Vitamin D Deficiency in Inflammatory Rheumatic Diseases Isn’t a Proven Disease Modifier

A comprehensive IOF review finds vitamin D deficiency is common in inflammatory rheumatic diseases and linked to higher disease activity and worse symptoms, but current evidence does not support vitamin D as a disease-modifying therapy. Supplementation safely corrects deficiency and may offer modest benefits for those with low baseline vitamin D, yet large randomized trials and Mendelian randomization studies do not show a causal role in disease onset or remission. Vitamin D remains important for bone and muscle health, but better-designed trials are needed to identify which patients (if any) may experience meaningful immunological or clinical benefits; maintain serum 25-hydroxyvitamin D around 30 ng/mL for skeletal health, while higher levels for immune modulation remain uncertain.