Vitamin D Supplementation: Is More Better?

The “if some is good, more is better” approach to supplementation has led to as many as 3% of U.S. adults taking high-dose vitamin D supplements (≥4000 IU daily). To address uncertainty about incremental benefit of vitamin D doses higher than 400 to 1000 IU daily, Canadian investigators randomized 311 adults (mean age, 62); without osteoporosis and with normal hydroxyvitamin D (25[OH]D) and serum calcium levels to one of three levels of supplementation (400 IU, 4000 IU or 10,000 IU) daily. At baseline, mean serum 25(OH)D was 32 ng/mL (79 nmol/L). Patients with prior high-dose vitamin D use, disorders of vitamin D metabolism, or high 10-year risk for osteoporotic fractures were excluded. Dietary calcium intake was supplemented to recommended…