Vitamin D supplementation reduces insulin resistance in South Asian women living in New Zealand who are insulin resistant and vitamin D deficient - a randomised, placebo-controlled trial.
Low serum 25-hydroxyvitamin D (25(OH)D) has been shown to correlate with increased risk of type 2 diabetes. Small, observational studies suggest an action for vitamin D in improving insulin sensitivity and/or insulin secretion. The objective of the present study was to investigate the effect of improved vitamin D status on insulin resistance (IR), utilising randomised, controlled, double-blind intervention administering 100 microg (4000 IU) vitamin D(3) (n 42) or placebo (n 39) daily for 6 months to South Asian women, aged 23-68 years, living in Auckland, New Zealand. Subjects were insulin resistant - homeostasis model assessment 1 (HOMA1)>1.93 and had serum 25(OH)D concentration < 50 nmol/l. Exclusion criteria included diabetes medication and vitamin D supplementation >25 microg (1000 IU)/d. The HOMA2 computer model was used to calculate outcomes. Median (25th, 75th percentiles) serum 25(OH)D(3) increased significantly from 21 (11, 40) to 75 (55, 84) nmol/l with supplementation. Significant improvements were seen in insulin sensitivity and IR (P = 0.003 and 0.02, respectively), and fasting insulin decreased (P = 0.02) with supplementation compared with placebo. There was no change in C-peptide with supplementation. IR was most improved when endpoint serum 25(OH)D reached > or = 80 nmol/l. Secondary outcome variables (lipid profile and high sensitivity C-reactive protein) were not affected by supplementation. In conclusion, improving vitamin D status in insulin resistant women resulted in improved IR and sensitivity, but no change in insulin secretion. Optimal vitamin D concentrations for reducing IR were shown to be 80-119 nmol/l, providing further evidence for an increase in the recommended adequate levels. Registered Trial No. ACTRN12607000642482.
von Hurst
Pamela R
PR
Institute of Food, Nutrition and Human Health, Massey University, Private Bag 102 904, North Shore Mail Centre, Auckland, New Zealand. p.r.vonhurst@massey.ac.nz
Stonehouse
Welma
W
Coad
Jane
J
D000328:Adult; D001208:Asia / Q000208:ethnology; D044466:Asian People; D002097:C-Reactive Protein / Q000378:metabolism; D002762:Cholecalciferol / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance / Q000208:ethnology; D000078790:Insulin Secretion; D008875:Middle Aged; D009520:New Zealand; D009752:Nutritional Status; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000188:drug therapy* / Q000208:ethnology; D014815:Vitamins / Q000494:pharmacology / Q000627:therapeutic use*
D007328:Insulin; D014815:Vitamins; D014807:Vitamin D; D002762:Cholecalciferol; D002097:C-Reactive Protein; C104450:25-hydroxyvitamin D