Two loaves of bread each sliced up to half way

What is gluten intolerance?

06 Jun 2023


If you always feel tired, have been losing weight, and experiencing abdominal pain and/or diarrhoea, a gluten intolerance could be the culprit. Get the low down on all things gluten and see if you could benefit from going gluten-free in this guide.

What is gluten?

Gluten is a family of proteins naturally found in grains like wheat, rye, oat and barley. The proteins help to hold foods together and create a soft and chewy texture like in bread, pizza and pastas. The two main proteins that gluten is made from are glutenin and gliadin.

Gluten is found naturally in some foods, but it can also be found in processed foods to improve its texture.

Many can digest gluten, and foods containing it, with no problems, but those that have a gluten sensitivity or gluten intolerance can experience uncomfortable symptoms.

What is an intolerance?

An intolerance to a food group is described by the NHS as ‘difficulty digesting certain foods and having an unpleasant physical reaction to them’

Intolerance symptoms

Symptoms include stomach pain, bloating, wind, diarrhoea, skin rashes and itching. Symptoms are often delayed, striking several hours after you have eaten the food that you are intolerant of.

Symptoms may also appear only if you eat a lot of the food you are intolerant of – or if you eat that food very often.

People who are intolerant of a particular food can sometimes eat a small quantity of that food without any symptoms at all.

How is intolerance different to an allergy?

By comparison, food allergy symptoms are immediate and potentially serious. An allergic reaction to food by your immune system will trigger allergy symptoms such as a rash and itching but can also cause difficulty swallowing, abdominal pain and which is an extreme and severe allergic reaction.

What is gluten intolerance?

Often mistaken for coeliac disease, a gluten intolerance is where your body isn’t able to digest foods that contain gluten. It is also known as non-coeliac gluten sensitivity (NCGS).

What are the symptoms of gluten intolerance?

There are many different symptoms of NCGS, which usually occur in a person soon after they have consumed gluten. These symptoms tend to improve or disappear within hours or a couple of days (if the person stops consuming gluten) and then relapse when it is re-introduced.

Here are some of the most common symptoms of gluten intolerance:

Bloating, abdominal pain and gas

Ever feel like your belly is swollen or full of gas after a meal? Although it is not the only possible cause, a gluten intolerance could be the culprit. It’s one of the most common symptoms of gluten intolerance or sensitivity.

Diarrhoea, constipation and foul-smelling faeces

Most people get constipated or have diarrhoea from time to time, but it shouldn’t be a regular thing. Gluten intolerance can cause both. As well as toilet troubles, it can also result in exceptionally smelly stools because foods containing gluten aren’t getting digested properly.

Farting more often and feeling generally gassy after consuming gluten can also be a sign of intolerance.


Everyone gets headaches, but if you experience headaches and migraines on a regular basis, you could be sensitive to gluten.


Feeling tired is normal, especially at the end of a long day or if you’ve been working out. However, if you feel tired or fatigued all the time, there may be an underlying cause. Gluten intolerance is a possibility.

Skin problems

Skin complains such as rashes, swelling and eczema could be linked to a gluten sensitivity or intolerance.


If you tend to feel sick after a gluten-heavy meal like pasta, pizza or sandwiches, this may be a sign that you have a gluten intolerance.

Joint pain

When someone is sensitive to gluten, their immune system could see it as a threat (like it does in celiac disease) and cause inflammation. Chronic or intermittent joint pain could be a sign you are intolerant to gluten.

Other symptoms include brain fog, numb arms and legs, difficulty breathing and night sweats.

Do I have gluten intolerance?

There are no tests to determine an intolerance, however, you can identify what foods are causing symptoms by keeping a food diary. Make a note of the foods you eat, the symptoms you experience and the time between eating and experiencing them. The pattern and type of symptoms you record can help to distinguish food intolerance from food allergy reactions.

You may then be able to identify the culprit and eliminate it from your diet. Some like to eliminate gluten for a few weeks, then re-introduce it to their diet in small amounts to see if the symptoms return.

