Anal gas evacuation and colonic microbiota in patients with flatulence: effect of diet

Abstract

Objective: To characterise the influence of diet on abdominal symptoms, anal gas evacuation, intestinal gas distribution and colonic microbiota in patients complaining of flatulence.

Design: Patients complaining of flatulence (n=30) and healthy subjects (n=20) were instructed to follow their usual diet for 3 days (basal phase) and to consume a high-flatulogenic diet for another 3 days (challenge phase).

Results: During basal phase, patients recorded more abdominal symptoms than healthy subjects in daily questionnaires (5.8±0.3 vs 0.4±0.2 mean discomfort/pain score, respectively; p=<0.0001) and more gas evacuations by an event marker (21.9±2.8 vs 7.4±1.0 daytime evacuations, respectively; p=0.0001), without differences in the volume of gas evacuated after a standard meal (262±22 and 265±25 mL, respectively). On flatulogenic diet, both groups recorded more abdominal symptoms (7.9±0.3 and 2.8±0.4 discomfort/pain, respectively), number of gas evacuations (44.4±5.3 and 21.7±2.9 daytime evacuations, respectively) and had more gas production (656±52 and 673±78 mL, respectively; p<0.05 vs basal diet for all). When challenged with flatulogenic diet, patients' microbiota developed instability in composition, exhibiting variations in the main phyla and reduction of microbial diversity, whereas healthy subjects' microbiota were stable. Taxa from Bacteroides fragilis or Bilophila wadsworthia correlated with number of gas evacuations or volume of gas evacuated, respectively.

Conclusions: Patients complaining of flatulence have a poor tolerance of intestinal gas, which is associated with instability of the microbial ecosystem.

Keywords: Colonic Bacteria; Colonic Fermentation; Colonic Microflora; Functional Bowel Disorder; Visceral Sensitivity.

Figure 1

Effect of diet on the number of daytime anal gas evacuations. Note the higher number in patients than in healthy subjects both during basal (B) and challenge diet (C), and marked increase during challenge diet. Data are individual values (average of three daily measurements during basal phase and last 2 days challenge phase). Dotted line represents upper limit of normal range during basal diet.

Figure 2

Effect of diet on clinical parameters. Symptoms (scored from 0 to 10) and digestive comfort (scored from +5 to −5) on the last day of basal and challenge phases. Data are means±SE.

Figure 3

Postprandial rectal gas collection. Cumulative data (means±SE) after test meal.

Figure 4

Changes in microbiota at taxonomy level after challenge diet. (A) For each individual (20 healthy subjects and 29 patients) the abundance of Firmicutes (in blue) and Bacteroidetes (in red) during basal (•) and challenge phases (▴) is shown (connected by line). (B) Variations from baseline induced by challenge diet of the four most abundant bacterial phyla (individual data and mean values are shown).