Probiotics (cont.)

Side effects and risks

Some live microorganisms have a long history of use as probiotics without causing illness in people. Probiotics' safety has not been thoroughly studied scientifically, however. More information is especially needed on how safe they are for young children, elderly people, and people with compromised immune systems.

Probiotics' side effects, if they occur, tend to be mild and digestive (such as gas or bloating). More serious effects have been seen in some people. Probiotics might theoretically cause infections that need to be treated with antibiotics, especially in people with underlying health conditions. They could also cause unhealthy metabolic activities, too much stimulation of the immune system, or gene transfer (insertion of genetic material into a cell).

Probiotic products taken by mouth as a dietary supplement are manufactured and regulated as foods, not drugs.

Some other points to consider

  • If you are thinking about using a probiotic product as CAM, consult your health care provider first. No CAM therapy should be used in place of conventional medical care or to delay seeking that care.


  • Effects from one species or strain of probiotics do not necessarily hold true for others, or even for different preparations of the same species or strain.


  • If you use a probiotic product and experience an effect that concerns you, contact your health care provider.


  • You can locate research reports in peer-reviewed journals on probiotics' effectiveness and safety through the resources PubMed and CAM on PubMed

NCCAM-sponsored research on probiotics

Among recent NCCAM-sponsored research are the following projects:

  • Investigators at Tulane University School of Public Health and Tropical Medicine are studying the effectiveness of selected probiotic agents to treat diarrhea in undernourished children in a developing country.


  • At the Mayo Clinic College of Medicine, researchers have been examining probiotics for possibly decreasing the levels of certain substances in the urine that can cause problems such as kidney stones.


  • A team at Tufts-New England Medical Center is studying probiotics for treating an antibiotic-resistant type of bacteria that causes severe infections in people who are hospitalized, live in nursing homes, or have weakened immune systems.