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Gastrointestinal (GI) Tract

The Benefits of a Probiotics Supplement for a Healthy Gut

Probiotics are live microorganisms (in most cases, bacteria) that are similar to beneficial microorganisms found in the human gut. They are also called “friendly bacteria” or “good bacteria.” Probiotics are available to consumers mainly in the form of dietary supplements and foods.


There is mounting evidence that probiotics can have beneficial effects on human health. Possible mechanisms under active investigation include altering the intestinal “microecology” (e.g., reducing harmful organisms in the intestine), producing antimicrobial compounds (substances that destroy or suppress the growth of microorganisms), and stimulating the body’s immune response.

The body, especially the lower gastrointestinal tract (the gut), contains a complex and diverse community of bacteria. Although we tend to think of bacteria as harmful “germs,” many bacteria actually help the body function properly. Probiotics are available to consumers in oral products such as dietary supplements and yogurts, as well as other products such as suppositories and creams. It is important to be aware that the U.S. Food and Drug Administration (FDA) has not approved any health claims for probiotics.

Scientific Evidence

A recent Cochrane review of the scientific evidence on the effectiveness of probiotics in acute infectious diarrhea concluded that there was evidence that probiotics may shorten the duration of diarrhea and reduce stool frequency but that more research was needed to establish exactly which probiotics should be used for which groups of people.

In 2008, the journal Clinical Infectious Diseases published a special issue on probiotics, which included an overview of clinical applications. Based on a review of selected studies, the authors classified several applications according to the strength of evidence supporting the efficacy of probiotics in prevention and/or treatment.

For example, the authors concluded that strong evidence exists for acute diarrhea and antibiotic-associated diarrhea, and substantial evidence exists for atopic eczema (a skin condition most commonly seen in infants).

Promising applications include childhood respiratory infections, tooth decay, nasal pathogens (bacteria harbored in the nose), gastroenteritis relapses caused by Clostridium difficile bacteria after antibiotic therapy, and inflammatory bowel disease.

Studies also indicate that probiotics may reduce side effects associated with treatment for Helicobacter pylori infection, the cause of most stomach ulcers.

A systematic review suggests that there is strong evidence that probiotics may reduce the risk of necrotizing enterocolitis, a severe intestinal condition of premature newborns. Other potential future applications include use in reducing cholesterol levels, treating obesity, and managing irritable bowel syndrome.

Side Effects and Risks

It appears that most people do not experience side effects from probiotics or have only mild gastrointestinal side effects such as gas. But there have been some case reports of serious adverse effects, and research on safety is ongoing.

A 2011 Agency for Healthcare Research and Quality assessment of the safety of probiotics, partly funded by NCCAM, concluded that the current evidence does not suggest a widespread risk of negative side effects associated with probiotics.

Similarly, a 2008 review of probiotics safety noted that Lactobacillus rhamnosus GG has been widely studied in clinical trials for a variety of conditions and generally found to be safe.

“As a chiropractic physician who has personally used probiotics and prescribed them to patients for 25 years I have seen very few people have any side effects, and the ones that did had complete resolution within a day after discontinuing use of the probiotic. Typically if a patient has side effects from probiotic use they are taking the wrong strain or a product that contains unnecessary ingredients that are resulting in the side effects."

Information for this page comes from: https://nccih.nih.gov/health/providers/digest/probiotics-science