Fecal Hydrogen Production and Consumption Measurements (Response to Daily Lactose Ingestion by Lactose Maldigesters)

Abstract

The alteration of hydrogen (H2)metabolism, which accounts for the large decrease inbreath H2 excretion following prolongedingestion of malabsorbed carbohydrate (lactulose,lactose in lactose maldigesters) was studied in six lactose-maldigesting adults.Metabolic inhibitors of the three mainH2-consuming reactions (methanogenesis,sulfate reduction, and acetogenesis) were used toindependently measure H production and consumption in fecal samples obtained after10 days of either dextrose or lactose feeding. Absolutefecal H2 production (net of production minusconsumption) after 3 hr of incubation with lactose was approximately threefold lower after lactoseadaptation (242 ± 54 μl) compared to dextroseadaptation (680 ± 79 μl, P = 0.006). FecalH2 consumption was not affected by eitherfeeding period. We conclude that decreased absolute H2 production,rather than increased H2 consumption, isresponsible for the decrease in breath H2observed with lactose feeding.