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Urine excretion of caffeine and select caffeine metabolites is common in the US population and associated with caffeine intake 1,2,3,4
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Feb 04 2015
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Source: J Nutr. 145(4):766-774.
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Details:
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Alternative Title:J Nutr
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Description:Background
Caffeine is a widely consumed psychoactive stimulant and is of epidemiological interest. Major sources of caffeine are challenging to standardize, and the use of biomarkers has been proposed as an alternative means of assessing intake.
Objective
We described urine caffeine and caffeine metabolite concentrations (n = 2466) and excretion rates (n = 2261) in the U.S. population ≥6 y by age, sex, race-ethnicity and caffeine intake (from foods, beverages and dietary supplements).
Methods
We measured caffeine and 14 of its metabolites in spot urine samples from the cross- sectional NHANES 2009–2010 by use of liquid chromatography-tandem mass spectrometry.
Results
Caffeine and its metabolites were detectable in the urine of most persons, generally at concentrations ≥1 μmol/L. Median concentrations (95% CI) ranged from 0.560 (0.497–0.620) μmol/L to 58.6 (48.6–67.2) μmol/L; median excretion rates from 0.423 (0.385–0.468) nmol/min to 46.0 (40.7–50.2) nmol/min. Urine concentrations and excretion rates for 9 analytes (caffeine, theophylline, paraxanthine, 1-methylxanthine, 1-methyluric acid, 1,3-dimethyluric acid, 1,7- dimethyluric acid, 1,3,7-trimethyluric acid, and 5-acetylamino-6-amino-3-methyluracil) had moderate correlations with caffeine intake (Spearman |r| 0.55–0.68, P <0.0001); the remaining analytes had low correlations (|r| 0.15–0.33, P <0.0001). We observed larger differences in geometric mean concentrations and excretion rates between the highest vs. lowest quartiles of caffeine intake for these 9 compounds compared to the rest. Consistent with dietary caffeine intake, we observed that urine concentrations and excretion rates for most compounds were significantly (P <0.05) higher in males vs. females, non-Hispanic whites vs. Hispanics and non- Hispanic blacks, and highest in persons aged 40–59 y.
Conclusion
Excretion of caffeine and its metabolites in urine was common in the U.S. population. Based on the observed associations between spot urine concentrations or excretion rates with caffeine intake, several of these compounds show promise as potential biomarkers of caffeine intake.
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Pubmed ID:25833779
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Pubmed Central ID:PMC5724768
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