Effects of 6-month vitamin D supplementation on insulin sensitivity and secretion: a randomised, placebo-controlled trial

Abstract

Objective To determine whether vitamin D3 supplementation improves insulin sensitivity, using the hyperinsulinemic-euglycemic clamp. Design This single-centre, double-blind, placebo-controlled trial randomised 96 participants at high risk of diabetes or with newly diagnosed type 2 diabetes to vitamin D3 5000 IU daily or placebo for 6 months. Methods We assessed at baseline and 6 months: (1) primary aim: peripheral insulin sensitivity (M-value using a 2-h hyperinsulinemic-euglycemic clamp); (2) secondary aims: other insulin sensitivity (HOMA2%S, Matsuda) and insulin secretion (insulinogenic index, C-peptide area under the curve, HOMA2-B) indices using a 2-h oral glucose tolerance test (OGTT); β-cell function (disposition index: M-value × insulinogenic index); fasting and 2-h glucose post OGTT; HbA1c; anthropometry. Results Baseline characteristics were similar between groups (% or mean ± s.d.): women 38.5%; age 58.7 ± 9.4 years; BMI 32.2 ± 4.1 kg/m2; prediabetes 35.8%; diabetes 20.0%; 25-hydroxyvitamin D (25(OH)D) 51.1 ± 14.2 nmol/L. At 6 months, mean 25(OH)D reached 127.6 ± 26.3 nmol/L and 51.8 ± 16.5 nmol/L in the treatment and placebo groups, respectively (P < 0.001). A beneficial effect of vitamin D3 compared with placebo was observed on M-value (mean change (95% CI): 0.92 (0.24–1.59) vs −0.03 (−0.73 to 0.67); P = 0.009) and disposition index (mean change (95% CI): 267.0 (−343.4 to 877.4) vs −55.5 (−696.3 to 585.3); P = 0.039) after 6 months. No effect was seen on other outcomes. Conclusions In individuals at high risk of diabetes or with newly diagnosed type 2 diabetes, vitamin D supplementation for 6 months significantly increased peripheral insulin sensitivity and β-cell function, suggesting that it may slow metabolic deterioration in this population.

Serum Vitamin D Concentration ≥75 nmol/L Is Related to Decreased Cardiometabolic and Inflammatory Biomarkers, Metabolic Syndrome, and Diabetes; and Increased Cardiorespiratory Fitness in US Adults

“…They also demonstrated that administration of 1,25(OH) 2 D into the brain dramatically decreased the food intake and body weight in obese rodents. Although a clear cause and effect for vitamin D in glucose and insulin metabolism and body weight has been established, it is surprising that studies on vitamin D supplementation and CVD have yielded inconsistent results [41][42][43][44][45][46][47].…”

<p>The Relationship Between Vitamin D Deficiency and Glycated Hemoglobin Levels in Patients with Type 2 Diabetes Mellitus</p>

“…by Lemieux et al found that, in subjects at high risk of diabetes or with newly diagnosed T2DM who received 5000 IU vitamin D3 daily for 6 months, peripheral insulin sensitivity and β-cell function increased significantly, suggesting that supplementation with vitamin D3 may slow metabolic deterioration in this population. 21 Previous studies have explored the relationship between vitamin D and blood glucose levels. One study performed in adolescents (aged 12-17 years) in the United States found that vitamin D levels were negatively correlated with fasting blood glucose levels, but were not related to HbA1c in male subjects.…”

Vitamin D Supplementation for Prevention of Type 2 Diabetes Mellitus: To D or Not to D?

“…In humans, mechanistic studies show inconsistent results. Vitamin D supplementation for participants at high risk for or with newly diagnosed type 2 diabetes has shown an effect ( 27 ) as well as no effect ( 28 ) on insulin sensitivity and secretion. However, such studies are inconclusive because they are underpowered; have included populations with sufficient vitamin D status, with a low risk for diabetes or with established diabetes; have co-administered vitamin D with other interventions, which may confound the effect of vitamin D; or have followed participants for short periods of time (about 2–6 months), which are likely inadequate to affect the pathophysiology of type 2 diabetes.…”