Degree Type

Dissertation

Date of Award

2003

Degree Name

Doctor of Philosophy

Department

Food Science and Human Nutrition

First Advisor

Wendy S. White

Abstract

Lutein may affect the bioefficacy of beta-carotene in humans. By using gas chromatography-combustion interfaced-isotope ratio mass spectrometry (GC-C-IRMS) and highly-enriched 13C-labeled tracers of beta-carotene and lutein, we compared the appearance of 13C-beta-carotene and its cleavage product, 13C-retinol, in plasma after subjects ingested 13C-beta-carotene with or without 13C-lutein. Women (n = 7) each ingested both a single dose of 1 mg perlabeled 13C-beta-carotene and a combined dose of 1 mg perlabeled 13C-beta-carotene and 3 mg perlabeled 13C-lutein in random order. Blood samples were collected at selected time intervals. Lutein, beta-carotene, and retinol were extracted from plasma and purified by using HPLC. Plasma retinol fractions were directly analyzed using GC-C-IRMS; lutein and Rcarotene were derivatized to thermally-stable derivatives which were analyzed using GC-C-IRMS. The appearance of 13C-beta-carotene in plasma was not different after the single or combined doses; nor was the appearance of 13C-retinol. The ratio of the 0--96 h area under the concentration vs. time curve (AUC) for 13C-retinol to the 0--528 h AUC for 13C-beta-carotene, an index for conversion of 13C-beta-carotene to 13C-retinol, was not different after the single or combined doses. Plasma beta-carotene concentration at baseline was negatively correlated with the 0--96 h AUC for 13C-retinol after the combined dose (r = -0.84, P = 0.02). Plasma lutein concentration at baseline was positively correlated with the 0--528 h AUC for 13C-lutein after the combined dose (r = 0.82, P = 0.02), and positively correlated with the 0--528 h AUC for 13C-beta-carotene after the single 13C-beta-carotene dose (r = 0.84, P = 0.02). The responses from the subjects to the doses were highly variable. The interindividual coefficient of variance (CV) of the 0--528 h AUC for 13C-beta-carotene was 59% after the single dose and 36% after the combined dose. The CV of the 0--96 h AUC for 13C-retinol was 64% after the single dose and 53% after the combined dose. The CV of the 0--528 h AUC for lutein was 44%. We conclude that, when ingested with beta-carotene in an amount and dose ratio typically found in dark green leafy vegetables, lutein does not affect the bioefficacy of beta-carotene.

DOI

https://doi.org/10.31274/rtd-180813-12692

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu

Copyright Owner

Xixuan Hu Collins

Language

en

Proquest ID

AAI3118220

File Format

application/pdf

File Size

102 pages

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