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The best probiotic depends on the individual and their health goals. Other important factors include the strain of bacteria, how much bacteria the supplement contains, and whether it contains prebiotics.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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Medical News Today chooses probiotics based on the following criteria:

  • Colony forming units (CFU): We include products with a high CFU stated clearly on the product.
  • Bacteria strains: We have chosen probiotics with different strains, including options with a blend of multiple bacteria strains.
  • Safety: We include products that clearly state ideal use, including recommended dosage, when to take them, storage suggestions, and any contraindications.
  • Effectiveness: We select brands that outline possible timelines for seeing health benefits.
  • Reputation: We only choose products from vetted brands that do not make unsubstantiated health claims or promises.

Medical News Today follows a strict product selection and vetting process. Learn more here.

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Please note that the writer of this article has not tried these products. All information presented is purely research-based and correct at the time of publication.

The following table compares the probiotics in this article on key points:

PriceProduct size
(Daily supply)
Daily dosePrice per doseCFU count
Ritual$5430 capsules
(30 days)
1 capsule$1.8011 billion
Care/of$1230 capsules
(30 days)
1 capsule$0.048 billion
HUM$4060 capsules
(30 days)
2 capsules$1.3340 billion
MegaFood$26.9930 capsules
(30 days)
1 capsule$0.9020 billion
Thornearound $4730 capsules
(30 days)
1 capsule$1.635 billion
Garden of Lifearound $4290 capsules
(30 days)
3 capsules$1.4085 billion
Align$63.7821 capsules
(21 days)
1 capsule $3.035 billion
Jarrow Formulas$37.49120 capsules
(60 days)
2 capsules$0.6210 billion
Persona$1428 capsules
(28 days)
1 capsule$0.503 billion
Nurish$13.3330 capsules
(30 days)
1 capsule$0.448 billion
Culturelle$21.9930 capsules
(20 days)
1 capsule$0.7320 billion

Probiotics are harmless microorganisms that may support the presence of healthy bacteria in the body.

The human body contains millions of live bacteria. Many exist in the gut. Gut bacteria make up a person’s “gut microbiome.”

The gut microbiome is unique to each individual, and research shows it may be determined before birth. 2021 research suggests that the microbiome changes throughout a person’s life based on their diet, lifestyle, and exposure to different environmental influences.

Probiotics can help populate the gut with good bacteria. This is a key part of a person’s immune system. Gut bacteria have many bodily functions and affect weight, mood, and inflammation.

In recent years, there has been a lot of interest in how probiotics can support health and reduce a person’s risk and symptoms of certain conditions.

Some people take probiotics to maintain everyday health. When using a probiotic for a specific health concern, people should speak to a healthcare professional about the best strategy. Clinical trials show that different probiotics and dosages are effective for different conditions and situations.

Probiotic manufacturers measure amounts of bacteria in colony-forming units (CFUs). Supplements can vary, but most have a CFU in the billions. Foods with added probiotics often contain lower numbers of bacteria. Generally, people take higher-CFU products for specific conditions and lower-CFU products for general health maintenance.

Some research suggests that probiotics can help keep the gut healthy and may help relieve the symptoms of some health conditions.

A 2018 review states that probiotics may be beneficial in preventing or treating the following five conditions:

Some other potential uses and benefits of probiotics include:

Probiotics for gut health

Probiotics may support a person’s gut health and relieve gastrointestinal issues.

Damage to the gut’s lining may lead to intestinal permeability or “leaky gut.” This can allow molecules to enter the bloodstream and cause inflammation or immune reactions.

Antibiotics can kill both bad and good bacteria. Sometimes, this can cause a person to experience symptoms of diarrhea when taking them. Taking probiotics alongside antibiotics may help repopulate a person’s gut with beneficial bacteria and ease symptoms of diarrhea.

In particular, the probiotic yeast Saccharomyces boulardii has effectively prevented and treated diarrhea that occurs when taking antibiotics or following infection. The yeast may also effectively treat irritable bowel syndrome (BS) and inflammatory bowel disease (IBD), but more research is needed to confirm this.

Probiotics for constipation

An older review of studies indicates that probiotics may reduce gut transit time — the time it takes for food to pass as a bowel movement — by 12.4 hours and increase total bowel movements by 1.3 per week.

The Bifidobacterium lactis strain seems most efficient in improving gut transit time, stool frequency, and consistency, and in reducing flatulence.

However, the researchers advise caution when interpreting the results, as there may be bias in some of the studies included.

Probiotics for weight loss

The bacteria in a person’s gut may connect with their weight. A small 2019 study found that people following a low calorie diet for 15 weeks experienced changes in their gut bacteria. They also had a reduction in bacteria associated with atherosclerosis, which occurs when the arteries become clogged with plaque.

The links between weight and gut bacteria could indicate that probiotics may support weight loss.

