Systematic review of the effectiveness of vitamin D supplement for type 2 diabetes mellitus patients

Abstract

Background Worldwide, as of 2010, about 285 million people suffered diabetes mellitus (DM), with type 2 constituting about 90% of the cases. DM is more common, in particular, type 2 diabetes mellitus (T2DM) in developed countries. The greatest increase in prevalence appears in Asia and Africa. More important, it associated with complications including uremia, heart disease and diabetic retinopathy. Recent research has investigated whether there would have effect of vitamin D (VD) supplementation in addition to other treatment or/and relevant interventions that would improve health outcomes of patients diagnosed with T2DM. Furthermore, the costs of using VD supplements are relatively low.

Methods A systematic review was conducted by searching for relevant studies published from the year of 2004 to 2014 (all the studies were randomized controlled trials) from database of PubMed with specified keywords. All studies were conducted in Asia and all subjects were T2DM patients. Studies were included when they were in relation to the association between VD supplementation and T2DM patients. After filtering, ten trials were identified to be relevant and adopted in this systematic review. The effects of calcium intake were also explored whenever applicable.

Results Ten studies were included, with all of them conducted in Asia. In seven trials, VD supplementation indicated insignificantly differences of VD effects on T2DM through impact of metabolic parameters such as glycated hemoglobin (HbA1c), Fasting plasma glucose (FPG), insulin, insulin resistance (IR).etc. However, three trials revealed significant differences in HbA1c, FPG, insulin, IR and insulin sensitivity (IS) with VD supplementation.

Conclusions There were insufficient evidences concerning the effectiveness of VD supplementary for T2DM patients in Asian populations, in terms of improving their health outcomes. It could be likely to be useful for our Hong Kong Chinese population. Because some included trials were subject to small sample sizes, incompletely follow up, and/or low methodological quality, these might influence the validity of the findings. Future studies on the effectiveness of VD for T2DM would be warranted for Chinese population.