title: Vitamin A equivalency of beta-carotene in healthy adults: limitation of the extrinsic dual-isotope dilution technique to measure matrix effect.
abstract: Data on the vitamin A equivalency of beta-carotene in food are inconsistent. We quantified the vitamin A equivalency (microg) of beta-carotene in two diets using the dual-isotope dilution technique and the oral-faecal balance technique. A diet-controlled, cross-over intervention study was conducted in twenty-four healthy adults. Each subject followed two diets for 3 weeks each: a diet containing vegetables low in beta-carotene with supplemental beta-carotene in salad dressing oil ('oil diet') and a diet containing vegetables and fruits high in beta-carotene ('mixed diet'). During all 6 weeks, each subject daily consumed a mean of 55 (sd 0.5) microg [13C10]beta-carotene and 55 (sd 0.5) microg [13C10]retinyl palmitate in oil capsules. The vitamin A equivalency of beta-carotene was calculated as the dose-corrected ratio of [13C5]retinol to [13C10]retinol in serum and from apparent absorption by oral-faecal balance. Isotopic data quantified a vitamin A equivalency of [13C10]beta-carotene in oil of 3.4 microg (95 % CI 2.8, 3.9), thus the bio-efficacy of the beta-carotene in oil was 28 % in the presence of both diets. However, data from oral-faecal balance estimated vitamin A equivalency as 6:1 microg (95 % CI 4, 7) for beta-carotene in the 'oil diet'. beta-Carotene in the 'oil diet' had 2.9-fold higher vitamin A equivalency than beta-carotene in the 'mixed diet'. In conclusion, this extrinsic labelling technique cannot measure effects of mixed vegetables and fruits matrices, but can measure precisely the vitamin A equivalency of the beta-carotene in oil capsules.
authors.affiliation: Department of Gastroenterology and Hepatology, Radboud University Nijmegen Medical Centre, Geert Grooteplein 8, PO Box 9101, 6500 HB Nijmegen, The Netherlands. VanLooBouwman@hotmail.com
authors.forename: Carolien A
authors.initials: CA
authors.lastname: Van Loo-Bouwman
authors.forename: Clive E
authors.initials: CE
authors.lastname: West
authors.forename: Richard B
authors.initials: RB
authors.lastname: van Breemen
authors.forename: Dongwei
authors.initials: D
authors.lastname: Zhu
authors.forename: Els
authors.initials: E
authors.lastname: Siebelink
authors.forename: Pieter
authors.initials: P
authors.lastname: Versloot
authors.forename: Paul J M
authors.initials: PJ
authors.lastname: Hulshof
authors.forename: Machteld
authors.initials: M
authors.lastname: van Lieshout
authors.forename: Frans G M
authors.initials: FG
authors.lastname: Russel
authors.forename: Gertjan
authors.initials: G
authors.lastname: Schaafsma
authors.forename: Ton H J
authors.initials: TH
authors.lastname: Naber
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D002214:Capsules; D002247:Carbon Isotopes / Q000494:pharmacology; D018592:Cross-Over Studies; D004032:Diet; D004042:Dietary Fats, Unsaturated; D019587:Dietary Supplements; D002149:Energy Intake; D005243:Feces / Q000737:chemistry; D005260:Female; D005638:Fruit; D006801:Humans; D007201:Indicator Dilution Techniques; D007553:Isotope Labeling; D008297:Male; D013810:Therapeutic Equivalency; D014675:Vegetables; D014801:Vitamin A / Q000032:analysis / Q000097:blood*; D055815:Young Adult; D019207:beta Carotene / Q000032:analysis / Q000097:blood / Q000494:pharmacology*
chemical_list: D015415:Biomarkers; D002214:Capsules; D002247:Carbon Isotopes; D004042:Dietary Fats, Unsaturated; D019207:beta Carotene; D014801:Vitamin A