title: Effects of vitamin D and calcium supplementation on pancreatic β cell function, insulin sensitivity, and glycemia in adults at high risk of diabetes: the Calcium and Vitamin D for Diabetes Mellitus (CaDDM) randomized controlled trial.
abstract: BACKGROUND
  A suboptimal vitamin D and calcium status has been associated with higher risk of type 2 diabetes in observational studies, but evidence from trials is lacking.
  
  
  OBJECTIVE
  We determined whether vitamin D supplementation, with or without calcium, improved glucose homeostasis in adults at high risk of diabetes.
  
  
  METHODS
  Ninety-two adults were randomly assigned in a 2-by-2 factorial-design, double-masked, placebo-controlled trial to receive either cholecalciferol (2000 IU once daily) or calcium carbonate (400 mg twice daily) for 16 wk. The primary outcome was the change in pancreatic β cell function as measured by the disposition index after an intravenous-glucose-tolerance test. Other outcomes were acute insulin response, insulin sensitivity, and measures of glycemia.
  
  
  RESULTS
  Participants had a mean age of 57 y, a body mass index (BMI; in kg/m(2)) of 32, and glycated hemoglobin (Hb A(1c)) of 5.9%. There was no significant vitamin D × calcium interaction on any outcomes. The disposition index increased in the vitamin D group and decreased in the no-vitamin D group (adjusted mean change ± SE: 300 ± 130 compared with -126 ± 127, respectively; P = 0.011), which was explained by an improvement in insulin secretion (62 ± 39 compared with -36 ± 37 mU · L(-1) · min, respectively; P = 0.046). Hb A(1c) increased less, but nonsignificantly, in the vitamin D group than in the no-vitamin D group (0.06 ± 0.03% compared with 0.14 ± 0.03%, respectively; P = 0.081). There was no significant difference in any outcomes with calcium compared with no calcium.
  
  
  CONCLUSIONS
  In adults at risk of type 2 diabetes, short-term supplementation with cholecalciferol improved β cell function and had a marginal effect on attenuating the rise in Hb A(1c). This trial was registered at clinicaltrials.gov as NCT00436475.
authors.affiliation: Division of Endocrinology, Diabetes, and Metabolism, Tufts Medical Center, Boston, MA 02111, USA.
authors.forename: Joanna
authors.initials: J
authors.lastname: Mitri
authors.forename: Bess
authors.initials: B
authors.lastname: Dawson-Hughes
authors.forename: Frank B
authors.initials: FB
authors.lastname: Hu
authors.forename: Anastassios G
authors.initials: AG
authors.lastname: Pittas
mesh_terms: D001786:Blood Glucose / Q000032:analysis*; D002136:Calcium, Dietary / Q000008:administration & dosage*; D003924:Diabetes Mellitus, Type 2 / Q000209:etiology / Q000517:prevention & control*; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D012306:Risk; D014807:Vitamin D / Q000008:administration & dosage*
chemical_list: D001786:Blood Glucose; D002136:Calcium, Dietary; D007328:Insulin; D014807:Vitamin D