Observations on the distribution of anti-rachitic substances

Abstract

When Mellanby found that the rickets produced in dogs was prevented or cured by cod liver oil, he thought that since cod liver oid is extremely rich in the fat-soluble A vitamin, that this substance was responsible for the cure and that the deficiency of fat-soluble A is the cause of rickets. This assumption was soon proved to be erroneous, and a second natural assumption was made by McCollum that the deficiency of another vitamin was responsible for rickets production. No one doubts the existence in cod liver oil of a substance having a favorable influence on mineral metabolism. If this substance is concerned in the rickets of infants then we must be able to show that a normal diet for infants contains the substance in sufficient amount and that when rickets occurs the substance is deficient. It is perfectly well known, however, that rickets occurs quite freely in infants on mother's milk or on best grades of fresh cow's milk. It is, furthermore, a well established fact that rachitic infants are not cured by the addition of liberal amounts of cream to their diet.

Both Park and Howland believe that an anti-rachitic vitamin occurs in foods probably associated with the fat-soluble A in green leaves. Having found a method by which we can materially concentrate the active substance from cod liver oil, we investigated the occurrence of this material in various plant and animal substances. We have subjected the following materials to the processes similar to those by which we obtained a substance from cod liver oil one thousand times as active as cod liver oil itself: butter, cocoanut oil, spinach, carrots, pig's liver and sheep's adrenals. From none of these materials were we able to obtain an extract which even without dilution approached the action of cod liver oil, while from cod liver oil itself we obtained extracts at least one hundred and later more than one thousand times more active than the original cod liver oil.