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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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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 $5890 capsules
(30 days)
3 capsules$1.9385 billion
Align$35.4021 capsules
(21 days)
1 capsule $1.685 billion
Jarrow Formulas$37.49120 capsules
(60 days)
2 capsules$0.6210 billion
Persona$1428 capsules
(28 days)
1 capsule$0.503 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 symptoms of various health conditions.

Probiotics may help relieve gastrointestinal issues such as a leaky gut where molecules enter the bloodstream and cause inflammation or immune reactions. Research also reports that the probiotic yeast Saccharomyces boulardii is effective in treating antibiotic-induced diarrhea, IBS, and IBD.

Other probiotics such as Bifidobacterium lactis effectively reduce gut transit time, which is the time it takes for food to pass as a bowel movement. This means it may be effective in easing constipation.

Probiotics may support weight loss. For example, some experts suggest that supplementation with synbiotics — a combination of prebiotics and probiotics — using Lactobacillus and Bifidobacterium strains, may lead to weight reduction. Adding certain fibers may increase these effects.

Other studies have shown that mixtures of probiotic strains including the probiotic Bifidobacterium may be effective in treating obesity and reducing body mass index (BMI).

Researchers have also explored the connection between gut microbiota and the central nervous system, also known as the gut-brain axis. In one study the probiotics Bifidobacterium and Lactobacillus were effective in treating symptoms of major depressive disorder (MDD).

Studies have also highlighted how probiotics may help improve certain behaviors in male children with autism and reduce the risk of attention deficit hyperactivity disorder (ADHD) in males. As this condition affects males and females differently, this may also highlight the importance of gender-specific research into probiotics.

An older 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.

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.

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.

Research suggests that taking probiotics daily may have certain health benefits. These benefits include better gut health that may lead to a strengthened immune system, lower stress levels, better cardiovascular health, and fewer upper respiratory tract infections.

However, more research is necessary to determine recommendations on the strains, dosage, and length of time people should take probiotics to see these benefits.

If a person has an existing health condition or a weakened immune system, they should speak with a doctor before taking any probiotic supplements.

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.