Hydrogen breath test of lactose absorption in adults: the application of physiological doses and whole cow’s milk sources

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Abstract
The absorption of lactose at pharmacological and physiological doses from conventional aqueous solutions and from whole cow's milk has been studied in healthy adults using a noninvasive hydrogen (H2) breath-analysis technique using thermal conductivity gas chromatography and interval collection of expired air. A discomfort score based on the presence or absence of symptoms (meteorism, flatulence, and diarrhea) during a 6-hr observation period was also recorded. Basal breath H2 concentrations were found to be stable for up to 12 nr. Of 20 subjects available for study, seven showed a rise in breath H2 of 20 ppm; they were classified as lactose intolerant malabsorbers. Follow-up studies using other forms and doses of lactose were conducted in these latter subjects. Fifty grams of lactose as whole milk produced a significant rise in breath H2 in 10 of the 13 subjects (77%). Nine of the 11 intolerant malabsorbers (82%) ingesting 12.5 g of lactose in aqueous solution showed an increment in breath H2 concentration of >20 ppm, and eight of these nine low dose malabsorbers (89%) also manifested a >20 ppm rise with 12.5 g of lactose as a 250-ml glass of milk. However, although no significant differences in symptom score were seen between milk and aqueous administration of equivalent doses of lactose, significantly fewer symptoms were experienced with the physiological (12.5 g) dose than with the pharmacological (50 g) dose. Several subjects who had been classified as intolerant to the 50 g of lactose, had no symptoms with the 12.5-g dosages. Using a technique that indicates the amount of carbohydrate that is not absorbed, no evidence for a difference in gastrointestinal transit between milk and aqueous solution could be detected. We conclude that the use of physiological doses and natural sources of lactose in combination with the simple H2 breath analysis technology adds a new dimension to the clinical evaluation of lactose malabsorption and milk intolerance in medical practice.