A STUDY OF THE BIOLOGICAL UTILIZATION OF CAROTENOIDS OF CARROT AND SWAMP CABBAGE IN RATS

The biological utilization of carotenoids is related to their provitam in A activity and the efficiency of their absorption and conversion to retinol and also their function as antioxidants. For practical purpos es, various authorities have taken the efficiency of conversion of bet a-carotene to retinol to be in the ratio of 6:1, and that of other pro vitamin A carotenoids as 12:1. This paper presents results of a study carried out to determine the bioavailability of carotenoids present in two carotenoid-rich vegetables (namely carrot and swamp cabbage, kang kong) and aims to provide further information on the nutritional value of these important sources of provitamin A compounds. The growth and the levels of retinol and carotenoids in the liver and serum of rats p rovided with these carotenoids in the daily diet were monitored. These results were compared with the biological utilization of crystalline retinol and beta-carotene concentrates. Two different experimental pro cedures were adopted for the study, namely supplementation and depleti on-repletion procedures using the rat as the test animal. Both procedu res showed that the bioavailability of the major carotenoids in carrot (alpha- and beta-carotene) and kangkong (beta-carotene) was high, as evidenced by the accumulation of retinol in the liver of the experimen tal rats, in relation to crystalline retinol concentrate. The provitam in A. activity of alpha- and beta-carotenes in the vegetables approxim ates the commonly used factors of 1/12 and 1/6 that of retinol, respec tively. Either one of the experimental procedures may be used for the study of bioavailability of carotenoids in plant sources. The suppleme ntation procedure, however, takes a shorter time to carry out and coul d be advantageous. The 4-week supplementation period was quite suffici ent to obtain clearly observable differences. To further reduce time a nd cost of analysis, a 2-week supplementation would suffice, and liver retinol and carotenoid concentrations could be determined before and after supplementation. Such studies on the bioavailability of caroteno ids should be extended to human subjects. (C) 1996 Elsevier Science Lt d.