those individuals over 70 years of age with limited sun exposure and stores. In order to cover the needs of adults over age 70, regardless of exposure to sunlight and stores, the above value is doubled for an AI of 15 µg (600 IU)/day.

Medications. Glucocorticoids are well known for their anti-inflammatory properties. One of the most undesirable side effects of glucocorticoid therapy is severe osteopenia. One of the mechanisms by which glucocorticoids induce osteopenia is by inhibiting vitamin D-dependent intestinal calcium absorption (Lukert and Raisz, 1990). Therefore, patients on glucocorticoid therapy may require additional vitamin D in order to maintain their serum 25(OH)D levels in the mid-normal range (25 to 45 ng/ml [62.5 to 112.5 nmol/liter]).

Medications to control seizures, such as phenobarbital and dilantin, can alter the metabolism and the circulating half-life of vitamin D (Favus and Christakos, 1996). Holick (1995) recommended that patients on at least two antiseizure medications who are institutionalized, and therefore not obtaining most of their vitamin D requirement from exposure to sunlight, increase their vitamin D intake to approximately 25 µg (1,000 IU)/day to maintain their serum 25(OH)D levels within the mid-normal range of 25 to 45 ng/ml (62.5 to 112.5 nmol/liter). This should prevent the osteomalacia and vitamin D deficiency associated with antiseizure medications.

Serum 25(OH)D. Paunier et al. (1978) evaluated the vitamin D intake from foods, supplements, and sunshine exposure of 40 healthy women at the time of delivery of their babies during the months of January and February. Women taking less than 3.8 µg (150 IU)/day had an average serum 25(OH)D concentration of 9.1 ± 1.5 ng/ml (22.75 ± 3.75 nmol/liter), while women taking more than 12.5 µg (500 IU)/day had a concentration of 11.1 ± 1.3 ng/ml (27.75 ± 3.25 nmol/liter). Although the authors noted no significant difference between