Probiotics: mechanisms and established effects

The definition for probiotics has gradually changed with increasing understanding of the mechanisms by which they influence human health. Health effects related to changes in the intestinal microflora also accompany or are related to adhesion and immune system effects, competitive exclusion or metabolic and nutritional effects, with an increasing array of other potential modes of action. Most clinically documented and validated health effects have been studied using either fermented milks containing viable cultures or viable pure cultures. Specific targets for the future include controlled studies comparing foods containing viable strains to those containing non-viable strains and to assess the combined effects of multiple probiotics. (C) 1999 Elsevier Science Ltd. All rights reserved.