Impact of dose on the bioavailability of coffee chlorogenic acids in humans
Single servings of coffee beverage containing low (412 μmol), medium (635 μmol) and high (795 μmol) amounts of chlorogenic acids were administered to eleven healthy volunteers in a double-blind randomised controlled trial. Analysis of plasma and urine collected for 24 h revealed the presence of 12 metabolites in plasma and 16 metabolites in urine, principally in the form of sulphates, and to a lesser extent glucuronides of caffeic, ferulic, dihydrocaffeic and dihydroferulic acids, as well as intact feruloylquinic and caffeoylquinic acids, and sulphated caffeoylquinic acid lactones. Median values of peak plasma concentrations after increasing doses of chlorogenic acids were 1088, 1526 and 1352 nM. In urine the median amounts of metabolites excreted after 24 h following consumption of the three coffees were 101, 160 and 125 μmol, accounting for 24%, 25% and 16% of the doses ingested. Peak plasma concentration and urinary excretion values showed trends towards a reduced bioavailability of chlorogenic acids associated with the highest dose ingested, when expressed as percentages of intake. Potential biomarkers of coffee intake were identified as feruloylquinic acids and sulphated caffeoylquinic acid lactones in plasma and urine with positive moderate to strong coefficients of determination for peak plasma concentrations (0.60–0.81) and amounts excreted in urine (0.36–0.73) (P < 0.05).