The role of vitamin D and calcium in type 2 diabetes. A systematic review and meta-analysis.
BACKGROUND
Altered vitamin D and calcium homeostasis may play a role in the development of type 2 diabetes mellitus (type 2 DM). EVIDENCE ACQUISITION AND ANALYSES: MEDLINE review was conducted through January 2007 for observational studies and clinical trials in adults with outcomes related to glucose homeostasis. When data were available to combine, meta-analyses were performed, and summary odds ratios (OR) are presented.


RESULTS
Observational studies show a relatively consistent association between low vitamin D status, calcium or dairy intake, and prevalent type 2 DM or metabolic syndrome [OR (95% confidence interval): type 2 DM prevalence, 0.36 (0.16-0.80) among nonblacks for highest vs. lowest 25-hydroxyvitamin D; metabolic syndrome prevalence, 0.71 (0.57-0.89) for highest vs. lowest dairy intake]. There are also inverse associations with incident type 2 DM or metabolic syndrome [OR (95% confidence interval): type 2 DM 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 type 2 DM 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, whereas intervention studies were short in duration, included few subjects, used a variety of formulations of vitamin D and calcium, or did post hoc analyses.


CONCLUSIONS
Vitamin D and calcium insufficiency may negatively influence glycemia, whereas combined supplementation with both nutrients may be beneficial in optimizing glucose metabolism.
Pittas
Anastassios G
AG
Division of Endocrinology, Diabetes and Metabolism, Tufts-New England Medical Center, Boston, MA 02111, USA. apittas@tufts-nemc.org
Lau
Joseph
J
Hu
Frank B
FB
Dawson-Hughes
Bess
B
D000818:Animals; D002118:Calcium / Q000172:deficiency* / Q000378:metabolism* / Q000627:therapeutic use; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000453:epidemiology / Q000378:metabolism*; D006801:Humans; D015995:Prevalence; D014807:Vitamin D / Q000378:metabolism* / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000188:drug therapy / Q000453:epidemiology / Q000378:metabolism*
D014807:Vitamin D; D002118:Calcium