Probiotics are live bacteria and yeasts that have beneficial effects on your body. These species already live in your body, along with many others. Probiotic supplements add to your existing supply of friendly microbes. They help fight off the less friendly types and boost your immunity against infections.


What are probiotics?

Probiotics are live microorganisms (microbes) that can have beneficial effects on or inside your body. Every human body is home to trillions of microorganisms that live with us and help support our bodily functions and health. Not all of the microbes we may carry are helpful to us — some types (germs) can be harmful. But beneficial microbes, like probiotics, help to control the potentially harmful types.

Probiotic products contain select, beneficial types of microbes to add to the populations already living in your body. Many probiotics are oral supplements designed to be ingested into your gastrointestinal tract. Others are topical products that you can apply to your skin or to the mucous membranes inside your body cavities, like your nose or genitals. These are all places where beneficial microbes commonly live.


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What do probiotics do?

Probiotics are food and health products that contribute live, beneficial microbes to the populations within your gut and elsewhere, in order to strengthen those communities. They’re meant to prevent and treat dysbiosis — an imbalance or a deficit of beneficial microbes in your microbiome. When they work, the microbes take up residence on or in your body, adding to the populations already living there.

Not all probiotics are alike, though. Different types of microbes function differently within your body, so different types might be better or worse for your condition. Probiotics also aren’t regulated by the FDA, so manufacturers don’t have to prove the quality or even the contents of their products. It’s a good idea to consult a knowledgeable healthcare provider about which probiotics might work best for your needs.

When are probiotics recommended?

If you have symptoms of dysbiosis, in your digestive system or elsewhere, your healthcare provider might recommend probiotics to help bring your microbiome back to balance. If you’ve recently had an illness or treatment that weakened your microbiome, your provider might suggest probiotics to help rebuild it. For example, they might suggest taking or using probiotics after finishing a course of antibiotics.

Some people take a daily probiotic supplement to maintain their general wellness. You might want to do this if you’re prone to gut health issues and you notice it helps. A healthy gut microbiome can boost your overall immunity, reduce inflammation and help keep your bowels regular. Everyday things like stress and food choices can diminish your gut microbiome, and probiotics are one way to help restore it.


Which probiotics are effective?

For a probiotic to have any benefit to your health, it must:

  • Be of a variety that has proven benefits for your body.
  • Be in a form that’s safe to consume or apply to your body.
  • Contain viable microbes that have survived the commercial process.
  • Be able to survive the journey through your digestive tract (if it’s an oral probiotic).

Some of the most frequently studied and recommended probiotics include:

  • The Lactobacillus genus, including L. acidophilus, L. rhamnosus, L. casei and L. plantarum.
  • The Bifidobacterium genus, including Bifidobacterium longum and Bifidobacterium breve.

Acidophilus (L. acidophilus) may be the most well-known probiotic on the market today, possibly because it has so many different applications. Acidophilus is found naturally in your mouth, gut, stomach, lungs, vagina and urinary tract, and it can help restore balance in all of these microbiomes.

These products are all available over the counter (OTC), in grocery stores, drug stores and health and wellness stores. They come as dietary supplements (capsules, liquids or powders) or as topical lotions or creams for different uses. Your healthcare provider can help you select a good one to try for your needs.

You can also get probiotics in less concentrated quantities from fermented foods and drinks, including:

Fermented foods and drinks are one way to get more probiotics into your GI tract. Food processing can sometimes destroy these natural probiotics, though, so check the labels for “live and active cultures”.

Risks / Benefits

What are the potential health benefits of probiotics?

The beneficial microbes that live in different parts of our bodies assist us in a variety of ways. One of the most important ways is by fighting off the more harmful types of bacteria, fungi, viruses and parasites that might also want to live with us. Probiotics, in theory, fight on the side of your beneficial microbes.

Many probiotic products are formulated with beneficial bacteria and yeasts for the purpose of preventing or recovering from bacterial or yeast infections in your different body parts, including:

Your healthcare provider might suggest using these products preventively if you have a history of infections, or using them to help restore your microbiome after treatment with antibiotics.

Oral probiotics may have many additional benefits. Your gut microbiome — the community of microbes living in your GI tract — plays a complex role in your digestive system, and in many other body systems.

