Everything You Need To Know About Probiotics

Walk through a supermarket and you will see the word 'probiotics' added to all sorts of foods - cheeses, juice, yoghurt and of course the probiotics packaged up into a handy capsule.

But what exactly are probiotics? Do they actually improve our gut and health?

And do we really need to pay for fancy probiotic supplements?

I'll be taking a good look at the science on probiotics and answering all these questions plus much more. 

Though I'll give you a quick sneak peek of whats to come - It turns out that probiotics and gut health are far more fascinating than you can possibly imagine!

You can either read the entire article or skip to a section you think is interesting:

  1. What Are Probiotics?
  2. Types Of Probiotics And Benefits
  3. Using Probiotics For Different Conditions
  4. Possible Side-Effects
  5. Probiotic-Rich Foods
  6. The Best Probiotics And How To Use Them
  7. Why Managing Gut Health Involves More Than Popping A Pill
  8. Closing Thoughts: How To Fix Gut Health

(By the way, you can learn more about my best natural sources of probiotics in THIS downloadable guide.)

Let's get started...

Affiliate Disclosure - This article contains affiliate links to products that, if purchased, this site will receive part of the sale proceeds. One noteable mention is the Seed Daily Synbiotic. The products linked to, and endorsed in this article (including Seed) are used and recommended by the authors of this article and these authors do earn a commission if you purchase these products through the links on this site.

Everything You Need To Know About Probiotics

In this blog post, I'll first tell you about what probiotics exactly are and tell you about different types of them.

I then consider why you could use probiotics, for both overall health benefits as well as using probiotics to aid in managing health conditions.

I then talk about probiotic-rich foods and the best supplements. Lastly, I consider why taking a pill alone will never take your health to the next level.  

Curious yet?

Keep reading!

1. What Are Probiotics?

Probiotics are supplemental bacteria that you ingest which affect gut function. The goal of taking probiotics is to positively influence your gut health, which in turn, can contribute to your overall health.

Why ingest bacteria? Well, many people don't know that the human gut is loaded with different bacteria. 

These bacteria, taken together, partially make up your "gut microbiome" - a collection of microorganisms found in your gut. Let's explore that concept of "microbiome" more closely:

What Is A "Microbiome"

Crazy fact: some scientists estimate that up to 10 times as many foreign cells exist within the human body as human cells (12). Recently, however, estimates have moved closer to a 1:1 ratio (3).

Many bodily places besides the gut contain bacteria as well, such as your skin, mouth, and lungs (456). Bacteria thus make up an important part of the human body.

Those microorganisms present in many places of the body are called the "microbiome". If the microbiome in your mouth is off, for instance, you're at greater risk for getting cavities (6).

And it's not just bacteria making up that microbiome--many different organisms can be found there as well, such as bacteria, fungi, and viruses.

The presence and state of these microorganisms can turn South. In that case, a "dysbiosis" - also known as a "poor state of co-existence" - of your gut microbiome is created. That dysbiosis is associated with gut conditions such as inflammatory bowel disease or "SIBO" (78).

Phrased differently, you want to have a healthy gut to have a healthy body and mind. Many people's gut microbiome is in a state of dysbiosis nowadays, meaning that:

  1. Healthy micro-organisms are absent
  2. Too many unhealthy microorganisms are present
  3. A combination of 1 and 2

Simply put, the viruses, bacteria, fungi, and other organisms need to live in harmony. Without harmony, their state is in "dysbiosis".

So let's consider in more detail why the gut microbiome is so important:

Gut Microbiome

Depending on the estimate you refer to, your gut actually contains up to 1 quadrillion, or 1,000,000,000,000,000 organisms (9). Yes, I know that's a big number.

