title: Absorption and retinol equivalence of beta-carotene in humans is influenced by dietary vitamin A intake.
abstract: The effect of vitamin A supplements on metabolic behavior of an oral tracer dose of [14C]beta-carotene was investigated in a longitudinal test-retest design in two adults. For the test, each subject ingested 1 nmol of [14C]beta-carotene (100 nCi) in an emulsified olive oil-banana drink. Total urine and stool were collected for up to 30 days; concentration-time patterns of [14C]beta-carotene, [14C]retinyl esters, and [14C]retinol were determined for 46 days. On Day 53, the subjects were placed on a daily vitamin A supplement (10000 IU/day), and a second dose of [14C]beta-carotene (retest) was given on Day 74. All 14C determinations were made using accelerator mass spectrometry. In both subjects, the vitamin A supplementation was associated with three main effects: 1). increased apparent absorption: test versus retest values rose from 57% to 74% (Subject 1) and from 52% to 75% (Subject 2); 2). an approximately 10-fold reduction in urinary excretion; and 3). a lower ratio of labeled retinyl ester/beta-carotene concentrations in the absorptive phase. The molar vitamin A value of the dose for the test was 0.62 mol (Subject 1) and 0.54 mol (Subject 2) vitamin A to 1 mol beta-carotene. Respective values for the retest were 0.85 and 0.74. These results show that while less cleavage of beta-carotene occurred due to vitamin A supplementation, higher absorption resulted in larger molar vitamin A values.
authors.affiliation: Department of Nutrition, University of California, Davis, One Shields Ave, Davis, CA 95616, USA.
authors.forename: Shawna L
authors.initials: SL
authors.lastname: Lemke
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Dueker
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Follett
authors.forename: Yumei
authors.initials: Y
authors.lastname: Lin
authors.forename: Colleen
authors.initials: C
authors.lastname: Carkeet
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Buchholz
authors.forename: John S
authors.initials: JS
authors.lastname: Vogel
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Clifford
mesh_terms: D000042:Absorption / Q000187:drug effects; D000328:Adult; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D005243:Feces / Q000737:chemistry; D005260:Female; D006207:Half-Life; D006801:Humans; D015394:Molecular Structure; D028521:Musa; D000069463:Olive Oil; D010938:Plant Oils; D014801:Vitamin A / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology* / Q000652:urine; D019207:beta Carotene / Q000032:analysis / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine
chemical_list: D000069463:Olive Oil; D010938:Plant Oils; D019207:beta Carotene; D014801:Vitamin A