A randomized, controlled trial of vitamin D supplementation upon musculoskeletal health in postmenarchal females.

This was a randomized, placebo-controlled trial in healthy postmenarchal girls aged 12 to 14 years from an inner-city, multiethnic school in Manchester, United Kingdom. The vitamin D2 arm included 36 randomized participants, and the cohort was predominantly South Asian with low baseline vitamin D status and no clinical signs of deficiency.

Participants in the active arm received oral ergocalciferol (vitamin D2) 150,000 IU per dose, given four times at 3-month intervals over 12 months. The placebo tablets were identical in appearance.

Vitamin D2 supplementation clearly improved vitamin D status and lowered PTH, but it did not improve bone mineral density, bone geometry or strength, or muscle force and power. In the vitamin D2 arm, 25(OH)D increased from 18.1 (8.0) to 56.0 (8.9), while placebo changed from 17.9 (7.4) to 15.7 (6.6); PTH fell from 4.8 (3.9) to 2.0 (1.0). No meaningful benefits were seen for spine BMAD, radius CSMA, maximal force, Esslinger Fitness Index, or jump height; movement efficiency improved modestly (P=0.02). Overall, the findings suggest that vitamin D2 repletion alone did not translate into broad musculoskeletal benefit, although a subgroup with the lowest baseline vitamin D showed greater jump-velocity improvement.

The active arm was small and the study was conducted in a single, predominantly South Asian school-based cohort, which limits generalizability. Participants were low in vitamin D but had no overt clinical deficiency, and the trial may have been underpowered to detect modest skeletal or performance effects.