Within your digestive system, we know that a healthy gut microbiome:

  • Helps break down and absorb certain nutrients and medications.
  • Produces other important nutrients as byproducts.
  • Helps break down and recycle bile after digestion.
  • Helps train your immune system to recognize and eliminate harmful microbes.

We also know that an unhealthy gut microbiome — one in which harmful microbes outnumber the helpful types — can contribute to a variety of chronic gastrointestinal diseases, including:

Taking oral probiotics might help prevent or treat these conditions, although results may vary.

Beyond your digestive system, we know that your gut microbiome also interacts with your brain and nervous system, your immune system and your endocrine system. Some researchers believe that the health of your gut microbiome might influence many aspects of your overall health, including your:

  • Mood and pain tolerance.
  • Mental acuity and fatigue.
  • Inflammation and immune response.
  • Metabolism, blood sugar and fat storage.

All of this is still under active research, though. We don’t fully understand how it all works yet, or what effects probiotics might have within these body systems, if any. There’s not enough evidence to draw solid conclusions, but there’s enough for some healthcare providers to recommend trying them.


Are there any risks or side effects to taking probiotics?

While there’s little specific research on the safety of probiotics, they appear to be safe for healthy people to take. They have a long history of widespread and regular use among the public. There’s a small risk of adverse side effects for people with weaker immune systems. This includes people taking immunosuppressant drugs, people with critical illnesses and infants who’ve been born prematurely.

The risk is that a probiotic product might contain a harmful type of microbe along with the helpful types. Microbes are very small, so it’s possible for the wrong kind to slip in under the radar if a product isn’t rigorously tested. This is rare, and it’s not a serious risk for most people. A healthy immune system will easily clear out the imposter. But in a weakened immune system, it could cause a serious infection.

Additional Common Questions

How can I tell if probiotics are working for me?

If you’re taking probiotics for a specific purpose, and the probiotics are working, you should be able to tell that you’re feeling better. For example, if you’re taking them to help relieve constipation or diarrhea, you should notice your poops becoming more regulated over time. If you’re taking them to relieve a bacterial or yeast infection or overgrowth, you should notice your symptoms improving.

Make sure you’re taking them consistently, and at the recommended dosage, so you can properly judge how well they’re working. If you’re taking them preventively, it might be harder to tell. For example, some people take probiotics to improve their immunity during the cold and flu season. You might notice that you haven’t been sick as often as usual, but it’s hard to know if that’s due to the probiotics.

Can probiotics cause diarrhea, constipation or stomach pain?

Many people take probiotics to help relieve diarrhea, constipation or stomach pain. Over the long term, probiotics should improve your overall gut health, including your bowel regularity and digestion, reducing discomfort. But in the short term, it’s possible that introducing new probiotics could trigger similar symptoms, especially if you’re taking a large dose or if your gut tends to be sensitive in general.

Many probiotics produce a byproduct called short-chain fatty acids in your gut. These byproducts have many benefits to your gut health, but a sudden influx of them could cause temporary diarrhea. Other probiotics produce gases in your gut as byproducts. If you suddenly have more of them than usual, you might notice increased bloating and gas during digestion. These symptoms should resolve within a few days.

What’s the best way to take probiotics?

You can take probiotics as a dietary supplement, or you can get them through fermented foods and drinks. There are benefits to both methods. In general, food and drink sources might help to promote a greater diversity of microbes in your biome, which is good for maintaining your general health. Some food sources may also include prebiotics, the fibers that probiotics need to feed on to thrive.

If you want to treat a particular issue, you might want to take a specific probiotic supplement that your healthcare provider has recommended for that purpose. A supplement will typically provide a higher dose of probiotics than food sources will. Take it as recommended on the label. Some probiotics work better with food, and others on an empty stomach. Most need to be taken daily for the best results.

A note from Cleveland Clinic

There’s a lot of research in progress on the potential benefits of probiotics, and initial results are promising. Different probiotic products may help improve your skin health, your vaginal health or your gut health and build up your immunity in general. While they may not be the total solution to your health issues, they might provide an important piece of the puzzle. Ask your provider about taking probiotics. They can help you pick the best one for you, ensure your safety and monitor your results.

Medically Reviewed

Last reviewed on 10/30/2023.

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