No discernible effect of vitamin D supplementation on secondary outcomes in chronic spinal cord injury: Findings from a randomized controlled trial.

Context: Sufficient vitamin D levels (serum 25(OH)D>75 nmol/L) have been associated with secondary health conditions and functional outcomes in individuals with chronic spinal cord injury (SCI). This study evaluated the effects of vitamin D3 supplementation on these outcomes.

Design: Randomized, placebo-controlled, double-blind clinical trial.

Setting: Specialized SCI center.

Participants: Participants included 42 individuals living with SCI for at least three years and exhibiting insufficient 25(OH)D levels at baseline (seven females, 35 males, mean age 48±10 years, 10 with tetraplegia, 32 with paraplegia).

Interventions: Participants were randomly assigned to receive placebo, medium-dose (24'000 IU every four weeks), or high-dose (24'000 IU every two weeks) vitamin D3 supplementation for 12 months.

Outcome measures: For 12 months, the following parameters were evaluated at three-month intervals: 25(OH)D levels; occurrence of urinary tract infections, pressure injuries, falls, and pain; handgrip strength; functional independence; levels of fatigue, anxiety, and depression.

Results: Of the participants who received supplementation, 33% achieved sufficient 25(OH)D levels. Pain was reported by 79% of participants during the study, while falls (57%), urinary tract infections (55%), and pressure injuries (21%) were reported less frequently. Vitamin D3 supplementation demonstrated no measurable effect on any of the investigated parameters (all P-values ≥ 0.19).

Conclusion: Vitamin D3 supplementation resulted in sufficient 25(OH)D levels in only a minority of participants, which may account for the absence of effects on secondary outcomes relevant to SCI. Future studies should investigate the efficacy of higher supplementation doses, particularly for individuals with clinically relevant levels of the respective outcomes.Trial registration: The study was registered at ClinicalTrials.gov (registration ID: NCT04652544).