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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.
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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.

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

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
Wisp$30180 tablets
(90 days)
2 tablets$0.33200 billion
Garden of Life$39.5090 capsules
(30 days)
3 capsules$1.3285 billion
Care/of$1130 capsules
(30 days)
1 capsule$0.368 billion
MegaFood$26.9930 capsules
(30 days)
1 capsule$0.9020 billion
Thorne$4930 capsules
(30 days)
1 capsule$1.635 billion
HUM$4060 capsules
(30 days)
2 capsules$1.3340 billion
Hers$2530 capsules
(30 days)
1 capsule$0.831 billion
Persona$1428 capsules
(28 days)
1 capsule$0.503 billion
Nurish$13.3330 capsules
(30 days)
1 capsule$0.448 billion
Culturelle$22.2520 capsules
(20 days)
1 capsule$1.1110 billion
Align$29.9921 capsules
(21 days)
1 capsule $1.435 billion
Jarrow Formulas$40.95120 capsules
(60 days)
2 capsules$0.6810 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 “microbiome.”

The microbiome is unique to each individual, and studies show it may be determined before birth. 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 the “strongest evidence in favor of probiotics lies in the prevention or treatment” of 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 and inflammatory bowel disease, but more research is needed to confirm this.

Probiotics for constipation

A 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).

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 anxiety, depression, and obsessive-compulsive disorder.

Studies into using probiotics to treat mental illness 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 and help address issues such as Autism Spectrum Disorder (ASD), Attention Deficit Hyperactivity Disorder (ADHD), IBS, and depression. These conditions affect males and females differently, highlighting the importance of gender-specific research into probiotics.

In an older 2014 study, researchers gave females and males with obesity Lactobacillus rhamnosus. The results suggested that females lost weight and fat during the trial and maintained the loss after study completion. The males in the study, however, did not.

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 instead including plenty of fiber and resistant starch in their diets and eating foods such as garlic, onions, bananas, and oats.

Learn more about the relationship between prebiotics and probiotics here.

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

Learn about the best food sources of probiotics here.

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

Learn more about fermented foods here.

The following are common questions and answers about probiotics:

What is the most effective form of probiotic?

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.

What probiotic do gastroenterologists recommend?

The American Gastroenterological Association (AGA) does not recommend using probiotics as a primary treatment for most digestive conditions.

The AGA only recommends using probiotics in the following cases:

  • preventing Clostridioides difficile
  • when taking antibiotics
  • necrotizing enterocolitis in preterm or low birth weight infants
  • managing pouchitis, a complication of irritable bowel disease.

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

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

Which probiotics actually work?

The effectiveness of probiotics depends on a person’s unique gut microbiome, lifestyle factors, and the CFU and strains of bacteria in the supplement.

People may need probiotics consistently for at least two weeks to notice any benefits.

Are some probiotic strains better than others?

Many probiotics contain mixtures of two or more individual strains of bacteria or yeasts.

Products often contain Lactobacillus or Bifidobacterium species, although many other species exist. According to some research, different strains of the same species of probiotics can act in different ways.

The best probiotic strain depends on the health goals a person has.

Should you take a probiotic every day?

Research states that it is safe for people to take a probiotic daily. Probiotics can protect people against gastrointestinal diseases such as diarrhea or enteritis and help with urogenital infections, depression, anxiety, and obesity.

However, some rare side effects may occur in people who are immunocompromised or are seriously or chronically ill. Therefore, people should always consult their healthcare professionals before taking probiotics.

What probiotics are good for UTI and yeast infections?

Research reports that L. rhamnosus GR-1, L. fermentum RC-14, and Lactobacillus acidophilus LA-14 are good for UTI and yeast infections as they aid in restoring the urogenital flora.

In recent years, the extensive research into probiotics and the microbiome leaves no doubt that these novel products 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 can do their research into which specific strains might work for their particular condition. A healthcare professional can help with this.

They can choose probiotics according to their CFU, the strains included, and whether or not the product also contains prebiotics. Choosing a product with a lower CFU for general health maintenance can be more cost-effective.

Those taking probiotics for the first time might want to monitor any effects and build up their dosage slowly, especially if the product contains prebiotics, which can cause excess gas.

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