The present invention relates to the use of a supernatant of lactic acid bacteria or of Bifidobacteria capable of preventing colonization of intestinal cells by Giardia intestinalis, for the preparation of an ingestible carrier for the treatment and/or prophylaxis of disorders associated with the colonization of the gut by Giardia intestinalis. The present invention also pertains to specific strains of Bifidobacterium having the above traits and to the ingestible carrier, such as a food or pharmaceutical composition, containing such supernatant or the microorganisms.