QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Online Supplemental Material All Versions of this Article: 139/8/1480    most recent jn.109.105114v1 Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Ho, C. C. Articles by Clifford, A. J. PubMed PubMed Citation Articles by Ho, C. C. Articles by Clifford, A. J.

---

Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

A Minute Dose of ¹⁴C-β-Carotene Is Absorbed and Converted to Retinoids in Humans^1–3,

⁴ Department of Nutrition, University of California, Davis, CA 95616-8669 and ⁵ Western Human Nutrition Research Center, Davis, CA 95616-8669

Our objective was to quantify the absorption and conversion to retinoids of a 1.01-nmol, 3.7-kBq oral dose of ¹⁴C-β-carotene in 8 healthy adults. The approach was to quantify, using AMS, the elimination of ¹⁴C in feces for up to 16 d after dosing and in urine for up to 30 d after dosing. The levels of total ¹⁴C in undiluted serial plasma samples were measured for up to 166 d after dosing. Also, the levels of ¹⁴C in the retinyl ester (RE), retinol (ROH), and β-carotene fractions that were isolated from undiluted plasma using HPLC were measured. The apparent digestibility of the ¹⁴C was 53 ± 13% (mean ± SD), based on the mass balance data, and was generally consistent with the area under the curve for zero to infinite period of ¹⁴C that was eliminated in the feces collections made up to 7.5 d after dosing. Metabolic fecal elimination, calculated as the slope per day (% ¹⁴C-dose/collection from d 7.5 to the final day), was only 0.05 ± 0.02%. The portion of the ¹⁴C dose eliminated via urine was variable (6.5 ± 5.2%). Participants [except participant 6 (P6)] had a distinct plasma peak of ¹⁴C at 0.25 d post-dose, preceded by a shoulder at 0.1 d, and followed by a broad ¹⁴C peak that became indistinguishable from baseline at 40 d. Plasma ¹⁴C-RE accounted for most of the absorbed ¹⁴C early after dosing and P1 had the longest delay in the first appearance of ¹⁴C-RE in plasma. The data suggest that plasma RE should be considered in estimating the ROH activity equivalent of ingested β-carotene.

^* To whom correspondence should be addressed. E-mail: ajclifford{at}ucdavis.edu.

Manuscript received 27 January 2009. Initial review completed 13 February 2009. Revision accepted 24 May 2009.

Published online 17 June 2009.