Summary

A plain language guide to vitamin D and immune health. Explains what vitamin D does in the body and how people get it from sunlight, foods like fatty fish and fortified milk or cereals, and supplements. Lists recommended daily amounts, groups at higher risk of low vitamin D, and why too much from supplements can be harmful. Encourages talking with a healthcare provider about testing and supplement needs and notes there is not enough evidence to recommend vitamin D for preventing or treating COVID-19.