Overview

• A 10-week randomized trial showed indoor exercise reduces winter vitamin D level drops by 40% compared to non-exercisers.
• Participants maintained stable body weight, isolating exercise as the key factor in preserving vitamin D levels.
• Exercise fully sustained the active form of vitamin D, critical for bone, immune, and organ health, where supplements often fall short.
• The study, conducted October–April, excluded sunlight exposure and supplements to ensure reliable results.
• Researchers recommend incorporating exercise into public health strategies for winter vitamin D maintenance, especially for overweight individuals.