Probiotics—whether from food or supplements—are a hot topic of consumer interest. However, would a relatively healthy person benefit from supplementation of probiotics, or is a fiber-rich diet sufficient for cultivating a robust gut microbiome? Learn more about probiotics, and review available research on supplements and health.
What Are Probiotics?
Probiotics are dubbed the “good gut bugs” that live in our digestive tract. They include bacteria, viruses, fungi, and other microbes that make up what we call the gut microbiome. Each person’s microbiome is different, influenced by what we eat, our lifestyle habits, our genes, and environment. Although studies have shown that the types and amounts of gut bugs differ between healthy individuals and those with disease, and that many health experts believe that a diversity of bacteria in the colon is beneficial, what a healthy gut microbiome looks like is still unknown, as it would likely vary from person to person.
However, there are known probiotics that live in the human intestine, such as Lactobacillus, Bacteroides, and Bifidobacterium. The World Health Organization defines probiotics as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.” Early research on probiotics used nonharmful bacteria to change or replace intestinal microbes in patients who had intestinal disorders or diarrhea.
What are prebiotics?
Prebiotics consist of non-digestible fermentable carbohydrates that act as food for probiotics. An example is oligofructose naturally found in wheat, onions, banana, garlic, leeks, and chicory root or inulin. The fermentation of prebiotics by gut bacteria may help increase the amount of beneficial bacteria strains in the colon, prevent the growth of potential pathogens, reduce constipation, support healthy immune function, and lower blood cholesterol levels.
What are synbiotics and postbiotics?
Synbiotics are supplements that contain a mix of probiotics and prebiotics, with the intention that the bacterial strains are fed and thrive in the gut. Postbiotics are the “waste” made by gut bacteria after digesting prebiotic fibers, which can include beneficial short-chain fatty acids and vitamin K.
These are terms promoted by industry, as they are marketed as supplements alongside probiotics. However, at this time there is little quality scientific evidence supporting the use of prebiotic, symbiotic, and postbiotic supplements to improve health.
Sources of Probiotics
Probiotics can be found naturally in or added to certain foods and beverages, and are sold as supplements.
Food sources
Foods that are fermented tend to contain probiotics, such as:
However, to cultivate a robust gut microbiome, rather than adding just these foods to your diet, focus on implementing a long-term dietary pattern rich in various types of fibers from fruits, vegetables, whole grains, beans, nuts, and seeds that act as prebiotics.
Do all fermented foods contain probiotics?
Fermented foods are foods or beverages that are produced with the intentional, controlled growth of microorganisms with the conversion of food components by enzymes. Historically, fermentation was commonly used to preserve foods as it protected the food from contamination by pathogenic bacteria. It also imparts a unique taste and texture to foods created by the specific types of bacteria used. Certain foods like olives are inedible without fermentation that removes bitter compounds. Fermented foods may benefit the gut microbiome, promote the production of short-chain fatty acids, and support a healthy immune system.
Processing of fermented foods, such as by heating, baking, or pasteurization, reduces or kills probiotics. So popular foods like sourdough bread and commercially prepared fermented vegetables like kimchi and sauerkraut do not contain probiotics unless they have been added back (the label may state “contains live and active cultures”). Additionally, the International Scientific Association for Probiotics and Prebiotics state that the term “probiotic” should not be used interchangeably with “fermented foods.” Instead, fermented foods should be labeled as “containing probiotics” only when there is evidence that the live microbes provide health benefits. For example, yogurt is a fermented food but should only be labeled as “containing probiotics” if the bacterial strains used in its production have been shown to provide health benefits.
Processed foods and probiotics
You may be surprised to see probiotics advertised on packages of chocolate, cookies, juices, and tea as the food industry has cashed in on growing consumer interest in digestive health and probiotic supplements by conveniently including them in common foods and beverages.
Be wary of ultraprocessed foods advertising on front of label, “includes probiotics (or prebiotics) to support digestive health.” This addition may create a favorable impression of their nutritional value but does not make brownies and chips suddenly healthful. Manufacturers also tend to choose familiar-sounding bacterial strains that a consumer will recognize and be more likely to purchase.
Are prebiotic sodas good for me?
There is overwhelming scientific evidence of the harmful health effects of soda and sugary drinks. While soda intake has declined, sodas containing prebiotics have surged in popularity, thanks to the inclusion of a fiber called inulin and growing consumer interest in gut health. Inulin is naturally found in small amounts in fruits and vegetables like bananas, onions, artichokes, and asparagus. But the type found in ultra-processed foods is usually extracted from chicory root and blended into sweet foods like brownies, yogurt, nutrition bars – and now sodas. These sodas are sweetened with sugar but contain much less than traditional sodas per 12-ounces: about 4-5 grams compared with 40 grams in a cola drink. A soda lower in sugar and containing fiber, especially a fiber type that boasts “prebiotics for gut health” is surely attractive to a consumer. However, it is unproven that the small amount of prebiotics in these sodas will truly improve gut health, and drinking more of them daily to potentially achieve gut health also drives up sugar intake. In fact, a class action lawsuit was filed in 2024 against one of these soda manufacturers due to false health claims.
The best use for these prebiotic sodas might be to replace a traditional soda if you’re trying to wean down and lower sugar intake. But they should not be viewed as a health beverage, and remember that the more you drink, the sugar will add up. Check out Healthy Drinks for best beverage options.
