Understanding the Interplay Between Food Structure, Bacterial Fermentation and Appetite Sensing: A Randomized Crossover Human Trial

Abstract

Abstract Objectives Complex food structures can act like barriers towards digestive enzymes and reduce nutrient bioavailability. Nutrients that escape digestion in the upper gut (mainly fibre), becomes available for bacterial fermentation in the distal gut and generates short chain fatty acids (SCFA) which stimulate the release of appetite suppressing hormones Glucagon like peptide 1 (GLP-1) and Peptide YY (PYY). Processing can alter food structures, leading to more digestible products, but reducing nutrients reaching the distal gut, fermentation and appetite suppression. This study aimed to investigate the impact of food structures on the level of carbohydrate reaching the distal ileum and its subsequent effect on SCFA production and appetite hormone release. Methods Healthy volunteers (n = 10, 18–65 years) attended three separate 4-day inpatient visits. A nasoenteric tube was inserted into their distal ileum. During each visit, participants had one of three dietary interventions: Low fibre, processed diet (LF); High fibre, unprocessed diet (HF); same as HF but domestically processed (HFP). On day 4, ileal, blood and breath hydrogen (BH) samples were collected at baseline and hourly following food intake for 8 h. Blood samples were analyzed for appetite hormones and SCFAs using radioimmunoassay and GC-MS. Ileal samples were analyzed for metabolic profiling using 1H-NMR spectroscopy, partial least squares discriminant analysis with Monte-Carlo cross-validation and repeated-measures design. Results HFP but not HF had higher PYY levels than the LF (P = 0.004). BH and serum total SCFAs were higher in HF and HFP than LF indicating a higher bacterial fermentation (P = 0.021, 0.015 and P = 0.000, 0.003). HFP group had higher total SCFA than HF (P = 0.015). Distinct metabolic differences were identified in ileal samples from groups (e.g., time = 2 h, HF vs HFP R2Y: 0.99, Q2Y: 0.65). Ileal samples will be analysed for microbial profile (16 s rRNA, Illumina MiSeq), glucose and starch (spectroscopy) and SCFAs (GC-MS). Conclusions Current data suggests a potential benefit of domestically processed food structures on appetite suppression as measured by postprandial PYY levels. This may be related to the different metabolic profiles generated in the ileum. Better understanding of this link can aid the design of diets that enhance appetite suppression and reduce food intake. Funding Sources BBSRC.