Abstract
Antirachitic agents obtained from different sources but containing identical numbers of rat units appear to have different values for various species when used in the prevention or treatment of rickets. Steenbock et al. 1 have shown the difference that exists in the reaction of chickens to irradiated ergosterol, irradiated yeast and natural fish liver oils. Our own experience 2 with infants, which has since been amply confirmed, sufficiently demonstrated this difference when the same daily rat unit dose of specially assayed cod liver oil and irradiated ergosterol were used. Hess 3 has shown satisfactory results with small prophylactic doses, i. e., 40 to 50 rat units per day, when taken as irradiated milk.
Accepted standards for the proper dosage of cod liver oil, irradiated ergosterol and irradiated milk are still based largely upon clinical opinion rather than controlled observational material. The statement of Hess 4 is that the relative equivalent rat unit dosage is: of cod liver oil, 240 rat units; viosterol, 600 rat units; irradiated milk, 40 rat units. His conclusions seem to have been arrived at without careful comparative studies having been made. It was with the idea of approaching the minimal prophylactic dosage of cod liver oil vitamin D that this study, giving each infant daily 50 Steenbock units of vitamin D as the Zucker 5 cod liver oil concentrate (emulsified in milk), was made. It also affords an opportunity to compare a carefully measured intake of cod liver oil vitamin D with vitamin D from other sources. This makes no provision obviously for the occasional refractory case that is best safeguarded by a more liberal intake of vitamin D.
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