Are vitamin D supplements helpful?

Dr. Rhonda Patrick AI:

Yes, vitamin D supplements can be helpful, especially for those who are deficient or insufficient in vitamin D. They can help prevent respiratory tract infections and activate the innate immune system. However, it's best to get your vitamin D levels measured by a doctor and then take a supplement to bring them up if necessary. The National Institute of Medicine set the tolerable upper intake of vitamin D at 4000 international units a day.