These bacteria actually play many roles, such as:

  • Keeping your immune system healthy (10; 11). A healthy microbiome can protect you against infectious diseases, for example.
  • Aiding digestion and increasing the nutritional value of food (12; 13; 14). 
  • Producing nutrients (18; 19). With an optimal gut microbiome, healthy fats called "short-chain fatty acids" will be produced in your gut - which are similar to the fats found in butter
  • Helping your body detox (151617). The microbiome in your gut can either aid or impede the processing of certain toxins such as heavy metals, for instance.
  • Determining how much energy you experience on a daily basis (20; 21). If your gut doesn't function well, your energy levels will also be off.

Gut health also determines disease risk, among others. 

Recall that the gut microbiome actually hosts many different species. In general, having a more diverse microbiome is healthier (although there are limits to that causal connection) (18; 19).

Many studies show that hunter-gatherer societies have more diverse microbiome than people living in developed countries. These hunter-gatherers are almost always also healthier than people living in a big city.

Why Gut Health Matters

About 70 million people in the US have digestive problems (35). The US has a population of 330 million people, so about 20% of people experience gut problems at any given time.

Poor gut health is not a problem that you can simply ignore.

Remember that your microbiome is responsible for the digestion of food? Well, I've you've got a condition called "inflammatory bowel disease" all the food you eat will be absorbed less well than if you were healthy (36; 37; 38).

In that case, you can eat the most expensive grass-fed organic beef there is--but you won't experience (all) the benefits.

The result is that ~45% of people with that gut condition are malnourished, while ~15% are severely malnourished (36). The worse the symptoms, the greater the malnutrition becomes (38).

Weight loss can be another consequence of that condition, in part because you're prone to have diarrhea. You may also eat less than you'd otherwise do because digestion can be plainly painful.

The end result of a gut condition is that you may lose lots of muscle mass, which makes you weaker and less healthier overall.

Pain, moreover, is also a frequent symptom experienced by people with inflammatory bowel syndrome (39; 40; 41). Just imagine: if you're in pain most of the time after eating a simple meal, are you going to perform at your best? Hell no!

Depending on the circumstances, one solution to these gut problems can be probiotics:

What Do Probiotics Do?

Probiotics are supplements you take to move your gut microbiome to a healthier state - often containing bacteria such as Lactobacillus and Bifidobacterium (42; 43).

The term "probiotic" literally means pro-life ("bios" is the Greek word for life).

Just like you can supplement with certain vitamins and minerals, supplementing the microbiome in your gut is thus also possible. 

How Do Probiotics Work?

Two main forms of probiotics exist: supplements and foods.

Probiotic-rich foods are almost always fermented foods. So yoghurt, kimchi, and kefir are rich sources of probiotics.

On the internet, it's frequently claimed that these foods don't work as a source of probiotics as your stomach acid allegedly breaks down the bacteria in these foods before they hit the small intestine.

Such statements are a myth because plenty of studies show that foods like kefir or yogurt affect the microbial makeup of the gut (29; 30; 31). Are many microbes killed during the initial digestive process? Sure--but some survive as well.

Additionally, thousands upon thousands of studies wouldn't exist showing an effect of probiotics because there simply wouldn't be any change in any study. What 90%+ of these studies show instead, is that probiotics do affect gut health - sometimes negatively, sometimes positively.

Nonetheless, you cannot simply grab any probiotic supplement in the supermarket and assume you'll be curing your gut issues. Let me explain why:

Reading Supplement Labels

Most probiotic manufacturers use similar strains, such as the aforementioned two bacteria as well as BacillusEscherichia, Enterococcus, and others.

And just like you can see which vitamins and minerals are included in a supplement, the names of probiotics also have to be included in supplement packaging.

For instance, your bottle may say: "Lactobacillus gasseri, KS-13 - 5 Billion CFU".

In that case, there's:

  • The "Lactobacillus" is the genus - a more general group. The word "genus" is derived from classification systems in biology.
  • Then there's the "gasseri" part, which is the specific species. So the Lactobacillus genus is made up of different species, such as Lactobacillus gasseri and Lactobacillus acidophilus.
  • All probiotics have specific strains. "KS-13" is the strain listed in the bacterium above.
  • Lastly, the number of bacteria is listed in the CFU measurement. "CFU" stands for "Colony Forming Unit", which equals the number of healthy cells contained in the supplement which can multiply. A 5 billion CFU supplement thus contains 5 times as many microorganisms as a 1 billion unit.

