This multicentric, randomized, double-blind and controlled study aims to examine the effect of a fermented dairy product containing the probiotic Lactobacillus casei DN-114 001 (Actimel® = tested product) on the incidence of respiratory and gastro-intestinal common infectious diseases (cumulated number of infections during the intervention period: primary criteria) in children aged 3-6 years, attending day care centers.Volunteers received either 200g/day of tested product (N=300) or control product (N=299) for 3-months, followed by a 1-month follow-up.

Inclusion Criteria:

• Subject whose parents/legal guardians had given written informed consent,
• Male or female, aged 3 to 6 years (upper bound excluded),
• Attending day-care centres or preschools 5 days a week in the Moscow area,
• Subject found medically healthy (in particular, free of respiratory and GI tract symptoms),
• Subject who appreciated dairy products and multi-fruit flavour.

Exclusion Criteria:

• Subject whose parents were not reading and writing Russian, or not understanding informed consent or study protocol.
• Subject with allergy or hypersensitivity to milk proteins or dairy foods components (ex: lactose, milk proteins), or with any known food or respiratory allergy.
• Subject presenting a severe evolutive or chronic pathology (Ex: cancer, tuberculosis, Crohn disease, cirrhosis, multiple sclerosis, Type I diabetes…) or any past or actual health condition that could interfere with the outcome of the study (Ex: HIV, Chemotherapy, malabsorption, ulcer, celiac disease, failure to thrive…).
• Subject having experienced any infectious disease during the last 7 days.
• Subject with current diarrhoea or constipation Subject who was frequently using laxatives or who had been using laxatives during the week prior his participation to the study.
• Subject who was under artificial nutrition, had gastro-intestinal surgery or any intervention requiring general anaesthesia the last 2 months prior to his participation to the study.
• Subject with special medicated diet (obesity, anorexia, metabolic pathology, nutritional complementation…) or with eating disorders (anorexia, bulimia…).
• Subject currently receiving, or who had received during the last months, systemic treatment or topical treatment likely to interfere with evaluation of the study parameters: antibiotics, antiseptics, antifungal, corticoids, vaccines, anti-histaminic molecules, non-corticoid antiinflammatory substances, immunosuppressant treatment…
• Subject already enrolled in another clinical study, or currently under an exemption period from a previous study.
• Subject in a situation which in the investigator's opinion could interfere with optimal participation in the present study or could constitute a special risk for the subject.