High- vs standard-dose vitamin D provides no added benefit on muscular strength, balance
High-dose vitamin D supplementation for 12 months does not improve muscular strength, balance or quality of life in postmenopausal women with osteopenia or osteoporosis as compared with standard-dose supplementation, according to a study.
Researchers randomized 297 postmenopausal women with osteoporosis or osteopenia to 12-month treatment with vitamin D3 (20,000 IU) or matching placebos taken twice a week. All women also received daily elemental calcium (1,000 mg) plus vitamin D3 (800 IU).
Evaluations including muscle strength (handgrip and knee extensor strength), balance (tandem test) and quality of life (EQ-5D) were performed at baseline and after 12 months. In addition, the women were genotyped for single nucleotide polymorphisms (SNPs) in genes encoding vitamin D-related enzymes.
Among the 275 women who completed the study, mean serum 25(OH)D levels significantly increased in the high-dose group (from 64.7 to 164.1 nmol/L; p<0.01) and moderately increased in the standard-dose group (from 64.1 to 81.8 nmol/L; p<0.01). However, no significant between-group difference was observed in change in muscular strength, balance or quality of life over the intervention period.
Of note was the observed association of polymorphisms in rs3829251 (located in the 7-dehydrocholesterol reductase gene) with muscle strength and treatment effects.
Findings of the present study, designed to compare two doses of supplemental vitamin D and not to assess the effect of vitamin D itself, do not lend support for the use of high-dose vitamin D supplements in already vitamin D-replete women in terms of improving muscular strength, balance or quality of life, researchers said.
While not having shown any indication of harmful clinical effects, high-dose vitamin D supplementation might lead to a minor increase in serum and urinary calcium, they added. Furthermore, the safety assessment in the study was limited by the inability to specifically assess falls. Future studies should include vitamin-D deficient participants only, as well as assess fall as an outcome measure in all high-dose vitamin D trials.
Vitamin D has an important and well-known effect on calcium homeostasis and skeletal health. In light of the discovery of vitamin D receptors and the vitamin D activating enzyme 1-alfa-hydroxylase in extraskeletal tissues, recent data have demonstrated associations between higher serum 25(OH)D levels and lower risk of multiple pathological conditions. [Ann N Y Acad Sci 2016;1376:29-52; Am J Clin Nutr 2004;80:1689s-96s; J Clin Endocrinol Metab 2007;92:2058-65]