Aya Mousa1, Negar Naderpoor1,2, Maximilian Pj de Courten3, Helena Teede1,2, Nicole Kellow4, Karen Walker4, Robert Scragg5, Barbora de Courten6,2. 1. Monash Center for Health Research and Implementation, School of Public Health and Preventive Medicine, and. 2. Diabetes and Vascular Medicine Unit, Monash Health, Melbourne, Australia. 3. Center for Chronic Disease, Victoria University, Melbourne, Australia; and. 4. Department of Nutrition and Dietetics, Be Active Sleep and Eat Facility, Monash University, Melbourne, Australia. 5. School of Population Health, University of Auckland, Auckland, New Zealand. 6. Monash Center for Health Research and Implementation, School of Public Health and Preventive Medicine, and barbora.decourten@monash.edu.
Abstract
Background: Vitamin D supplementation has been proposed as a potential strategy to prevent type 2 diabetes. Existing clinical trials have been limited by short duration, low doses of vitamin D, variability in participants' vitamin D-deficiency status, and the use of surrogate measures of body composition, insulin sensitivity, and insulin secretion.Objective: To address existing knowledge gaps, we conducted a double-blind, randomized, placebo-controlled trial to investigate whether vitamin D supplementation that is provided in a sufficient dose and duration to vitamin D-deficient individuals would improve insulin sensitivity or secretion as measured with the use of gold-standard methods. We hypothesized that vitamin D supplementation would improve insulin sensitivity and secretion compared with placebo.Design: Sixty-five overweight or obese, vitamin D-deficient (25-hydroxyvitamin D [25(OH)D] concentration≤50 nmol/L) adults were randomly assigned to receive either a bolus oral dose of 100,000 IU cholecalciferol followed by 4000 IU cholecalciferol/d or a matching placebo for 16 wk. Before and after the intervention, participants received gold-standard assessments of body composition (via dual X-ray absorptiometry), insulin sensitivity (via hyperinsulinemic-euglycemic clamps), and insulin secretion [via intravenous-glucose-tolerance tests (IVGTTs)]. Results:Fifty-four participants completed the study [35 men and 19 women; mean ±SD age: 31.9 ± 8.5 y; body mass index (in kg/m2): 30.9 ± 4.4]. 25(OH)D increased with vitamin D supplementation compared with placebo (57.0 ± 21.3 compared with 1.9 ± 15.1 nmol/L, respectively; P = 0.02). Vitamin D and placebo groups did not differ in change in insulin sensitivity (0.02 ± 2.0 compared with -0.03 ± 2.8 mg · kg-1 · min-1, respectively; P = 0.9) or first-phase insulin secretion (-21 ± 212 compared with 24 ± 184 mU/L, respectively; P = 0.9). Results remained nonsignificant after adjustment for age, sex, percentage of body fat, sun exposure, physical activity, and dietary vitamin D intake (P > 0.1).Conclusions: Vitamin D supplementation does not improve insulin sensitivity or secretion in vitamin D-deficient, overweight or obese adults, despite using high-dose vitamin D supplementation and robust endpoint measures. Therefore, it is unlikely that vitamin D supplementation would be an effective strategy for reducing diabetes risk even in vitamin D-deficient populations. This trial was registered at clinicaltrials.gov as NCT02112721.
RCT Entities:
Background: Vitamin D supplementation has been proposed as a potential strategy to prevent type 2 diabetes. Existing clinical trials have been limited by short duration, low doses of vitamin D, variability in participants' vitamin D-deficiency status, and the use of surrogate measures of body composition, insulin sensitivity, and insulin secretion.Objective: To address existing knowledge gaps, we conducted a double-blind, randomized, placebo-controlled trial to investigate whether vitamin D supplementation that is provided in a sufficient dose and duration to vitamin D-deficient individuals would improve insulin sensitivity or secretion as measured with the use of gold-standard methods. We hypothesized that vitamin D supplementation would improve insulin sensitivity and secretion compared with placebo.Design: Sixty-five overweight or obese, vitamin D-deficient (25-hydroxyvitamin D [25(OH)D] concentration ≤50 nmol/L) adults were randomly assigned to receive either a bolus oral dose of 100,000 IU cholecalciferol followed by 4000 IU cholecalciferol/d or a matching placebo for 16 wk. Before and after the intervention, participants received gold-standard assessments of body composition (via dual X-ray absorptiometry), insulin sensitivity (via hyperinsulinemic-euglycemic clamps), and insulin secretion [via intravenous-glucose-tolerance tests (IVGTTs)]. Results: Fifty-four participants completed the study [35 men and 19 women; mean ± SD age: 31.9 ± 8.5 y; body mass index (in kg/m2): 30.9 ± 4.4]. 25(OH)D increased with vitamin D supplementation compared with placebo (57.0 ± 21.3 compared with 1.9 ± 15.1 nmol/L, respectively; P = 0.02). Vitamin D and placebo groups did not differ in change in insulin sensitivity (0.02 ± 2.0 compared with -0.03 ± 2.8 mg · kg-1 · min-1, respectively; P = 0.9) or first-phase insulin secretion (-21 ± 212 compared with 24 ± 184 mU/L, respectively; P = 0.9). Results remained nonsignificant after adjustment for age, sex, percentage of body fat, sun exposure, physical activity, and dietary vitamin D intake (P > 0.1).Conclusions: Vitamin D supplementation does not improve insulin sensitivity or secretion in vitamin D-deficient, overweight or obese adults, despite using high-dose vitamin D supplementation and robust endpoint measures. Therefore, it is unlikely that vitamin D supplementation would be an effective strategy for reducing diabetes risk even in vitamin D-deficient populations. This trial was registered at clinicaltrials.gov as NCT02112721.
Authors: Michal L Melamed; Michel Chonchol; Orlando M Gutiérrez; Kamyar Kalantar-Zadeh; Jessica Kendrick; Keith Norris; Julia J Scialla; Ravi Thadhani Journal: Am J Kidney Dis Date: 2018-10-05 Impact factor: 11.072