Postbiotics: You Are What You Digest

By Hayley Philip May 26, 2021 | 6 MIN READ

The Dirt

Are you getting your daily intake of fiber? Recent reports suggest that almost all of us do not get the recommended 30 grams of fiber in our diets. But what most of us don’t realize is that fiber fuels our gut microbiome, which keeps us strong and healthy. So, what role does fiber play in the relationship between our gut and our immune system?


Postbiotics: You Are What You Digest

Health and Nutrition

By Hayley Philip May 26, 2021 | 6 MIN READ

The Dirt

Are you getting your daily intake of fiber? Recent reports suggest that almost all of us do not get the recommended 30 grams of fiber in our diets. But what most of us don’t realize is that fiber fuels our gut microbiome, which keeps us strong and healthy. So, what role does fiber play in the relationship between our gut and our immune system?

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We may think of ourselves as ’23 and me’ based on our pair of chromosomes, but really, we are closer to ‘3 million and me’ based on our microbiome. If you add up all of our genes, we are really 90% microbial.

3 million and me?

What do we mean? Throughout our intestines, we have about a mango-sized bag of hungry microbiota – which scientists are now considering an organ just like the liver or heart. This kind of tiny, powerful, and hungry bacteria, archaea, eukaryotes, and viruses determine your mood, immune system, and nutrition absorption. What type of microbiota you have depends on what you eat!

Because of its importance, microbial health has been a topic of significant discussion in the nutrition world for the last few years. By now, we’ve heard of the many gut-health-enhancing suggestions on how to boost pre- and probiotic production, such as fermented foods, daily probiotics, and a range of various fruits and veggies. But have you heard of postbiotics? They are a result of these pre- and pro-biotics you eat every day.

In relation to prebiotics and probiotics, postbiotics are the outcome of these efforts. What do I mean? Let’s do a quick pre- and probiotic 101:

  • Prebiotics are a wide variety of fiber, such as whole fruits, veggies, mushrooms, and even seaweed. Diversity is critical as it helps support a broad range of beneficial bacteria. For instance, some bacteria will thrive when you eat black beans, and some will happily multiply with spinach. If your diet is not varied, then those microbes that like certain foods will not flourish.
  • Probiotics are made up of fermented foods; specifically, 12 strains of bacteria synergistically grown together, shown to positively affect overall gut health. Think kombucha, yogurt, and kimchi.

Now for the new guy…

  • Postbiotics are compounds (or metabolites) created by the probiotic bacteria that help protect, renew, and assist the body’s essential and critical functions.

, Postbiotics: You Are What You Digest

More on Postbiotics

Postbiotics are a relatively new term in the ‘biotics’ field. That said, there is substantial scientific consensus surrounding pre- and probiotics, but with postbiotics, this is not yet the case.

Here is what we do know: postbiotics are a byproduct of pre-and probiotics. They are metabolites or cell-wall components generated during fermentation in the gut. They are soluble byproducts secreted by live probiotic bacteria that include short-term fatty acids, extracellular polysaccharides, cell fractions, functional protein, and so on. What does this mean, and what do they do for you?

Postbiotics have drawn attention as of late due to recent research indicating they can have direct immune effects.  

Clinical evidence on postbiotics shows that in healthy individuals, they improve overall health and relieve symptoms in a range of diseases, such as infant colic and adult atopic dermatitis, different causes of diarrhea, and many more.

Postbiotics can also help with:

The Journey of a Bean

Let’s take black beans, for example. You prepare a black bean salad for lunch. You chew it all up, enjoy all the rich flavors, but then what happens when it leaves your mouth? Well, digestion is not just a simple food-in, excrement-out process. These beans you just ate are going to encounter a variety of microbial players in the gut along the winding gastrointestinal tract and in the colon.

One cool part about all this is that the foods (like the beans) determine your body’s specific microbial “players”. So, you can actually think of your gut as your own personal fingerprint – it is unique to you, it is unlike anyone else’s, and it is based on what you feed it. The foods we eat make up the bacteria that live and thrive in our gut!

I like to think about it in these two equations:

Variety of Fiber + Prebiotic foods = Healthy Gut Microbiome (Healthy Bacteria makeup)

Healthy Gut Microbiome (Healthy Bacteria makeup) = Multitude of Postbiotics

But, let’s get back to the beans! A bean is a legume packed with protein and fiber. Digestion starts in your mouth with enzymes in your saliva that begin the process of breaking down your food. It travels through your esophagus, where even more enzymes jump in to help them break down the process. These broken-down food particles feed the gut microbiota to produce short-chain fatty acids.

