Altered vitamin D and calcium homeostasis may play a role in the development of type 2 diabetes (t2DM).
Evidence Acquisition and Analyses
MEDLINE review through January 2007 for observational studies and clinical trials in adults with outcomes related to glucose homeostasis. When data was available to combine, meta-analyses were performed and summary odds ratios (OR) are presented.
Observational studies show a relatively consistent association between low vitamin D status, calcium or dairy intake and prevalent t2DM or metabolic syndrome (OR [95% CI]: t2DM prevalence, 0.36 [0.16 – 0.80] among non-blacks for highest vs. lowest 25-OHD; metabolic syndrome prevalence, 0.71 [0.57 – 0.89] for highest vs. lowest dairy intake). There are also inverse associations with incident t2DM or metabolic syndrome (OR [95% CI]: t2DM incidence, 0.82 [0.72 – 0.93] for highest vs. lowest combined vitamin D and calcium intake; 0.86 [0.79 – 0.93] for highest vs. lowest dairy intake). Evidence from trials with vitamin D and/or calcium supplementation suggests that combined vitamin D and calcium supplementation may have a role in the prevention of t2DM only in populations at high risk (i.e. glucose intolerance). The available evidence is limited because most observational studies are cross-sectional and did not adjust for important confounders while intervention studies were short in duration, included few subjects, used a variety of formulations of vitamin D and calcium or did post-hoc analyses.
Vitamin D and calcium insufficiency may negatively influence glycemia while combined supplementation with both nutrients may be beneficial in optimizing glucose metabolism.
Key terms: Vitamin D, calcium, type 2 diabetes