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Prebiotics, Probiotics, and Postbiotics: What Are They and How Do They Differ?

Do They Improve Gut Health?

Various forms of pre, post, and pro -biotics

The definitions of pre-, pro-, and post- biotics

At ZBiotics, we know the importance of the gut microbiome. It’s at the heart of why we started this company. But as microbiologists, we often see confusion about microbiome-related products.

Today, we want to clear up confusion related to three key products: prebiotics, probiotics, and postbiotics.

Unfortunately, – whether because they sound the same or because there is a lot of misinformation out there – understanding what differentiates these ‘-biotics’ can be difficult. They’re all intended to interact with your microbiome in some way, but they are quite different.

Prebiotics, probiotics, and postbiotics each serve a specific function. In the same way that we don’t think of bacteria as "good" or "bad,” we don’t think about each ‘-biotic’ as healthy or unhealthy. It takes some effort to get to know each of them.

Before you decide to adopt pre-, pro-, or postbiotics into your lifestyle, let’s take a closer look at what they actually are and how they differ. From the microbiologists behind the world's first genetically engineered probiotic, here are some fast facts about prebiotics, probiotics, and postbiotics.

What Are Prebiotics?

Prebiotics are, essentially, a food source for microbes in your gut. On a molecular level, prebiotics are primarily fibers, resistant starches, and sugars your body can’t digest. Beneficial gut bacteria* turn prebiotics into food and “eat” them using fermentation, growing and thriving in the process.

*Note: When we refer to “bacteria” we are not excluding other non-bacterial microbes in the microbiome.

What Foods Are Prebiotics Found In?

Many of the foods humans eat are good sources of prebiotics. They include, but are not limited to (citation):

Prebiotics in food

  • Chicory root
  • Asparagus
  • Sugar beets
  • Rye
  • Honey
  • Bananas
  • Tomatoes
  • Onions
  • Garlic
  • Seaweed
  • Cow’s milk
  • Peas
  • Beans
  • Lentils
  • Cooked and rapidly cooled potatoes

What Are Probiotics?

In practice, probiotics are live microbes (usually bacteria or fungi) that are safe to eat.

Probiotics are typically defined as live microorganisms intended to have health benefits when consumed or applied to the body. However, studies have yet to demonstrate that commercial probiotics provide health benefits across large, diverse populations. This raises doubts about the claims often made about conventional probiotics.

We dig deeper into this issue in another blog post: What’s the Problem with Probiotics?

What Foods Are Probiotics Found In?

In addition to purified probiotic supplements, you primarily find probiotics in cultured, unpasteurized foods. These are fermented foods that still have live microbial communities.

Probiotics in food

Examples include:

  • Yogurt
  • Kombucha (fermented tea)
  • Tempeh (fermented soybeans)
  • Sauerkraut (fermented cabbage)
  • Natto (soybeans fermented by Bacillus subtilis, a microbe near and dear to our hearts)
  • Some soft cheeses

What Are Postbiotics?

Postbiotics are molecules produced when the microbes in and on your body (i.e. your microbiota) eat or break down prebiotics and other molecules. These molecules form during a fermentation process that occurs in your gut. Essentially, postbiotics are the chemical outputs released by your microbiota.

Some postbiotics can be good for your body. These include:

  • Short-chain fatty acids, such as butyrate, propionate, and acetate
  • Microbial cellular fragments or debris
  • Metabolites or other microbial end-products
What Foods Are Postbiotics Found In?

Postbiotics in food

Postbiotics are found in foods that have (or had) live and metabolically active microbes. Again, these tend to be fermented foods. Examples of foods that may contain postbiotics include:

  • Sauerkraut
  • Kimchi
  • Soft cheeses
  • Slow-fermented bread
  • Buttermilk

What Are Engineered Probiotics?

We’ve been talking about conventional prebiotics, probiotics, and postbiotics, but we’d be remiss if we didn’t mention a new class of probiotics that operates a bit differently: engineered probiotics. Unlike conventional probiotics, engineered probiotics perform specific, defined functions – often by producing an enzyme that does something beneficial.

The first of this class is the ZBiotics pre-alcohol probiotic, which we engineered to help break down acetaldehyde – an unwanted byproduct of alcohol.

While ostensibly a “probiotic,” ZBiotics (or, more specifically, the bacteria Bacillus subtilis ZB183™) is unlike conventional probiotics in the following ways:


  • ZBiotics wasn’t developed for general gut health. It was engineered with a specific purpose: to be consumed before you drink alcohol to help you to wake up fresher the next day.
  • ZBiotics was engineered to produce a very specific enzyme (called acetaldehyde dehydrogenase) at a higher rate and with greater reliability than any conventional probiotic.
  • The fact that ZBiotics is a probiotic is merely incidental. It is a chassis for the function of breaking down acetaldehyde.
  • ZBiotics was developed over years of research using patented, in-house technology.
  • ZBiotics uses a particular species of bacteria called B. subtilis, because it minimally impacts the resident microbiome. This is unlike other probiotics, which need to change your microbiome in some way to have their intended effect. This can result in undesirable side effects. By using B. subtilis, ZBiotics avoids these side effects entirely.

To learn more about the science behind ZBiotics, visit our homepage.