Even though probiotic labels may look pretty complicated, they're actually pretty straightforward.

Note: many companies don't list the strain of the probiotic. Different strains do have different biological effects, and thus, it's very important to differentiate between them (35; 36). 

To really know what a probiotic supplement does to you, you need to know 1) the genus; 2) the species; 3) the strain; 4) the number of microorganisms you're taking in.

Most probiotic supplement companies don't tell you about the third category, which makes interpreting effects derived from studies difficult.

Just think about that statement: what if a vitamin company didn't tell you which type of vitamin K they're selling to you, would you trust them? Vitamin K1 and K2 have very different effects in the body, and if you're unsure which form you're taking, it's hard to extrapolate the health effect.

And yet, taking probiotics is not enough for improving gut health:

Prebiotics And Synbiotics?

Your diet has a huge impact on your gut microbiome. 

While following a Mediterranian diet with more plant-based foods, for instance, you'll get more Bifidobacteria in your microbiome (22).


Well, many plant foods can be categorized as "prebiotics". Prebiotics are fiber-rich plant foods.

The fiber in these foods acts as a "feed" for your gut's microbiome. In other words, if you feed the bacteria in your gut fiber they're more prone to survive and multiply.

These prebiotic-rich foods include:

  • Onions, leeks, and garlic
  • Grains such as oats and barley
  • Fruits like bananas and apples
  • Dark chocolate
  • Different types of seaweeds
  • Potatoes (especially the skins)

By eating these prebiotics you can influence your gut microbiome (23; 24; 25). One example is a prebiotic called "inulin". Inulin feeds healthy bacteria in your gut, lowers your appetite so that you're better able to regulate your weight, and aids in blood sugar regulation (26; 27; 28).

While I'm talking mostly about probiotics in this blog post, the topic cannot be fully separated from prebiotics because the latter can be necessary for optimal gut function as well.

Additionally, many foods contain some microorganisms as well. Some bacteria also thrive at higher temperatures, so you'll almost always ingest some of them through your food--even when cooked.

Spores of bacteria can survive the cooking process, for instance. These spores can result in new bacteria in foods that are stored after cooking.

Synbiotics, lastly, simply combine prebiotics and probiotics. 

Some modern supplements contain both prebiotics and probiotics (32; 33; 34). The word "syn" in that name is derived from "synergism" - implying that the two categories strengthen each other. 

So taking prebiotics and probiotics together potentially leads to better results than taking either alone.

The goal of this blog post is thus to find the best synbiotic on the market - for an overall gut health strategy.


2. Types Of Probiotics And Benefits

In this section I'll briefly consider a few probiotic strains, to give you a sense of what kind of benefits these can have. 

Keep in mind that the benefits listed below are in no way exhaustive because tens of thousands of studies have been carried out in this area. Just one important species, like Bifidobacterium longum, already leads to 1,620 different studies:

I'll thus consider a couple of the most important species of probiotics and look at which benefits they can have for your health:

  •  Bifidobacterium longum is a bacteria found in the human gastrointestinal tract.  Bifidobacterium longum is actually very well studied, and can lower inflammation, counter gut conditions such as Celiac disease (gluten intolerance) and inflammatory bowel disease, and may combat depression (95; 96; 97; 98).
  • L. acidophilus is derived from lactic acid and frequently used in dairy products. L. acidophilus helps your gut absorb nutrients such as B-vitamins, may prevent seasonal allergies, and helps create healthy fats in the gut (99; 100; 101).
  • Lactobacillus casei is yet another bacteria found in milk products - especially foods like yogurt and kefir. This probiotic counters stress, lowers pain if you've got an autoimmune condition such as rheumatoid arthritis (which results in joint pain), and helps you lose weight (102; 103; 104; 105).

