Influence of ascorbic acid supplementation on type 2 diabetes mellitus in observational and randomized controlled trials; a systematic review with meta-analysis

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#antioxidants #ascorbic-acid #blood-glucose #diabetes-mellitus-type-2 #dietary-supplements

Influence of ascorbic acid supplementation on type 2 diabetes mellitus in observational and randomized controlled trials; a systematic review with meta-analysis

Tabatabaei-Malazy et al., 2014 | J Pharm Pharm Sci | Meta Analysis

Citation

Tabatabaei-Malazy Ozra, Nikfar Shekoufeh, ... Abdollahi Mohammad. Influence of ascorbic acid supplementation on type 2 diabetes mellitus in observational and randomized controlled trials; a systematic review with meta-analysis. J Pharm Pharm Sci. 2014;17(4):554-82

Abstract

PURPOSE: There are controversial data regarding the beneficial effects of ascorbic acid (AA) supplementation in type 2 diabetes mellitus (T2DM). In this systematic review, we aimed to criticize the current relevant data from both observational and randomized controlled trials (RCTs). METHODS: All observational and RCTs conducted to assess anti-hyperglycemic effects of AA in diabetics, published before January 2013, were included. To obtain all related studies Google Scholar, PubMed, Scopus, IranMedex, and Magiran web databases were searched. Exclusion criteria were animal studies, and studies conducted in Type 1 DM, children or pregnant women. Main outcome measures were fasting blood sugar (FBS), and glycated hemoglobin (HbA1c). According to degree of heterogeneity, fixed or random effect models were employed. Meta-analyses were done using Stats Direct software, version 3.0.97. The quality of included articles and publication bias were also assessed. RESULTS: We selected 38 articles; 26 observational studies and 12 RCTs. Due to severe methodological heterogeneity in all observational studies and some of RCTs, we could pool data from only 5 RCTs in a meta-analysis. Single intake of AA versus placebo showed a significant effect on FBS; with the standardized mean difference (SMD): -20.59, 95% confidence intervals (95% CI): -40.77 to -0.4 (p= 0.04), but non-significant effect on HbA1c; SMD: -0.46, 95% CI: -1.75 to 0.84 (p= 0.4). Effect of other antioxidants with/without AA supplementation on FBSwere nonsignificant; SMD: -4.26 (p= 0.8), and SMD: -12.04 (p= 0.3), respectively. Also, their effect on HbA1c was non-significant; SMD: 0.53 (p= 0.11), and SMD: 0.28 (p= 0.34), respectively. CONCLUSIONS: Our study supports the positive effect of AA in reduction of FBS in diabetics, however, due to insufficient evidence ragarding long term safety of AA supplementation and limited number of RCTs, the long term use of this vitamin for its anti-diabetic properties cannot be strongly recommended.

Key Findings

We selected 38 articles; 26 observational studies and 12 RCTs. Due to severe methodological heterogeneity in all observational studies and some of RCTs, we could pool data from only 5 RCTs in a meta-analysis. Single intake of AA versus placebo showed a significant effect on FBS; with the standardized mean difference (SMD): -20.59, 95% confidence intervals (95% CI): -40.77 to -0.4 (p= 0.04), but non-significant effect on HbA1c; SMD: -0.46, 95% CI: -1.75 to 0.84 (p= 0.4). Effect of other antioxida

Outcomes Measured

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Population

Field Value
Population See abstract
Sample Size 12
Age Range See abstract
Condition diabetes

MeSH Terms

  • Antioxidants
  • Ascorbic Acid
  • Blood Glucose
  • Diabetes Mellitus, Type 2
  • Dietary Supplements
  • Glycated Hemoglobin
  • Humans
  • Hypoglycemic Agents
  • Randomized Controlled Trials as Topic

Evidence Classification

  • Level: Meta Analysis
  • Publication Types: Journal Article, Meta-Analysis, Systematic Review
  • Vertical: vitamin-c

Provenance

  • PMID: 25579434
  • DOI: (not available)
  • PMCID: Not in PMC
  • Verified: 2026-04-09 via PubMed E-utilities API

Source extracted via PubMed E-utilities API on 2026-04-09