The human gastrointestinal system is a huge, complex ecosystem where microbiota, nutrients, and host cells interact extensively in a process crucial for body homeostasis and regeneration. The various bacterial communities that make up the gastrointestinal microbiota have many functions including metabolic and trophic functions.
The gastrointestinal tract functions as a barrier against antigens from microorganisms and undigested food. Dysbiosis or microbe-imbalance can have negative consequences in terms of health and many diseases have been associated with impairment of the gastro-intestinal microbiota.
These close relationships between gastro-intestinal microbiota, health, and disease have led to great interest in using probiotics (i.e. live micro-organisms), or prebiotics (i.e. non-digestible substrates) to positively modulate the intestinal microbiota to prevent or treat diseases. Research shows that probiotics can be used as innovative tools to alleviate intestinal inflammation, normalize gastrointestinal mucosal dysfunction, and down-regulate hypersensitivity reactions.
Basically, probiotics are microbial cell preparations or components of microbial cells that have a beneficial effect on the health and well-being of the host. Probiotics were first described by a few visionary scientists like Metchnikoff, Nissle, and Shirota about a century ago. This concept of “useful microbes” as written by Metchnikoff in his publication On the prolongation of life, in 1907, has led many years later to the use of “probiotic” strains to deliberately manipulate the microbiota. This concept was largely forgotten during the expansion of the era of antibiotics and vaccines. Research on the roles of the commensal microbiota, however, brought a renewed interest in these beneficial microorganisms. Probiotic formulations are now intensively being developed and standardized for both human and animal consumption.
A prebiotic is a non-digestible food ingredient that confers benefits on the host by selectively stimulating the growth and/or activity of one bacterium or a group of bacteria in the colon, thereby improving the health of the host. Prebiotics are dietary carbohydrates that escape digestion in the upper gastrointestinal tract, altering the bacterial composition of the gut by changing the type of the substrate provided to the existing microbial population in the gastrointestinal tract e.g. fructooligosaccharides, glucooligosaccharides and inulin. Together probiotics and prebiotics have a greater effect – symbiotics that improve the survival of the bacteria in the gastrointestinal tract.
Probiotics may contain a variety of microorganisms. The most common are bacteria that belong to groups called Lactobacillus and Bifidobacterium. Other bacteria may also be used as probiotics, including many yeasts such as Saccharomyces boulardii. Different types of probiotics may have different effects. For example, if a specific kind of Lactobacillus helps prevent an illness, that doesn’t necessarily mean that another kind of Lactobacillus or any of the Bifidobacterium probiotics would do the same thing.
Lactobacillus and Bifidobacterium species have been shown to enhance the innate immune system and to enhance macrophage phagocytosis. Scientific results also provide evidence of the advantages of the utilization of certain Bacillus strains as probiotics. These bacteria can produce a very stable duration form called the endospore. Compared to the widely used lactic acid bacteria, bacterial spores offer the advantage of a higher survival rate during the acidic stomach passage and better stability during the processing and storage of food products.
The articles on this page describe the functions of probiotics and specific bacteria.