Absorption of Phenolic Acids From Coffee in Humans

Phenolic acids are naturally-occurring constituents of plant-derived foods and beverages and are characterised by a phenol ring in their structure. The phenolic compounds we are going to focus on in this study are the Chlorogenic acids (CGAs), a family of esters conjugates formed between a Hydroxycinnamic acid and quinic acid (1) and that show a strong antioxidant activity (2).

HCAs represent about 50% of the total polyphenolic coumpounds intake in a typical UK diet (3) and for people who drink it, coffee is a/the major dietary source of/for HCAs (4). A few studies suggest protective effects for cardiovascular diseases (5), neurodegenerative diseases, type 2 diabetis and liver and kidneys cancer risk. However, many data in the field are obtained from in vitro and/or in animal, and it is difficult and dangerous to extrapolate between these and risk in humans of development or progression of particular health conditions, more human studies are therefore needed.

We aim to compare people that metabolise the best CGAs from coffee to those that metabolise them the least well. This will be achieved by measuring the metabolites in urine. The effect of CGAs on the human body does not only depend on the amount ingested, but also on the quality of the metabolism, we therefore also want to determine which mechanisms are responsible for inter-individual variations in order to identify any link with health biomarkers, these including non-cellular inflammation and cardiovascular risk indicators.

For this cohort study funded by the University of Leeds, approximately 60 healthy volunteers will be recruited at the School of Food Science & Nutrition. If they meet the selection criteria, participants will be asked to undergo a 36-hour wash-out period. During those 36 hours, participants won't be allowed to drink coffee, they will be asked to follow a diet low in phenolic acids and keep a record of their meals. On the first day of the study, a single dose of coffee rich in antioxidants will be given to the participant and urine will be collected from that time until 36 hours after coffee consumption. Participants will be followed again after 5 to 6 weeks.