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The Four Biotics

Updated: Aug 20, 2021

Probiotics, Prebiotics, Synbiotics & Metabiotics (aka Postbiotics)

We’ve all heard about probiotics. They’re everywhere. They’re good for us. They’re in our yogurt and we can take them as pills. And yeah, they’re very expensive. So, before we throw all this money at probiotics what exactly are they? Bacteria, yes. But what does that mean? How do they help us and what else can we do for our health? And didn’t you say there were four?

Well, let’s look at them one by one.

  • ProBiotics: The word itself is a chimera of the Latin pro – meaning for or instead of – and the Greek biōtikos – a derivative of bios, meaning life. Putting this together, probiotics are live, active bacteria taken or eaten to supplement our gut microbiome. They do this by directly adding bacteria to our bodies. Hence probiotics are taken instead of bacteria usually found in our body.

  • PreBiotics: Again, originating in Latin and Greek, pre – meaning before – and biōtikos – deriving from life – prebiotics are what come before the life, they’re the substrate (food) that the bacteria in our colon eat to live. That is to say, prebiotics are necessary for bacteria to thrive in our gut.

  • SynBiotics: Stemming from the Greek syn – meaning together – synbiotics are the combination of probiotics and prebiotics. This means that synbiotics contain both good bacteria to colonize your colon and prebiotic fiber to sustain it.

  • MetaBiotics (also known as Postbiotics): Meta – meaning “after” in Greek – are the byproducts of the bacteria living with us. The waste products and residual biomass after the life cycle of the microbiota. Quite literally, metabiotics are what’s left after life.


ProBiotics, the one we all know. Probiotics are live, active bacteria taken as a pill or eaten in foods to supplement our gut microbiome. They do this by directly adding bacteria to our bodies. Hence probiotics are taken instead of bacteria found usually in our body. So, if you’re like me, you’re thinking, “how does that help us understand anything?” Well, the idea behind probiotics is that there can be fundamental lack of biosis, of life, in our gut. It sounds weird, but this life, i.e. bacteria, is vital to our body’s normal functioning.

Why? Probiotics Benefits?

Probiotics provide an influx of ‘good bacteria that are meant to colonize the gut and out-compete any ‘bad bacteria’ currently living there causing inflammation. Once there, these good bacteria live in harmony with our bodies, digesting the foods we can’t and turning them into vital nutrients, vitamins and cell signaling molecules that our body couldn’t get without them. Some of the most important of which are Short Chain Fatty Acids (SCFAs). SCFA’s are vital sources of energy our bodies and intestinal cells that also act as ubiquitous signaling molecules throughout the body. To learn more about SCFAs and the microbiome check out our article focusing on them, but for now, all we need to know is that they’re incredibly important and they’re produced when the good gut bacteria ferment fiber in your colon.

The bottom-line?

Probiotics are bacteria found in special (i.e. fermented) foods or taken as pills that colonize the gut. Once there they out-compete harmful bacteria and provide us with vital nutrients and energy. The crucial aspect of this to keep in mind is that these bacteria are incredibly important to our health and live off the foods we don’t digest, i.e. fibers, which brings us to our next category.


PreBiotics are less well known than their similarly named counterparts but they’re even more critical. Prebiotics are the substrate (food) that the bacteria in our colon eat to live. Just like humans, bacteria need a few key things to live: a safe environment and food. Despite where you and I may want to live, the gut is an ideal place for bacteria to live. First requirement: check. But how are they going to get food in there? Well, they’re more than happy to eat our leftovers. These bacteria thrive by digesting what we don’t. So, to cultivate a healthy gut microbiome, we need to ensure they are well fed or, like my pet fish when I went on holiday, they’ll die. (I’m kidding about the fish.)

PreBiotic Benefits: Floral Food

So, what do these guys eat? Fiber of course. Our body does an incredible job of absorbing nutrients, by the time what we eat gets to the colon, where most of our bacteria live, the vast majority of our foods nutrients and 90% of its water is absorbed. This leaves scarcely little for the bacteria to live on unless you have a diet high in undigestible fiber. Therefore, to have a healthy and thriving microbiome, not only do the proper bacteria need to be present but they also need to have a sufficient source of prebiotic fiber to eat. Through this process, our gut microbiome produces around 10% of our daily energy and many vital nutrients that we can get nowhere else.


SynBiotics are the best of both worlds, containing a combination of probiotics and prebiotics. This means that the food includes both good bacteria to colonize your colon and the prebiotic fiber to sustain it. Fermented foods are often excellent examples synbiotics since they contain a plethora of good bacteria because of the fermentation they undergo and are often also a good source of fiber if they’re derived from vegetables. However, the best, and tastiest, synbiotics can be made yourself by combining a probiotic with a prebiotic. A great example would be yogurt and flax seeds or kimchi and a high fiber bread. These combinations provide both the good bacteria to colonize your gut and the fiber they need to thrive.


Finally, but most importantly, we have metabiotics. In fact, we briefly mentioned metabiotics earlier, SCFAs. Metabiotics are the waste products of bacterial fermentation of fibers – a bacteria’s leftovers if you will. Luckily for us, one bacteria’s trash is our body’s treasure. Most of the ‘waste’ produced by these bacteria are actually vital nutrients and cell signaling molecules. These in turn have profound and farreaching effects on everything from our mood, immune system, blood glucose, energy and inflammation levels. So rather than certain bacteria being inherently “healthy”, it is these waste products that confer most of the gut microbiomes benefit. Thus, a significant portion of a healthy microbiome isn’t the physical bacteria living within us, but rather what these bacteria produce by digesting the fiber that we can’t.

