Benefits of Vitamin D on Diabetes Progression

A new study from investigators at Laval University in Quebec is adding fuel to the debate about the overarching impact of vitamin D supplementation on a patient’s health.

A little more than a month after a study presented at ADA 2019 found evidence that vitamin D supplements do not reduce diabetes risk, the current study found that high-dose supplementation can improve glucose metabolism and help prevent the progression of diabetes.

"The reason we saw improvements in glucose metabolism following vitamin D supplementation in those at high risk of diabetes, or with newly diagnosed diabetes, while other studies failed to demonstrate an effect in people with long-standing type 2 diabetes is unclear,” said Claudia Gagnon, MD, endocrinologist at Laval University. “This could be due to the fact that improvements in metabolic function are harder to detect in those with longer-term disease or that a longer treatment time is needed to see the benefits."

To evaluate the impact of Vitamin D3 supplementation on insulin sensitivity and secretion, investigators carried out a single-center, double-blind, placebo-controlled trial that involved 96 patients at a high risk of diabetes or with newly diagnosed type 2 diabetes. Investigators also aimed to evaluate the effects of vitamin D3 on fasting and glucose tolerance test-derived indices of insulin sensitivity, insulin secretion, B-cell function, metabolic markers, blood pressure, and anthropometric measurements.

A total of 96 patients were included in the study and they were randomized in a 1:1 ratio to receive vitamin D3 5,000 IU daily or placebo for a 6-month period. Randomization was corn acted by a biostatistician to balance treatment arms according to sex, BMI, and age.

The study included multiple outcome measurements. The primary outcome of the study was peripheral insulin sensitivity. Secondary outcome measures included other insulin sensitivity and insulin secretion indices, B-cell function, fasting, and HbA1c among others.

Investigators noted that baseline characteristics were similar between both groups. The group was 38.5% and the median age was 58.7 years. Median BMI was 32.2, the prevalence of predicates was 35.8%, and 20.0% in regard to diabetes. The mean 25-hydroxyvitamin D (25(OH)D) was 51.8 nmol/L.

Upon analyses, investigators found that the mean 25(OH)D reached 127.6 nmol/L and 51.8 nmol/L in the treatment and placebo groups, respectively at the 6-month mark (p<0.001). Additionally, investigators noted a beneficial effect of vitamin D3 compared with placebo was observed on M-value (mean change [95% CI]: 0.92 (0.24 to 1.59) versus -0.03 (-0.73 to 0.67; p=0.009) and disposition index (95% CI; 267.0 [-343.4 to 877.4]) versus -55.5 (-696.3 to 585.3; p=0.039) after 6 months.

“Further studies are required to confirm our findings, to identify whether some people may benefit more from this intervention, and to evaluate the safety of high-dose vitamin D supplementation in the long term,” Gagnon said. “Until then I would suggest that current vitamin D supplementation recommendations be followed.”

This study, titled “Effects of 6-Month Vitamin D Supplementation on Insulin Sensitivity and Secretion: A Randomized, Placebo Controlled Trial,” is published in the European Journal of Endocrinology.