What is vitamin D and what does it do?

Vitamin D is a nutrient you need for good health. It helps your body absorb calcium, one of the main building blocks for strong bones. Together with calcium, vitamin D helps protect you from developing osteoporosis, a disease that thins and weakens the bones and makes them more likely to break. Your body needs vitamin D for other functions too. Your muscles need it to move, and your nerves need it to carry messages between your brain and your body. Your immune system needs vitamin D to fight off invading bacteria and viruses.

How much vitamin D do I need?

Recommended Amounts: (Source: National Institute of Health)
Birth to 12 months10 mcg (400 IU)
Children 1–13 years15 mcg (600 IU)
Teens 14–18 years15 mcg (600 IU)
Adults 19–70 years15 mcg (600 IU)
Adults 71 years and older20 mcg (800 IU)
Pregnant and breastfeeding teens and women15 mcg (600 IU)