Among 396 community-dwelling Taiwanese adults (mean age 65, mean serum 25(OH)D 28.3 ng/mL, mean gait speed 0.91 m/s), higher vitamin D was associated with faster walking in men (p = 0.047) but not in women. Age and BMI predicted slower gait in both sexes, while hypertension and diabetes predicted slower gait only in women. The design was cross-sectional with sex-stratified linear regression.
The male-only signal rests on a borderline p-value in 164 men, with no correction for multiple testing, so treat it as hypothesis-generating. Cross-sectional data also cannot separate cause from reverse causation: slower, less active people spend less time outdoors and make less vitamin D, which alone could produce this pattern. The stronger and more consistent findings are the familiar ones. Age, adiposity and, in women, cardiometabolic disease each tracked with slower gait, and gait speed below about 0.8 to 1.0 m/s is a well-validated marker of sarcopenia risk and mortality. Randomized trials of vitamin D supplementation, including large ones such as VITAL, have generally shown little benefit for muscle function or falls in people who are not clearly deficient, with benefit most plausible at severe deficiency. Here, mean levels sat in the insufficient range rather than the deficient range. The practical takeaway: keeping weight and blood sugar under control and staying physically active likely matters more for preserving walking speed than raising vitamin D. Confirmatory at best, and not a reason to start supplements on its own.