Does vitamin D deficiency cause muscle weakness, pain, and impaired physical performance?

Clinical evidence

• Extensive observational studies and clinical trials demonstrate that individuals with low 25-hydroxyvitamin D levels [25(OH)D < 20 ng/mL] frequently present with proximal muscle weakness, chronic musculoskeletal pain (myalgia), and reduced physical performance (e.g., lower gait speed and decreased grip strength).
• Correcting severe deficiency [25(OH)D < 12 ng/mL] via supplementation significantly improves proximal muscle strength and functional mobility. For example, clinical trials note improvements in chair-rise tests and balance scores, particularly in individuals with low baseline levels, whereas benefits are generally minimal or absent in those who are already vitamin D-replete.

Mechanistic explanations

• VDR and calcium homeostasis: Active 1,25-dihydroxyvitamin D bind to vitamin D receptors (VDR) in skeletal muscle tissue. This signaling regulates genomic transcription of proteins essential for intracellular calcium transport, such as calbindin-D9k. Deficiency impairs rapid calcium influx into sarcoplasmic reticulum, which disrupts excitation-contraction coupling and reduces contractile force.
• Mitochondrial dysfunction: VDR signaling is crucial for mitochondrial biogenesis and respiratory chain function. Experimental VDR knockdown decreases oxygen consumption rates and downregulates ATP-generating pathways in muscle cells, causing rapid fatigability and weakness.
• Sensory hyperinnervation and pain: Vitamin D deficiency alters sensory growth cone guidance, leading to abnormal sprouting and selective hyperinnervation of peptidergic nociceptors (pain fibers) within skeletal muscle. This structural remodeling, alongside elevated systemic inflammatory cytokines, directly drives muscular hypersensitivity and chronic myalgia.

Bottom line

Vitamin D deficiency is a clinically and mechanistically verified cause of muscle weakness, pain, and impaired physical performance. This impairment is driven by defective VDR signaling that induces calcium handling errors, mitochondrial ATP depletion, and muscle fiber nociceptive hyperinnervation. Correcting a deficiency is essential for restoring optimal neuromuscular and mitochondrial function.