T-cells Taking Action

While they may sound little, these short-chain fatty acids are robust and directly affect T-cell production. What’s a T-cell? Glad you asked! A T-cell is a type of white blood cell that, at its core, tailor’s the body’s immune response to specific pathogens or invaders. You can think of T-cells like soldiers who seek out invaders and destroy them!

Here is the Science: Fiber is digested in your colon by bacteria and turns into short-chain fatty acids. Short-chain fatty acids serve as messengers to tell certain cells to turn on as immune cells, or T cells. These T cells multiply and turn into helper, regulatory, or cytotoxic T cells. They can also become memory T cells. The T cells are sent to peripheral tissues and can circulate in the blood or lymphatic system. Once they detect an antigen, helper T cells send out chemical messengers called cytokines. These cytokines (are good and not to be confused with the cytokine storm) fuel the differentiation of B cells into plasma cells (antibody-producing cells- these are what you need to fight off viruses!). Regulatory T cells act to power immune reactions. Cytotoxic T cells, which are activated by various cytokines, bind to and kill infected cells and cancer cells—helping to protect us against multiple viruses, like Covid. 

Now, what if your body didn’t have enough fiber variety to produce these fatty acids needed for the T-cells? This can happen when we don’t feed our body enough variety of fruits, vegetables, and whole grains. It takes a combination of many types of these foods to maintain a healthy gut microbiota, which enables our body to break down and absorb nutrients from our food correctly and ultimately provides for our immune system defenses.

Here is another set of equations for you:

Fruits + Veggies + Whole Grains (Fiber) = Short-chain fatty-acids +Vitamins +Minerals

Short-chain fatty-acids +Vitamins + Minerals = More T-cell Production

More T-Cell Production = Better defense against pathogens & invaders

While beans are a great probiotic, many plant and animal foods can provide the fiber and protein needed to produce the fatty acids that produce T-cells. Think of T-cells as the ultimate result of postbiotics.

Who would have thought that a bean salad could achieve all that? I bet you’ll have a whole new appreciation for your lunch now that you know what an important role your food plays in preventing pathogens from attacking you.

How Can I Maximize Postbiotic Production?

Well, here is the deal: postbiotics are only produced in a body with a diverse microbiome. When you feed your gut a diverse array of dietary fibers and prebiotics, the probiotics are plentiful and varied. This variety of probiotics allows for more diverse postbiotic metabolites to be secreted. Postbiotic compounds play a critical role in regulating your organ system, your immune system, and your brain.

Think of your postbiotics as tools in your tool belt. You acquire those tools through fiber varieties. The broader range of tools you have, the more effective tool kit you have for your overall health.

, Postbiotics: You Are What You Digest

As gastroenterologist Dr. Will Bulsiewicz, M.D., author of Fiber Fueled, puts it, “when you take a prebiotic or probiotic, people don’t realize that at the end of the day, the hope is to get some postbiotics. The entire point is about postbiotics.”

While part of the issue is many people don’t know this is the end game, it is also that our microbiome is not diverse in most cases. In The Mind-Gut Connection by Dr. Emeran Mayer, M.D., he notes that an alarming 90% of children and adults in the United States do not consume the recommended amount of daily fiber. We should eat at least 30 grams of fiber a day.

How much of each pre- and probiotic food is enough? 2-3 servings of prebiotics and 1-2 servings of probiotics each day – ingested in different ways—will suffice. The idea here is that if you fuel your body with enough pre- and probiotics regularly and in a variety of ways, your body will, in turn, produce myriad postbiotics—adding to that tool belt! And the conjunction of all these components is proven to have a significant impact on our overall health.

Your probiotic bacteria’s ability to make postbiotic metabolites is solely dependent on the amount of and diversity of fiber in your diet.

Maybe we should consider changing the phrase from “You Are What You Eat” to “You Are What You Digest”!

Getting More Dietary Fiber in Our Diet

While taking a daily probiotic can help diversify our microbiome, it is simply not enough. As we know, functional foods are critical to a healthy diet, which goes for fiber consumption as well. We must learn to feed our bodies with probiotic bacteria from whole foods.

Feeding our microbiome with a wide variety of plant foods is the best thing you can do to boost postbiotic production; you will need 5-7 daily servings of a variety of the below foods:

, Postbiotics: You Are What You Digest

The Bottom Line

Our bodies are advanced systems that are connected in many ways. The food we eat directly impacts critical processes that help keep us functioning at a high level and protect us from outside intruders. Fiber intake and variety directly affect the makeup of the probiotics in our gut, which in turn determines our postbiotic output. These outputs aid in lowering chronic inflammation and boosting our immune system. Prioritize your gut health and ensure you are getting enough fiber daily in a variety of ways!