Discussion
non-obese, tumour, CRC
DNA DAMAGE, GENOTOXICITY, TUMOUR
The present study investigated the impact of replacing a high red and processed meat diet with mycoprotein on faecal water genotoxicity and markers related to intestinal health. We recognise faecal water genotoxicity is poorly validated against tumour incidence in humans; however, it has been widely used as a non-invasive surrogate risk marker in short-term interventions exploring dietary components (notably meat) and CRC risk [We observed that the Meat phase increased faecal water genotoxicity which corroborates previous findings [Both diets significantly influenced the composition of the gut microbiota. The most notable changes were increases in the relative abundance of In contrast, the Meat phase caused the enrichment of the bile-resistant, putrefactive Prior to our study, gut fermentation of mycoprotein has only been reported in an in vitro model, which found an increase in total SCFA production [Applying untargeted metabolomics, we were able to decipher the predominant metabolic pathways in urine and stool. We found an enrichment in sphingolipid metabolism after the Meat phase. Sphingolipids are important mammalian signalling molecules with various biological activities, and importantly increased sphingolipid metabolism may be a response to DNA damage [The rich metabolomic datasets also enabled the identification of other potential genotoxins as well as our targeted NOC analysis. We identified p-cresol sulphate in urine, a product of tyrosine fermentation in the gut [The present study has several strengths. We used a randomised crossover control investigator-blind study design, thus significantly reducing bias. The meat and mycoprotein products included are regularly consumed by the public, and the dose is achievable in a real-world setting. We also incorporated a variety of products in the dietary regimens to aid participant compliance, and to reflect the variety in real-world food exposures. It is noteworthy that once randomised to the study, we encountered no participant dropouts, which may be in part due to this approach. The Thermo IDX LCMS platform uses automated data acquisition and peak annotation resulting in improved metabolite profiling efficacy in comparison to alternative platforms. This allowed the ability to obtain a greater number of identifiable metabolites, which in turn enabled a rich dataset to determine metabolic pathways hitherto relatively unexplored in this type of study.Our work also has limitations. The cohort included exclusively healthy, non-obese adult males. This cohort was selected to control external factors, but future studies might use larger, more diverse cohorts. We advised participants to avoid certain foods and supplements; however, we did not control dietary intake other than the supplied study products. Other dietary factors during the study phases may have influenced our findings. 16S amplicon sequencing was used for microbial analysis which limits the coverage to genus. We also collected single-day faecal samples, but the stool microbiome can show intraday variation.In conclusion, this work demonstrates that substituting red and processed meat for the meat alternative mycoprotein reduces faecal genotoxins and the genotoxic load and increases SCFA production, as well as the abundance of beneficial genera in the human gut. Thus, mycoprotein may be considered a good alternative to meat when consumed as part of a balanced diet in the context of gut health and long-term CRC risk.