title: Carotenoids and the risk of developing lung cancer: a systematic review.
abstract: BACKGROUND
  Carotenoids are thought to have anti-cancer properties, but findings from population-based research have been inconsistent.
  
  
  OBJECTIVE
  We aimed to conduct a systematic review of the associations between carotenoids and lung cancer.
  
  
  METHODS
  We searched electronic databases for articles published through September 2007. Six randomized clinical trials examining the efficacy of beta-carotene supplements and 25 prospective observational studies assessing the associations between carotenoids and lung cancer were analyzed by using random-effects meta-analysis.
  
  
  RESULTS
  The pooled relative risk (RR) for the studies comparing beta-carotene supplements with placebo was 1.10 (95% confidence limits: 0.89, 1.36; P = 0.39). Among the observational studies that adjusted for smoking, the pooled RRs comparing highest and lowest categories of total carotenoid intake and of total carotenoid serum concentrations were 0.79 (0.71, 0.87; P < 0.001) and 0.70 (0.44, 1.11; P = 0.14), respectively. For beta-carotene, highest compared with lowest pooled RRs were 0.92 (0.83, 1.01; P = 0.09) for dietary intake and 0.84 (0.66, 1.07; P = 0.15) for serum concentrations. For other carotenoids, the RRs comparing highest and lowest categories of intake ranged from 0.80 for beta-cryptoxanthin to 0.89 for alpha-carotene and lutein-zeaxanthin; for serum concentrations, the RRs ranged from 0.71 for lycopene to 0.95 for lutein-zeaxanthin.
  
  
  CONCLUSIONS
  beta-Carotene supplementation is not associated with a decrease in the risk of developing lung cancer. Findings from prospective cohort studies suggest inverse associations between carotenoids and lung cancer; however, the decreases in risk are generally small and not statistically significant. These inverse associations may be the result of carotenoid measurements' function as a marker of a healthier lifestyle (higher fruit and vegetable consumption) or of residual confounding by smoking.
authors.affiliation: The Prevention and Research Center, Mercy Medical Center, Baltimore, MD, USA.
authors.forename: Lisa
authors.initials: L
authors.lastname: Gallicchio
authors.forename: Kristina
authors.initials: K
authors.lastname: Boyd
authors.forename: Genevieve
authors.initials: G
authors.lastname: Matanoski
authors.forename: Xuguang Grant
authors.initials: XG
authors.lastname: Tao
authors.forename: Liwei
authors.initials: L
authors.lastname: Chen
authors.forename: Tram K
authors.initials: TK
authors.lastname: Lam
authors.forename: Meredith
authors.initials: M
authors.lastname: Shiels
authors.forename: Edward
authors.initials: E
authors.lastname: Hammond
authors.forename: Karen A
authors.initials: KA
authors.lastname: Robinson
authors.forename: Laura E
authors.initials: LE
authors.lastname: Caulfield
authors.forename: James G
authors.initials: JG
authors.lastname: Herman
authors.forename: Eliseo
authors.initials: E
authors.lastname: Guallar
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Alberg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002338:Carotenoids / Q000008:administration & dosage* / Q000097:blood*; D004032:Diet; D019587:Dietary Supplements; D005260:Female; D005638:Fruit; D006801:Humans; D008175:Lung Neoplasms / Q000097:blood / Q000453:epidemiology* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D009752:Nutritional Status; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects; D014675:Vegetables
chemical_list: D002338:Carotenoids