The invention relates to methods for reducing the duration of an episode of diarrhea in an individual comprising administering to said individual viable Lactobacillus casei CRL 431 in an amount of at least 106 CFU per 24 hours and calcium in an amount of at least 300 mg per 24 hours. The invention further relates to nutritional compositions comprising viable Lactobacillus casei CRL 431 in an amount of at least 104 CFU per ml and calcium in an amount of at least 0.6 mg per ml which is suitable for the treatment of diarrhea. The composition may be in the form of a kit of parts.