Many recent studies have shown the health effects of various strains of lac
tic acid bacteria in humans and animals and have tried to describe their ac
tion mechanism in the digestive tract. A number and a variety of potential
beneficial effects have been published. Some of these effects have already
been described such as the improvement of lactose digestion and the treatme
nt of diarrheal disorders. Other health effects are still a subject of cont
roversy such as the decrease of serum cholesterol and the reduction of tumo
r formation. The aim of this article is to summarize the probiotic effects
of lactic acid bacteria, their mechanisms, and the fate of these microorgan
isms during their transit in the digestive tract.