Across 5 studies, 2 reported beneficial effects of vitamin D on handgrip strength, while 3 found no significant effect. The predominant effect size was small, and the median study duration was 112 days (approx. 16 weeks). Most evidence comes from clinical populations (sarcopenia, COPD, postmenopausal women), and the only reported form was vitamin D3, though its use was not consistent across studies.
Caveats: Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests. Evidence base is small (only 5 studies) — conclusions should be considered preliminary.
no significant differences in grip strength or short physical performance battery (SPPB) scores between the experimental and control groups were noted.
Whey-D supplements improved HGS, GS, and total SPPB scores in patients with COPD (all p <0.05), unlike the placebo group.
Overall effect of four strength measurements including handgrip, one repetition maximum Bench Press (1-RM BP), vertical jump, and quadriceps contraction was not significantly improved (SMD 0.18, 95% CI: -0.02 to 0.37, p = 0.08)
The WTD group showed significant improvement in BMI, handgrip strength, and gait speed compared to all other groups (p > 0.05); Vitamin D3 supplementation improved handgrip strength compared to the control group (p < 0.05)
Vitamin D3, omega-3s or SHEP did not improve physical function.