LOW AND HIGH RESPONDERS TO PHARMACOLOGICAL DOSES OF BETA-CAROTENE - PROPORTION IN THE POPULATION, MECHANISMS INVOLVED AND CONSEQUENCES ON BETA-CAROTENE METABOLISM

The aim of this study was to assess the interindividual variability of chylomicron. beta-carotene response to a pharmacological load of beta -carotene in the population, to identify the mechanisms responsible fo r this variability, and to evaluate its consequences on beta-carotene status and metabolism. The variability, as estimated by the 3-h chylom icron if-carotene response to 120 mg beta-carotene in 79 healthy male volunteers, was high (CV = 61%), but it was unimodal and all the subje cts had detectable chylomicron beta-carotene, In 16 subjects randomly selected among the 79, the interindividual variability of the triglyce ride-adjusted chylomicron (beta-carotene + retinyl palmitate) response (0-12.5 h area under the curve) was high (CV = 54%), suggesting that there is a high interindividual variability in the efficiency of intes tinal absorption of beta-carotene. The chylomicron beta-carotene respo nse was correlated (r = 0.50, P < 0.05) with the chylomicron triglycer ide response. The beta-carotene status, as assessed by beta-carotene c oncentration in buccal mucosal cells, was correlated (r = 0.73, P < 0. 05) with the triglyceride-adjusted chylomicron beta-carotene response, i.e., with the ability to respond to beta-carotene. The triglyceride- adjusted chylomicron retinyl-palmitate response was correlated (r = 0. 55, P < 0.05) with the triglyceride-adjusted chylomicron p-carotene re sponse. Plasma all-trans retinoic acid slightly, but significantly, in creased (+40%) 3 h after the beta-carotene load, bat this increase was not related to the triglyceride-adjusted beta-carotene response.jlr Z n conclusion, the ability to respond to beta-carotene is highly variab le, but there is probably a very small proportion of true non-responde rs to pharmacological doses of beta-carotene in the healthy population . This variability is apparently mainly due to interindividual differe nces in the efficiency of intestinal absorption of beta-carotene and i n chylomicron metabolism. The ability to respond to beta-carotene can affect the beta-carotene status and the provitamin A activity of beta- carotene, but it has apparently no effect on the amount of retinoic ac id appearing in the plasma after the ingestion of a pharmacological do se of beta-carotene.