Vitamin D prophylaxis during infancy: comparison of the long-term effects of three intermittent doses (15, 5, or 2.5 mg) on 25-hydroxyvitamin D concentrations.

Serum 25-hydroxyvitamin D [25(OH)D], calcium, phosphorus, and alkaline phosphatase activities were measured from birth to 6-9 mo of age in 60 healthy neonates to assess the effectiveness and potential toxicity of three intermittent oral doses of cholecalciferol. Two weeks after a first dose of 15, 5, or 2.5 mg, 25(OH)D concentrations reached 307 +/- 160, 150 +/- 55, and 92 +/- 42 nmol/L, respectively. Prolonged vitamin D overload, up to 6 mo, was found in 50% of the children given 15 mg, but not in the other infants. Serum calcium transiently increased 2 wk after 15 mg but not after the lower doses. Oral doses of 2.5 mg given every 3 mo appear to provide the best protection against vitamin D deficiency and vitamin D overload in high-risk infant populations that are unsuitable for daily vitamin D supplementation.