The incidence of
vitamin D deficiency is rising worldwide, yet in the vast majority of patients, the condition remains undiagnosed and untreated. Current evidence overwhelmingly indicates that supplemental doses greater than 800 IU/day have beneficial effects on the musculoskeletal system, improving skeletal homeostasis, thus leading to fewer falls and fractures. Evidence is also accumulating on the beneficial effects of
vitamin D on extraskeletal systems, such as improving immune health, autoimmune disorders,
cancer, neuromodulation, diabetes, and
metabolic syndrome. The cause-effect relationship of
vitamin D deficiency with increasing incidences of nonskeletal disorders is being investigated. Published reports support the definition of sufficiency, serum levels of
25-hydroxyvitamin D [25(
OH)D] greater than 30 ng/mL (75 nmol/L). To achieve this, most people need
vitamin D supplementation ranging from 600 to 2000 IU/day; consumption up to of 5000 international units (IU) per day of
vitamin D is reported as safe. Although light-skinned individuals need 1000 IU/day of
vitamin D, elderly and dark-skinned individuals are likely to need approximately 2000 IU/day to maintain serum 25(
OH)D levels greater than 30 ng/mL. Other vulnerable patients, such as the obese, those who have undergone
bariatric surgery, and those with gastrointestinal
malabsorption syndromes, may require higher doses of
vitamin D to maintain normal serum levels and be healthy.