The Effect of Vitamin D Supplementation on Pediatric Skeletal Muscle Strength: A Systematic Review

Background.  Vitamin D plays a key role in calcium absorption and contributes to several physiological functions. While serum vitamin D levels are positively associated with skeletal muscle strength, the effect of supplementation on pediatric skeletal muscle strength remains unclear. Purpose. To systematically review the literature on the effect of vitamin D supplementation on muscle strength in the pediatric population. Method.  This systematic review included only randomized controlled trials (RCTs) that investigated vitamin D supplementation and assessed muscle strength in healthy children or adolescents before and after the intervention. Non-experimental studies and trials involving additional supplementation were excluded. Results. This review was registered in PROSPERO (CRD42022314030). Five RCTs studies met the inclusion criteria, with excellent methodological quality on the PEDro scale. A total of 747 participants (mean age 12.6 years; two-thirds female) were included. VitD insufficiency was common at baseline but improved in most participants after supplementation. Only handgrip strength was measured in all studies, except one that assessed knee muscle strength. Overall, VitD supplementation did not significantly improve muscle strength, except in one trial involving premenarchal girls with VitD deficiency, where handgrip strength improved. Conclusion.  Vitamin D supplementation may be beneficial in improving muscle strength among premenarchal girls with vitamin D deficiency, possibly through suppression of parathyroid hormone (PTH).