Effect of Treating Vitamin D Deficiency in Uncontrolled Type 2 Diabetes: A Randomized, Placebo-Controlled Study

Efficacy of vitamin D supplementation on glycaemic control in type 2 diabetes: An updated systematic review and meta-analysis of randomized controlled trials

AIM

To assess the effects of vitamin D interventions on glycaemic control in subjects with type 2 diabetes (T2D).

METHODS

We searched PubMed, EMBASE, Web of Science and the Cochrane Library for relevant studies. Serum 25(OH)D, fasting blood glucose (FBG), HbA1c, fasting insulin and Homeostasis Model Assessment for Insulin Resistance (HOMA-IR) were analysed.

RESULTS

We identified 39 randomized controlled trials involving 2982 subjects. Results showed a significant decline in the vitamin D group, as shown by the FBG weighted mean difference (WMD; -0.49 [95% confidence interval {CI}: -0.69 to -0.28] mmol/L), HbA1c (WMD -0.30% [95% CI: -0.43 to -0.18]), HOMA-IR (WMD -0.39 [95% CI -0.64 to -0.14]) and insulin (WMD -1.31 [95% CI: -2.06 to -0.56] μIU/mL). Subgroup analyses indicated that the effects of vitamin D supplementation on glycaemic control depend on the dosage and duration of supplementation, baseline 25(OH)D levels and the body mass index of patients with T2D.

CONCLUSIONS

Vitamin D supplementation can significantly reduce serum FBG, HbA1c, HOMA-IR and fasting insulin levels in T2D patients; the effects were especially prominent when vitamin D was given in a short-term, high dosage to patients with a vitamin D deficiency, who were overweight, or had an HbA1c of 8% or higher at baseline. Our study suggests that vitamin D supplements can be recommended as complementary treatment for T2D patients.

The Effect of Vitamin D Supplementation on Glycemic Control and Cardiovascular Risk Factors in Type 2 Diabetes: An Updated Systematic Review and Meta-Analysis of Clinical Trials

Background and Aims: The purpose of this meta-analysis was to investigate the effect of vitamin D supplementation on hemoglobin A1C (HbA1C), fasting blood sugar (FBS), low-density lipoprotein (LDL), high-density lipoprotein (HDL), systolic blood pressure (SBP), and the total vitamin D level in patients with Type 2 diabetes (T2DM). Methods: A systematic search was conducted in databases such as PubMed (Medline), Scopus, Embase, Web of Science, Cochrane Library, and ClinicalTrials.gov using relevant keywords from January 1990 to January 2024. After screening and extracting data, a qualitative evaluation of articles was performed using the Cochrane risk-of-bias tool for randomized trials (RoB 2). Results: The findings revealed that vitamin D supplementation significantly decreased the mean HbA1C (SMD: -0.15; 95% CI: -0.29, -0.20; I square: 79.76%; p value < 0.001) and mean FBS (SMD: -0.28; 95% CI: -0.40, -0.15; I square: 70.13%; p value < 0.001), lowered SBP (SMD: -0.06; 95% CI: -0.16, -0.05; I square: 39.63%; p value = 0.23), and reduced LDL (SMD: -0.11; 95% CI: -0.28, -0.05; I square: 73.66%; p value < 0.001). Furthermore, vitamin D supplementation increased the average HDL (SMD: 0.13; 95% CI: 0.04, 0.29; I square: 79.33%; p value < 0.001) and vitamin D levels (SMD: 1.78; 95% CI: 1.53, 2.04; I square: 91.92%; p value < 0.001) in patients with T2DM. Subgroup analyses showed that weight gain, BMI, and duration of the disease could reduce the effect of vitamin D supplementation on diabetes control in affected patients. Conclusion: The results also indicated that taking vitamin D supplements in the amount of 50,000 IU had a significant effect on reducing the indicators related to diabetes control. Based on the combined evidence, the findings of this meta-analysis suggest that vitamin D supplementation can significantly improve glycemic control and reduce the risk of complications associated with T2DM, especially cardiovascular diseases (CVDs).

What is the impact of vitamin D supplementation on glycemic control in people with type-2 diabetes: a systematic review and meta-analysis of randomized controlled trails

BACKGROUND

There is conflicting evidence on the effect of vitamin D on glycemic control. Therefore, in the current meta-analyses, we aimed to assess the effect of vitamin D supplementation on the glycemic control of type 2 diabetes (T2D) patients.

METHODS

We conducted a comprehensive search in electronic databases including; PubMed/Medline, Web of Science, Scopus, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and NIH's Clinical Trials Registry, from the inception of each database up to January first, 2021.

