Scope: In order to validate the in vivo function of putatively healthy molecules in foods, human intervention studies are required. As the subject's compliance concerning intake or abstinence of a given food is considered mandatory to be monitored by biomarkers, the objective was to identify analytical markers for coffee consumption.
Methods and results: Urine samples collected from coffee drinkers were compared with those of non-coffee drinkers using hydrophilic liquid interaction chromatography (HILIC)/time-of-flight mass spectrometry-based metabolite profiling. Two urinary molecules, found to be contributing most to the dissimilarities between both groups, were identified as N-methylpyridinium (NMP) and trigonelline and their suitability as coffee-specific biomarkers was validated by means of a coffee intervention study. After the volunteers (five females and four males) consumed a single dose of coffee, morning urine was collected for 10 days while staying abstinent from any coffee. HILIC-MS/MS-stable isotope dilution analysis (SIDA) revealed elevated urinary concentrations of trigonelline and NMP for up to 48 (p=0.001) and 72 h (p=0.002), respectively, after coffee consumption when compared with non-coffee drinkers.
Conclusion: Analysis of urinary NMP allows to check for coffee consumption within a period of 3 days and is proposed as a dietary biomarker which might be used as an analytical probe to control compliance in human intervention studies on coffee.
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