5 Gut Health Myths (and Why They’re Wrong)

From leaky gut syndrome to fermented foods as probiotics, dietitian Kirsten Jackson reveals the myths to stop believing in the confusing world of gut health.

With the rising interest in gut health, there has been a lot of misinformation being spread online. This has sadly led to a lot of gut health myths which can be quite confusing if you are trying to improve your gut function.

In this article, we will go through the most common myths we see and why you should not believe them. Please note, this article does not cover every single myth out there so please always check who you are getting your information from and that they have the appropriate qualifications.

Myth 1: Gluten causes the gut to become ‘leaky’

There are many claims that gluten (a protein found in wheat, barley, and rye) can cause the gut lining to become ‘leaky’ and allow pathogens across which can result in inflammation in the body. These claims come from people who are not trained to read research, drawing incorrect conclusions from the studies that they read.

This myth comes from the fact that gluten is resistant to being broken down by enzymes in your body. The claims state that it is this undigested gluten which causes the gut to become ‘leaky’ and lead to an inflammatory reaction. But there is simply no research to back up these claims.

Here is an example of one study in the area that is often misinterpreted: the study showed that gliadin (a protein found in wheat) causes the activation of another protein called zonulin. Now we know zonulin does cause the gut lining to become leakier so at first glance you may think this study proves that gluten should be avoided. However, the study was done in a test tube which is an entirely different environment to the human gut and it doesn’t show us if the gut becomes ‘leaky’ enough to cause inflammation.

Not only do we have no research to prove the leaky gut theory, but following a gluten-free diet has also been shown to be lower in fibre. Given that fibre is well known to reduce your risk of multiple inflammatory conditions it is definitely not a good idea to follow a diet that would reduce your ability to get enough fibre in.

Myth 2: Fermented foods are probiotics

Fermented foods refer to foods which have been processed using live microorganisms such as bacteria or fungi. They’ve become particularly popular recently with supermarket shelves now stacked with fermented foods like kimchi and kefir marketed as containing “probiotics”.

You may be particularly interested in taking probiotics as they can improve digestive symptoms or conditions such as constipation, irritable bowel syndrome or even diarrhea. How probiotics do this is not entirely clear, but it is thought to be related to the live microorganisms being able to improve your microbiota levels in some way.

Sadly however the claim that fermented foods are probiotics is incorrect.

To be a ‘probiotic’ the live microorganism has to be able to reach the ‘target site’ in large enough quantities to provide a health benefit. This means if you were hoping to improve your gut function, those live microorganisms would need to reach your gut in high enough quantities and resolve an issue like bloating or constipation. There is no proof that fermented foods are able to do this.

The sad reality is that even if a fermented food still contains live microorganisms in the end product, they will likely be killed off in your stomach before they ever reach your gut.

Although fermented foods are not ‘probiotics’ they can still provide other health benefits so if you enjoy them then continue to include them in your diet. However, if you find they are stretching your budget too much or you struggle to get them in then do not lose sleep over it.

Myth 3: A microbiome test can guide your diet

The term ‘microbiome’ means the collection of all microbes, such as bacteria, fungi, viruses, and their genes, that naturally live on our bodies and inside us. When we talk about the microbiome, we are usually referring to the gut microbiome which we know can impact all areas of our health from our mental wellbeing, ability to produce vitamins and even our risk of certain diseases like dementia and diabetes.

There are a number of companies providing microbiome tests using a stool sample. Using the results, these companies then provide specific dietary advice. Which sounds great right? Well, the issue is that we do not yet know what an ‘optimal’ microbiome looks like so it is not yet possible to guide someone on specific dietary changes in this way.

The good news is that there is ongoing research in this area and so hopefully one day we will be able to use microbiome tests to guide dietary advice on a more specific level.

Myth 4: Coffee is ‘bad’ for gut health

Coffee seems to be demonized as being bad for your gut health when actually this drink could be very beneficial. Most people drink coffee due to the psychoactive drug it contains aka caffeine. Caffeine is a stimulant so it provides that alertness that many of us need to get through the day or even start it.

Now caffeine itself is not good for gut function unless you rely on it to help open your bowels, which can be a good side effect for some people. Caffeine blocks the sleep hormone known as adenosine which means that it makes it more difficult to fall asleep. The irony is that people struggling with poor sleep often rely on caffeine to get through the day. Caffeine can also worsen anxiety. Both anxiety and poor sleep are directly linked to worsening gut function.

But it is not all doom and gloom. Coffee contains more than just caffeine, coffee also contains something called polyphenols which are a type of antioxidant that are highly beneficial for your gut health. Polyphenols are particularly good at feeding gut bacteria which can help improve your levels.

If you enjoy coffee, the good news is that you do not need to cut it out entirely. Instead, swap over to decaf coffee to avoid the detrimental impact of caffeine whilst gaining the benefits of the polyphenols.

Myth 5: Leaky gut syndrome is real

We already touched on the concept of your gut lining becoming ‘leakier’ when discussing gluten. It is very normal for the gut to become more or less ‘leakier’ to allow (i.e. nutrients) or stop (i.e. pathogens) things moving across into your body. However, we usually call this permeability.

If your gut is in some way damaged, then it can become too ‘leaky’ and allow pathogens to cross into your body and make you unwell. This situation is very much a symptom of specific conditions such as inflammatory bowel disease or uncontrolled coeliac disease where there is inflammation in the gut lining.

But, ‘leaky gut syndrome’ is a specific syndrome that is claimed to be a standalone condition that can lead to various issues such as autism, diabetes and brain fog. Those who believe in leaky gut syndrome often go on to propose specific supplements or diets to help with the supposed syndrome. However, to date, there is not a single bit of research to back up these claims.


There are many myths surrounding the complex world of gut health but the good news is that you do not need a gluten-free diet, fermented foods or have to go cold turkey on the coffee to achieve good gut function.

In this article, we have highlighted that despite there being a lot of research on gut function, the wrong interpretation of that research can lead to some pretty wild claims. So please always check that the person giving you advice has the correct qualifications to be able to read and interpret research correctly and safely.

Words: Kirsten Jackson

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