[The role of lactic acid bacteria in nutrition and health].

Lactic acid bacteria possess both positive as well as negative aspects in relation to health. On the one side metabolic activities such as the production of extracellular polysaccharides or lactic acid from carbohydrates, are responsible for plaque formation and demineralisation of enamel. On the other hand, further down in the digestive tract, these groups of micro-organisms can have a beneficial effect by locally influencing the microbial composition, specific metabolic activities or stimulation of the immune response. Lactic acid bacteria also play a major role in food preservation. When plants or animals become food after harvesting or slaughter, endogenous resistance mechanisms such as the immune systems are lost and consequently foods become susceptible to spoilage. Food spoilage can be retarded or prevented by application of certain external factors; for example, storage at low temperatures of fermentation by lactic acid bacteria. Similarly, the mature dentition also consist of non-living tissue and is therefore also subject to 'spoilage' (decay). Lactic acid bacteria now play a negative role. However, the metabolism of lactic acid bacteria in plaque and consequently de- and remineralisation may also be influenced by application of external factors as diet, oral hygiene and fluorides. This paper will discuss the functional similarities and differences of lactic acid bacteria in different areas of the digestive tract.