Carotenoids, vitamin A, and their association with the metabolic syndrome: a systematic review and meta-analysis

Nutr Rev. 2019 Jan 1;77(1):32-45. doi: 10.1093/nutrit/nuy044.


Context: Modifiable factors that reduce the burden of the metabolic syndrome (MetS), particularly plant-derived biomarkers, have been a recent focus of rising interest.

Objective: This systematic review and meta-analysis, which follows PRISMA guidelines, evaluates evidence from a period of 20 years that links vitamin A and carotenoids with the occurrence of MetS and following the PRISMA guidelines.

Data sources: PubMed and Cochrane databases (January 1997 through March 2017) were systematically assessed for studies, including case-control, cross-sectional, and cohort studies, that evaluated the associations of MetS with carotenoids and retinyl esters and retinol (vitamin A).

Data extraction: Key measures of associations were harmonized into odds ratios (ORs) and 95% confidence intervals (95%CI) of MetS per 1 standard deviation (SD) of exposure using forest plots and random effects models that pooled data points from 11 cross-sectional studies. Begg's funnel and harvest plots were constructed.

Results: An inverse association between total carotenoids and MetS was found [ORpooled, 0.66; 95%CI, 0.56-0.78; 1 SD ∼ 0.82 µmol/L; n = 5 studies]. This association was the strongest for β-carotene, followed by α-carotene and β-crypotoxanthin. No association was detected between retinol and MetS (ORpooled, 1.00; 95%CI, 0.88-1.13; 1 SD ∼ 2.14 µmol/L; n = 6 studies). Publication bias was absent, and harvest plots indicated consistency upon replication for β-carotene and total carotenoid exposures.

Conclusions: This review and meta-analysis suggests that, unlike retinol, total and individual carotenoids were inversely related to MetS.

Publication types

  • Meta-Analysis
  • Research Support, N.I.H., Intramural
  • Systematic Review

MeSH terms

  • Carotenoids / administration & dosage*
  • Case-Control Studies
  • Cohort Studies
  • Cross-Sectional Studies
  • Humans
  • Metabolic Syndrome / epidemiology*


  • Carotenoids