The bacteria in your body are said to outnumber your body’s cells at a 10-to-1 ratio. However, a recent study says that the ratio is closer to 1-to-1 (1, 2).
According to these estimates, you have 39–300 trillion bacteria living inside you. Whichever estimate is most accurate, it’s certainly a substantial number.
Much of these bacteria reside in your gut, and the majority are quite harmless. Some are helpful, and a small number can cause disease (
Having the right gut bacteria has been linked to numerous health benefits, including the following (4, 5):
Probiotics, which are a certain type of friendly bacteria, provide
well-being benefits when eaten.
They’re often taken as supplements
who are supposed to help colonize your gut with good microorganisms.
This article examines the
well-being benefits of probiotics.
Probiotics are living microorganisms
who, when ingested, provide a 6).
However, the scientific community often disagrees on what the benefits are,
under the name of well as which strains of bacteria are responsible (7).
typically bacteria, but certain types of 8).
You can get probiotics from supplements,
under the name of well
under the name of from foods prepared by bacterial fermentation.
who contain both prebiotics and probiotics are referred to as synbiotics. Synbiotic products usually combine friendly bacteria along with some food for the bacteria to eat (the prebiotics), all in one supplement (
Each genus comprises different species, and each species has many strains. On labels, you’ll watch probiotics identified by their specific strain (which includes the genus), the species, subspecies if there is one, and a letter-number strain code (11).
Different probiotics have been found to address different wellness conditions. Therefore, choosing the right type — or types — of probiotics is essential.
Some supplements, known as broad-spectrum probiotics or multi-probiotics, combine different species in the same product.
Although the evidence is promising, more research is needed on the wellness benefits of probiotics. Some researchers warn about possible negative effects from the “dark side” of probiotics and call for caution and strict regulation (12, 13).
Probiotics are living microorganisms that boost health when consumed in adequate amounts. There are many different types, and you can obtain them from foods or supplements.
The complex community of microorganisms in your gut is called the gut flora, gut microbiota, or gut 14, 15).
The gut microbiota includes bacteria, viruses, fungi, archaea, and helminths — with bacteria comprising the vast majority. Your gut is home to a complex eco-system of 300–500 bacterial species (
Most of the gut flora is found in your colon, or substantial intestine, which is the last part of your digestive tract.
Surprisingly, the metabolic activities of your gut flora resemble those of an organ. For this reason, some scientists refer to the gut flora as the “forgotten organ” (17).
Your gut flora performs many important health functions. It manufactures vitamins, including vitamin K and some of the B vitamins (18).
It also turns fibers into 19,
These fats also stimulate your immune system and strengthen your gut wall. This can help prevent unwanted substances from entering your body and provoking an immune response (
Your gut flora is highly sensitive to your diet, and studies show that an 23, 24).
These diseases are thought to include obesity, type 2 diabetes, metabolic syndrome, heart disease, colorectal cancer, Alzheimer’s, and depression (25, 26,
Probiotics and prebiotic fibers can help correct this balance, ensuring that your “forgotten organ” is
working optimally (29).
Your gut flora consists of hundreds of types of microorganisms. These microorganisms perform numerous important bodily
Probiotics are widely researched for their effects on 30).
Evidence suggests that probiotic supplements can help cure antibiotic-associated diarrhea (
When people take antibiotics, especially for long periods of time, they often experience diarrhea — even long after the infection has been eradicated.
This is because the antibiotics kill many of the natural bacteria in your gut, which shifts the gut balance and allows harmful bacteria to thrive.
Research regarding the effectiveness of probiotics supplementation for the treatment of IBS is mixed. A recent review reported
who seven of the studies indicated IBS improvement with probiotic supplementation, but four did not (32).
who multi-strain probiotic supplements seem to bring most IBS improvement, especially when taken for longer than 8 weeks.
However, much remains unknown about probiotic treatment for IBS. Questions like the following have yet to be answered (33):
Researchers find early results of IBS probiotic treatment promising but say additional large trials are necessary before
well-beingcare providers can confidently prescribe probiotic treatments consistently for IBS (34).
