The purpose of this study is to assess that two β-galactosidase Producing Probiotic Strains help improve lactose digestion in subjects with lactose maldigestion.

The trial will be cross over, randomized in incomplete blocks, controlled, double-blind:

each subject will be administered 3 products out of 4 (positive control, probiotic Streptococcus (S.) thermophilus, probiotic Bifidobacterium (B.) longum, negative control) in a random order on 3 different days separated by a washout period of at least one week, and maximum 2 weeks between each challenge.

The total sample size is 42 enrolled subjects/37 completed Patients will be males and females aged between 20 and 65 years with positive hydrogen breath test.

Inclusion Criteria:

1. HBT> delta 20ppm (compared with the baseline value) measured at screening visit before challenge tests
2. Having signed the informed consent or having provide his/her legal representative's informed consent

Exclusion Criteria:

1. Known Food allergy
2. Any obstructive (COPD, asthma…) or restrictive respiratory syndrome that may impact breath test measurements
3. Any medically relevant malabsorption syndrome
4. Any medically relevant chronic gut motility disorder other than Irritable Bowel Syndrome (IBS), assessed with Rome III questionnaire
5. Ongoing therapy with drugs known to affect gut motility
6. Any general antibiotherapy taken during or within 4 weeks of study onset
7. Use of lactase pill (eg. Lacdigest®), as well as yoghurt and probiotics, for at least 2 days prior to Visit 0b
8. Subject who cannot be expected to comply with the study procedures
9. Currently participating or having participated in another clinical trial during last 8 weeks prior to the beginning of this study.
10. To be a close collaborator to the Investigators, either in terms of Family relationship and/or professional relationship
11. Pregnancy, based on anamnesis