Probiotics and Prebiotics: What’s the Difference?

Woman Looking at YogurtProbiotics and prebiotics are both pretty big topics in nutrition these days.

Yet even though they sound similar, the two play different roles for your health.

Probiotics are beneficial bacteria, while prebiotics are food for these bacteria.

This article explains what you need to know about the two.

What Are Probiotics and Prebiotics?

Both prebiotics and probiotics are important for human health. However, they play 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 pro- and prebiotics can help ensure that you have the right balance of these bacteria, which should improve your health.

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

Why Are the Gut Bacteria Beneficial?

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

They also send signals to your immune system and help regulate inflammation (1, 2).

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 reduces inflammation, and may reduce the risk of cancer (3).

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

How Does Food Affect the Gut Microbiota?

Yogurt and Blueberries

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 influences the gut bacteria negatively, allowing harmful species to overgrow (4, 5, 6).

Once you regularly feed the wrong bacteria, they are able to grow faster and colonize more easily, without as many helpful bacteria to prevent them from doing so (7, 8).

The harmful bacteria may also cause you to absorb more calories than people with a healthy balance of gut bacteria, who tend to be leaner (9).

Additionally, foods treated with pesticides like Roundup may have negative effects on the gut bacteria. However, more human research is needed on this (10, 11, 12).

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 (13, 14).

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Bottom Line: Gut bacteria are affected by the foods you eat. Chemical residues and antibiotics may also disrupt balance in the gut bacteria.

Which Foods Are Prebiotic?

Whole Sliced and Peeled Bananas

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.

These types of fiber are not digestible by humans, but your good gut bacteria can digest them.

Foods that are high in prebiotic fiber include:

  • Legumes, beans and peas.
  • Oats.
  • Bananas.
  • Berries.
  • Jerusalem artichokes (not the same as regular artichokes).
  • Asparagus.
  • Dandelion greens.
  • Garlic.
  • Leeks.
  • Onions.

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 have anti-inflammatory effects inside the colon (15).

It may also influence gene expression, block the growth of cancerous cells and help provide fuel to healthy cells so that they can grow and divide normally.

Bottom Line: 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.

Which Foods are Probiotic?

Woman Looking at Spoonful of Yogurt

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:

  • Sauerkraut.
  • Kimchi.
  • Kombucha tea.
  • Kefir (dairy and non-dairy).
  • Some types of pickles (non-pasteurized).
  • Other pickled vegetables (non-pasteurized).

If you are going to eat fermented foods for their probiotic benefits, make sure they are 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.

One example of a synbiotic food is sauerkraut.

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

What About Probiotic Supplements?

Yellow Vitamin Bottle

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

They are 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.

They also usually do not come with fibrous food sources for the bacteria to eat.

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.

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.

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

Bottom Line: 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.

Take Home Message

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

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

At the end of the day, optimizing your gut flora may have major benefits for your health.