Effect of Vitamin D Supplementation on Human Gut Microbiota: A Systematic Review of Randomized Controlled Trials.
Level 1 - systematic review of randomized trials
Systematic review of randomized controlled trials
PubMed 40673989 · doi:10.1093/nutrit/nuaf120
What was done
A systematic review (following PRISMA, PROSPERO CRD42024628080) searching MEDLINE, Web of Science, Scopus, and the Cochrane Library (2015 to 2024) evaluated the effects of vitamin D supplementation on gut microbiota assessed via high-throughput sequencing. It included 14 randomized controlled trials totaling 1,458 participants with varying health statuses and supplementation regimens.
What was found
The abstract reports qualitative narrative findings without pooled numeric effect sizes or confidence intervals. Vitamin D supplementation was reported to increase taxa associated with anti-inflammatory properties (such as Bifidobacterium and Lactobacillus), increase the Bacteroidetes to Firmicutes ratio, and alter microbial biomarkers such as calprotectin and trimethylamine N-oxide. Alpha and beta diversity improvements varied based on dosage, duration, and baseline vitamin D status.
Why it matters
This review synthesizes clinical trial evidence showing vitamin D supplementation influences human gut microbiome composition toward potentially beneficial, anti-inflammatory taxa.
Limits
The abstract reports no quantitative meta-analytic estimates or effect sizes. The included RCTs had substantial heterogeneity in study design, participant health status, baseline vitamin D levels, dosing regimens, intervention durations, and microbiome sequencing methodologies.