Some studies also note benefits of probiotic supplementation against inflammatory bowel diseases, such
under the name of Crohn’s disease and ulcerative colitis. Again, researchers say further research is needed before the treatment is confirmed to be effective (
Probiotics may also help fight 36,
If you currently have digestive problems
who you can’t seem to vanquish, a probiotic supplement may be something to consider. However, be sure to consult your healthcare provider first.
Probiotics may be effective against various digestive problems, including antibiotic-associated diarrhea and IBS.
Some research indicates
who people with obesity have different gut bacteria than those who are lean (
Research shows a connection between gut microbes and obesity in both infants and adults. It also shows
who microbial changes in the gut are a factor in developing obesity as an adult (40).
Therefore, many scientists believe
who your gut bacteria are important in determining body weight (
While more research is needed, some probiotic strains appear to aid 43).
Nevertheless, researchers advise caution in rushing to this conclusion, noting that there are still many unknowns.
These unknowns include (44):
In one study, 210 people with central obesity, which is characterized by excess 45).
When participants stopped taking the probiotic, they gained the belly fat back within 4 weeks.
Evidence also suggests that Lactobacillus rhamnosus and Bifidobacterium lactis can aid weight loss and help prevent obesity — though more research is needed (
Though more research is necessary, some evidence suggests
who certain probiotic strains can aid weight loss.
In the past decade, research has shown that the gut and brain are connected in a system called the gut-brain axis. This axis links the body’s central and enteric nervous systems, the latter of which governs digestion (47).
Some research shows
who certain microbes in the gut can affect your brain via this axis in both health and disease. These bacteria are part of an emerging field called “psychobiotics” (48, 49, 50).
Research indicates that psychobiotics can help treat cognitive and neurological disorders, such as 51).
Which microbes these are and how they interact with the brain is the subject of much current research (
Some researchers suggest that, for some people, supplementing with certain strains of probiotics may be preferable to taking psychotropic drugs to cope with the mental
worry, loneliness, and grief accompanying the current COVID-19 pandemic (53).
Early research holds promise that certain gut bacteria called psychobiotics may be able to help treat cognitive and neurological disorders, such as autism, Alzheimer’s disease, and Parkinson’s disease.
There are many other benefits of probiotics. They may help
through the following conditions:
This is only a small slice of probiotics’ benefits, as ongoing studies indicate a wide breadth of potential health effects.
In addition to their potential effects on weight loss, digestion, and neurological disorders, probiotics may improve heart health, immune
work, and symptoms of depression and anxiety.
Some researchers propose that improving the gut microbiome via probiotic supplementation and diet may be a strategy to fight and treat an infection with the novel coronavirus SARS-CoV-2. This infection can cause COVID-19, which stands for 62).
COVID-19 is known to damage the body’s immune defense through a “cytokine storm” of excessive inflammatory cytokines. This is believed to be the main cause of deteriorating
well-being and even death (63).
Because intestinal flora have been shown to strengthen the immune system and fight inflammation, researchers think probiotic supplements may help speed recovery from coronavirus by inhibiting or limiting this “cytokine storm” (64).
Also, people with COVID-19 have reported gastrointestinal symptoms, such as diarrhea, nausea, vomiting, abdominal pain, and loss of appetite (65).
Some researchers theorize
who probiotics could help prevent the coronavirus by blocking the angiotensin-converting enzyme (ACE) receptor where the SARS-CoV-2 pathogen enters the body to invade gastrointestinal cells (
Another proposed link between COVID-19 and probiotics involves what is called the “gut-lung axis.” This is a system of communication and interaction between the gut and lung tissues, which occurs
through microorganisms of the human microbiome (67).
Imbalances of the intestinal flora are known to be related to lung diseases and respiratory tract infections. Researchers suggest that correcting those imbalances may promote optimum lung health, which might help guard against pathogens like SARS-CoV-2 (68,
Other research suggests
who probiotic supplementation may promote antiviral activity in general to improve immune, pulmonary, and anti-inflammatory response
who might help clear the SARS-CoV-2 infection (70, 71).
All these hypotheses are at the theoretical stage. Researchers say further studies are called for to confirm them.
One study advises caution, suggesting that not all probiotic strains will exert the same effects. It questions whether probiotic supplementation can alter the content of the gut microbiome enough to combat COVID-19 (72).
