What Are Probiotics? A Complete Guide

what are probiotics

Friendly bacteria living inside your body? It can be a bit of a strange concept, but getting up close and personal with the world of probiotics to find out how they can benefit you is now easier than ever before.

With so much information and research out there it can be a little overwhelming when you’re first starting out.

WHAT YOU’LL LEARN: We’ve created this simple and comprehensive guide to tell you exactly what probiotics are, a few of the awesome benefits they can give you and exactly how to find the best probiotic for you – let’s get stuck into it!

What are probiotics?

The current definition used to describe probiotics by the Food and Agriculture Organization of the United Nations World Health Organization is:

“live microorganisms which when administered in adequate amounts confer a health benefit on the host.” 

World Health Organisation

Probiotics live in your small and large intestines making up your ‘gut flora’ and influencing a huge amount of your healthy bodily functions. They are highly beneficial bacteria and you actually have trillions of them inside your body, mixed in with harmful bacteria as well.

The aim is to keep the balance between good and bad so that your probiotics vastly outweigh the pathogens (harmful microorganisms) that would otherwise make you sick.

It’s estimated that you have around 500 different species of bacteria in your gut, and each species has different strains. The most common and beneficial species of probiotics for humans are Lactobacillus and Bifidobacterium, so when you’re looking for a probiotic product, these are the names you should be searching for. 

Here’s a few quick benefits of probiotics:

  • Improves digestion and absorption of nutrients 
  • Can combat digestive troubles like bloating, cramping, gas, etc.
  • Supports healthy immune function and is actually responsible for around 70% of your immune response
  • Creates an acidic environment in the body where pathogens cannot survive
  • Reduces symptoms of illnesses such as irritable bowel syndrome (IBS), diarrhea, eczema, Crohn’s and more
  • Reduces inflammation throughout the body
  • Assists with regulation of moods, improves memory function, reduces brain fog, decreases inflammation in the brain to combat cognitive degenerative diseases

Probiotics are naturally found in many fermented foods, which we will go into more detail about below. However, many people find it easier to ingest probiotics in supplement form – capsules and powder being the most common.

This provides a convenient alternative, but it can be a little tricky knowing which probiotic to purchase because of high market saturation. We’ve included some tips and tricks for purchasing the perfect probiotic supplement a little later on in this article, be sure to take a look.

Probiotic-rich foods 

The most natural way to get your daily probiotic hit is by consuming fermented food and drinks that are rich in beneficial bacteria. Here’s a list of some of the most popular probiotic foods:


This is definitely the most popular and readily accessible probiotic-rich food on the market right now. With so many options though, be sure to carefully read the ingredients list to make sure you’re getting a yoghurt that contains a high amount of probiotics, it should list both the amount of live cultures and the strains included – the more the merrier!


Kefir grains are lactic acid and yeast cultures that resemble cauliflower, they are added to milk and will generally contain a few of the most beneficial and popular strains of probiotic. Some lactose intolerance sufferers find kefir is easier for their digestive systems to handle as the probiotics contained in it allow easier digestion of lactose – the sugar in milk.


This is a popular, spicy, fermented cabbage dish that originates from Korea. It may not sound very appetising but it’s flavoured with spices like garlic, ginger and chilli and contains lactic acid bacteria strains.


Another fermented cabbage dish, but this one is popular in European countries. It’s rich in vitamins like C, B and K, plus fibre and is super rich in probiotics.


A high-protein meat substitute that is made from fermented soybeans and has a similar texture to mushrooms. It’s said to contain around 10 billion colony forming units (CFU) of probiotics per gram!


This is a Japanese seasoning paste that’s generally put into soups. Like tempeh, it’s made from fermented soybeans but has added salt and a fungus called koji. It’s high in protein, fibre, vitamins and minerals.

If these foods don’t tickle your fancy you can also try pickles, buttermilk, sourdough bread, kombucha, and some soft, aged cheeses.

How can probiotics improve my health? 

Now you know what probiotics are and where to find them, let’s take a closer look at some of the most common ways probiotics can benefit your health.

Alleviating digestive troubles

The main and most beneficial effect of probiotics is how they improve your digestive system. They ensure that all the nutrients, vitamins and minerals that you consume in your everyday diet are extracted and optimised so that you get the most out of your food. They also assist with decreasing the amount of harmful bacteria in your intestines by either crowding them out or creating an acidic environment where they can’t thrive and cause illness.

Although more research is needed, it’s thought that these properties combined can assist with reducing and managing the symptoms of digestive illnesses like IBS, inflammatory bowel disease (IBD), Crohn’s, ulcerative colitis, many different kinds of diarrhea and more. They create protective barriers in the gut to decrease sensitivity and reactions to triggers.

Optimal immune function

The other main function of probiotics is supporting your immune system. Probiotics actually control around 70% of your immune response because the majority of your immune molecules originate in the gut. Probiotics are able to modulate your immune reactions effectively to decrease excess inflammation which can otherwise wreak havoc on the body, both in the short and long term. This can decrease the severity of allergies and infections like asthma and eczema as your body manages the response to triggers more effectively.

