Respiratory excretion of hydrogen and methane in Italian subjects after ingestion of lactose and milk

Abstract

Lactose malabsorption, by the breath H2 test and lactose intolerance (presence of symptoms) were studied in 20 healthy Italian subjects after intake of 12.5, 25 and 50 g lactose, whole milk and low-lactose milk. A rise in respiratory concentration of H (> 20 ppm) (malabsorption) was found in 15 subjects after 50 g lactose, in 13 after 25 g and in 7 after 12.5 g. Symptoms generally occurred in subjects presenting a rise in respiratory H2 excretion, but such a rise was often observed without symptoms. Thirteen subjects presented symptoms after 50 g lactose, but only 3 after 25 g and 1 after 12.5 g. Whole milk (500 ml) gave a lower incidence of lactose malabsorption that 25 g lactose (7/20 vs. 13/20, P < 0.05) and more subjects developed symptoms (7/20 vs. 3/20, NS [not significant]). Low-lactose milk produced no malabsorbers and 1 intolerant. Breath methane was detected constantly in 7 subjects and in 3 on some of the days of observation. Respiratory methane excretion generally appeared to be unrelated to lactose ingestion.