Berries, Inflammation, and Gut Microbiome

Overview

The primary objectives are to characterize changes in indices of systemic and gut inflammation, assess host- and microbial-derived metabolite pools, and describe and link functional metagenomics and metatranscriptomic alterations in the gut microbiome with metabolite and inflammatory outcomes after acute (24hr) and chronic (4 week) intake of anthocyanins and ellagitannins from strawberry and red raspberries compared to a control diet (negative control), FOS (positive control, non-polyphenol, carbohydrate-based fermentable fiber/pre-biotic), or combination diet (berry composite + FOS) in human participants with low-grade inflammation.

The proposed study will be conducted in humans according to Good Clinical Practice (GCP) guidelines. All subjects will review and sign an Informed Consent Form approved by the Illinois Institute of Technology's Institutional Review Boards (IRB) prior to screening. This is a single-center, randomized, single-blinded, 4-arm, placebo-controlled clinical trial. It features an acute single exposure 24-h protocol and a chronic 4-week daily intake protocol to evaluate the effects of anthocyanins and ellagitannins from strawberry and red raspberry intake compared to a control diet, FOS, or FOS and berries combined on gut inflammation, in adults with chronic low-grade inflammation. A planned sample size of 88 will be enrolled in the study. This study will require one initial screening visit, a pre-study visit, and 5 study visits. This study will take 5 weeks per subject to complete. The initial screening visit will provide subject with their site-specific, IRB-approved informed consent document prior to the start of any study-related procedures. Subject eligibility will be determined through a high sensitivity C-Reactive Protein (hs-CRP) marker value, anthropometric measurements, vital signs, fasting blood glucose test (finger prick), and completion of a survey related to general eating, health, mood and exercise habits. Eligible subjects will follow a limited polyphenolic diet throughout the duration of their participation, although stricter guidelines will be imposed during the 3 days prior to a study visit that involved blood/urine/fecal collection. Shopping lists and meal plans will be provided to subjects, along with counseling by the investigator's study investigators, to help subjects adhere to the limited polyphenolic diet. The trial will initiate with a 3-day food diary to assess background (pre-study) dietary intake followed by counseling to follow a diet relatively low in (poly)phenolic rich-beverages/foods, which will be maintained for the duration of the experiment. After an initial 7-day wash-in period on the limited polyphenolic diet, subjects will be randomized to 1 of 4 treatment sequences in the form of a drink: a mixed berries diet (raspberries and strawberries), a FOS diet (non-polyphenol, carbohydrate-based fermentable fiber/pre-biotic), a combination diet (mixed berries + FOS), or a control diet (negative control). Subjects will receive the same treatment for the duration of the study. Treatment codes will be maintained by the principal investigator. Each visit will last \~2 hours and subjects will be required to remain at the Clinical Nutrition Research Center for the duration of the visit. Fasting blood samples will be collected at the 0 and 24h time points via a butterfly needle placed by a certified phlebotomist.