Effects of vitamin D supplementation on HbA1c and fasting glucose in hypertensive patients - a randomized controlled trial.
Diabetes Obes Metab. 2016 Jun 23. Epub 2016 Jun 23. PMID: 27334070
Martin R Grübler
BACKGROUND: Experimental data have indicated that vitamin D insufficiency has an important influence on glucose metabolism. The majority of epidemiological studies have demonstrated an association between low vitamin D and insulin resistance and/or type 2 diabetes mellitus. Nevertheless evidence from randomized controlled trials remains inconclusive.
OBJECTIVE: To investigate the efficacy of vitamin D supplementation on glycaemic control.
DESIGN: The Styrian Vitamin D Hypertension Trial is a single-centre, double-blind, placebo-controlled study conducted between 2011 and 2014 at the Medical University of Graz, Austria. We enrolled 200 persons with arterial hypertension and 25-hydroxyvitamin D (25(OH)D) concentrations below 30 ng/mL. Study participants were randomized to receive either 2800 IU of vitamin D or placebo per day for 8 weeks. The present investigation is a post-hoc analysis that incorporated analysis of covariance (ANCOVA) approach while adjusting for baseline differences.
RESULTS: A total of 185 participants (mean±SD age, 60.1 ± 11.3 years; 47% women; mean 25-hydroxyvitamin D, 21.2 ± 5.6 ng/mL, mean HbA1c 44.8 ± 11.8 mmol/mol and mean BMI 30.4 ± 5.4 kg/m(2) ) completed the trial. ANCOVA revealed a mean treatment effect (95% confidence interval) on HbA1c of -3.52 mmol/mol (95%CI-6.7 to -0.34; P = 0.045). There was no difference in fasting glucose -4.7 mg/dL (95%CI -16.3 to 6.9; P = 0.426).
CONCLUSIONS: Vitamin D supplementation in obese hypertensive patients with low 25-hydroxyvitamin D reduces HbA1c. This finding warrants further investigations on potential vitamin D effects on glucose homeostasis.