A Method of Evaluation of Antioxidants Based on Vitamin A Protection

MATTERSON and co-workers (1955 (1956) have clearly shown that antioxidants can reduce dietary requirements for vitamin A or its provitamins. This reduction may be the result of action at a number of sites: antioxidants may prevent or decrease destruction of vitamin A and carotene in the diet (Siedler et al., 1956), in the digestive tract (Lease et al., 1938; Quackenbush et al., 1942), and in tissues (Sherman, 1941; Hickman et al., 1944). While the increase in liver or plasma vitamin A and carotene has often been taken as an index of effectiveness of antioxidants, such a determination is not entirely representative of the total action of a biologically active agent, as it does not take into account possible protective effects in tissues. The validity of the method is also impinged by the fact that, particularly under conditions of stress, blood levels of vitamin A and carotene may be so low …