November 9, 2009 — Best practices for recognition, prevention, and management of vitamin D deficiency in the family practice setting are reviewed in the October 15 issue of American Family Physician. Vitamin D is essential for optimal skeletal development, maintenance of bone health, and neuromuscular function. In addition, vitamin D may play important roles in guarding against cardiovascular disease, depression, and colon cancer.
"In the 19th century, vitamin D deficiency was identified as the cause of the rickets epidemic in children living in industrialized cities," write Paula Bordelon, DO; Maria V. Ghetu, MD; and Robert Langan, MD, from St. Luke's Family Medicine Residency Program in Bethlehem, Pennsylvania. "This discovery led to the fortification of various foods, and the resolution of a major health problem associated with vitamin D deficiency. However, recent studies have shown that vitamin D deficiency and insufficiency are associated with other pathologic conditions in persons of all ages."
The diagnosis of vitamin D deficiency is often missed and the condition untreated because the signs and symptoms develop slowly or are nonspecific. These may include symmetric low back pain in women; proximal muscle weakness; muscle aches; and throbbing bone pain in the low back, pelvis, or lower extremities, or when pressure is applied to the sternum or tibia. Vitamin D deficiency may also be recognized in patients who have increased risk for falls and impaired physical function.
Risk factors for vitamin D deficiency include age older than 65 years, exclusive breast-feeding without vitamin D supplementation; dark skin; insufficient exposure to sunlight; sedentary lifestyle; and obesity, defined as body mass index greater than 30 kg/m2. In addition, use of anticonvulsants, glucocorticoids, or other medications that affect vitamin D metabolism may give rise to deficiency.
Diagnosis of suspected vitamin D deficiency is confirmed with a 25-hydroxyvitamin D level of less than 20 ng/mL (50 nmol/L). Vitamin D insufficiency is defined as a serum 25-hydroxyvitamin D level of 20 to 30 ng/mL (50 - 75 nmol/L).
The American Academy of Pediatrics recommends that infants and children have vitamin D intake of at least 400 IU/day from diet and supplements to prevent vitamin D deficiency.
Supplementation of 400 IU/day is recommended for all breast-fed infants until they are ingesting at least 1 L/day (33.8 fl oz) of vitamin D–fortified formula or milk and for all infants who are not breast-fed but who are consuming less than 1 L/day of vitamin D–fortified formula or milk.
In addition, supplementation of 400 IU/day is recommended for all children and adolescents who do not get regular sunlight exposure, who do not consume at least 1 L/day of vitamin D–fortified formula or milk, or who do not take a daily multivitamin supplement containing at least 400 IU of vitamin D.
Studies in adults suggest that vitamin D supplementation of at least 700 to 800 IU per day is associated with lower rates of falls and fractures. Contraindications to vitamin D supplementation include tuberculosis or other granulomatous diseases, metastatic bone disease, sarcoidosis, or Williams syndrome.
When vitamin D deficiency or insufficiency is present, the goal of treatment is to normalize vitamin D levels to alleviate symptoms and lessen the risk for fractures, falls, and other adverse health outcomes. Oral ergocalciferol (vitamin D2), 50,000 IU per week for 8 weeks, may be effective treatment in patients with vitamin D deficiency.
Serum 25-hydroxyvitamin D levels should be checked when this 8-week course is completed, and if values have not reached or exceeded the minimal level, the patient should receive a second 8-week course of ergocalciferol.
"The optimal time for rechecking the serum levels after repletion has not been clearly defined, but the goal is to achieve a minimum level of 30 ng per mL," the review authors write. "If the serum 25-hydroxyvitamin D levels still have not risen, the most likely cause is nonadherence to therapy or malabsorption. If malabsorption is suspected, consultation with a gastroenterologist should be considered."
Once vitamin D levels normalize in patients who were deficient, they should receive maintenance dosages of cholecalciferol (vitamin D3), 800 to 1000 IU per day from dietary sources and/or supplements.
Because vitamin D is fat soluble and can be stored in fat, there are concerns regarding toxicity from excessive supplementation. Signs and symptoms of vitamin D toxicity may include headache, metallic taste, nephrocalcinosis or vascular calcinosis, pancreatitis, nausea, and/or vomiting.
Key clinical recommendations for practice, and their accompanying level of evidence rating, are as follows:
In older adults, vitamin D supplementation of 700 to 800 IU per day is associated with a lower risk for falls (level of evidence, B). In older adults, vitamin D supplementation of 700 to 800 IU per day is associated with a lower risk for fractures (level of evidence, A). To prevent vitamin D deficiency, infants and children with inadequate sun exposure should have vitamin D intake of 400 IU/day (level of evidence, C). To prevent vitamin D deficiency, adults with inadequate sun exposure should have vitamin D intake of 400 to 600 IU per day (level of evidence, C). Adults with vitamin D deficiency, except for those with malabsorption syndromes, should receive maintenance dosages of 800 to 1000 IU of vitamin D per day (level of evidence, C). The review authors have disclosed no relevant financial relationships.