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
  • Clostridium difficile Infection
  • Constipation
  • Diarrhea Caused by Cancer Treatment 
  • Diverticular Disease
  • Inflammatory Bowel Disease
  • Irritable Bowel Syndrome
  • Traveler’s Diarrhea

Conditions in Infants:

  • Infant Colic
  • Necrotizing Enterocolitis
  • Sepsis in Infants 

Dental Disorders:

  • Dental Caries (Tooth Decay)
  • Periodontal Diseases (Gum Disease)

Conditions Related to Allergy:

  • Allergic Rhinitis (Hay Fever)
  • Asthma
  • Atopic Dermatitis
  • Prevention of Allergies

Other Conditions:

  • Acne
  • Hepatic Encephalopathy
  • Upper Respiratory Infections
  • Urinary Tract Infections

Can probiotics be harmful?

  • Probiotics have an extensive history of apparently safe use, particularly in healthy people. However, few studies have looked at the safety of probiotics in detail, so there’s a lack of solid information on the frequency and severity of side effects. 
  • The risk of harmful effects from probiotics is greater in people with severe illnesses or compromised immune systems. When probiotics are being considered for high-risk individuals, such as premature infants or seriously ill hospital patients, the potential risks of probiotics should be carefully weighed against their benefits. 
  • Possible harmful effects of probiotics include infections, production of harmful substances by the probiotic microorganisms, and transfer of antibiotic resistance genes from probiotic microorganisms to other microorganisms in the digestive tract. 
  • Some probiotic products have been reported to contain microorganisms other than those listed on the label. In some instances, these contaminants may pose serious health risks. 

NCCIH-Funded Research

NCCIH sponsors a variety of research projects related to probiotics or the microbiome. In addition to the previously mentioned studies on diet-microbiome interactions in the digestive tract, recent topics include:

  • The mechanisms by which probiotics may help to reduce postmenopausal bone loss
  • Engineering probiotics to synthesize natural substances for microbiome-brain research
  • The mechanisms by which certain probiotics may relieve chronic pelvic pain
  • The effects of a specific Bifidobacterium strain on changes in short-chain fatty acid production in the gut that may play a role in antibiotic-associated diarrhea.

More To Consider

  • Don’t use probiotics as a reason to postpone seeing your health care provider about any health problem.
  • If you’re considering a probiotic dietary supplement, consult your health care provider first. This is especially important if you have health problems. Anyone with a serious underlying health condition should be monitored closely while taking probiotics.
  • Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.
  • Don’t use probiotics as a reason to postpone seeing your health care provider about any health problem.
  • If you’re considering a probiotic dietary supplement, consult your health care provider first. This is especially important if you have health problems. Anyone with a serious underlying health condition should be monitored closely while taking probiotics.
  • Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

This article was originally published here