Chylomicron β-carotene and retinyl palmitate responses are dramatically diminished when men ingest β-carotene with medium-chain rather than long- chain triglycerides

Abstract

The effect of the ingestion of β-carotene with medium-chain triglycerides (MCT) or long-chain triglycerides (LCT) on the bioavailability and the provitamin A activity of β-carotene was investigated in humans. Sixteen healthy young men ingested, on two different days, a test meal containing 120 mg β-carotene incorporated into 40 g LCT (LCT meal) or 40 g MCT (MCT meal). This meal was followed 6 h later by a β-carotene-free meal containing 40 g LCT. Chylomicron β-carotene, retinyl palmitate and triglycerides were measured every hour for 12.5 h after the first meal. No significant increase in chylomicron triglycerides was detected for the 6 h after the MCT meal intake, whereas a significant increase in chylomicron triglycerides was observed after the LCT meal intake. The chylomicron β- carotene and retinyl palmitate responses to the MCT meal (0-6 h area under the curves, AUC) were significantly (P < 0.05) lower [AUC = 68.1 ± 26.8 and 43.4 ± 10.4 nmol/(L·h), for β-carotene and retinyl palmitate, respectively] than those obtained after the LCT meal [301.4 ± 64.0 and 166.0 ± 29.0 nmol/(L·h), respectively]. The chylomicron β-carotene and retinyl palmitate responses obtained after the β-carotene-free meal (6-12.5 h AUC) were also significantly lower when the first meal provided MCT rather than LCT. The chylomicron (retinyl palmitate/β-carotene) ratios were constant during the postprandial periods, whatever the meal ingested. We conclude that the chylomicron β-carotene response is markedly diminished when β-carotene is absorbed with MCT instead of LCT. This phenomenon is apparently due to the lack of secretion of chylomicrons in response to MCT; however, a lower intestinal absorption of β-carotene or a higher transport of β-carotene via the portal way in the presence of MCT cannot be ruled out. Finally, the data obtained show that MCT do not affect the rate of intestinal conversion of β- carotene into vitamin A.