Plant (poly)phenols is what we call a large number of substances that are produced by plants as secondary plant metabolites, which means substances that are not used for their growth and development but are necessary for them to survive. (Poly)phenols are divided in two major groups, flavonoids, and non-flavonoids, and each group contains a varied set of subgroups and substances. They are widely spread in fruit and vegetables that are part of the human diet, and, in general, studies have attributed many biological effects to the ingestion of (poly)phenols, especially in the prevention of non-communicable diseases. For this reason, research aims to understand their role in the health benefits of a diet that is rich in fruits and vegetables. When ingested, (poly)phenols are digested by both the human organism and the gut microbiota and are broken down into several smaller substances (catabolites) that are called low-molecular weight (poly)phenols (LMWP). Most of the absorbed (poly)phenols that reach our bloodstream and organs are LMWP.
For the proposed study, 30 healthy adults will be recruited and, if considered able to participate, will follow a standardized diet that is restricted in (poly)phenol intake and will be randomly divided into two groups: one will receive a known source of (poly)phenols (coffee) and the other will receive water, keeping the restriction of (poly)phenol from the diet. The duration of one phase is 4 days + 12 hours, during which urine, feces, and saliva will be collected. Then, after a 2-week-interval, subjects will repeat the experiment, except that this time the group who had coffee will have water, and vice versa. Again, urine and feces will be collected. The objective of the study is to identify and quantify LMWP mainly in urine, but also in feces, and try to understand how much was produced when there was no (poly)phenols in the diet compared with when there was ingestion of coffee (poly)phenols. The production of LMWP without coffee could be because of their production from other sources, like the metabolism of amino acids, proteins, and catecholamines (i.e. dopamine). The composition of the gut microbiota and relevant genetic information can alter the metabolism of (poly)phenols and will be considered in the analyses. Knowing how much of LMWP actually comes from the diet is important to understand the relevance and health benefits of these molecules.