A New Vitamin D in Cod Liver Oil

In previous studies (1) it was shown that the liver oils of different species of fish are unequally effective, per rat unit, for the prevention of rickets in chickens. The experiments indicated the existence of more than one kind of vitamin D in the oils. More recently it was found (2, 3) that commercial cod liver oil, when subjected to molecular distillation, gives physical evidence of containing two principal, and two minor vitamins D, with traces of still two more forms. The present report covers the bioassay of the most volatile vitamin D of cod liver oil. This is one of the minor forms. It was separated (2,3) in the Eastman laboratory as the first fraction of the first fraction of the vitamin D-bearing distillate obtained from 2 tons of commercial Norwegian cod liver oil. The bioassay techniques for rats and for chickens, with procedures for estimating errors, are also elsewhere described (4,5). The rat assay technique is in a somewhat improved form, and includes the use of a reference oil such as is used in the chicken technique. The cod liver oil was assayed against the U.S.P. reference cod liver oil. 50 rats were used in the final assembly, twenty-five on the test oil and twenty-five on the reference, other rats used in exploratory trial assays not being counted. The oil contained 270 international units of vitamin D per gm. Since the liver oil of the common codfish, Gadus morrhua, contains on the average 100 international units per gm., and rarely more than 150 international units, it is reasonable to suppose that this inordinately potent oil represented some codfishes other than Gadus morrhua.