Do be careful: if you decide to follow a gluten-free diet, it is pretty restricting and could lead to nutrient deficiencies, like fibre and B vitamins. Ditching gluten without exploring if it is in fact coeliac disease (read more about that below) could be very detrimental to your health. Please talk to your doctor or a nutritionist before going cold turkey.

Foods that contain gluten

The most common foods that do contain gluten and may cause symptoms are;

  • Pasta
  • Bread and pastries
  • Breakfast cereals
  • Flour
  • Biscuits
  • Cakes
  • Crackers
  • Some sauces
  • Some ready meals
  • Beers and malt-based drinks contain barley and sometimes wheat, so these are also best avoided.

Is gluten intolerance the same as wheat intolerance?

Wheat intolerance is closely linked to gluten intolerance, but they are not the same. Being intolerant or sensitive to wheat means that your body struggles to break down wheat in the gut but could potentially have no reaction to rye or barley.

What are the symptoms of wheat intolerance?

Intolerance to wheat symptoms are quite similar to the gluten intolerance symptoms above, they just don’t appear when you consume rye or barley.

What is coeliac disease?

One in 100 people are now diagnosed with which is much more common than previously thought, while thousands more could have it and not realise.

Coeliac disease (pronounced see-liac) is an autoimmune condition which means the immune system mistakenly attacks healthy tissues. When those with coeliac disease eat something containing gluten, the immune system overreacts and attacks the lining of the gut.

The damage results in the body not being able to absorb nutrients from food correctly and causes symptoms such as severe gut pain, weight loss and fatigue. Left untreated, coeliac disease can lead to serious health complications including malnutrition and osteoporosis.

If you experience symptoms when eating foods that contain gluten, it’s important to first rule out coeliac disease. Ask your GP for tests including a blood test and a small bowel biopsy. Remember, you need to keep eating gluten during this time in order for the results to be accurate.

Gluten-free diet

If you or a family member has gluten intolerance or has been diagnosed with coeliac disease, you’ll need to avoid or eliminate gluten from your diet.

The only way to live symptom-free from coeliac disease or gluten intolerance is to avoid foods with gluten.

Naturally gluten-free foods

Lots of healthy, nutritious food is naturally gluten-free – for example, meat (but not if it’s covered in breadcrumbs), fish, fruit and vegetables, most milk and cheese products (but check ice-cream and blue cheese), nuts, seeds and some grains (e.g., rice and quinoa). Generally speaking, the plainer the food, the less likely it is to have any gluten on it or in it.

Which grains are gluten free?

The following grains are gluten free, just check for cross contamination warnings on the packaging.

  • Agar
  • Almond flour
  • Amaranth
  • Buckwheat
  • Carrageenan
  • Cassava (manioc)
  • Chestnut
  • Corn
  • Flax / linseed
  • Gram flour
  • Hemp
  • Hops
  • Maize
  • Millet
  • Mustard
  • Oats
  • Polenta
  • Potato
  • Pulses (bean, peas, lentils)
  • Quinoa
  • Rice
  • Sago
  • Seseame
  • Sorghum
  • Soya
  • Tapioca
  • Teff
  • Urd flour

What has gluten in it?

Most ready-meals, snacks and cereals contain gluten. In the UK and the EU, labels on all packaged foods are required to contain allergen information. If you eat food that has been processed or packaged in any way, you’ll need to become familiar with food labels.

The easiest thing to do is look for a ‘gluten-free’ label on food but, to allow you to eat a wider selection of food, you should learn which common ingredients contain gluten.

Manufacturers change ingredients often, so check the label every time you shop to make sure no ingredients that may contain gluten have been added.

You may even find gluten in medicines, lip balms and vitamins.

Gluten-free restaurants

If you’re eating out, you’ll need to ask questions, even about the ingredients in spice blends. Breaded items, or sauces made with flour, will probably be out and, unless the restaurant or venue has two fryers to avoid cross-contamination, you won’t be able to order deep-fried food.

You can ask if there’s a gluten-free menu or dishes. Supermarkets may also have a list of gluten-free products available.

To avoid gluten altogether, remember that preparation areas and appliances must also be gluten-free. In your kitchen you’ll need a separate toaster (or toaster bags), boards and utensils.

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Last updated: 1 October 2020