Some experts suggest that supplementation with synbiotics — a combination of prebiotics and probiotics — , using strains such as Lactobacillus gasseri, may lead to weight reduction. Adding certain fibers may increase these effects.

A 2019 review of obesity and probiotics concluded that mixtures of probiotic strains may be more effective in treating obesity than single strains. In particular, Bifidobacterium may be effective for reducing body mass index (BMI).

A 2021 review concluded that certain probiotic strains from the Lactobacillus and Bifidobacterium genus showed promising results for weight loss.

One 2018 review concluded that probiotics may result in a reduction of weight and fat percentage. However, there have not been enough high quality studies to confirm that probiotics have this effect.

Most research into this has used Lactobacillus and Bifidobacterium strains. However, there are still unanswered questions about specific strains, duration of treatment, and appropriate dosages.

Probiotics for mental health

Research into the effects of probiotics on mental health is limited, but early studies suggest there may be a connection between gut microbiota and the central nervous system. This is referred to as the gut-brain axis.

Researchers have used Bifidobacterium and Lactobacillus to treat the symptoms of major depressive disorder (MDD).

Studies into using probiotics to treat mental health conditions are ongoing and showing promise.

Probiotics for females and males

The effects of probiotics may be different in females and males.

Emerging research indicates that probiotics could improve gut-brain wellness, help improve certain behaviors in autistic male children, and reduce the risk of attention deficit hyperactivity disorder (ADHD) in males. These conditions affect males and females differently, highlighting the importance of gender-specific research into probiotics.

A study in people with Salmonella infection suggested that the effects of taking Lactobacillus plantarum varied according to sex. Although the study authors saw little evidence that this probiotic may treat Salmonella, they noted how males and females experienced the symptoms and clearance of the infection differently.

Scientists need to conduct more studies to establish whether probiotic therapy should differ depending on a person’s sex.

Some probiotic supplements also contain prebiotics, compounds that the probiotics can feed on. If a formula contains both probiotics and prebiotics, it is called a “synbiotic.”

Some formulas may also contain prebiotics. Including prebiotics can be beneficial, as they provide substances for probiotics to digest. This process can produce short-chain fatty acids, which can help maintain the health of a person’s colon and immune system.

Research indicates that prebiotics are effective because they withstand food processing and reach the colon undigested. Oligosaccharides are some of the most common prebiotics in supplements and foods.

Some people’s bodies can be sensitive to prebiotics, so taking too much of them can cause flatulence or diarrhea. Such people can obtain the health benefits of prebiotics by including plenty of fiber and resistant starch in their diets and eating foods such as garlic, onions, bananas, and oats instead.

Learn more about the relationship between prebiotics and probiotics.

People can take probiotics in supplement form, or the form of foods and beverages such as yogurt and drinks with live cultures added.

Learn about the best food sources of probiotics.

Fermented foods naturally contain beneficial bacteria. Examples of fermented foods include:

Learn more about fermented foods.

The best probiotic is one which meets a person’s unique health needs. Every individual biome is different. Look for probiotics with a high CFU count, multiple or specific bacteria strains, and clear usage recommendations.

Ritual Synbiotic+ is suitable for most people and health goals. However, a person should consult a doctor for guidance on probiotics.

Although scientific research shows promise for probiotics, the American Gastroenterological Association (AGA) does not recommend using probiotics as a primary treatment for most digestive conditions.

The AGA only recommends using probiotics to prevent Clostridioides difficile, manage pouchitis, a complication of irritable bowel disease, or in the case of necrotizing enterocolitis in preterm or low birth weight infants, and if someone is taking antibiotics.

For conditions such as Crohn’s diseaseulcerative colitis, IBS, and acute infectious gastroenteritis, probiotics are only recommended in the context of a clinical trial.

People should speak to a gastroenterologist for specific probiotic guidance and recommendations based on their health conditions and goals.

People who have weakened immune systems and serious health conditions should avoid probiotics. The National Center for Complementary and Integrative Health (NCCIH) states that probiotics can increase the risk of infections and antibiotic resistance.

The best probiotic will differ for each person, as everyone’s microbiome is unique. People should speak with a doctor before trying a probiotic for a particular health condition, as research is in its early stages in many cases.

Recent research into probiotics and the microbiome provides some evidence that these supplements can benefit some aspects of human health. Specifically, science has identified areas of use for diarrhea, respiratory conditions, and some infant illnesses and conditions. Probiotics may also help with weight management, gut issues, constipation, and mental health.

People should do their research into which specific strains might work for their particular condition. A healthcare professional can help with this. Those taking probiotics for the first time should monitor any effects and build up their dosage slowly.

People with an immune condition or severe illness should speak to a doctor before taking probiotics, as they may not be suitable. Also, people with allergies or intolerances should read product labels carefully to avoid a reaction.