To highlight metabiotics vast importance let’s look at the benefits and effects of just one category of them, Short Chain Fatty Acids (SCFAS):

· Energy Source: Are primary energy source for colonic cells

· Anti-inflammatory: promote anti-inflammatory properties that are important for keeping colon cells healthy.

· Anticarcinogenic: butyrate inhibits the growth and proliferation of tumor cell lines

· Weight loss: SCFAs play a positive role along with probiotics in preventing metabolic syndrome, which almost always includes abdominal obesity and type 2 diabetes

· Irritable Bowel Syndrome (IBS) & Crohn’s Disease: help improve IBS and Crohn’s by keeping the gut lining healthy and sealed

· Type 2 Diabetes: promotes GLP a protein produced naturally in the gut in response to SCFAs but which is also used as a highly effective diabetes drug by pharmaceutical companies (Victoza, Trulicity)

· And many, many more that are constantly being discovered.

As you can see, metabiotics are some of the most important molecules in our body and contribute significantly to our health. So, it makes sense that we want to maximize our body’s production of them however possible.

Probiotics vs Prebiotics, which is the best?


In recent years, there has been a massive focus on probiotics. You see them advertised everywhere: in your yogurt, in pills, and in hipster products like kombucha. These are good, especially when they’re found in naturally fermented foods like yogurt, kefir and kombucha. However, this is only half the story and honestly, a drop in the bucket.

Probiotic supplements love to measure their “dosage” in CFUs – that is colony forming units, i.e., viable cells – these are often in the billions of CFUs. While that may sound like a lot it’s a drop in the bucket when you consider that your body contains tens of trillions of bacterial cells. In fact, our bodies have just as many, if not more, bacterial cells living on and within us than human cells. All told we have about .2 kilos of bacteria living in us. Moreover, many of these probiotic supplements and foods only provide a handful of bacterial strains, whereas hundreds of unique species characterize a healthy gut microbiome. Additionally, once you stop eating or taking the probiotic, their benefit goes away since there is rarely enough prebiotic to sustain them. Therefore, one can only surmise that probiotics alone are a woefully insufficient tool to improve gut health.


Just consuming probiotics isn’t enough. It’s necessary and more important to have a prebiotic component as well. Not only are the byproducts of bacterial prebiotic (metabiotics/fiber) fermentation the vital nutrients and cell signaling molecules that we discussed above but, the gut microbiome has been shown to spontaneously flourish in the presence of appropriate substrate, i.e. fiber. Moreover, it is only a diet sufficiently high in diverse prebiotic fibers that can produce and sustain the quantity and complexity of bacteria found in healthy digestive systems.

So, it’s impossible to escape that fact that prebiotics, rather than probiotics, are key to a healthy digestive system and a healthier life. Probiotics are still good but should not be the cornerstone of a healthy diet. Probiotics are best thought of as toppings on a sundae; they make it more interesting, but a sundae of only toppings is no sundae at all.

Alright, enough with the science, so what should I do?

In short, it is paramount to our digestive health and overall wellbeing that we have diets high in prebiotic fiber. Meanwhile, fermented foods containing probiotics are the cherry on top. It's specifically worth noting that we need to eat foods with a diverse amount of different prebiotic fibers because certain bacteria can only survive on certain fibers. SynBiotics are the perfect marriage of pro and prebiotics, providing exciting combinations of both, but not many foods qualify. Therefore, its likely best to focus on consuming a diverse range of high fiber foods while also consuming natural sources of probiotics when possible. This way our gut microbiome has a solid foundation based on a sustainable source of prebiotic fiber. Thereby allowing it to develop a natural, complex and highly functioning ecosystem of healthy bacteria that will go on to outcompete bad bacteria and produce a plethora of vital nutrients, SCFAs and other cell signaling molecules crucial to our overall health.


  • Probiotics are live bacterial cultures that supplement existing bacteria in our gut. However, the quantity and type of the bacteria found in probiotics are insufficient to cultivate a truly healthy gut microbiome. Moreover, once you stop taking probiotics you quickly lose any benefit they did confer, thus making them an expensive and ineffective path to intestinal health.

  • Prebiotics, i.e. fibers, have the unique ability to foster the growth of healthy bacteria found in everyday foods, creating a large and diverse microbiome. Importantly, prebiotics are one of the only ways to do this.

  • SynBiotics are the perfect marriage of pro and prebiotics, providing interesting combinations of both, but not many foods qualify.

  • Metabiotics, the byproducts of bacterial fiber fermentation, are the driving force behind the gut microbiomes vast health benefits. These byproducts are what confer most of the microbiomes benefits improving the outcomes in type two diabetes, reducing anxiety, reducing inflammation, reducing fat deposition, enhancing the immune system and etc. MetaBiotics are vital to our body’s functioning and a healthy life.

Once again, it’s worth emphasizing that prebiotics are the key to a healthy gut microbiome as they are the foundation of a natural and sustainable gut microbiome as well as the source of metabiotics.

For a more in-depth and hard science look at the four biotics check out our other analysis here.



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