Functional fermented milk products.

Fermented foods have been used since prehistoric times. Their number, variety and geographic origin are considerable, and different substrates and agents including bacteria, yeasts and moulds have been used in their preparation. In the last few decades the scientific approach to the study of the participating microorganisms and the resulting products have provided a better understanding of their biological importance. Among the many health-related properties of fermented foods, effects on blood pressure have been described after casein hydrolysis by lactic acid bacteria. Peptides with antimicrobial activity, mainly against Gram-negative bacteria, and derived from casein have also been identified. This could explain, at least in part, the antidiarrheal effects of fermented products including those on traveler's diarrhea and against colonization by Helicobacter pylori. One of the best known advantages of fermented milk products is their capacity to improve lactose tolerance in hypolactasic subjects. With the growing prevalence of allergies and inflammatory bowel diseases, considerable interest has been focused on the effects of lactic acid bacteria in these conditions; there is evidence that these agents are associated with improvements in allergy; no such evidence exists for Crohn's disease or ulcerative colitis. A cholesterol-lowering capacity has also been described for some microorganisms. Not all the fermenting microorganisms have probiotic capacities as the latter are strain-specific.