Milk Consumption on Digestive Comfort.

The study will be carried out on healthy volunteers, aged 18 to 65 and self-declared sensitive, even intolerant to the consumption of milk.

The main objective of the study is to assess the impact of milk β-caseins (A2A2 vs A1A2) on the digestive comfort felt during the consumption of milk in subjects declaring that they do not tolerate milk.

• Group (A1 → A2) (Other): Before each start of consumption of the products under study, a wash-out period of 2 weeks (no consumption of milk) must be observed by the subjects. 25 subjects will consume A1A2 milk for 2 weeks (period 1), then they will consume A2A2 milk for 2 weeks (period 2). During each consumption period, various questionnaires will be completed by the subjects: frequency and consistency of stool, analog visual scales on digestive comfort and dietary surveys. Stool collections will also be carried out.
• Group (A2 → A1) (Other): Before each start of consumption of the products under study, a wash-out period of 2 weeks (no consumption of milk) must be observed by the subjects. 25 subjects will consume A2A2 milk for 2 weeks (period 1), then they will consume A1A2 milk for 2 weeks (period 2). During each consumption period, various questionnaires will be completed by the subjects: frequency and consistency of stool, analog visual scales on digestive comfort and dietary surveys. Stool collections will also be carried out.

Primary outcomes

• Analog visual scales [4 weeks]: Digestive comfort will be assessed daily by the average of the following analog visual scales (score : 0 to 10), completed within 30 min to 3 hours after consumption of the daily dose of milk, depending on the usual occurrence of symptoms in individuals: * I have bloating * I have abdominal pain * I have flatulence (gas) * I have borborygmas (gurgling) * I have reflux (return, rise) * Overall, I estimate my digestive comfort. The average of these 6 analog visual scales, called Global Digestive Discomfort (IDG), will therefore be available every day for 14 days; the final variable analyzed will be the average of these 14 IDG values, and will be called Global Average Digestive Discomfort (IDGM).

Secondary outcomes

• Analysis of the average per period of each analog visual scales independently [4 weeks]: The analogue visual scales will be completed daily during each period of milk consumption (4 weeks)
• Difference Calprotectin at the end of the period - Calprotectin at V0 (measured in mg/kg) [4 weeks]: Stool collections are made during inclusion visits, V1 follow-up and V3 end of study.
• For each of the inflammatory markers (CRP us, IL-1β, TNF-α, IL-6) : difference between value at the end of the period and value at V0 [4 weeks]: Blood samples are taken during inclusion visits, V1 follow-up and V3 end of study. All of the inflammatory markers are measured in pg/ml.
• Average stool frequencies and consistencies [4 weeks]: This questionnaires will be completed daily during each period of milk consumption (4 weeks). Bristol scale: stool type 1 (separate hard balls) to stool type 7 (watery, structureless stools)

Sex: All, ages: 18 Years to 65 Years, accepts healthy volunteers

Inclusion Criteria:

* Man or woman;
* 18 to 65 years old;
* Declaring to have sensitivity or intolerance when consuming cow's milk;
* Agreeing to follow the constraints generated by the study;
* Having signed the informed consent form;
* Social insured.

Exclusion Criteria:

* Subject with an allergy to cow's milk proteins;
* Subject suffering from a severe eating disorder (anorexia, bulimia, binge eating);
* Subject with chronic pathology interfering with the parameters studied during this study (inflammatory intestinal disease, celiac disease);
* Subject suffering from acute intestinal infection at the time of inclusion (gastroenteritis, etc.);
* Subject with immunodeficiency or any other serious pathology (cancer, hemopathy);
* Pregnant or planning to be pregnant during the study period;
* Subject participating in another clinical study or in period of exclusion from another study;
* Subject deprived of liberty;
* Subject under judicial protection measure;
* Whose main investigator or a qualified co-investigator judges that the state of health or the concomitant treatments are not compatible with the good progress of the clinical study.

• Jean-Michel LECERF, MD, Principal investigator, Institut Pasteur de Lille - NutrInvest