Q&A on lactose intolerance

Lactose intolerance diagnostic

The proper way to diagnose lactose intolerance, called the Breath test, is to measure, in the exhaled air, the hydrogen produced by the intestinal microbiota after consumption of a standard dose of lactose (usually 20 to 50 g). This diagnosis should be performed under medical control. (20)


The diagnosis is only complete when one or many of the following symptoms occur: bloating, diarrhea, and flatulence. For some patients, this test can be improved by simultaneous measurement of methane. (21)diagnosis-lactose-intolerance


A real medical diagnosis is especially important as, when it is performed, only 50 % of self-diagnoses of lactose intolerance are confirmed. (20, 22, 23) Furthermore, perceived or even diagnosed lactose intolerance is one of the reasons for limiting or avoiding dairy food, which could lead to possible nutrient shortcomings and health consequences. (24)



 20. Marteau, A et al. Cahiers de nutrition et de diététique 2005;40:20-23.

21. Hermans, MM et al. Am J Gastroenterol 1997;92:981-4.

22. Suarez, FL et al. N Engl J Med 1995;333:1-4.

23. Suarez, FL et al. Am. J. Clin. Nutr., 1997, 65 1502-6.

24. Suchy, FJ et al. NIH Consens State Sci Statements 2010;27:1-27.

25. Crittenden, RG et al. J Am Coll Nutr 2005;24:582S-91S.

26. Luyt, D et al. Clin Exp Allergy 2014;44:642-72.