The best way to get vitamin D is from the sun. We need about 10 minutes a day of sunlight to reach recommended amounts. But concerns about skin cancer, the challenges of living in northern climes, older age and some medical conditions require other vitamin D sources.
Food: Very few foods naturally contain vitamin D. Fish, including salmon, tuna and mackerel, and fish liver oils are the best. Small amounts also are found in beef liver, cheese, egg yolks and some mushrooms. Almost all milk sold in the United States is fortified, and some orange juice and yogurt contain vitamin D as well.
Requirements: Most adults need 600 International Units (IU) a day. People 71 and older may require as much as 800 IUs.
Toxicity: Adults, 4,000 IUs daily; levels vary for children, depending on age, from 2,500 to 3,000 IUs.Sources: National Institutes of Health, Institute of Medicine