Probiotics-- often called "friendly" or "good" bacteria-- are live, lactic-acid producing microorganisms that are similar to those found in the human digestive tract. These beneficial bacteria are associated with numerous health benefits. They are also widely used in clinical nutrition and complementary alternative medicine. Experts at the National Institutes of Health note that probiotics show some promise in the treatment of diarrhea, irritable bowel syndrome, vaginal infections, tooth decay and skin disease.
Probiotics are found in commercial supplements, as well as fermented foods like tempeh, miso and yogurt. The majority of probiotic microbes are members of the Lactobacillus or Bifidobacterium genera, and many species, sub-species and strains exist within these two categories. Additionally, some food manufacturers use patented or proprietary strains that are unavailable through other sources.
L. acidophilus is one of the most common and versatile probiotics on the market. It is frequently used in yogurt cultures and hundreds of subspecies and strains have been developed. According to the National Institutes of Health, L. acidophilus' most reliable use is in the treatment of bacterial vaginosis.
Lactobacillus rhamnosus shows some medicinal effects similar to its relative, L. acidophilus, but it is more expensive and has not been subjected to the same amount of study. The "Indian Journal of Medical Microbiology" notes that it "has proven beneficial affects on intestinal immunity."
Once erroneously classified in the Lactobacillus genus, B. coagulans is relatively rare on the supplement market. Unlike Lactobacillus and Bifidobacterium species, B. coagulans has never been used in commercial foods.
B. animalis is famed for its ability to improve digestive regularity. It is frequently used for people with irritable bowel syndrome or chronic constipation. One subspecies of B. animalis is used by the yogurt manufacturer Dannon, which markets strain under the patented name "Bifidus regularis."
While E. coli is rarely considered to be a "good" species of bacteria, some nonpathogenic strains actually hold therapeutic value. One Japanese study, published in 2005 by the journal "Inflammatory Bowel Disease," found that friendly strains of E. coli can actually prevent and treat ulcerative colitis.
L. lactis has only limited medicinal value compared to other probiotic species, but it offers extensive commercial and culinary value. Almost all forms of cheese and buttermilk are manufactured using appropriate strains of L. lactis.
Sometimes called the universal probiotic, L. reuteri is found in the colons of most animals, where it can fight pathogenic bacteria. L. reuteri is found in human breast milk and may be responsible for some of the immunosupportive and anti-gas effects associated with breastfeeding.