The effect of high-dose vitamin D supplementation on muscular function and quality of life in postmenopausal women – a randomized controlled trial

Abstract

Objective

Observational studies have suggested positive associations between serum 25-hydroxyvitamin D (25(OH)D) levels and muscular strength, balance and quality of life. Our aim was to examine whether high-dose vitamin D supplementation would improve these measures as compared to standard-dose vitamin D, as well as the possible muscular effects of Single Nucleotide Polymorphisms (SNPs) in genes encoding vitamin D-related enzymes.

Design

A 12-month randomized, double-blind, controlled trial where the participants received daily elemental calcium (1,000 mg) plus vitamin D₃ (800 IU). In addition, the participants were randomized to receive either capsules with vitamin D₃ (20,000 IU) or matching placebos to be taken twice a week.

Patients

297 postmenopausal women with osteopenia or osteoporosis.

Measurements

Muscle strength (handgrip and knee extensor strength), balance (tandem test) and quality of life (EQ-5D) were measured at baseline and after 12 months. The subjects were genotyped for SNPs related to vitamin D metabolism.

Results

Of the 297 included women, 275 completed the study. Mean serum 25(OH)D levels dramatically increased in the high-dose group (from 64.7 to 164.1 nmol/l; p<0.01), while a more moderate increased was observed in the standard-dose group (from 64.1 to 81.8 nmol/l; p<0.01). There was no significant difference between the groups in change in muscular strength, balance or quality of life over the intervention period. Polymorphisms in rs3829251 (located in the 7-dehydrocholesterol reductase gene) was associated with muscle strength and treatment effects.

Conclusion

One-year treatment with high-dose vitamin D had no effect on muscular strength, balance or quality of life in postmenopausal women with osteopenia or osteoporosis as compared to standard-dose. The association between rs3829251 and muscle strength needs confirmation in other populations

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