Probiotics have been researched extensively and shown to be most effective on antibiotic-associated diarrhoea and infectious diarrhoea, bowel disorders like lactose intolerance, and allergies, but there is always more exciting information coming out regarding their positive effects on human health.

Mental health and mood regulation

More research needs to be done on this topic, but there is evidence to suggest that probiotics can affect mental health through the “gut-brain axis”.

This is a connection that allows a healthy gut microbiome to quickly mobilise immune molecules and nerve signals from within the gut to combat negative changes in the brain faster than other organs may be able to react.

Not only does this help with the regulation of moods and sleep, clearing brain fog and improving your memory, but the long-term effects of decreased inflammation are thought to assist with degenerative brain disorders like Alzheimer’s.

Tips and tricks for purchasing your probiotic supplements

Now for the tricky part; selecting the right probiotic for you. Each individual’s health is personal and unique, and so, you should choose a probiotic that targets your specific health concerns. However, you can use these general tips and tricks below when scouring the shelves for your next supplement.

CFU count

Colony forming units (CFU) is the measure of live, viable microorganisms in your probiotic supplement. 10 billion is a great starting point for any beginners, but once your body is used to probiotic supplements, you should be aiming a lot higher than this. Everyone is different, but around 50-80 billion is an ideal range to really feel the intended benefits.


You want to aim for a variety of probiotic strains so that you can feel a wide range of benefits. As a general guideline, the most beneficial bacteria for humans will belong to the Lactobacillus and Bifidobacterium families, so look out for those. Some of the most popular probiotic strains include:

If you’re purchasing a probiotic for a particular health concern, do a little research into the studies on probiotic strains that have been shown to help with that concern.

Enteric coating on capsules

Your stomach acid is very harsh on probiotics and will kill them if given half the chance. So, probiotics with an enteric coating on the capsules or acid and bile resistant technology will ensure the highest amount of probiotics make it through your body safely.


If you can, find a probiotic that doesn’t require refrigeration as this will mean it’s a shelf-stable product and more hardy than a probiotic that needs to be kept cold. It also reduces the risk of their potency declining whilst waiting for you to purchase them, but regardless, always grab the bottle with the furthest expiry date. 

Fillers and allergens

This is an easy one, look for a supplement that contains no fillers and allergens. This will ensure you’re getting the most bang for your buck with extra unnecessary padding in your probiotic mix. 

Daily dose

It’s difficult to specify the best time to take probiotics. For convenience, try to find a probiotic that only requires you to take 1 capsule daily. As an added bonus, you can be on the lookout for supplements that also include vitamins and minerals so you can combine your daily multivitamin and probiotic routine instead of taking multiple different products.


Prebiotics are basically food for your probiotics, they are found naturally in foods like bananas, asparagus, garlic and onions. Prebiotic fibres are indigestible for humans, but probiotics gobble them up to help them grow, multiply and become stronger as they battle your body’s harsh conditions on their way to your intestines. A “synbiotic” supplement will contain prebiotics as well, that’s the kind you’ll want to choose for the best results!

Are there any side-effects of taking probiotics?

The great thing about taking a probiotic supplement is that, generally, there’s no risk of overdosing yourself. This is because probiotics don’t hang around in the gut forever. They populate the area, do their thing and then any excess friendly bacteria are flushed out of the body naturally. However, there are a few potential side effects to be aware of if you’re new to probiotics:

Mild digestive issues

During the first 2 weeks of taking a new probiotic supplement, it’s common to experience some mild digestive issues like gas and bloating. These should subside once your body grows accustomed to the new bacteria and can usually be avoided if you start off with a lower CFU count first. However, if your symptoms are any more than mildly uncomfortable, or if they continue after the first couple weeks then it’s recommended to cease use and speak to your doctor about your symptoms to be on the safe side.

Allergic reactions

Although uncommon, probiotic supplements can sometimes contain allergens like soy, dairy or egg. You should be able to easily avoid any ingredients you’re intolerant or allergic to by carefully reading the ingredients list.

Risk of infection

About one in every million people will develop an infection from the Lactobacilli bacteria, which is one of the most popular species of bacteria included in probiotic products. These infections can be treated with antibiotics. Additionally, individuals with autoimmune diseases, those who have undergone recent surgeries or anyone who’s been in a hospital for an extended time will have an increased risk of infection from probiotics. If you fall into any of these categories it would be wisest to consult your doctor before beginning use.


Welcome to the wide world of probiotics, where your immune health, cognitive health, digestive health and more can all be supported by microscopic beneficial bacteria! Whether you’re consuming your probiotics and prebiotics in your diet or you’ve chosen to purchase a supplement to get your daily dose, we hope the information we’ve provided in this guide will help you on your journey to better health and wellbeing.

As with all new health supplements, always be sure to speak with your doctor before starting to use them to be sure that your specific health needs are being met.