Probiotics are live bacteria and yeasts present in the human digestive system and in some foods and supplements. They may benefit gastrointestinal heath, 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 grows, interest in probiotics is increasing.

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.

Learn more about the difference between prebiotics and probiotics.

A woman serves herself kimchi, which is full of probiotics, at a restaurant.Share on Pinterest
Consuming probiotics through supplements or foods, such as kimchi, may help improve the gut microbiome.

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.


Certain strains of probiotics have shown positive results in treating diarrhea and gastroenteritis — inflammation of the gut’s lining, which can cause diarrhea.

A 2011 review concluded that probiotics may help combat different forms of diarrhea, including sporadic infectious diarrhea, acute watery diarrhea, and diarrhea due to a rotavirus.

However, the effects would likely depend on the type and dosage of probiotic.

Mental health problems

Studies have pointed to a link between the gut microbiota and the central nervous system, including the brain. This link is known as the gut-brain axis.

Some scientists believe that bacteria in the gut could affect the nervous system and the way that people think and feel.

The findings suggest that probiotics could one day support the treatment of mental health issues, such as anxiety and depression, and possibly some neurological conditions, too.

High cholesterol

A 2017 review concluded that consuming foods containing probiotic Lactobacillus bacteria could reduce levels of low-density lipoprotein, or “bad” cholesterol, as well as total cholesterol.

In 2018, authors of a meta-analysis also looked at the impact that probiotics could have on total cholesterol.

After studying data from nearly 2,000 people, the researchers concluded that probiotic supplements could significantly reduce total cholesterol levels in the blood.

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

One review has found that milk fermented with strains of Lactobacillus may help lower blood pressure.

The review also showed that consuming probiotics could lead to an increase in levels of vitamin D — which helps prevent high blood pressure — in the blood.

If further research confirms that probiotics can help manage blood pressure, these bacteria could one day play a role in treating and preventing heart disease.

Irritable or inflammatory bowel

There is evidence that probiotics may help treat irritable bowel syndrome (IBS). A 2019 review concluded that a multi-strain probiotic might improve IBS symptoms.

The researchers called for further investigations into whether strains of Akkermansia, Bacteroides, and Faecalibacterium bacteria could play a role in future therapies.

A different 2019 review found that probiotics did not consistently support the treatment of inflammatory bowel disease, or IBD, except possibly for one type of the disease: ulcerative colitis.


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.

A 2017 review found further evidence that probiotics could help treat and prevent Listeria infection. Probiotics, if proven useful, would be less likely to disturb the balance of the microbiome than the standard antibiotic treatment for this infection.

Psoriasis and chronic fatigue syndrome

In 2013, researchers found evidence that Bifidobacterium infantis 35624 could benefit people with conditions such as psoriasis and chronic fatigue syndrome.

This specific type of bacteria is often included in supplements to fortify the digestive system.

Foods that contain natural probiotics include some types of:

  • yogurt
  • kefir
  • buttermilk
  • soft cheese
  • soy-based products, such as miso, tempeh, and some soy beverages
  • kimchi
  • unpasteurized sauerkraut
  • nutrition bars
  • juice
  • cereal

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.

Learn more about foods that contain probiotics.

Probiotics are available as supplements, though there is not yet enough 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.

Also, it is not always clear how long a probiotic stays active in the body.

As a result, a person cannot be sure how effective any product is likely to be or which condition it may help with.

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 note 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.

Probiotic supplements are available for purchase online.