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Research Summary
Analyzed using Evidence Intelligence™

Vitamin D may not delay diabetes in women with prediabetes

Powered by the Dediabetes Evidence Intelligence™ framework

Last updated July 6, 2026

Key finding

There was no statistical significance in the incidence of diabetes in the control group as compared to the intervention group at the end of 2 years (P = 0.701).

This randomized controlled trial investigated the effects of vitamin D supplementation on women with prediabetes, finding no significant impact on diabetes incidence or related metabolic markers.

Quick read

Study at a glance

The essential study design details in one scan.

EvidenceScore™

Moderate

Study type

RCTs

Follow-up

Extended (5–20+ y)

Risk of bias

Some Concerns

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Plain-language summary

What this paper says

A plain-language read of the study’s main message and where it applies.

Study focus

This randomized controlled trial investigated the effects of vitamin D supplementation on women with prediabetes, finding no significant impact on diabetes incidence or related metabolic markers.

Clinical relevance

These findings are important for clinicians and patients as they suggest that vitamin D supplementation may not be an effective strategy for preventing type 2 diabetes in women with prediabetes. Understanding the limitations of vitamin D in this context can help guide treatment decisions and patient education.

Keep in mind

The study may have limited generalizability due to the specific population studied. The duration of the study may not have been sufficient to observe long-term effects. Potential unmeasured confounding factors could have influenced the results.

Published in

Journal Reference

Publication details and source links for this paper.

Puneet M, Shashi K, Anoop M, et al. Vitamin D Supplementation in Women with Prediabetes: A Randomized Controlled Trial. Journal of Family Medicine and Primary Care. 2021;10(8):3122-3129. doi:10.4103/jfmpc.jfmpc_311_21

View DOIView on PubMedView on PMC

Main Effects

No significant difference in the incidence of type 2 diabetes between the vitamin D and placebo groups (P = 0.701).

No statistically significant effect of vitamin D supplementation on serum HbA1c levels.

No statistically significant effect of vitamin D supplementation on serum cholesterol levels.

Evidence network

How this study fits

Understand where this research contributes within the broader evidence network.

Evidence Context

This study contributes evidence to Vitamin D supplementation and HbA1c, LDL cholesterol, type 2 diabetes mellitus.

This study contributes evidence to

Intervention

Vitamin D supplementation

Outcome

HbA1c

Evidence topic

Supplements and Nutraceuticals

Primary intervention

Vitamin D supplementation

Primary outcomes

  • HbA1c
  • LDL cholesterol
  • type 2 diabetes mellitus

Evidence topics

Supplements and NutraceuticalsDiabetes PreventionHbA1c Reduction

Primary intervention

Vitamin D supplementation

Primary outcomes

HbA1cLDL cholesteroltype 2 diabetes mellitus

Evidence relationships

Intervention and outcome relationships this study adds to the evidence network.

3
Evidence pairs
3
Relationships
3
Evidence topics
contributes_evidence

Editorial context

Why this study matters

See why this paper is useful beyond its individual results.

Evidence network role

This section describes how the study fits into the current evidence network. It does not determine whether an intervention works on its own.

Moderate contributionModerate confidenceNetwork score: 68

3

Related topics

3

Evidence pairs

1134

Related studies

High relevance in at least one topic

Why it is useful

  • Contributes to 3 evidence relationships
  • Includes primary outcome data
  • Linked to 3 direct semantic evidence topics

Topic contributions

Evidence topic

Contributes evidence

Evidence topic

Contributes evidence

Evidence topic

Contributes evidence

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Primary evidence

Evidence topic

Supplements and Nutraceuticals

matched_intervention_and_outcome

Related evidence

Evidence topic

Diabetes Prevention

Save evidence

Core evidence

Study findings

The primary outcomes reported in this study.

