Vitamin D for Chronic Back Pain

Vitamin D is worth testing when back pain comes with diffuse aching and low sun exposure. It is corrective for deficiency, not analgesic in general.

Severe vitamin D deficiency causes osteomalacia, in which poorly mineralised bone matrix produces deep, diffuse skeletal pain and proximal muscle weakness. Vitamin D also influences muscle function through receptors in skeletal muscle, relevant to the trunk endurance that back pain rehabilitation depends on.

Observational studies report lower 25-hydroxyvitamin D in people with chronic low back pain, and uncontrolled series of deficient patients receiving replacement show substantial pain improvement, consistent with treating unrecognised osteomalacia. Randomised trials in unselected populations tell a different story: supplementing people with adequate baseline levels produces no meaningful reduction in back pain, and large trials of vitamin D for chronic pain generally have been negative. The reconciliation is straightforward. Vitamin D helps the deficient because it treats a deficiency disease; it does nothing for pain that has another cause. The practical approach is to measure rather than assume, replace when the level is low, and continue the exercise-based management that drives outcomes either way.

People with sufficient vitamin D levels, nerve root compression, or predominantly fear-avoidance driven pain will not improve from supplementation.