Background: Vitamin D supplementation is widely recommended to infants, but the optimal dose remains unclear. Vitamin D regulates calcium metabolism, and overdosing and high intake may result in hypercalcemia.
Objective and hypotheses: We measured serum pH-adjusted ionized calcium (Ca-ion/pH 7.40) concentrations at 6 and 12 months and 25-hydroxyvitamin D (S-25-OHD) at 12 months in order to evaluate the risk of hypercalcemia during vitamin D3 supplementation.
Method: In an ongoing double-blinded vitamin D3 intervention trial 987 healthy children were randomized to receive daily vitamin D3 supplementation of 400 IU (10 μg) or 1200 IU (30 μg) from 2 weeks to 2 years of age. In addition to S-25-OHD concentration at 12 months, as a part of the safety protocol, Ca-ion concentration was analyzed at 6 and 12 months. Significant hypercalcemia was defined as a level exceeding the upper reference limit (ref.1.161.39) by 10%.
Results: Ca-ion concentrations at 6 months (n=890) ranged between 1.28 and 1.52 mmol/l (median 1.37, mean 1.38, S.D. 0.04) and at 12 months (n=850) between 1.17 and 1.43 mmol/l (median 1.33, mean 1.33, SD 0.03). None of the participants had significant hypercalcemia. S-25-OHD levels at 12 months (n=801) ranged between 23.0 and 241.0 nmol/l (median 96.7, mean 99.1, SD 29.0). A correlation between S-25-OHD and Ca-ion concentration at 12 months was seen (P=<0.001). S-25-OHD in infants with Ca-ion exceeding the upper reference limit (n=14) did not differ from infants with Ca-ion within normal range (n=777) (P=0.127; mean 110.8 vs. 98.9 nmol/l).
Conclusion: At 12 months S-25-OHD did not exceed 250 nmol/l. None of the participants had severe hypercalcemia. Mild hypercalcemia at 12 months was present in 2%; no symptoms of hypercalcemia were observed. It remains unknown how these values relate to actual vitamin D dosage. Further analyses are warranted at the end of intervention later in 2016, when the randomization code will be opened.
10 - 12 Sep 2016
European Society for Paediatric Endocrinology