Probiotics are live bacteria and yeasts present in the human digestive system and in some foods and supplements. They may benefit gastrointestinal health, the immune system, and more.

Probiotics are useful bacteria. They exist throughout the body, although people largely associate them with the stomach and intestines. As evidence of a link between the gut microbiome and overall health continues to grow, interest in probiotics is increasing.

A woman serves herself kimchi, which is full of probiotics, at a restaurant.Share on Pinterest
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People often consume probiotics in the hope of balancing their intestinal flora, also known as the gut microbiome.

There are many strains of probiotic bacteria, but the main ones are of the Lactobacillus or Bifidobacterium groups.

Prebiotics are different from probiotics. They are nutrients in food. The body does not digest prebiotics, but these nutrients help stimulate the growth or activity of useful bacteria.

Food sources of probiotics include fermented foods, such as some yogurts and kimchi. Probiotic supplements are also available.

Probiotics may benefit the body in various ways, such as:

  • boosting the health of the gut microbiome
  • restoring balance to the microbiome after an illness or treatment
  • supporting the immune system

Probiotics may benefit people with various health conditions. However, determining exactly who would benefit from which type of bacteria will require more research.

Below are some ways in which probiotics may help maintain health.

Treating diarrhea

Certain strains of probiotics have shown limited positive results in treating diarrhea and gastroenteritis, a condition characterized by inflammation of the gut’s lining that can cause diarrhea.

For example, authors of a 2025 review note that probiotic intake may have a small beneficial impact on diarrhea symptoms in critically ill adults.

However, further research is necessary to fully assess their efficacy in diarrhea treatment.

Managing mental health problems

There is a link between the gut microbiota and the central nervous system, including the brain. Experts refer to this as the gut-brain axis. The two-way communication of the gut-brain axis means that emotions can cause gastrointestinal issues, and gut health can influence mood and mental health.

Limited research suggests that using probiotics can reduce the severity of mental health symptoms, including depression and anxiety.

High cholesterol

Multiple studies show that taking probiotics can have a positive effect on cholesterol levels, according to a 2023 review.

However, the effectiveness may depend on the type and dosage of the supplement. More studies are needed to confirm the results and clarify which probiotics would be useful.

High blood pressure management

Limited research suggests that probiotic supplementation may reduce both systolic and diastolic blood pressure, presenting a potential role in high blood pressure (hypertension) management.

Bowel inflammation management

The gut microbiota play a significant role in inflammatory bowel disorders. While probiotics can support overall gut health, there is a lack of definitive evidence to suggest they can have a direct positive impact on inflammatory disorders.

However, some studies have highlighted the potential of probiotics in the management of irritable bowel syndrome (IBS) and ulcerative colitis, a type of inflammatory bowel disease (IBD). More research is necessary to fully assess these claims.

Infection

In laboratory tests, scientists have found that a specific form of the probiotic bacteria Lactobacillus paracasei may protect the gut from infection by Listeria, a more harmful type of bacteria.

Foods that contain natural probiotics include some types of:

Many products are marketed as containing probiotics, but the body is more likely to benefit from certain items. Eating soft cheese, for example, may be a good way of making sure that probiotic bacteria reach the gut in a beneficial form.

Probiotics are available as supplements; however, there is not yet sufficient evidence to prove that a specific brand or type will help with a particular condition.

The Food and Drug Administration (FDA) regulate probiotics for medical purposes. However, they do not consider probiotic supplements to be medication and so do not monitor claims about probiotic contents. A person cannot be sure exactly what a product contains.

Probiotics are likely to be safe for most people, but there are some points to consider before using them or increasing the intake.

The National Center for Complementary and Integrative Health notes that while probiotics are likely safe for those in good health, these bacteria may pose a risk to people with weakened immune systems or other health issues.

These people may face a risk of:

It is always best to check with a doctor before taking supplements or making significant dietary changes, especially for people with existing health issues.

Probiotics are types of “friendly” bacteria that may boost the health of the gut microbiome. They are available in some foods and as supplements.

Check with a doctor before taking supplements or increasing the consumption of probiotics, to ensure that doing so is safe.