Does Vitamin D Supplementation Modulate Metabolic Risk Factors of Cardiovascular Disease? A Systematic Review and Meta-Analysis of Clinical Trials

BackgroundVitamin D supplementation has been investigated for potential associations with cardiometabolic risk factors related to cardiovascular disease (CVD); however, findings from randomized controlled trials (RCTs) remain inconsistent. This meta-analysis aimed to assess the effects of vitamin D supplementation on cardiometabolic risk factors--including lipid profile, blood pressure, and glycaemic parameters--and to explore whether age and baseline serum vitamin D concentrations modify these associations. Research Design and MethodsWe conducted a systematic review and meta-analysis of RCTs comparing oral vitamin D supplementation with placebo in adults. PubMed, the Cochrane Library, and ClinicalTrials.gov. Risk of bias was evaluated using the Cochrane tool, and pooled effect sizes with 95% confidence intervals (CIs) were calculated using random-effects models. Results14,051 abstracts were retrieved, of which 45 were used for data analysis. Vitamin D supplementation reduced low-density lipoprotein cholesterol (LDL-C) by 0.136 mmol/L (95%CI: -0.215, -0.56), systolic blood pressure by 2.79 mm Hg (95% CI: -4.648, -0.938), fasting blood glucose by -0.11 (95%CI:-0.185, -0.036), and hemoglobin A1c by 0.164% (95%CI: -0.322, -0.006) compared with placebo. Subgroup analyses revealed reductions in SBP and LDL cholesterol among participants aged [&ge;]55 years and reductions in fasting blood glucose in participants with age < 55 years. While favourable effects on fasting blood glucose and hemoglobin A1c were observed with a baseline blood level of vitamin D of concentrations (<50 nmol/L). ConclusionsVitamin D supplementation may be associated with modest modifications in selected cardiometabolic risk factors; including systolic blood pressure, LDL-cholesterol, fasting blood glucose, and hemoglobin A1c. Age and baseline vitamin D status appear to modulate these effects. The clinical relevance of these modest effects remains uncertain. Well-designed RCTs with standardized protocols are required to clarify potential effect modification by age and baseline vitamin D status. Trial RegistrationPROSPERO (CRD42020165293) FundingThis research received funding from the Hashemite University, P.O. Box 330127, Zarqa 13133, Jordan