CHYLOMICRON BETA-CAROTENE AND RETINYL PALMITATE RESPONSES ARE DRAMATICALLY DIMINISHED WHEN MEN INGEST BETA-CAROTENE WITH MEDIUM-CHAIN RATHER THAN LONG-CHAIN TRIGLYCERIDES

The effect of the ingestion of beta-carotene with medium-chain triglyc erides (MCT) or long-chain triglycerides (LCT) on the bioavailability and the provitamin A activity of beta-carotene was investigated in hum ans. Sixteen healthy young men ingested, on two different days, a test meal containing 120 mg beta-carotene incorporated into 40 g LCT (LCT meal) or 40 g MCT (MCT meal). This meal was followed 6 h later by a be ta-carotene-free meal containing 40 g LCT. Chylomicron beta-carotene, retinyl palmitate and triglycerides were measured every hour for 12.5 h after the first meal. No significant increase in chylomicron triglyc erides was detected for the 6 h after the MCT meal intake, whereas a s ignificant increase in chylomicron triglycerides was observed after th e LCT meal intake. The chylomicron beta-carotene and retinyl palmitate responses to the MCT meal (0-6 h area under the curves, AUC) were sig nificantly (P < 0.05) lower [AUC = 68.1 +/- 26.8 and 43.4 +/- 10.4 nmo l/(L.h), for beta-carotene and retinyl palmitate, respectively] than t hose obtained after the LOT meal [301.4 +/- 64.0 and 166.0 +/- 29.0 nm ol/(L.h), respectively]. The chylomicron beta-carotene and retinyl pal mitate responses obtained after the beta-carotene-free meal (6-12.5 h AUC) were also significantly lower when the first meal provided MCT ra ther than LCT. The chylomicron (retinyl palmitate/beta-carotene) ratio s were constant during the postprandial periods, whatever the meal ing ested. We conclude that the chylomicron beta-carotene response is mark edly diminished when beta-carotene is absorbed with MCT instead of LCT . This phenomenon is apparently due to the lack of secretion of chylom icrons in response to MCT; however, a lower intestinal absorption of b eta-carotene or a higher transport of beta-carotene via the portal way in the presence of MCT cannot be ruled out. Finally, the data obtaine d show that MCT do not affect the rate of intestinal conversion of bet a-carotene into vitamin A.