STIMULATION OF THE IMMUNE-SYSTEM BY LACTIC CULTURES

An optimally functioning immune system is essential for protection aga inst infectious diseases and cancers. Deficiency in any component of t he immune system can predispose an individual to a greater risk of inf ection or may enhance the severity of disease. Several studies have sh own that dietary supplementation with lactic acid bacteria (LAB) can b e used to promote health and wellbeing; LAB are normal components of t he human intestinal flora and are commonly used as starter cultures in dairy products. Consumption of LAB has been associated with a variety of health benefits including enhanced immune performance, increased r esistance to infectious diseases, alleviation of food allergies and th e suppression of cancer development. The precise mechanisms by which L AB act on the immune system are not fully understood. However, there i s sufficient evidence to suggest that LAB exert their immunity enhanci ng effects by augmenting both non-specific (e.g. phagocyte function, N K-cell activity) and specific (e.g. antibody production, cytokine prod uction, lymphocyte proliferation, delayed-type hypersensitivity) host immune responses. It is important to note that most of the evidence su pporting these immunoenhancing effects is derived from in vitro or ani mal studies and there is a scarcity of carefully designed and properly controlled clinical studies demonstrating immune health benefits for humans, especially healthy human subjects. This article discusses the impact of LAB on different immune functions, the role of LAB-induced i mmunoenhancement in disease resistance, and highlights gaps in our kno wledge that need further research. (C) 1998 Elsevier Science Ltd. All rights reserved.