And while you could make lists of many different probiotics and their specific benefits, I'll keep the story short. 

In general, depending on the species and strain you're using, you can expect benefits all the way from preventing cancer, increasing organ health, boosting cognitive performance, managing the immune system and inflammation levels, gut health, skin beauty, and much more.

Used properly, probiotics can thus affect every area of your health.

The problem is that the topic is so complex with thousands of studies being published every year alone. 

Potentially thousands of probiotics also exist, and listing them all here would lull you into sleep.

And if you're wondering: "so what probiotics do I need to get?" - I'll get back to that topic in a later section.

Let's first take a look whether these supplements actually influence your health if you've got a (chronic) condition:



3. Using Probiotics For Different Conditions

While I'm not going into specific strands for specific purposes here, in this section I'd like to consider what potential benefits probiotics can have for different conditions.

The fact that probiotics affect so many different conditions is a clear sign they have a major effect on your health.

So let's get into that topic:

  • Lowers your stress levels. Probiotics may counter depressive symptoms, for instance (44; 45; 46). Probiotics can also improve your performance and well-being if you're already under stress (47). In animal studies, probiotics can also have anxiety-lowering effects (48).
  • Helps you lose body fat. Your probiotic intake may affect what you eat, for example, which in turn influences your fat loss journey (49). Additionally, evidence exists that your gut microbiome affects the number of calories you're burning on a daily basis (50; 51). Improved overall gut function and lower inflammation may be two further mechanisms by which fat loss is stimulated (52).
  • Reduce your risk of heart disease. Yes, I know that may sound counterintuitive, but probiotics can really lower your blood pressure (53; 54; 55). The systolic pressure is lowered by more than 3 points and the diastolic pressure with more than 2. Blood pressure is one of the best markers to determine your risk of heart disease.
  • Enhances gut function. This benefit should come as somewhat of a no-brainer because most people use probiotics for this specific reason. Specifically, inflammation in the gut and poor bacterial makeups can be counteracted (56; 57). Many people with gut issues suffer from either inflammation or unhealthy bacteria in their gut. 
  • Improves the role of the immune system. Of course, simply activating the immune system is not helpful and is even harmful, usually. Nonetheless, probiotics seem to make the immune function in places such as your gut and nose more effective (58; 59). Some studies even go as far as linking probiotic usage to a lower risk of developing autoimmune conditions (60; 61).
  • Influence organ health such as the liver. Probiotics can literally affect "fatty liver disease" - a condition that plagues many people in developed countries due to poor lifestyle choices (62; 63). The liver is closely connected to the gut and gut health thus influences liver health (64).
  • Manage your allergies. Various types of allergies can be affected, such as food allergies or breathing problems (65; 66; 67). You can increase your tolerance of cow's milk, for instance.

Now, I could have treated all the categories listed above in far more detail. In the area of gut health, for instance, probiotics can affect the intestinal barrier in the gut, whether you've got constipation or diarrhea, influence irritation and inflammation, and much more.

Keep in mind that all of these effects are hypotheticals because much more (high-quality) research into probiotics is needed to draw definitive conclusions.

And yet, these supplements are not fully 100% safe either - whether you benefit from them depends on circumstance:


4. Possible Side-Effects

Probiotics are not always safe to take. In some instances, it's better to consult your physician first before trying to out supplement a problem.

If you've got a serious health condition, such as an autoimmune disease or debilitating gut problems such as chronic diarrhea I do not recommend taking probiotics without testing first.

If you're in poor general health - such as having a chronic condition or an infection - taking probiotics is also not recommended. Again, consult your physician first!

The reason is that in such cases, these supplements can make your condition worse

For instance, a couple of probiotic types such as Lactobacillus bulgaricus a.k.a. Lactobacillus Delbrueckii can increase your histamine levels. Histamine is intimately linked to the functioning of your immune system and to allergic responses.

Many of such species can simply be found in foods such as yogurt. Whether you tolerate that food thus depends on your personal circumstances. 

