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Gut Microbiome Testing - Is it worth it?

Gut microbiome.jpg

Posted: 20/08/2021

Updated: 20/08/2021

As I scroll through my social media, all these microbiome or gut-flora testing kits ads pop up which are available for purchase often coming in a hefty price (approximately £150-400 for the test).


Sounds intriguing, doesn't it? Before we dig deep into it, let's start with the basics!

what is the microbiome?

gut microbiome

There are trillions of microorganisms within the human body including bacteria, fungi, viruses and archaea. These collectively, are often referred to as our microbiome. The majority resides in our guts and each of them has a different role in our bodies - some important for health and some which may cause disease.


We now know that the gut has its nervous system known as the enteric nervous system or the "second brain", its involvement acting as the immune system protecting us from the questionable out of date food that we eat, production of hormones and so on!

Why Do We Care About our gut?

importance of gut health

New studies are emerging daily highlighting the importance of gut health due to its increasing association to different conditions such as inflammatory bowel syndrome (IBS), inflammatory bowel disease (IBD), diabetes, depression, cancer, obesity and so on.


Hence, there is an emphasis on creating or maintaining a healthy gut.


Our microbiomes are unique and drastic changes are seen during the first 3 years of life and remains relatively stable during adulthood and the diversity of microorganisms tend to decrease as we age. Major shifts to our microbiome composition can occur when we make radical changes to our lifestyle, diet, environment, medications such as antibiotics, etc.


As a result, new companies are set up to offer their services to tell you more about the microbes in your gut, how they may affect your health and providing advice on how to improve your health.

How Does Gut Microbiome Testing Work?

how does it work?

A poo sample is to be collected in a container and sent to a lab for analysis. This can include test tube experiments which look for bacteria that cause infection, gut markers e.g. calprotectin to see if there is inflammation in the gut but most new companies sequence your DNA (16S rRNA sequencing) to show the number of bacteria and types that are present in the poo sample.


After the analysis, you will receive a report which highlights the number of species of bacteria present in your poo as being "too high" or "too low". Some companies use an algorithm to assess if you are at "high", "average", "low risk" of developing a disease.


They often offer you a "fix" to improve the levels of bacteria in your gut. Examples could be a probiotic or prebiotic to stimulate the growth of certain beneficial microorganisms, supplements, diet and lifestyle recommendations, etc.


Often, you would be offered to retest your poo again to see if there are any improvements in your gut microbiome after implementing changes.

Is there any science backing this up?


The human microbiome project launched in 2007 helped to identify the microorganisms living in coexistence with us and the roles they play in human health which laid an important foundation to current research.


A study with 800 healthy and pre-diabetic participants has found that their blood glucose levels responded very differently towards the same meal. Personal information (bloods, dietary habits, anthropometry, exercise) and gut microbiota were gathered and an algorithm was generated. This was tested in another 100 people and this algorithm accurately predicted how a person's glucose level responded to specific meals.


Does this mean we could use this algorithm to recommend what foods people should be eating? There is potential to but there are limitations to this study it was quite a local study done in Israel which cannot represent us all and the algorithm was only tested on 100 people.


In a more recent study, the PREDICT study (with over 1000 participants) which was based in the UK led to the start-up company ZOE. They combined data including participants' gut microbiome, dietary habits, cardiometabolic blood markers to predict individual responses to food.


They found that:

  • Identical twins had very different gut microbiomes (on average 34% of the same microbes) suggesting that we cannot change our genetic makeup but our gut microbiome is easily changed through dietary and lifestyle changes

  • There is no "perfect" time to eat - some people metabolise better in the mornings, others see no difference

  • Specific foods and diet are linked to the microbes and in turn, certain microbes are linked to certain diseases (e.g. diabetes, heart disease and obesity)

  • More links between individual species and health e.g. Prevotella copri and Blastocystic species are associated with maintaining a favourable blood sugar level after a meal and other species were linked to lower cholesterol and markers of inflammation after meals

Pros and Cons

Pros and cons

1. The science is still in its infancy

There is so much that we don't know about the microbiome - not all the microbial genes have been sequenced and the information about how they interact is unknown! Making specific diet and lifestyle suggestions based on a single test is just... wrong. Hence, you may see statements on the websites such as:

"The information is not to be used for any diagnostic purpose and is not a substitute for professional medical advice. You should always seek the advice of your healthcare providers."


