[The requirements of vitamin D (cholecalciferol) and of 25-hydrocalciferol (25HCC) in premature children during their early life (author's transl)].

The necessary daily amount of vitamin D3 in premature infants was calculated by Hövels and his group as being 25 mcg (1000 I.U.). This was in agreement with our own investigations. Without vitamin D3, however, the incidence of rikkets in premature and small-for-dates newborns occurred usually at the beginning of the second month of life. Clinical signs of rickets are still absent at this time, while an increased activity of the serum alkaline phosphatase signals the beginning of the illness. Three groups of prematurely born infants received up to 50 days daily oral doses of 12.5 mcg vitamin D3 (=500 I.U.), 25 mcg vitamin D3 (=1000 I.U.) or 9 mcg 25-hydroxycholecalciferol (25-HCC), respectively, while one untreated group served as control. No differences were noted between the four groups in the serum values of calcium and phosphorus. The activity of the alkaline phosphatase tended to be higher in the untreated and the 500 I.U. groups. The differences were prouved by the chi2-test to be significant (see table 2 and 3). It appeared that 9 mcg of 25-HCC prevented the rise in alkaline phosphatase slightly better than 25 mcg of vitamin D3 (1000 I.U.). On a mcg base 25-HCC seems three times as effective as cholecalciferol. One could speculate about a delayed hydroxylation of cholecalciferol (vitamin D3) to 25-HCC.