Late last year, a group of leading scientists published an editorial in the American Journal of Clinical Nutrition calling for an "urgent need" to increase the AI for vitamin D.

CNN: Vitamin D is hot! Here's how to get it

The AI for vitamin D is 200 International Units for adults under age 50, 400 IU for those 51 to 70, and 600 IU for those age 71 and above.

CNN: Vitamin D is hot! Here's how to get it

The Institute of Medicine, a group that uses scientific research to formulate public health policies, currently recommends an Adequate Intake, or AI, rather than a specific daily amount of vitamin D.

CNN: Vitamin D is hot! Here's how to get it