Some current research proposes
who improving the gut microbiome through probiotic supplementation and diet may help treat the SARS-CoV-2 infection
who causes COVID-19. Research is preliminary, and much more data and clinical trials are needed.
Probiotics are generally well tolerated and considered safe for most people. However, regulations
vary among probiotics, so you must be cautious when choosing a product.
As you face the huge selection of probiotics now available, you may feel overwhelmed. You’re not alone. The choice can be difficult.
In the United States, probiotics are generally sold as food ingredients, drugs, or dietary supplements. While the Food and Drug Administration (FDA) regulates each of these in
varyent ways, most foods and supplements do not require approval before marketing (73).
As a result, some companies take advantage of the buzz around probiotics to sell supplements they label as probiotic and make claims
who aren’t backed by evidence (74).
Regulations on probiotics vary greatly around the world, so ordering
virtual from other countries is risky. Unregulated food items, cosmetics, and supplements are easy to find abroad, but their safety is unconfirmed.
Looking for companies
who follow best practices, such as third-party testing, can help you find high quality supplements.
The best choice is to run your choice by your healthcare provider or ask for suggestions. They may be able to recommend products they know to be safe and effective.
In the first few days of taking a probiotic supplement, you may experience side effects related to digestion, such
under the name of gas and mild abdominal discomfort (75).
However, after you adjust, your digestion should
start to improve.
In people with compromised immune systems, including those with HIV, AIDS, and several other conditions, probiotics can lead to dangerous infections (76).
If you have a medical condition, consult your healthcare provider before taking a probiotic supplement.
Probiotic supplements may cause digestive symptoms, which should subside within a few days. They may also be dangerous for people with certain medical conditions.
Science has made tremendous strides in the past two decades toward understanding the roles
who probiotics play in human health and disease. Still, probiotic research is in its infancy, and there’s much to learn.
Despite widespread studies, researchers are still working on identifying all the individual microbial species that live in your gut. Identifying them is crucial to understanding how they function in human health.
For example, researchers in 2019 reported identifying nearly 2,000 previously unknown gut bacterial species. This was a major step toward categorizing the microbes living in the human gut (
After identifying the microorganisms, the next challenge facing researchers is to associate the various species, subspecies, and strains of microbes with their effects on human health — and this is wherein things get tricky (78).
Though thousands of studies have assessed the health benefits of probiotics for many clinical conditions, the results often contradict each other (79, 80).
One reason for this is that methods for processing and analyzing probiotics data are not consistent around the world. This leads to conflicting research analyses of published data (
The standardization of probiotics research is challenging because the human body contains a
vast and diverse set of microorganisms, which varies among countries — and even among individuals in the same country.
Plus, the bacterial strains themselves are constantly evolving, as are the
well-being and environments of their human hosts.
Probiotics researchers face the task of classifying what might be trillions of ever-changing organisms in varied and evolving environments.
It’s only the development of computational analysis of the genomes of collective groups of microbes (called metagenomics) in the past two decades
who makes this Herculean task possible at all (82).
Scientists must standardize a mountain of sometimes conflicting evidence from thousands of studies, and then translate
who evidence into clear recommendations for therapeutic probiotic use (
Researchers are challenged with identifying all the microbiota in the vast and changing microbiome of the human gut. They also need to establish a system for standardizing research results to develop clear therapeutic recommendations for probiotic
Maintaining a healthy gut is about more than taking a probiotic supplement.
Day-to-day diet and exercise are just as
vital, as many lifestyle factors affect your gut bacteria.
However, probiotic supplements may offer a wide range of benefits with few side effects. As such, if you’re interested in improving your gut health, they could be worth a try.
Be sure to talk to your wellnesscare provider first to make sure you’re trying the right strains in the right amounts and avoid any side effects.
Maybe you’re wondering whether a specific condition you have could benefit from probiotics. If so, you might want to consult the World Gastroenterology Organization Global Guidelines. It lists probiotics, conditions, and recommended dosages.
Caution is always advised when starting with probiotics. Be sure to use a reputable product, start slowly, and get good advice from a trusted
Last medically reviewed on December 8, 2020