The MaPLE project aims to test the hypothesis that an increased intake of polyphenol-rich foods reduces intestinal permeability and lowers inflammogenic bacterial factors in the bloodstream, promoting a protective metabolic phenotype in the elderly.
The central activity of the project is a randomised, controlled, crossover design 8-week dietary intervention study in older participants. This study was conducted in a controlled setting, i.e. nursing home. A dietary protocol was developed that provided adequate energy and nutrient intake and allowed delivery of specific polyphenol-rich foods/beverages to the population under study. This involved incorporating three portions per day of polyphenol-rich food products which approximately doubled the participant’s polyphenol intake. These food products included berries and derived products, blood oranges and juice, pomegranate juice, Renetta apple and purée, green tea and dark chocolate products. All products were well tolerated by participants. The dietary intervention phase has been successfully completed and measurements of a series of biomarkers related to intestinal permeability, inflammation, the gut microbial ecosystem and the blood microbiomics are underway. Baseline assessments confirmed that the study population had high circulating zonulin levels that are indicative of increased intestinal permeability.
In addition, to the human study, in vitro experiments are focussed on exploring the potential effects of different polyphenols on gut permeability and exploring the mechanisms. We have shown that flavonols such as quercetin and kaempferol induce a fairly rapid and persistent increase in the trans-epithelial electrical resistance in the differentiated CaCo2 cell monolayer model of the small intestine. Potential changes in tight junction and cytoskeletal proteins are now being assessed. Using very old mice, we have also shown that supplementation of the diet with a mixture of polyphenols that are similar to those incorporated into the older human participant diets caused a significant reduction in intestinal permeability.