Open AccessBlood concentrations of carotenoids and retinol and lung cancer risk: an update of the WCRF – AICR systematic review of published prospective studies
Author(s) -
Abar Leila,
Vieira Ana Rita,
Aune Dagfinn,
Stevens Christophe,
Vingeliene Snieguole,
Navarro Rosenblatt Deborah A.,
Chan Doris,
Greenwood Darren C.,
Norat Teresa
Publication year - 2016
Publication title -
cancer medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.403
H-Index - 53
ISSN - 2045-7634
DOI - 10.1002/cam4.676
Subject(s) - carotenoid , lung cancer , retinol , prospective cohort study , confidence interval , medicine , cancer , carotene , physiology , gastroenterology , endocrinology , food science , vitamin , biology
Carotenoids and retinol are considered biomarkers of fruits and vegetables intake, and are of much interest because of their anti‐inflammatory and antioxidant properties; however, there is inconsistent evidence regarding their protective effects against lung cancer. We conducted a meta‐analysis of prospective studies of blood concentrations of carotenoids and retinol, and lung cancer risk. We identified relevant prospective studies published up to December 2014 by searching the PubMed and several other databases. We calculated summary estimates of lung cancer risk for the highest compared with lowest carotenoid and retinol concentrations and dose–response meta‐analyses using random effects models. We used fractional polynomial models to assess potential nonlinear relationships. Seventeen prospective studies (18 publications) including 3603 cases and 458,434 participants were included in the meta‐analysis. Blood concentrations of α ‐carotene, β ‐carotene, total carotenoids, and retinol were significantly inversely associated with lung cancer risk or mortality. The summary relative risk were 0.66 (95% confidence interval [CI]: 0.55–0.80) per 5 μ g/100 mL of α ‐carotene (studies [ n ] = 5), 0.84 (95% CI: 0.76–0.94) per 20 μ g/100 mL of β ‐carotene ( n = 9), 0.66 (95% CI: 0.54–0.81) per 100 μ g/100 mL of total carotenoids ( n = 4), and 0.81 (95% CI: 0.73–0.90) per 70 μ g/100 mL of retinol ( n = 8). In stratified analysis by sex, the significant inverse associations for β ‐carotene and retinol were observed only in men and not in women. Nonlinear associations were observed for β ‐carotene, β ‐cryptoxanthin, and lycopene, with stronger associations observed at lower concentrations. There were not enough data to conduct stratified analyses by smoking. In conclusion, higher blood concentrations of several carotenoids and retinol are associated with reduced lung cancer risk. Further studies in never and former smokers are needed to rule out confounding by smoking.