Use of electrochemical detection to quantify the effect of added fat on intestinal carotenoid absorption from fresh vegetables in humans

Abstract

<p>Previously, high pressure liquid chromatography (HPLC) with coulometric electrochemical array detection (ECD) was shown to have enhanced sensitivity compared with HPLC with ultraviolet/visible light detection (UV/VIS) in carotenoid analysis. The objective of this study was to apply HPLC with electrochemical detection to quantify and compare the appearance of carotenoids in plasma chylomicrons after subjects ingested fresh vegetable salads with fat-free, reduced-fat, and regular fat salad dressing. Healthy, male and female subjects (n = 7) consumed a single salad that consisted of 48 g spinach, 48 g romaine lettuce, 66 g carrots, and 85 g cherry tomatoes. Salad dressings with 0, 6, and 28 g fat were prepared. The salads with the three salad dressings were ingested in random order and separated by a washout period of at least two weeks. Blood samples were drawn at baseline and at hourly intervals for 12 hours after consumption of the test salad. The plasma chylomicron fraction was isolated by cumulative rate ultracentrifugation, and the carotenoids were extracted and quantified by HPLC-ECD. After ingestion of the salads with the fat-free salad dressing, the appearance of carotenoids in the plasma chylomicron fraction was negligible. After ingestion of the salads with reduced-fat as compared with fat-free dressing, the area under the curve (AUC) increased 20.9 nmol/L (P = 0.010), 97.5 nmol/L (P = 0.012), and 3.6 nmol/L (P = 0.016) for all trans-α-carotene, all trans-β-carotene, and all translycopene, respectively. After ingestion of the salads with regular fat as compared with reduced-fat salad dressing, the AUC for all trans-α-carotene, all trans-β-carotene, and all trans-lycopene increased 2.5-fold (P = 0.025), 2.0-fold (P = 0.033), and 4.0-fold (P = 0.031), respectively. The use of HPLC-ECD to measure the postprandial carotenoid response in chylomicrons is a sensitive and efficient approach to screen for dietary factors such as added fat that enhance β-carotene bioavailability. Consumption of a vegetable salad with fat-free salad dressing resulted in virtually no carotenoid absorption. Consumption of the salad with salad dressing containing dietary fat increased carotenoid absorption, and the increase in carotenoid absorption with regular fat dressing was higher than the absorption with reduced-fat dressing.</p>