Gases produced by Human Intestinal Microflora

Abstract

NITROGEN, carbon dioxide and hydrogen are normally present in samples of human colonic flatus, although they may occur in widely differing proportions; oxygen is nearly always found and, sometimes, methane and hydrogen sulphide1. The hydrogen and methane must clearly be produced endogenously, presumably from bacterial metabolism, because both are almost absent from or present in extremely low concentration in air. Fermentation can also account for at least part of the carbon dioxide and a preliminary study indicated that gaseous nitrogen was produced in vitro when the caecal contents of rats were incubated with mixed diets2. More recently, Costa et al. have briefly reported isotopic evidence of the evolution of nitrogen by man and both conventional and axenic mice3. Both groups of investigators have suggested that such loss of nitrogen might account for reports of prolonged positive nitrogen balance in adult man and animals in the absence of commensurate growth. Our studies show, however, that egestion as flatus of gaseous nitrogen produced in the intestine is not normally an important route of nitrogen loss.