OBJECTIVELow vitamin D status has been associated with impaired glycemic control in patients with type 2 diabetes. The purpose of our study was to evaluate the effect of vitamin D supplementation on glycemic control in patients with type 2 diabetes. RESEARCH DESIGN AND METHODSThis randomized, double-blind, placebo-controlled trial was conducted in 275 adult patients with type 2 diabetes without insulin treatment. Patients were randomly assigned to receive either vitamin D 3 (50,000 IU/month) or placebo for 6 months. To assess the primary outcome of the study, change in HbA 1c , we performed a linear regression analysis. RESULTS Mean baseline serum 25-hydroxyvitamin D [25(OH)D]increased from 60.6 6 23.3 to 101.4 6 27.6 nmol/L and 59.1 6 23.2 to 59.8 6 23.2 nmol/L in the vitamin D and placebo group, respectively. Mean baseline HbA 1c was 6.8 6 0.5% (51 6 6 mmol/mol) in both groups. After 6 months, no effect was seen on HbA 1c (mean difference: b = 0.4 [95% CI 20.6 to 1.5]; P = 0.42) and other indicators of glycemic control (HOMA of insulin resistance, fasting insulin, and glucose) in the entire study population. Subgroup analysis in patients with a serum 25(OH)D <50 nmol/L or an HbA 1c level >7% (53 mmol/mol) did not differ the results. CONCLUSIONSIn a well-controlled group of patients with type 2 diabetes, intermittent high-dose vitamin D supplementation did not improve glycemic control.Type 2 diabetes, characterized by peripheral insulin resistance and pancreatic b-cell dysfunction, represents a worldwide epidemic with significant comorbidity and mortality due to microvascular and macrovascular complications (1). Although therapies for type 2 diabetes have improved over the last few decades, new insights for the prevention and management of type 2 diabetes remain necessary due to the increased prevalence of the disease.

ObjectiveIncreased levels of depressive symptoms, fatigue or pain (all dimensions of reduced health-related quality of life (HRQOL)) are common in people with type 2 diabetes mellitus (DM). Earlier studies have reported associations between low vitamin D status and fatigue and depressive symptoms. The aim of the present study was to examine the effects of vitamin D supplementation on dimensions of HRQOL in people with type 2 DM.DesignRandomised, double-blind, placebo-controlled trial.MethodsThe effect of monthly cholecalciferol 50,000 IU vs placebo on HRQOL was assessed in 275 adults with type 2 DM derived from general practices. HRQOL at baseline and after six months using the Short Form 36 Health Survey (SF-36) was collected. Linear regression analyses were used to compare the change in HRQOL over time between the vitamin D and placebo group.Results187/275 (68%) completed baseline and follow-up SF-36 and were included in the analysis. Median serum 25-hydroxyvitamin D almost doubled in the intervention group compared to that in the placebo group (58.5–106.0 nmol/L vs 60.0–61.5 nmol/L, respectively). A small significant difference (adjusted B: −8.90; 95% CI: −17.16 to −0.65) between both groups was seen concerning the SF-36 domain role limitations due to physical problems in disadvantage of the vitamin D group.ConclusionsSix months of vitamin D supplementation did not improve HRQOL in non-vitamin D-deficient people with type 2 DM managed on oral antidiabetic therapy.

Vitamin D status was not associated with health-related quality of life in patients with Type 2 diabetes. This could be explained by the relatively high serum 25-hydroxyvitamin D concentration, good glycaemic control and relatively good health-related quality of life of all patients. A prospective study among patients with vitamin D deficiency and poor glycaemic control would be interesting for future research.

The study found no evidence that low vitamin D levels are a contributing factor to higher depression scores in people with Type 2 diabetes.

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