USA: A study published in The American Journal of Clinical Nutrition concluded that older adults with 25(OH)D concentrations of 18 to <30 ng/mL are not benefitted from Vitamin D supplementation (randomization to 2000 IU/d vitamin D3) relating to improvements in leg power, strength, or physical performance or muscle fibre composition and contractile properties.
Explaining the study background, they said Low 25-hydroxyvitamin D (25[OH]D) concentrations (<30 ng/mL [<50 nmol/L]) cause weakness in muscles and also leads to impairment in physical performance. This has been well proved in observational studies.
The results on the effect of vitamin D supplementation on changes in muscle strength and physical performance are mixed. This requires more clarification.
In the present study, researchers determined daily vitamin D supplementation's effect on leg power, strength, and physical performance in low-functioning older adults with 25(OH)D concentrations of 18 to <30 ng/mL in a randomized controlled trial.
The research summary is as follows:
One hundred thirty-six low-functioning adults aged 65–89 were included in the study.
These were randomly assigned to 2000 IU/d vitamin D3 or placebo for 12 months.
Primary and secondary outcomes were measured by Lower-extremity leg power and leg and grip strength, SPPB timed up and go or TUG, postural sway, and gait velocity and spatiotemporal parameters.
These outcomes were assessed at baseline, 4 and 12 months.
Thirty-seven participants underwent muscle biopsy for composition and contractile properties.
At baseline, Participants' mean ± SD age and SPPB scores were 73.4 ± 6.3 y and 7.8 ± 1.8, respectively.
At baseline and 12 months, mean ± SD 25(OH)D concentrations were 19.4 ± 4.2 ng/mL and 28.6 ± 6.7 ng/mL in the vitamin D group.
In the placebo, the values were 19.9 ± 4.9 ng/mL and 20.2 ± 5.0 ng/mL, respectively, with a difference of 9.1 ± 1.1 ng/mL.
They recorded no differences in change in leg power, leg or grip strength, SPPB score, TUG, postural sway, gait velocity and spatiotemporal parameters by intervention group over 12 mo or muscle fibre composition and contractile properties over four mo.
Concluding further, vitamin D supplementation in low-functioning older adults with 25(OH)D concentrations of 18 to <30 ng/mL did not improve leg power, strength, physical performance or muscle fibre composition and contractile properties.
Further reading:
https://www.sciencedirect.com/science/article/abs/pii/S0002916523473509