Vitamin D has no positive impact on Diabetes outcomes : Study

Vitamin D3 at 4000 IU/d has no impact on insulin secretion rate (ISR) and hemoglobin A1c (HbA1c) in patients with well-controlled type 2 diabetes on metformin, according to a study published in the Journal of the Endocrine Society.

This double-blind, randomized and placebo-controlled clinical trial was conducted by Edith Angellotti, Division of Endocrinology, Diabetes and Metabolism, Tufts Medical Center, Boston, Massachusetts, and colleagues to evaluate the effectiveness of oral daily vitamin D supplementation on pancreatic β-cell function and HbA1c, and its safety in the U.S. adults with well-controlled type 2 diabetes.

Although type 2 diabetes-specific pharmacotherapy is well studied and efficacious, it is associated with poor long-term adherence, potential side effects, and high costs. Therefore, there is a need for identification of alternative therapeutic options that can be applied at the public health level to decrease diabetes-related costs and burden.

Suboptimal status of vitamin D has emerged as a potential contributor to the pathophysiology of type 2 diabetes, with several lines of evidence supporting a role for vitamin D in pancreatic β-cell function and insulin sensitivity.

Although several meta-analyses have supported a beneficial effect of vitamin D supplementation on glycemia and insulin sensitivity in patients with type 2 diabetes, no definitive conclusions could be drawn from them as the trials were short-term and of varied quality, had small sample sizes, and had a varied mode of vitamin D administration. And also, the effect of vitamin D supplementation among American adults with type 2 diabetes is not known.

The study consisted of 127 patients (mean age, 60 years) with stable (HbA1c ≤7.5%) diabetes managed with lifestyle only or lifestyle plus metformin. The subjects were given 4000 units of vitamin D₃ (cholecalciferol) daily or placebo for 48 weeks. Patients were seen at 16, 24, 36, and 48 weeks, and blood was obtained after an 8-hour overnight fast.

Insulin secretion rate (ISR) was estimated from peripheral plasma C-peptide levels after a 3-hour 75-g oral glucose tolerance test done at baseline and week 24. Changes in HbA1c were assessed at 16, 24, 36, and 48 weeks.

Key Results:

• Baseline mean plasma 25-hydroxyvitamin D [25(OH)D] concentration was 26.6 ng/mL, mean HbA1c was 6.6%, and 78% of patients were on metformin.


• At week 24, mean 25(OH)D changed by 20.5 and −1.6 ng/mL in the vitamin D and placebo groups, respectively.


• The vitamin D and placebo groups did not differ in change in ISR or HbA1c.


• Among patients treated with lifestyle only (n = 28), vitamin D supplementation reduced HbA1c compared with placebo (−0.1% vs 0.3%, respectively) at week 24.

Based on the study, the researchers concluded that daily administration of 4000 IU vitamin D₃ compared with placebo did not improve HbA1c or OGTT-based indices of β-cell function or insulin secretion in the largest US-based trial among patients with well-controlled, stable type 2 diabetes not selected for vitamin D deficiency. A reduction in HbA1c was observed at week 24 among patients treated with lifestyle only; however, this result could be due to chance.

For further information click on the link: https://doi.org/10.1210/js.2018-00015