BUT there is a lot of research in this area so we may understand how combining information about the microbiome with other personal data may help people achieve optimal health in the future.

2. The companies analyse stool samples in different ways

The reports may tell you the number of bacteria you have down to the genus level but quite often not the species or strain level. The genus of a bacteria (a grouping to classify bacteria with common characteristics) is not helpful as there could be a wide range of strains.

E. coli.png

There are thousands of E. coli genomes that can be sequenced and some can be harmful e.g. E. coli O157:H7 causing chronic diarrhoea and some beneficial e.g. E. coli Nissile 1917 which is used as a probiotic!

3. Limitations of poo samples

Bacteria tends to vary from sample to sample from the same person so a single sample is unlikely to reveal much! Plus, some of your gut bacteria may be clinging to your gut wall which would not be present in your poo sample.

4. Interpretation of results

What does a healthy microbiome look like? There is no reference range for what constitutes a healthy happy gut microbiome because no company has yet sampled the entire population.


WAIT but what does "above average" gut microbiome mean? Companies may compare your results with thousands of others they have analysed in the past so you may be better than Andy who is munching away his veggies or Sandy who eats rocks (please don't).


Sometimes companies will also show the association between the type of bacteria found in your poo sample with some conditions e.g. heart disease, cancer, diabetes, obesity, gout, Alzheimer's disease, etc.


DO NOT PANIC - this does not mean the risk of developing that condition. No strong links have been made between the presence or absence of a certain bacteria! ASSOCIATION DOES NOT MEAN CAUSATION!


It would be better if the science behind the interpretation of results are explained to customers whilst highlighting the current limitations and how the results cannot be used as medical advice!

5. The recommendations are too specific

Companies may advise the types of foods to eat to boost levels of a particular bacteria. However, we do not have enough knowledge to safely and accurately recommend any specific dietary changes e.g. avoiding a specific food which is disastrous advice if someone has an eating disorder. Unless you have a low tolerance or an allergy to a food, please don't restrict what you are having and consult a dietitian instead!

Food ratings

They may make supplement suggestions based on test results and well... unsurprisingly sell you the supplements that they deem you need. Prebiotics and/or probiotics may be suggested - there is evidence that these are helpful in some cases. Please do your research or consult a dietitian for this!

6. The recommendations are very generic

"Have more fruit and veggies"

"A more plant-based diet"

"Increase your variety of foods"


They do provide some good advice but it is common sense which you would gather from a basic diet sheet. The current understanding is that having a high-fibre, varied, balanced, plant-based diet increases the diversity of our gut bacteria - is this not just standard advice?


Another limitation with some companies is that they don't consider your financial background, environment, availability of food, likes/dislikes, your relationship with food, cooking ability, etc. - all of which is necessary to consider!

7. However, it may motivate some people to make positive changes!

It is not all negative - some people when confronted with information related to their health (e.g. higher risk of developing heart disease, diabetes, etc.) may be more eager to learn and motivated in making positive lifestyle changes!



Gut microbiome testing can be interesting if you are interested to know what is in your poo. There is no harm in taking a test if you can AFFORD to do so but the science backing it is still in its infancy. Ensure that the results are being interpreted with caution as they can be confusing and to ensue actions with trusted healthcare professionals.


In the meanwhile, stick to a well-balanced diet with a variety of foods which would increase the types of bacteria in your gut plus giving you a good poo session :)

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