Vitamin D may affect skeletal muscle function. In a double-blind, randomised, placebo-controlled trial, we found that vitamin D-3 supplementation (400 or 1,000 I.U. vs. placebo daily for 1 year with bimonthly study visits) does not improve grip strength or reduce falls.
This study aimed to test the supplementation effects of vitamin D-3 on physical function and examine associations between overweight/obesity and the biochemical response to treatment.
In a parallel group double-blind RCT, healthy postmenopausal women from North East Scotland (latitude-57A degrees N) aged 60-70 years (body mass index (BMI), 18-45 kg/m(2)) were assigned (computer randomisation) to daily vitamin D-3 (400 I.U. (n = 102)/1,000 I.U. (n = 101)) or matching placebo (n = 102) (97, 96 and 100 participants analysed for outcomes, respectively) from identical coded containers for 1 year. Grip strength (primary outcome), falls, diet, physical activity and ultraviolet B radiation exposure were measured bimonthly, as were serum 25(OH)D, adjusted calcium (ACa) and phosphate. Fat/lean mass (dual energy X-ray absorptiometry), anthropometry, 1,25-dihydroxyvitamin D and parathyroid hormone were measured at baseline and 12 months. Participants and researchers were blinded throughout intervention and analysis.
Treatment had no effect on grip strength (mean change (SD)/year = -0.5 (2.5), -0.9 (2.7) and -0.4 (3.3) kg force for 400/1,000 I.U. vitamin D-3 and placebo groups, respectively (P = .10, ANOVA)) or falls (P = .65, chi-squared test). Biochemical responses were similar across BMI categories (<25.25-29.99, a parts per thousand yen30 kg/m(2)) with the exception of a small change at 12-months in serum ACa in overweight compared to non-overweight participants (P = .01, ANOVA; 1,000 I.U. group). In the placebo group, 25(OH)D peak concentration change (winter to summer) was negatively associated with weight (r = -.268), BMI (r = -.198), total (r = -.278) and trunk fat mass (r = -.251), with total and trunk fat mass predictive of winter to summer 25(OH)D change (P = .01/.004 respectively, linear regression).
We found no evidence of an improvement in physical function following vitamin D-3 supplementation for 1 year.
Bibliographical noteThis work was funded partly by the UK Food Standards Agency, the Department of Health and the National Osteoporosis Society. Any views expressed are the authors own. We thank Mrs. Lismy Cheripelli (Registered General Nurse, University of Aberdeen, UK) who made significant contributions to the acquisition of data and the continued welfare of our study participants; Prof. Roger Francis (University of Newcastle, UK) for his role as Trial Steering Committee Chair; Prof. Juliet Compston (University of Cambridge, UK) and Prof. Bernard Keavney and Dr. Mark Pearce (both of University of Newcastle, UK) as members of the Data Monitoring Committee; Mrs. Gladys McPherson (University of Aberdeen, UK), for providing randomization service, generating study codes to ensure blinding throughout data analysis, and performing code breaks after analysis; Ms. Katie Wilde (University of Aberdeen, UK) for developing and maintaining our electronic study database; Mrs. Lana Gibson (University of Aberdeen, UK) and Mrs. Jennifer Scott (University of Aberdeen, UK) for performing DXA scans; Mr. William Mutch (University of Aberdeen, UK) for contribution to biochemical analyses, and Ms Katrina Galbreith for help with data entry. Finally, we would like to thank all of the women who took part in our study.
- Accidental Falls
- Body Composition
- Body Mass Index
- Dietary Supplements
- Dose-Response Relationship, Drug
- Double-Blind Method
- Hand Strength
- Middle Aged
- Motor Activity
- Vitamin D
- Journal Article
- Randomized Controlled Trial
- Research Support, Non-U.S. Gov't