Vitamin D for Runners: Benefits, Deficiency Signs and Dosage

A 2008 study at the Cooper Clinic in Dallas found that 75% of runners averaging 20 miles per week had low vitamin D levels. This is not a minor nutritional detail — vitamin D deficiency is directly linked to stress fractures, impaired muscle function, reduced immune defence during heavy training, and potentially slower recovery and performance. Yet most runners have never had their levels tested…