title: A dose-response meta-analysis of dietary lutein and zeaxanthin intake in relation to risk of age-related cataract.
abstract: BACKGROUND
  Lutein and zeaxanthin are thought to have beneficial effects on protecting the lens against cataract formation, but findings from epidemiologic studies have been inconsistent. We aimed to conduct a meta-analysis of prospective cohort studies to examine the association between dietary lutein and zeaxanthin intake and risk of age-related cataract (ARC).
  
  
  METHODS
  We systematically searched MEDLINE, EMBASE, Web of Science, and Cochrane Library databases up to March 2013. Reference lists from retrieved articles were also reviewed. The adjusted relative risks (RRs) from each study were extracted to calculate a pooled estimate with its 95 % confidence interval (CI). The dose-response relationships were assessed by using generalized least-squares trend estimation.
  
  
  RESULTS
  Six prospective cohort studies were identified involving 4,416 cases and 41,999 participants. For the comparison between the highest and the lowest categories of dietary lutein and zeaxanthin intake, significant inverse association were found for nuclear cataract (RR: 0.75; 95 % CI: 0.65, 0.85), but not for cortical cataract (RR: 0.85; 95 % CI: 0.53, 1.17) and for posterior subcapsular cataract (RR: 0.77; 95 % CI: 0.40, 1.13). Dose-response analysis showed that every 300 μg/d increment in dietary lutein and zeaxanthin intake was associated with a 3 %, 1 %, or 3 % reduction in the risk of nuclear cataract (RR: 0.97; 95 % CI: 0.94, 0.99), cortical cataract (RR: 0.99; 95 % CI: 0.95, 1.02), or posterior subcapsular cataract (RR: 0.97; 95 % CI: 0.93, 1.01) respectively.
  
  
  CONCLUSIONS
  Dietary lutein and zeaxanthin intake is associated with a reduced risk of ARC, especially nuclear cataract in a dose-response manner, indicating a beneficial effect of lutein and zeaxanthin in ARC prevention.
authors.affiliation: School of Public Health, Xi'an Jiaotong University College of medicine, 76 Yanta West Road, Xi'an, Shaanxi, 710061, China.
authors.forename: Le
authors.initials: L
authors.lastname: Ma
authors.forename: Zhen-xuan
authors.initials: ZX
authors.lastname: Hao
authors.forename: Ru-ru
authors.initials: RR
authors.lastname: Liu
authors.forename: Rong-bin
authors.initials: RB
authors.lastname: Yu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Shi
authors.forename: Jian-ping
authors.initials: JP
authors.lastname: Pan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D002386:Cataract / Q000453:epidemiology*; D015331:Cohort Studies; D016208:Databases, Factual; D004032:Diet; D004305:Dose-Response Relationship, Drug; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D014975:Lutein / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D024341:Xanthophylls / Q000008:administration & dosage*; D065146:Zeaxanthins
chemical_list: D024341:Xanthophylls; D065146:Zeaxanthins; D014975:Lutein