The relation of passage of gas an abdominal bloating to colonic gas production.

OBJECTIVE

To determine the relation of gas passage and abdominal bloating to the production of gas in the colon.

DESIGN

Randomized, double-blind, crossover study of gaseous symptoms during a 1-week period.

SETTING

A Veterans Affairs medical center.

PARTICIPANTS

25 healthy medical center employees.

INTERVENTION

Participants' diets were supplemented with either a placebo (10 g of lactulose, a nonabsorbable sugar), psyllium (a fermentable fiber), or methylcellulose (a nonfermentable fiber).

MEASUREMENTS

All participants were polled for gaseous symptoms (including number of gas passages, impression of increased rectal gas, and abdominal bloating), and five were examined for breath hydrogen excretion.

RESULTS

Participants passed gas 10 +/- 5.0 times per day (mean +/- SD) during the placebo period. A significant increase in gas passages (to 19 +/- 12 times per day) and a subjective impression of increased rectal gas were reported with lactulose but not with either of the two fiber preparations. Breath hydrogen excretion, an indicator of hydrogen production in the colon, did not increase after ingestion of either of the fibers. However, a statistically significant (P < 0.05) increase in feelings of abdominal bloating (which the participants perceived as excessive gas in the bowel) was reported with both fiber preparations and with lactulose.

CONCLUSIONS

The physician should distinguish between excessive gas (which indicates excessive gas production) and feelings of bloating (which are usually unrelated to excessive gas production). Treatment of the former consists of limiting the supply of fermentable material to the colonic bacteria. Symptoms of bloating usually indicate the irritable bowel syndrome, and therapy should be directed accordingly.