Probiotics and prebiotics are both pretty big topics in nutrition these days. Yet even though they sound similar, the two play different roles in your health.

Probiotics are beneficial bacteria, and prebiotics are food for these bacteria. We’ll explain what you need to know about the two.

Both prebiotics and probiotics are important for human health. However, they have different roles:

  • Probiotics. These are live bacteria found in certain foods or supplements. They can provide numerous health benefits.
  • Prebiotics. These substances come from types of carbs (mostly fiber) that humans can’t digest. The beneficial bacteria in your gut eat this fiber.

The gut bacteria, collectively referred to as the gut flora, or gut microbiota, perform many important functions in the body.

Eating balanced amounts of both probiotics and prebiotics can help ensure that you have the right balance of these bacteria to keep your gut microbiota healthy.

Summary:

Probiotics are beneficial bacteria found in certain foods or supplements. Prebiotics are types of fiber that feed the friendly bacteria in the digestive system.

The good bacteria in your digestive tract help protect you from harmful bacteria and fungi.

A 2013 study on bacteria in the gut confirms that a wide variety of this good type of bacteria can aid in immune system functions, improve symptoms of depression, and help address obesity, among other benefits (1).

Additionally, some of your gut bacteria form vitamin K and short-chain fatty acids.

Short-chain fatty acids are the main nutrient source of the cells lining the colon. They promote a strong gut barrier that helps keep out harmful substances, viruses, and bacteria. This also helps reduce inflammation and may have the potential to reduce the risk of cancer (2).

Summary:

The gut bacteria help with a variety of biological tasks. They also provide important nutrition to the cells lining your digestive tract.

The food you eat plays an important role in the balance of good and bad gut bacteria.

For example, a high sugar and high fat diet negatively influences the gut bacteria and may contribute to insulin resistance and other conditions (3, 4).

Once you regularly feed the wrong bacteria, they’re able to grow faster and colonize more easily, without as many helpful bacteria to prevent them from doing so (5).

Harmful bacteria and less healthy gut flora has also been associated with higher body mass index (BMI) (6).

Additionally, foods treated with pesticides may have negative effects on the gut bacteria, although more research is needed to confirm this (7, 8).

Studies have also shown that antibiotics can cause permanent changes in certain types of bacteria, especially when taken during childhood and adolescence.

Because antibiotic use is so widespread, researchers are now studying how this may cause health problems in people later in life (9, 10).

Summary:

The foods you eat affect gut bacteria. Chemical residues and antibiotics may also disrupt balance in the gut bacteria.

Before you go out and buy expensive prebiotic supplements, remember that many foods naturally contain them.

That’s because prebiotics are types of fiber found in vegetables, fruits, and legumes.

Humans are not able to digest these types of fiber, but your good gut bacteria can digest them.

Foods that are high in prebiotic fiber include:

One of the things your good gut bacteria do with prebiotic fiber is turn it into a short-chain fatty acid called butyrate.

Butyrate has been extensively studied and has been shown to be challenging to preserve without short-chain fatty acids like butyrate (11).

Summary:

Prebiotics are types of fiber that humans cannot digest, but your gut bacteria can. These types of fiber provide nutrients to the bacteria that support healthy digestion and immune function.

There are also many probiotic foods that naturally contain helpful bacteria, such as yogurt.

A high quality, plain yogurt with live cultures can be a fantastic addition to your diet if you want to add beneficial bacteria.

Fermented foods are another great option, as they contain beneficial bacteria that thrive on the naturally occurring sugar or fiber in the food.

Examples of fermented foods include:

If you’re going to eat fermented foods for their probiotic benefits, make sure they’re not pasteurized, as this process kills the bacteria.

Some of those foods can also be considered synbiotic, because they contain both beneficial bacteria and a prebiotic source of fiber for the bacteria to feed on.

Some examples of synbiotic foods are cheese, kefir, and sauerkraut.

Summary:

Probiotic foods naturally contain helpful bacteria. Many of these foods can be made at home or purchased at a grocery store.

Probiotic supplements are pills, powders, or liquids that contain live beneficial bacteria or yeast.

They’re very popular and easy to find, yet not all of them are worth your money. They do not all have the same types of bacteria or the same concentrations. There are also many products on the market making claims with no proof of efficacy (12).

They also usually do not come with fibrous food sources for the bacteria to eat, which can hinder their effectiveness if someone isn’t also eating those foods.

Some probiotic supplements are designed to carry the bacteria all the way to your large intestine for better effects, while others probably don’t make it past your stomach acid (13).

There are some individuals who should not take a probiotic, or who may experience worsened symptoms if they do, such as people with small intestinal bacterial overgrowth (SIBO) or people sensitive to ingredients in the supplement.

However, the right strains of probiotics can be incredibly beneficial for some people. It depends on the type of strain, product formula, the quality of the product, and storage. (14, 15).

As with all supplements, you may want to consult with a healthcare professional who’s knowledgeable about probiotics.

Summary:

Probiotic supplements are designed to deliver very specific species of bacteria to the human gut. However, not all probiotic supplements are of the same quality or contain the same quantity of bacteria.

Keeping your gut bacteria balanced is important for many aspects of health.

To do this, eat plenty of both prebiotic and probiotic foods, as they will help promote the most ideal balance between good and bad gut bacteria.

Talk to your healthcare provider to make sure you’re eating the right amounts of each. It’s possible to go overboard or have side effects.

To see if you could benefit from a supplement, check out the World Gastroenterology Organization Global Guidelines list of evidence-based conditions that probiotics could potentially help. It also includes recommendations.

Make sure to read the labels on any supplements carefully and discuss any questions and recommendations with your healthcare provider.