Strength in a Supplement: Can Vitamin D Combat Sarcopenia in Older Adults?

Introduction: Sarcopenia, the age-related loss of muscle mass and strength, is a major contributor to frailty, falls, and functional decline in older adults, significantly increasing the risk of hospitalisations and mortality. While vitamin D is well known for its role in bone health, its potential benefit for skeletal muscle remains under investigation. This review critically evaluates the role of vitamin D supplementation in improving muscle health and function in older adults without vitamin D deficiency. 

Methods: A literature search across multiple databases identified 591 English-language studies published between 2011 and 2022; an update in 2025 increased the total to 632 studies for screening. Twenty-three studies met inclusion criteria, focusing on non-vitamin D-deficient older adults with or at risk of sarcopenia. Primary outcomes included changes in handgrip strength, knee extension strength, muscle mass, and physical function. Quantitative data were extracted and analysed descriptively. 

Results: Vitamin D supplementation alone showed limited effects on handgrip strength but modest improvements in knee extension strength in adults with pre-sarcopenia, with inconsistent findings across studies. In sarcopenic individuals, vitamin D alone was not associated with significant improvements in strength or function. In trials combining vitamin D with protein supplementation, muscle mass and handgrip strength improved significantly. No clear dose-response relationship was evident. Variability in outcomes appeared to be influenced by intervention duration, baseline vitamin D status, and co-supplemented nutrients. 

Conclusion: Vitamin D supplementation, particularly when combined with protein, may support muscle preservation and delay frailty in older adults at risk of sarcopenia, but has little impact on strength or function in those with established sarcopenia. These findings suggest a promising role in sarcopenia prevention, although inconsistent results highlight the need for further research to determine optimal dosage, duration, and supplementation strategies for clinical application.