The effect of L-rhamnose on intestinal transit time, short chain fatty acids and appetite regulation: a pilot human study using combined 13CO2/H2 breath tests

Claire S Byrne,Jerusa Brignardello,Tom Preston,Elaine Holmes,Isabel Garcia-Perez,Gary S Frost,Douglas J Morrison

doi:10.1088/1752-7163/aad3f1

Abstract

Background. The appetite-regulating effects of non-digestible carbohydrates (NDC) have in part previously been attributed to their effects on intestinal transit rates as well as microbial production of short chain fatty acids (SCFA). Increased colonic production of the SCFA propionate has been shown to reduce energy intake and stimulate gut hormone secretion acutely in humans. Objective. We investigated the effect of the propiogenic NDC, L-rhamnose, on gastrointestinal transit times using a combined 13CO2/H2 breath test. We hypothesised that L-rhamnose would increase plasma propionate leading to a reduction in appetite, independent of changes in gastrointestinal transit times. Design. We used a dual 13C-octanoic acid/lactose 13C-ureide breath test combined with breath H2 to measure intestinal transit times following the consumption of 25 g d−1 L-rhamnose, compared with inulin and cellulose, in 10 healthy humans in a randomised cross-over design pilot study. Gastric emptying (GE) and oro-caecal transit times (OCTTs) were derived from the breath 13C data and compared with breath H2. Plasma SCFA and peptide YY (PYY) were also measured alongside subjective measures of appetite. Results. L-rhamnose significantly slowed GE rates (by 19.5 min) but there was no difference in OCTT between treatments. However, breath H2 indicated fermentation of L-rhamnose before it reached the caecum. OCTT was highly correlated with breath H2 for inulin but not for L-rhamnose or cellulose. L-rhamnose consumption significantly increased plasma propionate and PYY but did not significantly reduce subjective appetite measures. Conclusions. The NDCs tested had a minimal effect on intestinal transit time. Our data suggest that L-rhamnose is partially fermented in the small intestine and that breath H2 reflects the site of gastrointestinal fermentation and is only a reliable marker of OCTT for certain NDCs (e.g. inulin). Future studies should focus on investigating the appetite-suppressing potential of L-rhamnose and verifying the findings in a larger cohort.

Highlights

Subjects and methodsEpidemiological evidence suggests that non-digestible carbohydrates (NDC) play a key role in body weight management [1,2,3]
Breath 13C enrichment profiles and intestinal transit times The profiles of breath 13CO2 recovery and breath H2 concentrations following the dual 13C breath test and the consumption of cellulose, inulin and L-rhamnose are shown in figure 2
Post-hoc tests revealed that the t1/2 was longer for L-rhamnose compared with cellulose and inulin (0.30 ± 0.11 h, P = 0.023), which suggests that L-rhamnose delayed Gastric emptying (GE) by 19.5 min on average

Summary

Introduction

Subjects and methodsEpidemiological evidence suggests that non-digestible carbohydrates (NDC) play a key role in body weight management [1,2,3]. Dietary supplementation with inulin has been shown to significantly increase caecal production of SCFA compared with cellulose in rodents [10] and been associated with a reduction in energy intake in humans, albeit at very high doses (>35 g d−1) [11]. It is currently unknown how L-rhamnose compares to inulin in terms of its propionate-producing and appetite-suppressing capacity. We used a dual 13C-octanoic acid/lactose 13C-ureide breath test combined with breath H2 to measure intestinal transit times following the consumption of 25 g d−1 L-rhamnose, compared with inulin and cellulose, in 10 healthy humans in a randomised cross-over design pilot study. Future studies should focus on investigating the appetite-suppressing potential of L-rhamnose and verifying the findings in a larger cohort

Methods

Results

Conclusion