The researchers determined that more than half of the people in the United States, and the rest of the world, are deficient in vitamin D. They also believe the currently recommended daily adequate intake of vitamin D - up to 600 IU per day - is outdated and too low. According to the study, most children and adults need at least 1000 IU per day, and persons with chronic musculoskeletal pain would benefit from 2000 IU or more per day of supplemental vitamin D3 (also called cholecalciferol).
Vitamin D is a fat-soluble vitamin that acts like a hormone in your body to help you absorb calcium. Your body makes vitamin D when your skin is exposed to sunlight, although you can also get a little vitamin D from fish and fortified foods like milk and breakfast cereal. Vitamin D supplements are generally safe to take, just be sure you follow the dosage instructions on the label unless you speak with your healthcare provider first.