What are probiotics?
Probiotics are live microorganisms that are intended to have health benefits when consumed or applied to the body. They can be found in yogurt and other fermented foods, dietary supplements, and beauty products.
Although people often think of bacteria and other microorganisms as harmful “germs,” many are actually helpful. Some bacteria help digest food, destroy disease-causing cells, or produce vitamins. Many of the microorganisms in probiotic products are the same as or similar to microorganisms that naturally live in our bodies.
What types of bacteria are in probiotics?
Probiotics may contain a variety of microorganisms. The most common are bacteria that belong to groups called Lactobacillus and Bifidobacterium. Other bacteria may also be used as probiotics, and so may yeasts such as Saccharomyces boulardii.
Different types of probiotics may have different effects. For example, if a specific kind of Lactobacillus helps prevent an illness, that doesn’t necessarily mean that another kind of Lactobacillus or any of the Bifidobacterium probiotics would do the same thing.
Are prebiotics the same as probiotics?
No, prebiotics aren’t the same as probiotics. Prebiotics are nondigestible food components that selectively stimulate the growth or activity of desirable microorganisms.
What are synbiotics?
Synbiotics are products that combine probiotics and prebiotics.
How popular are probiotics?
The 2012 National Health Interview Survey (NHIS) showed that about 4 million (1.6 percent) U.S. adults had used probiotics or prebiotics in the past 30 days. Among adults, probiotics or prebiotics were the third most commonly used dietary supplement other than vitamins and minerals. The use of probiotics by adults quadrupled between 2007 and 2012. The 2012 NHIS also showed that 300,000 children age 4 to 17 (0.5 percent) had used probiotics or prebiotics in the 30 days before the survey.
How might probiotics work?
Probiotics may have a variety of effects in the body, and different probiotics may act in different ways.
Probiotics might:
- Help your body maintain a healthy community of microorganisms or help your body’s community of microorganisms return to a healthy condition after being disturbed
- Produce substances that have desirable effects
- Influence your body’s immune response.
How are probiotics regulated in the United States?
Government regulation of probiotics in the United States is complex. Depending on a probiotic product’s intended use, the U.S. Food and Drug Administration (FDA) might regulate it as a dietary supplement, a food ingredient, or a drug.
Many probiotics are sold as dietary supplements, which don’t require FDA approval before they are marketed. Dietary supplement labels may make claims about how the product affects the structure or function of the body without FDA approval, but they aren’t allowed to make health claims, such as saying the supplement lowers your risk of getting a disease, without the FDA’s consent.
If a probiotic is going to be marketed as a drug for treatment of a disease or disorder, it has to meet stricter requirements. It must be proven safe and effective for its intended use through clinical trials and be approved by the FDA before it can be sold.
Learning About the Microbiome
The community of microorganisms that lives on us and in us is called the “microbiome,” and it’s a hot topic for research. The Human Microbiome Project, supported by the National Institutes of Health (NIH) from 2007 to 2016, played a key role in this research by mapping the normal bacteria that live in and on the healthy human body. With this understanding of a normal microbiome as the basis, researchers around the world, including many supported by NIH, are now exploring the links between changes in the microbiome and various diseases. They’re also developing new therapeutic approaches designed to modify the microbiome to treat disease and support health.
The National Center for Complementary and Integrative Health (NCCIH) is among the many agencies funding research on the microbiome. Researchers supported by NCCIH are studying the interactions between components of food and microorganisms in the digestive tract. The focus is on the ways in which diet-microbiome interactions may lead to the production of substances with beneficial health effects.
What has science shown about the effectiveness of probiotics for health conditions?
A great deal of research has been done on probiotics, but much remains to be learned about whether they’re helpful and safe for various health conditions.
Probiotics have shown promise for a variety of health purposes, including prevention of antibiotic-associated diarrhea (including diarrhea caused by Clostridium difficile), prevention of necrotizing enterocolitis and sepsis in premature infants, treatment of infant colic, treatment of periodontal disease, and induction or maintenance of remission in ulcerative colitis.
However, in most instances, we still don’t know which probiotics are helpful and which are not. We also don’t know how much of the probiotic people would have to take or who would be most likely to benefit. Even for the conditions that have been studied the most, researchers are still working toward finding the answers to these questions.
The following sections summarize the research on probiotics for some of the conditions for which they’ve been studied.
Gastrointestinal Conditions
Antibiotic-Associated Diarrhea
- Probiotics have been studied for antibiotic-associated diarrhea in general, as well as for antibiotic-associated diarrhea caused by one specific bacterium, Clostridium difficile. This section discusses the research on antibiotic-associated diarrhea in general. C. difficile is discussed in a separate section below.
- A 2017 review of 17 studies (3,631 total participants) in people who were not hospitalized indicated that giving probiotics to patients along with antibiotics was associated with a decrease of about half in the likelihood of antibiotic-associated diarrhea. However, this conclusion was considered tentative because the quality of the studies was only moderate. Patients who were given probiotics had no more side effects than patients who didn’t receive them.
- Probiotics may be helpful for antibiotic-associated diarrhea in young and middle-aged people, but a benefit has not been demonstrated in elderly people, according to a 2016 review of 30 studies (7,260 participants), 5 of which focused on people age 65 or older. It’s uncertain whether probiotics actually don’t work in elderly people or whether no effect was seen because there were only a few studies of people in this age group.
- A review of 23 studies (with 3,938 participants) of probiotics to prevent antibiotic-associated diarrhea in children provided moderate quality evidence that probiotics had a protective effect. No serious side effects were observed in children who were otherwise healthy, except for the infection for which they were being treated.
Clostridium difficile Infection
- The bacterium Clostridium difficile can infect the colon (large intestine) of patients who have received antibiotics, causing diarrhea that can range from mild to severe. C. difficile infection is difficult to treat and sometimes comes back after treatment. It’s more common in people who take antibiotics long-term and in elderly people, and it can spread in hospitals and nursing homes. C. difficile infection affects about half a million people a year in the United States and causes about 15,000 deaths.
- A 2017 analysis of 31 studies (8,672 total patients) concluded that it is moderately certain that probiotics can reduce the risk of C. difficile diarrhea in adults and children who are receiving antibiotics. Most of these studies involved hospital patients. The analysis also concluded that the use of probiotics along with antibiotics appears to be safe, except for patients who are very weak or have poorly functioning immune systems.
- The types of probiotics that would be most useful in reducing the risk of C. difficile diarrhea, the length of time for which they should be taken, and the most appropriate doses are uncertain.
Constipation
- A 2014 review of 14 studies (1,182 participants) of probiotics for constipation in adults showed some evidence of benefit, especially for Bifidobacterium lactis.
- A 2017 evaluation of 9 studies (778 participants) of probiotics for constipation in elderly people indicated that probiotics produced a small but meaningful benefit. The type of b