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Probiotics 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.

Probiotics and prebiotics are both pretty big topics in nutrition these days. Photo credit: LUNDS & BYERLYS
Probiotics and prebiotics are both pretty big topics in nutrition these days. Photo credit: LUNDS & BYERLYS

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.

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?

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?

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).

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?

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
  • Berries
  • Jerusalem artichokes (not the same as regular artichokes)
  • Asparagus
  • Dandelion greens
  • Leeks

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.

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