Probiotics are bacteria that help keep the natural balance of organisms (microflora) in the intestines. The normal human digestive tract contains about 400 types of probiotic bacteria that reduce the growth of harmful bacteria and promote a healthy digestive system. The largest group of probiotic bacteria in the intestine is lactic acid bacteria, of which Lactobacillus acidophilus, found in yogurt with live cultures, is the best known. Yeast is also a probiotic substance. Probiotics are also available as dietary supplements.
It has been suggested that probiotics be used to treat problems in the stomach and intestines. But only certain types of bacteria or yeast (called strains) have been shown to work in the digestive tract. It still needs to be proved which probiotics (alone or in combination) work to treat diseases. At this point, even the strains of probiotics that have been proved to work for a specific disease are not widely available.
What are probiotics used for?
Many people use probiotics to prevent diarrhea, gas, and cramping caused by antibiotics. Antibiotics kill "good" (beneficial) bacteria along with the bacteria that cause illness. A decrease in beneficial bacteria may lead to digestive problems. Taking probiotics may help replace the lost beneficial bacteria. This can help prevent diarrhea.
A decrease in beneficial bacteria may also lead to other infections, such as vaginal yeast and urinary tract infections, and symptoms such as diarrhea from intestinal illnesses.
Most probiotics are like what is already in a person's digestive system. Some probiotics have been used for a very long time throughout history, such as in fermented foods and cultured milk products. These don't appear to cause illness. But more study is needed on the safety of probiotics in young children, the elderly, and people who have weak immune systems.
As with any dietary supplement, be aware that probiotic supplements are regulated as foods, not drugs. Tell your doctor about everything you are taking, including the specific bacteria in your probiotic supplement.
National Institutes of Health, National Center for Complementary and Alternative Medicine (2012). Oral Probiotics: An Introduction. Available online: http://nccam.nih.gov/health/probiotics/introduction.htm.
Probiotics (2011). In A DerMarderosian et al., eds., Review of Natural Products. St Louis: Wolters Kluwer Health.
Thomas DW, et al. (2010). American Academy of Pediatrics Clinical Report: Probiotics and prebiotics in pediatrics. Pediatrics, 126(6): 1217â€“1231.
ByHealthwise StaffPrimary Medical ReviewerAdam Husney, MD - Family MedicineKathleen Romito, MD - Family Medicine