Vitamin D deficiency is common among Koreans and worldwide, leading both physicians and patients to become interested in whether vitamin D supplementation is needed. However, current levels of supplementation with vitamin D are insufficient, especially among aging Koreans. The musculoskeletal effects of vitamin D supplementation have been established, and its extraskeletal effects also have drawn particular interest. Nonetheless, more studies are needed to assess its extraskeletal effects with regard to cardiovascular disease, cancer, and diabetes, as well as its adverse effects. Serum 25-hydroxyvitamin D levels greater than 20 ng/mL are generally appropriate for preventing osteoporosis, while serum 25-hydroxyvitamin D levels greater than 30 ng/mL are probably helpful for the management of osteoporosis and the prevention of fractures and falls. The recommended dietary vitamin D intake is at least 800 IU per day, which appears to reduce the risk of fractures.