supraphysiologic dose in lung cancer prevention in relation to vitamin D. © 2014 UICC.