Supplements
In 2013, global sales of probiotic supplements was $32 billion, and is predicted to reach $85 billion by 2027.
In 2020, the International Scientific Association of Probiotics and Prebiotics expanded the definition of probiotics marketed as supplements to include their genus, species, strain, alphanumeric strain designation, and commercial name. For example:
- Genus: Lacticaseibacillus
- Species: rhamnosus
- Strain designation: GG
- International strain depository designation: ATCC 53103
- Strain nickname: LGG
- Product name: Culturelle†
† The inclusion of this brand-name is for reference only and does not constitute an endorsement. The Nutrition Source does not endorse specific brands.
Quality of supplements
The supplement industry as a whole is fraught with uncertainties: the quality of products from different sources can vary, and supplement manufacturers do not always have quality control programs in place. Sometimes a probiotic supplement contains lower than the stated dose of bacterial strains or may even contain different types of strains than are listed.
The quality of probiotic supplements depends on the manufacturer. Important factors include an assurance of potency (ensuring live bacteria in the amounts listed, typically in colony-forming units [CFU] through the end of shelf-life), purity (manufacturing processes that reduce the introduction of harmful pathogens), and identity (current nomenclature used to specify the genus, species, and subspecies, if applicable, and a strain designation for each strain in the product). Live probiotics are susceptible to dying during storage, which manufacturers account for when listing the potency and CFU. Responsible manufacturers will include the dose expected at the use-by date.
Probiotics and Your Health
There is tremendous interest in the use of probiotic supplements to treat various health conditions or for boosting immunity. As a consumer, you may see attractive claims of health benefits on supplement labels, but be wary as good-quality scientific evidence is still limited and conflicting as to which strains benefit which health conditions, effective doses, single versus multi-strain types, and an optimal length of time to use them. It can be difficult to disentangle scientific evidence from enticing marketing claims.
Probiotic supplements are backed by a billion-dollar industry that often funds published research that shows positive findings about their specific bacterial strain(s). Even if studies, particularly meta-analyses, do not show author disclosures of conflicts of interest, this does not guarantee there are not embedded financial ties. Do not be surprised if your physician or health care practitioner does not recommend probiotic supplements, which is based on low-quality evidence on their efficacy.
Due to lack of high-quality evidence and a largely unregulated supplement industry, buyer beware should be heeded. The American Gastroenterological Association released practice guidelines in 2020 on probiotic supplements to manage gastrointestinal disorders, and concluded only a few conditions in which they may benefit. They determined that drawing conclusions on probiotic research is difficult due to studies including different strains of microbes used, different doses, and different routes of administration, as well as differences in how the study was conducted and including only small numbers of patients followed for short periods.
That said, research is ongoing and some people find benefit in taking probiotic supplements for specific conditions in the short-term. Multi-strain types (more than one bacterial strain in the supplement) have not necessarily been found more effective than single-strain types. The following conditions have shown low-quality evidence for probiotic use:
- Severe diarrhea caused by C. difficile bacterial infections
- Diarrhea from antibiotic use
- Infectious diarrhea in children
- Irritable bowel syndrome
- Constipation
- Ulcerative colitis and Crohn’s disease only used in a clinical trial setting; prevention of recurrent pouchitis (an inflammatory condition that occurs after a surgery performed to treat ulcerative colitis)
- Non-alcoholic fatty liver disease
Are probiotic supplements safe?
As a rule, always discuss supplement use, including probiotics, with your doctor.
There are several species of microbes such as Lactobacillus and Bifidobacterium that are naturally found in the human colon and considered to be safe (not pathogenic). However, people who have weakened immune systems, are taking immunosuppressant drugs, or have severe disease conditions should not use probiotic supplements, because in specific cases they have been associated with harmful overgrowth or led to health complications.
Bottom Line
Probiotics have skyrocketed in consumer popularity. However, there is often industry funding for probiotic research, which can skew results in favor of using the supplements. Despite the hype, there exists mostly low-quality evidence for probiotic supplements. A relatively healthy person would not likely benefit from their use, and those with weakened immune systems should avoid them.
Research is ongoing, and the decision to use supplements should be preceded with caution, with an awareness that there is a level of “manufactured importance” created by industry. General recommendations for probiotics cannot be made, and people should not use them loosely, because each person’s gut microbiome is unique with different bacterial strains that are optimal for them.
Because the safety and effectiveness of probiotic supplements is unclear, the World Gastroenterology Organisation recommends that if clinicians advise probiotic supplements to patients, the strains, doses, and length of use should only be that of those used in human trials that were shown to be beneficial. However, most consumers and doctors do not have access to or the ability to sort through probiotics research, to be able to differentiate among various probiotics products.
A safer natural way to cultivate a healthy gut microbiome is to implement a dietary pattern that includes a variety of fiber-rich fruits, vegetables, whole grains, and legumes that will “feed” favorable gut bugs. This can include fermented foods that naturally contain probiotics.
About This Page
Written by: Nancy Oliveira, MS, RD, LDN, CDCES
Reviewed by: Teresa Fung, MS, RD, ScD
Updated: March 4, 2025
Page history
- March 4, 2025
- Page copyedited and published
- October 18, 2024
- Content and evidence reviewed
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