The relationship between carotene concentration and vitamin A activity of carrots for rats.

The vitamin A values of plant foodstuffs, as found by biological tests with rats, are often lower than would have been expected from the results of chemical estimations of the carotene content. The causes of this discrepancy presumably lie mainly in a less complete absorption of carotene from vegetables than from the oily solution in which the international /3-carotene standard is administered, and in the inability of the chemical methods, as commonly applied, to discriminate between /3-carotene and isomers of lower biological activity. The present paper is concerned with the experimental evaluation of the ratio between biological and chemical values for carrots.