Experiments carried out on infants revealed that vitamin A, as it occurs naturally in milk, was more effectively absorbed than when administered in an oily vehicle, but not quite as well absorbed as when given in an "aqueous" preparation. The high degree of absorbability of vitamin A in milk is due to the relatively small particle size of the butter fat globule.
By reducing the particle size of a fish liver oil preparation (oleum percomorphum) to 1 to 2 µ by homogenization into milk or water, the absorption of vitamin A was considerably enhanced in children and in rats.
The relationship of the particle size of the vehicle of vitamin A to absorption is further demonstrated by the results of the administration in children and in rats of three vitamin A preparations of varying particle size. Thus, the highest absorption occurred following the administration of a preparation containing particle size of submicroscopic proportion ("aqueous"); the lowest absorption resulted following the preparation containing particles macroscopic in size (oil) and intermediate absorption was observed following the use of a preparation containing particle sizes varying from 1 to 20 µ (emulsion).
Similarly, in a child having cystic fibrosis of the pancreas, the absorption of vitamin A was dependent upon the particle size of the vehicle employed.
