Evidence mapPaperPMID 40813680Full record

ReviewNutrition & metabolism2025

Effects of vitamin D supplementation on metabolic parameters, anthropometric measures, and diabetes risk in patients with prediabetes: an umbrella review of meta-analyses of randomized controlled trials.

Roghayeh Molani-Gol, Maryam Rafraf, Sara Safari

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In one paragraph

Review in Nutrition & metabolism, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 4 papers.

0numbers the graph read from it
0cells of the map it votes in
4citing papers in PubMed
field-weighted citation impact
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

4 citing papers in PubMed.

  1. Article
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  4. Observational
4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

3 authors.

Roghayeh Molani-GolStudent Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran.
Maryam RafrafNutrition Research Center, Department of Community Nutrition, Faculty of Nutrition and Food Science, Tabriz University of Medical Sciences, Tabriz, Iran. rafrafm@tbzmed.ac.ir.
Sara SafariStudent Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran.

Funding

Iran National Science Foundation 4030940Tabriz University of Medical Sciences 72938
6 · The paper itself

Abstract

backgroundThe prevalence of prediabetes and, consequently, type 2 diabetes is increasing around the world. Previous meta-analyses reported controversial findings regarding the association between vitamin D supplementation with glycemic control and diabetes risk. This comprehensive meta-analysis summarized existing research to provide an estimate of the impact of vitamin D supplementation on metabolic parameters and diabetes risk in individuals with prediabetes.

methodA comprehensive systematic search was conducted across the Web of Science, Scopus, PubMed, and Cochrane databases, and Google Scholar using relevant keywords until 22 July 2025. The AMSTAR2 scale was used to evaluate the methodological quality of the included articles. Moreover, the certainty of the evidence was assessed using the GRADE tool. Stata 17 software was used for data analysis.

resultsFourteen meta-analyses comprising 31 randomized controlled trials (RCTs) of 3856 prediabetic patients were included in this review. Combining the findings of RCTs revealed that vitamin D supplementation significantly reduced the levels of fasting blood sugar (WMD= -0.377 mg/dl, 95% CI (-0.589, -0.165), p < 0.001), insulin (WMD = -0.174 µU/mL, 95% CI (-0.274, 0.074), p < 0.001), hemoglobin A1c (WMD = -0.479%, 95% CI (-0.714, -0.245), p < 0.001), and serum triglyceride (TG) (WMD = -0.385 mg/dl, 95% CI (-0.622, -0.147), p = 0.002) in comparison with the control group. The effects of vitamin D on insulin resistance by homeostasis model assessment, 2-hour oral glucose tolerance test plasma glucose, homeostasis model assessment of β-cell function, body mass index, and diabetes risk of participants were not significant.

conclusionThe findings of this umbrella review suggested that vitamin D supplementation could help to improve some glycemic indices and TG levels. However, due to discrepancies among the results, more well-designed RCTs are warranted to confirm and clarify the impacts of vitamin D supplementation in prediabetic patients. CLINICAL TRIAL NUMBER: Not applicable.

Indexed as

Diabetes riskMeta-analysisPrediabetesSupplementationVitamin D

Identifiers

PMID40813680
PMCPMC12351829

What Socratic holds

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Registered trials

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the Socratic graph.