INTESTINAL-ABSORPTION OF BETA-CAROTENE, LYCOPENE AND LUTEIN IN MEN AND WOMEN FOLLOWING A STANDARD MEAL - RESPONSE CURVES IN THE TRIACYLGLYCEROL-RICH LIPOPROTEIN FRACTION

A high intake of fruit and vegetables is believed to be protective aga inst heart disease and cancer. beta-Carotene has been closely examined for evidence of these protective properties but evidence is still con flicting and there are many other carotenoids in plant foods which des erve attention. This paper reports studies on the concentrations of lu tein and lycopene in the triacylglycerol-rich lipoprotein (TRL) fracti on of plasma in comparison with beta-carotene following a large dose o f the respective carotenoids fed with a standard meal after an overnig ht fast. beta-Carotene (40 mg) was given to twelve Volunteers (six men and six women) and six of the same volunteers (three men and three wo men) also received 31.2 mg lutein or 38 mg lycopene. Plasma was collec ted at hourly intervals for 8 h and the TRL fraction was separated and subsequently analysed for the respective carotenoids and retinyl palm itate in the case of beta-carotene. Intestinal uptake of the three car otenoids was estimated using the 'area under the curve' method and app arent absorption was calculated from these results. The response curve s in the TRL fraction for beta-carotene and retinyl palmitate occurred maximally over the fourth to fifth hour postprandially. There was a c orrelation between the TRL concentrations of beta-carotene and retinyl palmitate (males r 0.62, P < 0.001; females r 0.52, P < 0.001) and th ere was no significant difference between men and women either in the total amount of beta-carotene appearing in the TRL fraction or in the amount converted to retinol. On estimation, approximately 1.4 mg of th e 40 mg beta-carotene dose was absorbed and this was not significantly different from the amount of lycopene (1.0 mg) but significantly diff erent (P < 0.05) from the amount of lutein (0.8 mg) absorbed, after co rrection for the smaller doses administered. There was approximately a twofold difference between subjects in the uptake of beta-carotene in to the TRL fraction, a two- to threefold variation in lycopene and a t wo- to threefold variation in lutein. Despite these inter-subject diff erences, in three volunteers between whom there was a threefold differ ence in beta-carotene in the TRL fraction and a twofold difference in retinol formation, repeat experiments with beta-carotene 4 months late r found differences of only 3-6 % in the TRL beta-carotene content and 4-9 % for the TRL retinol formed. In conclusion, large intersubject v ariation in TRL carotene uptake precluded any differences between sexe s but surprising intra-subject consistency was observed in TRL beta-ca rotene uptake of three subjects.