HbA1c

Vitamin D supplementation → HbA1c

Vitamin D supplementation → HbA1c

Evidence Intelligence™
EvidenceScore™
82
Strong
ImpactScore™
69
Positive
ConsistencyScore™
60
generally_consistent
Supporting studies: Based on 5 studies
Add to Evidence Tracker

LDL cholesterol

Vitamin D supplementation → LDL cholesterol

Vitamin D supplementation → LDL cholesterol

Evidence Intelligence™
EvidenceScore™
Moderate
Score 69 · Based on 2 studies
ImpactScore™
50
Neutral
ConsistencyScore™
100
consistent
Supporting studies: Based on 2 studies
Add to Evidence Tracker

type 2 diabetes mellitus

Vitamin D supplementation → type 2 diabetes mellitus

Vitamin D supplementation → type 2 diabetes mellitus

Evidence Intelligence™
EvidenceScore™
Moderate
Score 69 · Based on 2 studies
ImpactScore™
50
Neutral
ConsistencyScore™
100
consistent
Supporting studies: Based on 2 studies
Add to Evidence Tracker

Evidence Library

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evidence suggest

Evidence Suggest

  • Vitamin D supplementation did not significantly lower diabetes incidence over two years.
  • No impact on HbA1c levels was observed with vitamin D supplementation.
  • Cholesterol levels remained unchanged despite vitamin D intake.
who this applies

Who this applies to

  • Women diagnosed with prediabetes.
  • Individuals at risk for developing type 2 diabetes.
keep in mind

Keep in Mind

  • The findings may not apply to men or other age groups.
  • Results are specific to the supplementation dosage and duration used in the study.
  • Further research is needed to explore other potential benefits of vitamin D supplementation.
between the lines

Between the Lines

  • The study may have limited generalizability due to the specific population studied.
  • The duration of the study may not have been sufficient to observe long-term effects.
  • Potential unmeasured confounding factors could have influenced the results.

Evidence Library

Build your evidence library

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Connected Evidence

Explore related studies, evidence collections, and research questions.

Relationships organized using the Dediabetes Evidence Intelligence™ framework.

Powered by the Dediabetes Evidence Intelligence™ framework

This study contributes to evidence on Vitamin D supplementation and HbA1c, Vitamin D supplementation and Diabetes Incidence and Prevention.

Related evidence relationships

Explore in Evidence Explorer

This study contributes to the evidence on the following intervention-outcome relationships.

Questions answered by this study

Generated from the study's connected evidence using Evidence Intelligence™.

Does Vitamin D supplementation lower HbA1c?

Strong Evidence

Vitamin D supplementation may lower HbA1c.

ConsistencyScore™: Results are generally consistent across studies.

Ranked evidence signals

  1. 1

    HbA1c

    EvidenceScore™ Strong | EvidenceScore™ 81.9 | moderate positive | ConsistencyScore™ Generally Consistent | 1 study

Why this answer: This answer is based on a single supporting study.

Limitations

  • Only one supporting study is available.
1 supporting study
View Full Evidence

Does Vitamin D supplementation improve ldl cholesterol?

Moderate Evidence

Current evidence does not show a clear benefit of Vitamin D supplementation for ldl cholesterol.

ConsistencyScore™: Results are consistent across studies.

Ranked evidence signals

  1. 1

    LDL cholesterol

    EvidenceScore™ Moderate | EvidenceScore™ 69.0 | neutral | ConsistencyScore™ Consistent | 1 study

Why this answer: This answer is based on a single supporting study.

Limitations

  • Only one supporting study is available.
1 supporting study
View Full Evidence

Does Vitamin D supplementation improve type 2 diabetes mellitus?

Moderate Evidence

Current evidence does not show a clear benefit of Vitamin D supplementation for type 2 diabetes mellitus.

ConsistencyScore™: Results are consistent across studies.

Ranked evidence signals

  1. 1

    type 2 diabetes mellitus

    EvidenceScore™ Moderate | EvidenceScore™ 69.0 | neutral | ConsistencyScore™ Consistent | 1 study

Why this answer: This answer is based on a single supporting study.

Limitations

  • Only one supporting study is available.
1 supporting study
View Full Evidence
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Next steps

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Evidence topics

Follow the topics this study contributes to.

Supplements and Nutraceuticals Evidence HubDiabetes Prevention Evidence HubHbA1c Reduction Evidence Hub

Explore in Evidence Explorer

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All studies on Vitamin D supplementation and type 2 diabetes mellitusAll studies on Vitamin D supplementation and HbA1cAll studies on Vitamin D supplementation and LDL cholesterol

Related research

Read related research summaries.

Vitamin D may reduce inflammation in type 2 diabetesVitamin D supplementation may improve musculoskeletal pain in pregnant womenVitamin D supplementation reduces neonatal birth weight in gestational diabetesHigh-Dose Vitamin D3 Does Not Improve Glycaemic Control in Type 2 DiabetesVitamin C may reduce oxidative stress in type 2 diabetes patients.

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