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Open Access Study protocol

Study protocol: a randomised placebo-controlled clinical trial to study the effect of vitamin D supplementation on glycaemic control in type 2 Diabetes Mellitus SUNNY trial

Yvonne HM Krul-Poel1, Hans van Wijland2, Frank Stam1, Edwin ten Boekel3, Paul Lips4 and Suat Simsek14*

Author Affiliations

1 From the Department of Internal Medicine, Medical Centre Alkmaar, PO Box 7057, 1815 JD, Wilhelminalaan 12, Alkmaar, The Netherlands

2 Department of Family Medicine, Alkmaar, The Netherlands

3 Department of Clinical Chemistry, Haematology & Immunology, Medical Centre Alkmaar, Alkmaar, The Netherlands

4 Department of Internal Medicine/Endocrinology, VU University Medical Centre, Amsterdam, The Netherlands

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BMC Endocrine Disorders 2014, 14:59  doi:10.1186/1472-6823-14-59

Published: 17 July 2014

Abstract

Background

Besides the classical role of vitamin D on calcium and bone homeostasis, vitamin D deficiency has recently been identified as a contributing factor in the onset of insulin resistance in type 2 diabetes mellitus. However, it is uncertain whether vitamin D deficiency and poor glycaemic control are causally interrelated or that they constitute two independent features of type 2 diabetes mellitus. There are limited clinical trials carried out which measured the effect of vitamin D supplementation on glycaemic control.

The objective of this study is to investigate the effect of vitamin D supplementation on glycaemic control and quality of life in patients with type 2 diabetes mellitus.

Methods/design

In a randomised double-blind placebo-controlled trial conducted in five general practices in the Netherlands three hundred patients with type 2 diabetes mellitus treated with lifestyle advises or metformin or sulphonylurea-derivatives are randomised to receive either placebo or 50,000 IU Vitamin D3 at monthly intervals. The primary outcome measure is the change in glycated haemoglobin level between baseline and six months. Secondary outcome measures include blood pressure, anthropometric parameters, lipid profile, insulin resistance, quality of life, advanced glycation end products and safety profiles. Quality of life will be measured by The Short Form (SF-36) Health Survey questionnaire. Advanced glycation end products are measured by an AGE-reader.

Discussion

This trial will be the first study exploring the effect of vitamin D supplementation on both glycaemic control and quality of life in patients with type 2 diabetes mellitus. Our findings will contribute to the knowledge of the relationship between vitamin D status and insulin resistance in patients with type 2 diabetes mellitus.

Trial registration

The Netherlands trial register: NTR3154

Keywords:
Vitamin D; Type 2 diabetes mellitus; Quality of life; Advanced glycation end products; Insulin resistance