Heck, now that I'm talking about the topic of food anyway, let's discuss probiotic-rich foods:


5. Probiotic-Rich Foods

In this section, I'll consider some of the foods you may regularly consume for their probiotic content.

I won't treat these foods in great detail, and instead, just mention the main (potential) benefits of these foods as well as how they can be a possible detriment to your health:

  • Yogurt. Of course, the health benefits of yogurt always depend on the context. Yogurt will have very different benefits depending on the type of probiotics used - although there's lots of standardization in this area. Yogurt may improve gut condition, aid in digesting milk product, and can support the immune system (68; 69; 70; 71).
  • Kefir is made by adding specific grains to raw milk and having the bacteria in the grains ferment the whole. Kefir has tons of potential health benefits, such as supporting gut and digestive function, improving blood glucose control, and aiding in the management of allergies (72; 73; 74; 75; 76). For most people, kefir is actually more easily digestible than yogurt. Kefir contains more probiotic strands than yogurt as well.
  • Kimchi is made from fermented cabbage vegetables - a traditional Korean dish. Other vegetables such as garlic and peppers are frequently added as well. Kimchi is purported to counter cancer, obesity, and overall gut issues (especially constipation) - although research is sparse (77). Not all people tolerate fermented vegetables well due to the creation of "histamine" - a neurotransmitter and hormone associated with allergies (78; 79)
  • Sauerkraut - you surely know this veg, right?! Well, as you'd probably expect, sauerkraut has high histamine levels once again. 
  • Fermented cheese is great if you need a probiotic product but don't want to consume any lactose (80). Some people are intolerant to the carbohydrate in milk products called "lactose"--cheese doesn't contain that stuff. 
  • Soy-based products such as soy sauce. I'm just mentioning this food to tell you to steer clear from it. If you'd like to know why, read my post on how soy is one of the very worst foods in existence today. Miso and tempeh are other soy-based products that I'd avoid unless you've really done your research. Natto is somewhat different and contains lots of high-quality vitamin K2.
  • Alcoholic drinks such as wine and beer. I can already hear the excuses: "Alex told me to consume more probiotics for my gut health, so I started drinking beer and wine every day." Obviously, you shouldn't rely on alcoholic drinks to improve your gut health. Do these drinks affect the gut? Yes - but often not in a positive way because they also inhibit the integrity of your gut lining.

If you want to be absolutely sure these foods support your health instead of causing more gut issues or triggering food intolerance, I recommend doing some lab testing.

Also, keep in mind that many foods naturally contain some probiotics. If you're eating raw carrots, for instance, you'll ingest the probiotics located at the outside of that vegetable. 

Meats such as sausages are similar in that they often contain probiotics. The closer to a raw state any given food is, the more microorganisms found on them.

Raw New Zealand vegetables - fresh from my garden and FULL of probiotics.
Follow my journey to optimize my health and brain on Instagram.

 Organic Dry Farm wine - STILL not an excuse to use as a probiotic supplement


Prebiotic-Rich Foods

How about prebiotic-rich foods?  

The rule of thumb is very simple in that case: eat foods that contain more fiber.

Please keep in mind that not everyone does really well on including more fiber into their diets. Some people have lots of trouble with eating more fiber, while others do great making rice, fruits, and vegetable staples of their diets.

Experimenting is the best way to find out how you're doing in this department. If you'd like to know what I've been eating recently, check out my blog on my daily food intake.

And by the way, you can learn more about my best natural sources of probiotics in THIS downloadable guide. 

6. The Best Probiotics And How To Use Them

Remember I told you that knowing the group, species, and strain of probiotics is important?

That criteria then determines which probiotics I'm going to recommend to you.

Additionally, I also recommend buying high-quality products that contain very few fillers. If you're spending $15 dollars on a 3-month supply of probiotics at the supermarket, you can be certain you're not getting the highest quality product.

