There are over 400 species and thousands of strains of bacteria that are supposed to inhabit the lower intestines and colon.
These 400+ species are collectively called probiotics, which means “for life”, and were initially discovered in the early 1900’s. These bacteria have many roles in good health such as making short-chain fatty acids (SCFAs), polyamines, vitamins, antioxidants, and amino acids. Another function, especially in the case of Lactobacillus species, is to prevent food from decaying, preserve antioxidants and vitamins, remove toxins, and keep pathogenic organisms at bay. A third and major role of probiotics is to maintain proper immune function. Among the various effects on the immune system, a specific action is to stimulate the action of white blood cells like the macrophages, natural killer cells, monocytes, and neutrophils.
When buying a probiotic (see Natural Pharmacy), you want a multi-strain product called “broad spectrum”. It should have at least 8 different types of probiotic bacteria. Avoid supplements with fillers or preservatives. The probiotic formula should be designed to by-pass the stomach and deliver essential bacteria to the lower intestines. Extended periods of elevated temperatures will diminish the viability of the organisms. Therefore, probiotics should be kept refrigerated and used immediately.
References
Jeanne A. Drisko, MD, CNS; Cheryl K. Giles, MD; Bette J. Bischoff, RD. (2003). Probiotics in Health Maintenance and Disease Prevention. Alternative Medicine Review. Volume 8, Number 2.
John A. Catanzaro, N.D. and Lisa Green, B.Sc. (1997). Microbial Ecology and Probiotics in Human Medicine (Part II). Alternative Medicine Review. Volume 2, Number 4.
Yehuda Ringel, Eamonn MM Quigley and Henry C Lin. (2012). Using Probiotics in Gastrointestinal Disorders. The American Journal of Gastroenterology Supplements 1, 34-40.