Carotenoids supplementation and inflammation: a systematic review and meta-analysis of randomized clinical trials

The aim of this study was to perform a systematic review and meta-analysis on randomized controlled
trials investigating the effects of carotenoids on selected inflammatory parameters.
PubMed, SCOPUS, and Web of science were searched from inception until April 2021. The random-
effect model was used to analyze data and the overall effect size was computed as weighted
mean difference (WMD) and corresponding 95% of confidence interval (CI). A total of 26 trials
with 35 effect sizes were included in this meta-analysis. The results indicated significant effects of
carotenoids on C-reactive protein (CRP) (WMD: –0.54mg/L, 95% CI: –0.71, –0.37, P<0.001), and
interleukin-6 (IL-6) (WMD: –0.54 pg/mL, 95% CI: –1.01, –0.06, P¼0.025), however the effect on
tumor necrosis factor-alpha (TNF-a) was not significant (WMD: –0.97 pg/ml, 95% CI: –1.98, 0.03,
P¼0.0.059). For the individual carotenoids, astaxanthin, (WMD: –0.30 mg/L, 95% CI: –0.51, –0.09,
P¼0.005), lutein/zeaxanthin (WMD: –0.30 mg/L, 95% CI: –0.45, –0.15, P<0.001), and b-cryptoxanthin
(WMD: –0.35 mg/L, 95% CI: –0.54, –0.15, P<0.001) significantly decreased CRP level. Also,
only lycopene (WMD: –1.08 pg/ml, 95%CI: –2.03, –0.12, P¼0.027) led to a significant decrease in
IL-6. The overall results supported possible protective effects of carotenoids on inflammatory
biomarkers.