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

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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.