What Are Probiotics?

A dietary supplement that helps balance your gut bacteria

Probiotics are live microorganisms (bacteria or yeast) shown to have health benefits. They're thought to increase the level of "good" bacteria in your intestines, which can help support healthy digestive and immune systems.

Probiotics are available in supplement form and are found in certain fermented foods and drinks, such as yogurt, kefir, and pickles.

This article reviews the types of probiotics, their possible health benefits, conditions they may help treat, dietary sources, and how to find the right probiotic for you.

Probiotic foods and supplements


Types of Probiotics

Many types of probiotics are on the market. Two of the major types are lactobacillus and bifidobacterium.

Each type has a variety of strains. Although it is not confirmed, some scientists think different strains have different effects.

Still, all types of probiotics are believed to positively affect your gut flora, also known as the microbiome. This is the collection of bacteria in your gastrointestinal system.

When you have a healthy balance between "good" and "bad" bacteria, your body may benefit in many ways, from maintaining good digestion to supporting a robust immune system. When "bad" bacteria dominate, a host of health issues can result.

Possible Benefits

Several aspects of modern society can mess with the delicate balance of good bacteria in your gut. They include:

  • Taking antibiotics
  • Not eating enough plant-based foods
  • Refrigeration
  • Improved sterilization of foods

What isn't yet confirmed is whether probiotics can actually improve the health of your gut flora, as experts suspect.

Probiotics are being studied for a wide range of health benefits. They're theorized to:

  • Boost the immune system
  • Help ward off infection
  • Kill off harmful bacteria
  • Improve the strength of the mucus lining the intestines

Conditions Probiotics May Treat

Manufacturers make a lot of claims about what conditions probiotics can help treat. Research often doesn't back up those claims.

It's hard to conduct quality research on probiotics due to the many strains available. Some studies show mixed results as well. Research is ongoing.

However, some research supports probiotic use for:

Additionally, preliminary research indicates probiotics may help prevent:

How to Choose a Probiotic Supplement

Be sure to involve your healthcare provider in your decision to use probiotics.

If you decide to use a probiotic supplement, be sure to read the label carefully. You're looking for a product that offers:

  • Live strains
  • Assurance that the bacteria will be alive at the time of use (not the time of manufacture)

Each product should be labeled with the genus and species of the bacteria. Ideally, it will also include the strain, so you're sure you are getting the probiotic that fits your needs.

For example, L acidophilus CL1285 and Lactobacillus casei LBC80R is a two-strain combination recommended by the American Gastroenterology Association (AGA) for the prevention of C. difficile infection.

The amount of bacteria in the product should be listed in CFUs, or colony-forming units, so you know how much you're getting.

Buyer Beware

All of that said, the United States has no federal standards for probiotic supplements. Because of this, there is a risk of buying a product that does not actually contain what it says it does. For example, the bacteria may not be live or the supplement may have unhealthy ingredients.

It's best to choose a brand-name probiotic that has research backing its effectiveness. Some of these brands include:

  • Align
  • Culturelle
  • Florastor
  • VSL#3

Check any product you are considering using to see if it has been certified by a third party, such as USP or NSF International. These groups do not guarantee a product works, but they do verify that ingredients are pure and what's in the bottle matches what's on the label.


Remember probiotics are live organisms. Use them before the expiration date. Check package instructions for storage instructions.

Some probiotics need to be refrigerated. Others should be stored in a cool, dry place.

Probiotics in Food

You can get probiotics via your diet by adding certain fermented foods. Fermented dairy products are considered the best sources because they provide an ideal environment for the bacteria to thrive. Some dairy products also have added probiotics.

The most common sources of probiotic foods are:

  • Yogurt, especially Greek-style (only if live cultures are listed on the label)
  • Cultured milk or buttermilk
  • Some cheeses, including cheddar, mozzarella, gouda, and cottage cheese
  • Kefir
  • Kombucha
  • Japanese miso
  • Tempeh
  • Sauerkraut
  • Sourdough bread
  • Kimchi
  • Olives
  • Pickles

Not all fermented foods and beverages contain probiotics. For example, you can't get them from alcoholic beverages.

However, beer and wine contain plant-based substances called polyphenols, which may improve your balance of gut bacteria by providing food (prebiotics) for probiotic bacteria. (Even so, alcohol is best consumed in moderation.)

Even though it's not fermented, human breastmilk is a natural source of probiotics.

Are Foods or Supplements Better?

From the research that's been done so far, it appears that either food or supplements can effectively deliver probiotics to your gut.

But is one better than the other? That depends. It's easier to get a consistent amount of probiotics from supplements. But when you get probiotics from foods, you also reap the benefits of the other nutrients.

You may want to try both approaches and see what appears to give you better results.


Most probiotic studies have shown few, if any, negative side effects. Still, keep in mind research is still in its early phases.

Probiotics may pose some risk to people with certain health conditions or a compromised immune system.

As with any supplement or dietary change, it's essential that you talk to your healthcare provider before consuming large amounts of probiotics.


Probiotic foods and supplements are believed to increase the "good" bacteria in your gut, improve digestion, and support the immune system. Things that can throw off that balance include antibiotics and not eating enough plant-based foods.

Probiotics have some evidence showing they can help treat or prevent digestive disorders, several causes of diarrhea, and certain infections.

Food and supplement sources both appear effective. When choosing a probiotic supplement, look for respected brands that guarantee a live strain. Be sure to store it correctly.

Probiotics may not be safe for everyone. Talk to your healthcare provider before taking them.

A Word From Verywell

If you have a digestive or immune-related condition probiotics are thought to treat, probiotic foods or supplements may be a welcome addition to your regimen.

Get your healthcare provider's OK, buy a quality supplement or food-based sources, and then keep your eyes open for any negative side effects. Remember that natural doesn't always mean safe.

16 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Barbara Bolen, PhD
Barbara Bolen, PhD, is a licensed clinical psychologist and health coach. She has written multiple books focused on living with irritable bowel syndrome.