Probiotics are one of the most popular health supplements. But gaining more attention these days is prebiotics and postbiotics. Probiotics are confusing enough to understand. What’s a gut microbiome anyway? Add “pre-” and “post-” to the “biotics” mix and it’s easy to see why people throw their hands up, super confused and frustrated about nutrition. 

The purpose of this post is to make it really easy to understand what the difference is between the 3 types of biotics. 

And the easiest way to understand this is to use a garden as an analogy. 

In order to have a thriving garden, you need:

Fertilizer and sun. In the world of biotics (the community of teeny-tiny living things), mineral-rich fertilizer and sunlight is the equivalent of PREBIOTICS.

The healthy soil is PROBIOTICS. 

And lastly, a sprouting plant is POSTBIOTICS. 

What is Prebiotic Fiber?

Prebiotics are also called prebiotic fiber. Just like you can’t have healthy soil without mineral-rich fertilizer, you also can’t have a thriving community of friendly bacteria in your colon, aka large intestine (where most of your gut bacteria belong) — without prebiotic fiber. 

Prebiotic fiber, then, acts as fertilizer for your friendly colon bacteria (probiotics). Some people make the mistake thinking that if they just take a probiotic supplement, they can continue to eat lots of processed food and very little fresh fruits and veggies. 

But there’s two problems with this: first of all, many probiotic supplements are of poor quality. Remember, probiotics are living microorganisms and they have to make a dangerous journey through your highly-acidic stomach digestive juices in order to survive and settle in your colon. 

Problem number two with eating like crap and taking probiotics? Well, it’s the equivalent of trying to grow a plant in sand; there’s just not enough fertilizer to make things thrive. 

The interesting thing about prebiotic fiber is that your body doesn’t do a good job digesting that. But that doesn’t mean you’re going to get indigestion from eating prebiotic fiber (or foods that have prebiotic-like properties). When you eat prebiotic fibers (see list below), you’re not really feeding yourself. 

You’re feeding — and fertilizing — your gut microbiome. This helps the friendly bacteria in your colon multiply. And not only grow but successfully colonize in the colon. In other words, when you move into a new house, it takes some time to feel fully settled and comfortable. Prebiotics help the probiotics settle in!

Examples of Prebiotic Fiber and Prebiotics

You’re probably familiar with one type of prebiotic fiber: psyllium husk. For many people who struggle with constipation, psyllium husk is the go-to powder for relief; it’s the active ingredient in Metamucil. 

Other examples of prebiotic compounds include:

  • Acacia gum 
  • Larch arabinogalactan (gum arabic; larch gum)
  • Inulin
  • Glucomannan
  • Beta glucan
  • Pectin 

In addition, there are several curious veggies that have prebiotic fiber. These include:

  • Chicory root (which is approximately 70% inulin)
  • Apples (high in pectin)
  • Dandelion greens (high in inulin)
  • Garlic (high in a prebiotic “FOS” which may cause digestive issues, so test a small amount)
  • Onions (same issue as garlic)
  • Leeks (inulin)
  • Asparagus (inulin)
  • Green-tipped bananas (resistant starch; has prebiotic-like effects)
  • Non-GMO oats (rich in beta-glucan)
  • Shirataki noodles (zero-calorie noodles that have a little glucomannan)

If you’re not a big fan of most of these foods, I highly recommend using a prebiotic fiber supplement. (Need help choosing a probiotic or prebiotic supplement? I can make some unbiased recommendations for you. Just submit a comment below!)

What Are Postbiotics?

It’s a fact of life: not to gross you out, but all living things poop. And that includes the trillions of friendly bacteria in your gut (again, mostly in the colon). When the friendly bacteria in your gut consume the indigestible fiber (prebiotic fiber), the byproduct (metabolic poop, if you will) is a type of fatty acid called “short-chain fatty acids” or SCFAs. 

SCFAs are postbiotics. Are postbiotics important? You betcha! In fact, some studies (here’s one) suggest SFCAs are even more important than probiotics. Let me repeat that: probiotic poop is more important than the poop itself. Ok, I’ll stop using the “P” word because it’s unappetizing and the last thing I want to do is discourage you from eating prebiotic fibers. 

Why Are Short Chain Fatty Acids Important?

Now, here’s one reason why postbiotics are so important. And if you have brain fog, autoimmune conditions or any gut problems, you’ll want to pay attention. Ok, so SFCA postbiotics are like general contractors for your gut lining. They get to work by repairing the super-thin, single-layer of cells that serve as the border between your intestines and your blood circulation. So if you have a weak gut lining, all sorts of nasties can leak out into the blood and travel to distant organs like the brain. (Hello, brain fog!)

I could go on and on about why SFCAs are so important for health. And in a future post, I’ll do just that. But let me put it simply: every facet of your health, from your immune system to your mood, is influenced by short-chain fatty acids. I admit that I’m not sure exactly how postbiotics work. But even the most brilliant scientists devoted to the gut microbiome aren’t exactly sure how postbiotics work. 


Getting prebiotic fiber in your diet, along with consuming fermented foods like raw sauerkraut and no-sugar added yogurt will help ensure that your gut microbiome flourishes. Just like your backyard garden. 

Struggling with your weight and other health concerns? 
The first step towards reclaiming your health is to schedule a no-obligation call with me here.

Until next time,

Jenna Witt, NP, Functional Medicine Practitioner