Written by Aisling Moran BSc (Hons)
12th Aug 2022 • 7 minute read

Gluten-free diets have soared in popularity in recent years. While there are some very credible reasons to avoid gluten, some unvalidated claims are scaring people into a restrictive diet. Here’s everything you should know about gluten.

What is gluten?

Gluten is a family of proteins found in grains like wheat, barley, spelt, and rye. Gluten helps maintain the structure of foods — acting like a glue that holds it all together. It’s naturally found in many foods, and we’ve been eating it for at least 10,000 years. 

The main sources of gluten include:

  • bread
  • pasta
  • noodles
  • crackers
  • baked goods

Gluten is also sometimes found in things like soup, salad dressing, and sauces. 

The rise of gluten-free diets

The popularity of gluten-free diets has dramatically increased in people without any clinical need. Recent statistics estimate that about 1 in 10 people now completely avoid gluten

So, why has it become so popular? Well, a lot of people are now afraid of gluten because of scaremongering tactics. For example, gluten has been said to attack your brain or increase a child’s risk of developing ADHD. 

These claims are often tied to the possible link that gluten increases your intestinal permeability — how easily substances pass from your intestinal wall into the rest of your body. Increased intestinal permeability is sometimes called leaky gut syndrome and is linked to inflammation and disease. But the link between gluten and intestinal permeability is incredibly complex and an area of research that currently has a lot of unknowns. Here’s what we know so far. 

Gluten-free flours on wooden spoons

Leaky gut syndrome and gluten 

The cells of your intestinal wall form a barrier between your gut and the rest of your body. And in between these cells, you have junctions that act like doors. These doors open and close (although they’re usually closed) and help regulate what can pass into your body from your gut. A molecule called zonulin regulates the opening and closing of these doors. 

Some research suggests that eating gluten causes you to release zonulin, opening these doors — particularly if you have coeliac disease. So if you eat gluten and have coeliac disease, your body releases excessive amounts of zonulin. This opens your “doors” for an extended period of time, allowing the gluten to pass your gut barrier. Your body sees this as a foreign invader and launches an attack against it. In people with gluten sensitivity, you might also produce a little too much zonulin — which might cause some inflammation and symptoms. But it doesn’t damage your gut like it would in people with coeliac disease.

In healthy people (those without coeliac disease), some research suggests that eating gluten also causes you to release zonulin. But much less is produced so your doors open and close in minutes. Some gluten might get past your gut barrier, but your body can handle it. You won’t experience any symptoms, and there’s no harm done. Meaning there’s no need to avoid gluten.

Implications of a gluten-free diet

One of the main downsides to a gluten-free diet is eliminating whole grains from your diet. Research has looked at the risk of heart disease and diabetes in people who eat a little or a lot of gluten. It’s shown that avoiding whole grains as a way to avoid gluten is linked to an increased risk of heart disease and diabetes. This is because whole grains are a great source of fibre — which has a lot of protective effects. In fact, a diet high in whole grains can reduce your risk of heart disease, stroke, and type 2 diabetes by as much as 30%. 

People who don’t eat gluten tend to have a less diverse range of gut bacteria. Again, this is because of a reduced intake of fibre from whole grains. You can get fibre from gluten-free foods like fruit and vegetables, but the fibre in whole grains seems to be quite unique. 

Foods containing gluten also tend to be rich in B vitamins, magnesium, and iron. So if you do follow a gluten-free diet, it’s important to get these nutrients from other sources.

Finally, it might also contribute to social isolation because of its restrictive nature and create feelings of guilt if you ‘slip up’. 

When to avoid gluten

There are, of course, three main reasons to avoid gluten.

Coeliac disease
Coeliac disease is a lifelong autoimmune condition that causes your immune system to attack your small intestine when you eat gluten. Even trace amounts of gluten, like bread crumbs from a toaster, can trigger an attack and damage your small intestine. Over time, this can stop you from being able to absorb nutrients and lead to severe nutritional deficiencies — putting you at risk of things like osteoporosis. Coeliac disease can’t be cured, and the only way to manage it's to follow a strict gluten-free diet

Coeliac disease affects 1 in 100 people in the UK. Only 30% of people with it have been diagnosed — meaning there are nearly half a million people in the UK who don’t know they have it yet. 

Dermatitis herpetiformis (DH)
DH is a skin condition linked to coeliac disease. It causes a very itchy and bumpy red rash — usually found on your elbows, knees, and buttocks. To manage DH, you need to follow a strict gluten-free diet.

Non-coeliac gluten sensitivity (NCGS)
NCGS is a newly-defined condition. It’s used to describe people who experience symptoms similar to coeliac disease, like brain fog, abdominal pain, diarrhoea, and fatigue, but don’t have coeliac disease. Non-coeliac wheat sensitivity (NCWS) is often used interchangeably with NCGS. This is because there are questions around whether gluten is responsible for these symptoms or if other wheat proteins, like amylase-trypsin inhibitor (ATI), are the cause. Other research from Monash University has even posed the question of whether FODMAPs (groups of sugars in foods), like fructans, might be the culprit.

It’s worth mentioning that in people with autoimmune thyroid disease (who aren’t coeliacs), there’s some evidence to suggest that a gluten-free diet can help improve their symptoms. But evidence around this is currently very weak, so much more research is needed.

In all of these cases, you should seek advice from a qualified health professional if you decide to follow a gluten-free diet.

How to test for conditions related to gluten

If you suspect you have any of the above conditions, it’s important to see your doctor and get an accurate diagnosis. Coeliac disease is diagnosed with a blood test and a gut biopsy. To diagnose DH, a skin biopsy is usually done. These tests check for antibodies you make in response to eating gluten. So you need to be eating gluten at the time of testing — it’s recommended that you eat some gluten in more than one meal every day for at least six weeks before testing. 

For NCGS, a qualified professional will usually look at how you respond to a gluten-free diet and the effect of eating gluten after following this diet. 

Other than lactose intolerance, avoid any blood, breath, or stool tests that claim to diagnose food intolerances or sensitivities. These aren’t scientifically proven. For example, these commonly test for IgG antibodies in your blood which are likely present because of a normal immune response when exposed to food.

Feel better on a gluten-free diet?

Often, people who follow a gluten-free diet (who don’t have coeliac disease or NCGS) report feeling much better. This can happen for a number of reasons.

For a lot of people, the benefits of following a gluten-free diet aren’t a result of excluding gluten. It’s most likely because you’re excluding unhealthier foods from your diet — like cakes, pastries, and biscuits. This is why people might lose weight on a gluten-free diet.

There’s also the possibility of the placebo effect — which can be incredibly powerful. If you think something is good for you, you’ll most likely feel better physically or mentally. 

Another very real reason is that you might have undiagnosed coeliac disease or NCGS — as mentioned, half a million people in the UK have undiagnosed coeliac disease. So eliminating gluten will improve your symptoms.


Listen to your body. If you can eat foods containing gluten, like wholemeal bread and brown pasta, without any side effects, it’s unlikely you need to avoid it. Of course, what you eat is always up to you. But don’t let scaremongering tactics force you into a restrictive diet. And if you do have symptoms, see your doctor or a registered dietitian for help.