Background: Some patients complain of digestive symptoms related to diary products intake. This intolerance could be associated with an intestinal bacterial overgrowth or an increased fermentative intestinal profile and not due to lactose malabsorption.

Objective: To estimate the prevalence of bacterial overgrowth in subjects with digestive symptoms related to diary products intolerance.

Methods: Patients who had performed hydrogen breath test due to chronic functional distension syndrome (Rome III) were analyzed. Thirty of them (22 female, average age 52 years) complained of symptoms related to diary products intake. All subjects completed a nutritional survey that allowed to assess the degree of tolerance to milk products and performed the hydrogen breath test with lactulose as substrate. Bacterial overgrowth was considered when baseline values were over 15 parts per million (ppm), values before 80 minutes were greater than 20 ppm or values of area under the curve were greater than 3,000 ppm/min in the 180 studied minutes.

Results: Fifty four patients were analyzed. Thirty of them showed moderate, important or severe clinical milk intolerance. Of these patients, 23 (77%), had a positive breath hydrogen test according to used criteria.

Conclusions: The prevalence of small bowel bacterial overgrowth or an increased fermentative intestinal profile among individuals who complain of symptoms related to diary products is high and this fact should be considered in order to avoid empirical restrictive diets.