Relative contribution of α-carotene to postprandial vitamin A concentrations in healthy humans after carrot consumption. Issue 1 (17th May 2017)

• Record Type: Journal Article
• Authors: Cooperstone, Jessica L; Goetz, Hilary J; Riedl, Ken M; Harrison, Earl H; Schwartz, Steven J; Kopec, Rachel E
• Is Part Of: American journal of clinical nutrition. Volume 106:Issue 1(2017)
• Page Start: 59
• Page End: 66
• Publication Date: 2017-05-17
• Subjects: α-carotene -- α-retinol -- bioconversion -- carrot -- vitamin A; Diet therapy -- Periodicals; Nutrition -- Periodicals; Dietetics -- Periodicals; 613.205
• DOI: 10.3945/ajcn.116.150821
• Languages: English
• ISSNs: 0002-9165

Abstract

ABSTRACT: Background: Asymmetric α -carotene, a provitamin A carotenoid, is cleaved to produce retinol (vitamin A) and α -retinol (with negligible vitamin A activity). The vitamin A activity of α -carotene–containing foods is likely overestimated because traditional analytic methods do not separate α -retinol derivatives from active retinol. Objective: This study aimed to accurately characterize intestinal α -carotene cleavage and its relative contribution to postprandial vitamin A in humans after consumption of raw carrots. Design: Healthy adults ( n = 12) consumed a meal containing 300 g raw carrot (providing 27.3 mg β -carotene and 18.7 mg α -carotene). Triglyceride-rich lipoprotein fractions of plasma were isolated and extracted, and α -retinyl palmitate ( α RP) and retinyl palmitate were measured over 12 h postprandially via high-performance liquid chromatography–tandem mass spectrometry. The complete profile of all α -retinyl esters and retinyl esters was measured at 6 h, and total absorption of α - and β -carotene was calculated. Results: α RP was identified and quantified in every subject. No difference in preference for absorption of β - over α -carotene was observed (adjusting for dose, 28% higher, P = 0.103). After absorption, β -carotene trended toward preferential cleavage compared with α -carotene (22% higher, P = 0.084). A large range of provitamin A carotenoid conversion efficiencies was observed, with α -carotene contributing 12–35% of newly converted vitamin A (predicted contribution = 25.5%). In all subjects, a majority of α -retinol was esterified to palmitic acid (as compared with other fatty acids). Conclusions: α -Retinol is esterified in the enterocyte and transported in the blood analogous to retinol. The percentage of absorption of α -carotene from raw carrots was not significantly different from β -carotene when adjusting for dose, although a trend toward higher cleavage of β -carotene was observed. The results demonstrate large interindividual variability in α -carotene conversion. The contribution of newly absorbed α -carotene to postprandial vitamin A should not be estimated but should be measured directly to accurately assess the vitamin A capacity of α -carotene–containing foods. This trial was registered at clinicaltrials.gov as NCT01432210.