Dose-dependent effects of enteral nutrition on the faecal microbiota and short chain fatty acids

Introduction: Enteral nutrition (EN) involves replacing all or part of a person's habitual diet with a nutritional formula.The impact of varying doses of EN on the gut microbiome remains understudied. Methods:Healthy adults replaced all (100% EN) or part (85% EN, 50% EN and 20% EN) of their energy requirements with EN for 7 days.Faecal samples were collected before and on day 7 of interventions.Faecal pH, short chain fatty acids (SCFAs), branched-chain fatty acids (BCFAs) and 16S rRNA sequencing were performed.Dietary assessment was performed with 7-day food diaries.Results: Sixty-one participants (31 females; median (IQR) age: 24.7 (23.0-27.8)years) were recruited.A dose-dependent impact of EN on faecal microbiota, SCFAs, BCFAs) and pH was observed, with changes detectable at EN intakes of at least 50% of energy requirements.100% and 85% EN reduced the abundance of fibre-fermenting taxa such as Agathobacter, Faecalibaterium, Succinivibrio and Acidaminococcus.In parallel, potentially harmful organisms like Eubacterium, Actinomyces, and Klebsiella increased.In the 50% EN group, adherence to a diet high in fish, vegetables, potatoes, nonalcoholic beverages, and fat spreads, and low in cereal products, milk, and meat negatively correlated with changes in microbiota structure (r=-0.75,P=0.025).This signal was not observed when using compositional tools for microbiota analysis.Conclusions: EN detrimentally influences the faecal microbiota and diet-related bacterial metabolites in a dose-dependent manner, particularly at doses of at least 50%.The findings of this study have implications for the dietary management and counselling of patients receiving high volume EN.