# The Effect of Vitamin D Supplementation on Clinical and Laboratory Biomarkers in Patients with Rheumatoid Arthritis: A Systematic Review and Meta-Analysis of Randomised Controlled Trials

## TL;DR

This study finds that vitamin D supplements improve certain health markers in rheumatoid arthritis patients, but results vary across studies.

## Contribution

A meta-analysis showing vitamin D supplementation significantly improves specific biomarkers in rheumatoid arthritis patients.

## Key findings

- Vitamin D improved visual analog scale scores and reduced CRP levels in RA patients.
- Supplementation significantly increased serum vitamin D levels compared to controls.
- High heterogeneity was observed across studies for most outcomes.

## Abstract

Rheumatoid arthritis (RA) is recognised as an inflammatory condition. Evidence indicates that vitamin D modulates inflammation by influencing diverse immune cells. The purpose of this systematic review and meta-analysis was to assess the effectiveness of vitamin D as a supplement for RA in comparison to a control group.

We searched PubMed, Embase, Scopus, and Web of Science databases through March 2025 using targeted search terms. Our inclusion criteria encompassed clinical studies that enrolled RA patients and compared vitamin D supplementation against either placebo or standard care protocols. The results from the chosen studies were reported as Standardised mean differences (SMD) using random effect model with a 95% confidence interval.

Vitamin D supplementation resulted in a significant improvement in the VAS [SMD = −1.54, 95% CI (−2.53, −0.55), P = 0.002], serum vitamin D level [SMD = 1.52, 95% CI (0.86, 2.17), P = 0.001] and CRP [SMD = −0.88, 95% CI (−1.31, −0.44), P =0.001] but not in other outcomes. There was considerable heterogeneity among the studies for VAS (I2 = 97.4%, P = 0.001), DAS28 (I2 = 89.1%, P = 0.001), serum vitamin D Levels (I2 = 94.7%, P = 0.001), CRP (I2 = 84.1%, P = 0.001), and ESR (I2 = 84.1%, P = 0.001).

The intervention groups receiving vitamin D supplementation showed statistically significant improvements in serum vitamin D levels, visual analog scale VAS scores, and CRP levels compared to control groups among RA patients.