The effect of eating chocolate containing sugar alcohols as sweetening agents on colonic fermentation has been investigated by monitoring breath H2 levels. Levels were compared with those occurring after the consumption of normal, sugar-containing chocolate. Ten healthy volunteers aged 19 to 21 years ingested equal amounts of either sorbitol, isomalt or sucrose incorporated into standard chocolate bars. Breath H2 levels after consumption of chocolate containing either sorbitol or isomalt were significantly higher than those after consumption of chocolate containing sucrose (P < 0.001). After consumption of chocolate containing sorbitol, double the mean estimated volume of breath H2 was produced over 6 h compared with that produced after eating chocolate containing isomalt. Taken together with results relating to the incidence of intolerance symptoms, these findings demonstrate that sorbitol is associated with greater colonic fermentation compared with isomalt.