Across 4 studies, 1 reported a beneficial small-sized effect of Vitamin D on handgrip strength, while 3 found neutral effects. The beneficial finding came from a small 8-week RCT in postmenopausal women with low vitamin D levels, but larger and longer studies (median duration 576 days) in broader populations (sarcopenia patients, athletes, elderly) consistently showed no significant improvement. The evidence primarily draws from trials using vitamin D3, with doses up to 2000 IU/day in the longest study, but no clear effective dose range emerged.
Caveats: Evidence base is small (only 4 studies) — conclusions should be considered preliminary. Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests. The single beneficial study was small (n=40) and brief (8 weeks), contrasting with null results from larger, longer trials (e.g., DO-HEALTH with 2157 participants over 3 years). Benefit may be limited to populations with low baseline vitamin D levels.
no significant differences in grip strength or short physical performance battery (SPPB) scores between the experimental and control groups were noted.
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.