Impact of Inulin on Production of Phenolic Acids From Tomato Onion and Lovage Soup

Overview

This is an acute human bioavailability study in self-reported healthy participants aged 20-70 years old. The investigators hypothesize that combination of polyphenolics from a soup rich in rutin and quercitin and the non-digestible carbohydrate (NDC) inulin will increase the production of phenolic acids by bacteria in the human colon and these will be detected in urine. Participants will attend for three arms in a randomized order: Tomato, onion and lovage soup (high polyphenol food), Inulin (NDC) or Mixture of tomato, onion and lovage soup and inulin. During each feeding study, urine, blood and stool samples will be collected at regular intervals for the duration of 24 hrs after consumption of test food. Participants will be asked to follow a low polyphenol diet for 2 days prior to the feeding study.

Polyphenol rich plant foods have been associated with several health benefits but their bioavailability is generally low. The majority of plant polyphenols are poorly absorbed in the small intestine and enter the colon where the colonic microbiota metabolise them to release a range of phenolic acids, which are now thought to be the main bioactive components related to the reduction in disease risk. Very little is known about the impact of other constituents of the diet on the metabolism and bacterial catabolism of these polyphenols. Colonic bacteria are key agents in the release of the bioactive molecules from polyphenols but also ferment non-digestible carbohydrates (NDC) such as inulin to short chain fatty acids. It is likely that there are key interactions in the colonic bacterial metabolism of NDC and phenolics. The investigators hypothesize that combination of polyphenolics (in onions, tomatoes and lovage) with inulin (NDC) will increase the urinary output of bioactive phenolic acids.