Berry supplementation in healthy volunteers modulates gut microbiota, increases fecal polyphenol metabolites and reduces viability of colon cancer cells exposed to fecal water- a randomized controlled trial

Diets high in red and processed meat and low in plant-based foods are associated with an increased risk of colorectal cancer. We investigated whether berry supplementation can impact gut metabolism to counteract the presumably cancer promoting luminal environment sustained by high red and processed meat consumption. Altogether 43 healthy adults were randomized either into Meat group (150 g/d red and processed pork meat) or Meat & Berries group (150 g/d red and processed meat and 200 g/d of mixed berries). Fecal samples and 3-d food records were collected at baseline and at the end of the four-week intervention. Intakes of vitamin C, vitamin E, manganese, insoluble fiber, and the polyphenols available in the database were significantly higher in the Meat & Berries than Meat group. While between-group comparisons found no significant differences in the gut microbiota, the within-group analyses showed that the relative abundances of beneficial Roseburia and Faecalibacterium were decreased and an unclassified group of Peptostreptococcaceae increased significantly in the Meat group. In comparison to the Meat group, berry consumption resulted in higher fecal concentrations of p-coumaric and protocatechuic acids and lower viability of fecal water (FW) -treated CV1-P fibroblastoma and human colon adenocarcinoma HCA-7 and Caco-2 cells (P<.05 with 30% FW). Berry consumption provided protective nutrients and mitigated potentially unfavourable gut microbiota changes seen in the Meat group, increased fecal polyphenol metabolites, and reduced viability of FW-treated colon adenocarcinoma cells, collectively suggesting that berries may protect against colorectal cancer development.