The solution is to buy from companies that have an established reputation for selling high-quality products. Thorne offers some probiotics that contain information on specific strains, for instance. The Life Extension brand is similar if you look at THIS and THIS example.

(if you're ordering from iHerb, use discount code BHS654 to save on your order)

The product I'm currently experimenting with, however, comes from a company called Seed. So far I'm very impressed with their product.


Seed offers synbiotics and has included specific probiotic strains that are backed under high-quality studies in humans.

Even though many studies are performed, standardization is actually really bad regarding most probiotic and synbiotic companies. A lack of standardization - when companies include probiotics but don't tell you which strain is used or whether there are human backing that strain - is a big problem in the supplement industry.

Even though I used Thorne in the past, right now I consider the Seeds Daily Synbiotic the best on the market (use discount code ALEX15 to save on your Seed order. I get a commission if you use that code).

I'll soon post an extensive review on that product as well - while including lab testing for my gut - so that you'll learn more about what makes this product special. In all honesty, just check out that Seed website and learn about the science yourself.

They are even about to have two clinical studies carried out on their Daily Synbiotic (one is undertaken by Harvard Medical School).

Seed is managed by some of the most prominent probiotic scientists in the world, including the person who termed that coin in the first place.

But before you start thinking probiotic supplements are a magic pill, let's consider one important caveat:



7. Why Managing Gut Health Involves More Than Popping A Pill

Improving gut health involves far more than just popping a few probiotics and getting on with your day.

In fact, seeing probiotics as a magic pill to cure your gut issues may be doing more harm than good. 

Let's look at some examples:

  • In a mice study, ultraviolet light exposure independently alters the gut microbiome (81). Ultraviolet light is what potentially gives you a sunburn. Hence, your environment (and specifically that light in your environment) affects the bacteria in your gut.
  • Simple psychological stress affects that microbiome as well (82; 83; 84). So if you're anxious about your job all the time, taking all the best probiotics in the world might not even help! Stress also increases inflammation in the gut (83).
  • Sleep-deprived? Too bad for your microbiome (85; 86; 87). Fix the issue by increasing the amount of deep sleep you get each night, measure how you're progressing, and use additional tips to further improve sleep quality.
  • Antibiotic use. Sorry to say this: antibiotics are indispensable for your health, especially in many acute circumstances, but antibiotics can also completely wreck your gut microbiome (88; 89; 90; 91).
  • Yes, even air pollution influences your gut function (92; 93; 94). That polluted air can also end up on your food, affecting the microbiome that way. So if you're living in the city, read my blog posts about different air pollutants and on the best air purifiers out there.

I hope you're beginning to see a pattern here: almost every health-related domain cannot be understood in isolation.

So if you've pulled a muscle in your shoulder, injecting anti-inflammatory drugs into that joint won't fix the problem if your sleep is sub-par and you're under enormous stress. Probiotics are the same.


8. Closing Thoughts: How To Fix Gut Health

As you can see, lots of extra research is still needed to fully understand the effects of probiotics in the human body.

And if you do have gut health issues, probiotics are not your only solution - your overall lifestyle is very important for improving gut health as well.

Nonetheless, taking a high-quality supplement such as that offered by Seed can literally be life-changing. Many people reviewing that product report very significantly positive outcomes.  

So if you're carefully managing your lifestyle then I highly recommend you try the supplement to see how your gut health change.

For $45 you might find the missing puzzle piece towards creating a better gut. And remember: that gut is interconnected with many organs such as your lungs, brain, and heart - offering an opportunity to take your health to the next level.


This blog post was written by Alex Fergus. Alex is a ISSN Sports Nutrition Specialist, Fitness Professional and certified Superhuman Coach who continues to expand his knowledge base and help people across the world with their health and wellness. Alex is recognized as the National Record Holder in Powerlifting and Indoor Rowing and has earned the title of the Australian National Natural Bodybuilding Champion. Having worked as a health coach and personal trainer for over a decade, Alex now researches all things health and wellness and shares his findings on this blog. Learn more about Alex's Credentials HERE.


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