 This single-center, 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, and on immune functions in healthy shift workers. Volunteers received either 200gday of tested product N500 or control product N500 for 3-months, followed by a 1-month follow-up. 