Background:~Hydroxytyrosol is a phenolic phytochemical naturally occurring in olives with potential antioxidant, anti-inflammatory, and health benefits mainly related with cardiovascular diseases [for review see Covas et al., 2015]. OliPhenolia® bitter and OliPhenolia® are two food supplements resulting from the liquid by-product generated during olive oil production, that are rich in olive polyphenols, mainly hydroxytyrosol. Hydroxytyrosol and its derivatives (tyrosol and oleuropein) are present in higher levels in the watery extracts from olives when compared with the oil fraction.~Most studies on hydroxytyrosol bioavailability have been performed by consuming it with olive oil or as a highly purified molecule. In a study by D'Angelo and collaborators [D'Angelo et al, 2001] it was shown that hydroxytyrosol can be rapidly absorbed from the blood and distributed in the human body, metabolized and eliminated rapidly in urine mainly as a glucuronide. It has been estimated that the absorption process depends on the composition of the food matrix through which hydroxytyrosol is administered [Visioli et al, 2003], when consumed together with fats (e.g. olive oil) it is absorbed in a greater extent. By being a water-soluble molecule, hydroxytyrosol is only slightly soluble in fats, therefore naturally present in significantly higher concentrations in the olive fruit aqueous fractions than in the olive oil.~Overall, the human studies support the need to evaluate the bioavailability of hydroxytyrosol following its administration as a major component of the two aqueous food supplements, OliPhenolia® and OliPhenolia® bitter.~Study Procedure:~After detailed information and signed informed consent all males meeting the inclusion and exclusion criteria will be included into the study. During their study participation, participants are not allowed to consume any products with or made from olives or olive oil as well as alcohol and supplements with hydroxytyrosol, vitamins, minerals and antioxidants. Products high in polyphenols and antioxidants may only be consumed in moderate amounts. Three days prior to and at each intervention day, volunteers will be requested to avoid moderate or intense physical activity.~After a run-in period, participants will return in a fasted state to the site for the first intervention visit. Volunteers will be asked to empty their bladder at home 2h before IP intake. After arriving at the site, a baseline blood and urine sample (-5 min) will be collected and the participants receive according to the individual allocation determining the sequence of the IP intake either one of the olive watery extract supplements (OliPhenolia® bitter or OliPhenolia®) or the olive oil first. Further blood and urine samples will follow (+30 min, +60 min, +90 min, +120 min, +240 min, +12 h). Vital signs and AEs will be checked throughout the intervention visit. Participants will receive several snacks and water during their visit.~After a one-week washout phase each, participants will return to their second and third intervention visit. The same procedures as on intervention visit 1 will take place except the IP intake will vary according to the individual allocation.~At the end of the third intervention visit, participants will receive a study compensation.
The aim of this cross-over study is to assess the bioavailability of hydroxytyrosol in healthy males after the intake of two olive watery extract supplements and one olive oil. Blood and urine samples will be collected before and after intake of the investigational products. Sample will be analysed regarding the level of hydroxytyrosol and preventing lipid peroxidation.