RESULTS

A total of 46 randomized controlled trials (RCTs) consisting of 2164 intervention subjects and 2149 placebo controls were included in this meta-analysis. Pooled analyses for HbA1c showed a significant change between the intervention and placebo group, the weighted mean difference (WMD)(95% confidence interval(CI)) was -0.20%(-0.29, -0.11) with P < 0.001. Analyses for assessing changes in FPG found a significant reduction in the intervention group after vitamin D supplementation, the WMD (95%CI) was -5.02 mg/dl (-6.75,-3.28) with P < 0.001. The result of pooled analyses for HOMA-IR revealed a significant change between the intervention and control group, the WMD (95%CI) was -0.42(-0.76, -0.07) with P = 0.019. The subgroup analyses showed the most efficacy in a higher dose and short intervention period and in subjects with deficient vitamin D status.

CONCLUSION

Vitamin D supplementation might be beneficial for the reduction of FPG, HbA1c, and HOMA-IR in type 2 diabetes patients with deficient vitamin D status. This effect was especially prominent when vitamin D was given in large doses and for a short period of time albeit with substantial heterogeneity between studies and a probability of publication bias.

Dietary Magnesium Intake Level Modifies the Association Between Vitamin D and Insulin Resistance: A Large Cross-Sectional Analysis of American Adults

Background

Previous clinical studies and randomized controlled trials have revealed that low serum vitamin D levels are associated with the risk of developing insulin resistance. Magnesium has been reported to be a protective factor for insulin resistance, and magnesium has been considered an important co-factor for vitamin D activation. However, the effect of dietary magnesium intake on the relationship between vitamin D and the risk of developing insulin resistance has not been comprehensively investigated. Therefore, we designed this cross-sectional analysis to assess whether dietary magnesium intake modifies the association of vitamin D and insulin resistance.

Methods

A total of 4,878 participants (male: 48.2%) from 4 consecutive cycles of the National Health and Nutrition Examination Survey (2007-2014) were included in this study after a rigorous screening process. Participants were stratified by their dietary magnesium intake into low-intake (<267 mg/day) and high-intake (≥267 mg/day) groups. We assessed differences between serum vitamin D levels and the risk of developing insulin resistance (interaction test), using a weighted multivariate logistic regression to analyze differences between participants with low and high magnesium intake levels.

Results

There was a negative association between vitamin D and insulin resistance in the US adult population [OR: 0.93 (0.88-0.98)], P < 0.001. Dietary magnesium intake strengthened the association (P for interaction < 0.001). In the low dietary magnesium intake group, vitamin D was negatively associated with the insulin resistance [OR: 0.94 (0.90-0.98)]; in the high dietary magnesium intake group, vitamin D was negatively associated with insulin resistance [OR: 0.92 (0.88-0.96)].

Conclusion

Among adults in the United States, we found an independent association between vitamin D level and insulin resistance, and this association was modified according to different levels of magnesium intake.

Effect of vitamin D supplementation on glycose homeostasis and islet function in vitamin D deficient or insufficient diabetes and prediabetes: a systematic review and meta-analysis

Objective of the present study was to evaluate the effect of vitamin D supplementation on glycose homeostasis, islet function, and diabetes progress. Literatures were searched via electronic databases, websites, and previous reviews from the earliest available time to the end of May 2020. Randomized controlled trials initially designed for diabetes and prediabetes with 25-dihydroxyvitamin D [25(OH)D]<30 ng/ml were included. All data were analyzed and presented based on the Cochrane guidelines and PRISMA guidelines. In total, 27 articles (n = 1,932) were enrolled in this study. Vitamin D supplementation significantly improved fasting blood glucose, postprandial blood glucose, and quantitative insulin sensitivity check index in diabetes and prediabetes with baseline 25(OH)D<30 ng/ml. Higher percentages regressing from prediabetes to normal glucose status [1.60 (1.19, 2.17), p = 0.002, n = 564] and lower percentage progressing from prediabetes to diabetes [0.68 (0.36, 1.27), p = 0.23, n = 569] were found in the supplementation group. The positive effects of vitamin D supplementation on body mass index, waist, HDL-C, LDL-C, and CRP were also demonstrated. In conclusion, modest improvements in vitamin D supplementation on short-term glycose homeostasis, insulin sensitivity, and disease development in diabetes and prediabetes with 25(OH)D<30 ng/ml were demonstrated, but more research needs to be conducted in the future to support the clinical application. (Register ID: CRD42020186004)