Vitamin D and Reduced Body Mass Index

Research synthesisLow evidenceSmall effect3 studies · 0 beneficial · 3 neutral · 0 harmful

Across 3 studies, 0 reported beneficial effects, 3 reported neutral effects, and 1 of 3 reached statistical significance. The predominant effect direction is neutral with a small effect size. The available evidence does not support Vitamin D supplementation for reducing BMI, though one observational systematic review in women with PCOS found an inverse association between serum vitamin D levels and BMI.

Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests. Doses were not consistently reported across studies, limiting dose-response conclusions. One study was observational (women with PCOS), which may not imply causation.

Generated May 13, 2026

Safety in these studies

Overall tolerabilityReported
Vitamin D supplementation shows variable effects, it should not be considered a stand-alone therapy for PCOS.
from: The Association Between Vitamin D and Polycystic Ovary Syndrome (PCOS) in Women: A Systema

3 of 3 papersPopulation:

The Association Between Vitamin D and Polycystic Ovary Syndrome (PCOS) in Women: A Systematic Review.
- 2026-03-19
- Systematic Review · n = 1,063
- Nutrients 18(6)
- - Batoul Jaafar
  - Nour Chami
  - Mohamad Tlais
  - Maria Matar
  - Nazih Obeid
  - Nadia Taha
  - Karim El Haddad
  - Jessica Abou Chaaya
  - Sami Azar
- PubMed: 41901143
- DOI: 10.3390/nu18060968
7 Insights on
- Reduced Body Mass Index
- High evidence
- Rigorous Journal
- Clinical
Observational studies demonstrated inverse associations between serum 25(OH)D levels and insulin resistance, body mass index (BMI), and leptin, but not with total testosterone.
Effect
Neutral
Effect size
Small
Significant
Yes
Can vitamin D supplementation affect cardiometabolic factors in children and adolescence with overweight and obesity? A grade-assessed systematic review and meta-analysis of randomized controlled trials.
- 2025-11-25
- Meta-Analysis · n = 440
- BMC pediatrics 25(1)
- - Amir Hossein Faghfouri
  - Mahsa Mahmoudinezhad
  - Pedram Pam
  - Sanaz Barazandeh
  - Fatemeh Faramarzi
  - Yousef Mohammadpour
  - Vali Musazadeh
  - Shahsanam Gheibi
- PubMed: 41291584
- DOI: 10.1186/s12887-025-05795-2
9 Insights on
- Reduced Body Mass Index
- High evidence
- Children
vitamin D supplementation no significantly improved BMI, BMI-Z
Effect
Neutral
Effect size
Small
Significant
No
The effect of vitamin D2 on lipid profile, anthropometric indices, blood pressure, and inflammatory and glycemic biomarkers in humans: A systematic review and meta-analysis of randomized controlled trials.
- 2024-10
- Meta-Analysis
- Prostaglandins & other lipid mediators 174
- - Zhihong Zhou
  - Jiyuan Liu
  - Hui Zhang
  - Kousalya Prabahar
  - Benjamin Hernández-Wolters
  - Yuanhong Yuan
- PubMed: 39154789
- DOI: 10.1016/j.prostaglandins.2024.106883
12 Insights on
- Reduced Body Mass Index
- High evidence
No statistically significant association was observed between vitamin D2 administration and BMI
Effect
Neutral
Effect size
Small
Significant
No

Vitamin D and Reduced Body Mass Index

The Association Between Vitamin D and Polycystic Ovary Syndrome (PCOS) in Women: A Systematic Review.

Can vitamin D supplementation affect cardiometabolic factors in children and adolescence with overweight and obesity? A grade-assessed systematic review and meta-analysis of randomized controlled trials.

The effect of vitamin D2 on lipid profile, anthropometric indices, blood pressure, and inflammatory and glycemic biomarkers in humans: A systematic review and meta-analysis of randomized controlled trials.