Gluten is formed when two proteins (gliadin and glutenin), which are found in grains such as wheat, rye and barley, are mixed with water.

Gluten in cereals affects the texture of baked goods. Gluten is a tough, rubbery and elastic substance, which has the capacity to stretch and rise due to the action of baking powder or yeast. When flour is mixed with water, the gluten swells to form a continuous network of fine strands. This network forms the structure of bread dough and is responsible for the texture of bread as we know it.

Which foods contain gluten?

Grains that contain gluten are:

  • Wheat other names include spelt, semolina, durum
  • Rye
  • Barley
  • Triticale

Bread and other products (eg. biscuits, cakes) made with these grains will contain gluten. There are also a number of foods that contain ‘hidden’ gluten, such as sausages and stock powders.

What about oats?

Oats do contain gluten in very low quantities, so those with coeliac disease are recommended to exclude oats from their diet. Otherwise, if you can tolerate oats they can be included as a beneficial part of your diet.

What is gluten intolerance?

There are some medical conditions where gluten affects the immune system (an immunological reaction):

  • Coeliac Disease where gluten-containing foods cause damage to the small intestine and lead to reduced absorption of nutrients from food. This can lead to anaemia, osteoporosis and other conditions.
  • Dermatitis herpetiformis is an uncommon skin condition that involves watery, red and itchy blisters.

Both of these conditions require a diet where gluten must be totally avoided.

Gluten sensitivity or non-coeliac gluten intolerance is where people develop a variety of unpleasant symptoms when they eat gluten-containing products foods. The severity of these symptoms may depend on how much you eat and how sensitive you are.

Is it only gluten that causes symptoms could it be something else?

There are a number of things that can cause uncomfortable symptoms, not only gluten and wheat. These include intolerances to other substances, such as amines, salicylates, and sulphites, and also a group called FODMAPs (FODMAPs is short for fermentable, oligosaccharides, disaccharides, monosaccharides and polyols. These are short-chain carbohydrates that are not absorbed by our small intestine and which are then fermented by bacteria in the colon, producing hydrogen, carbon dioxide and methane gases.)

It may also be due to physical factors such as the amount you eat (too much stretching your stomach) and chewing gum (due to the amount of air you swallow as you chew). Stress can also affect the severity of symptoms.

You may only have a problem with one or two of these foods, the trick is determining which. Consult your doctor or dietitian to determine the right way to do this.

I have gone on a gluten-free diet and feel better – why?

People with gastrointestinal symptoms including abdominal pain, bloating, wind and diarrhoea often feel better on a gluten-free diet. These people may be suffering from Irritable Bowel Syndrome (IBS). Removing gluten from the diet may have also removed the irritant causing the symptoms. An example may be the FODMAPs fructan, which is found in gluten-containing foods. So, while people may experience a decrease in their symptoms, it may not necessarily be the gluten that was the cause.

Can a gluten-free diet be beneficial for IBS symptoms?

Some people experience a decrease in their symptoms by excluding gluten from their diet. Although there is no evidence that abdominal pain, bloating, wind, diarrhoea and constipation are caused by gluten, it is more likely that other food substances in gluten-containing foods are the real culprits. This might mean that you are being unnecessarily restrictive in your eating.

The removal of other foods when following a gluten-free diet, such as higher fat pizzas, cakes and biscuits may add to the feeling of improved well-being, along with increased consumption of fruit and vegetables which assist in relieving constipation and bloating.

Is a gluten-free diet healthier?

Not necessarily. Specialised gluten-free products are often higher in fat and sugar to make them taste better. The gluten-free flours used in bread and pasta are often highly refined, low in fibre and have a high Glycaemic Index (GI) rating, meaning they aren’t very filling and do not contain beneficial whole grains.

Are there any downsides to a gluten-free diet?

Gluten-free diets have been found to be lacking in fibre, calcium, iron and B vitamins (Vici et al., 2016). Gluten-free products are more expensive than their traditional counterparts. Before choosing a gluten-free diet, it is recommended you discuss your decision with your doctor, dietitian or registered nutritionist.

Do we need to completely cut out gluten?

Unless you have been diagnosed with coeliac disease or dermatitis herpetiformis, there is no evidence suggesting health benefits from cutting out all gluten from your diet.

IBS sufferers need to identify which foods are causing their symptoms. There is often a certain amount of gluten-containing foods you may be able to eat without triggering your symptoms. This needs to be worked through with a dietitian or registered nutritionist.

You should not put yourself on a gluten-free diet. This should only be done on the advice of a doctor, dietitian or registered nutritionist. They will guide you on an elimination diet, where all suspect foods are removed for a set time, then gradually reintroduced to find which particular foods caused symptoms to return. Removing foods or food groups from your diet can cause deficiencies in some nutrients, which may lead to health problems in the future. Food intolerance symptoms may be similar to those of other medical conditions, so consultation with your doctor before altering your diet is strongly recommended.

It is NOT a good idea for everyone to reduce the amount of gluten in their diet. Removing foods or food groups unnecessarily from your diet can lead to nutrient deficiencies, which may lead to health problems in the future. It has not been proven that gluten is responsible for symptoms such as bloating, and gluten-containing products (such as wheat bread) form an important part of the New Zealand diet.

More information:


Vici, G., Belli, L., Biondi, M., & Polzonetti, V. (2016). Gluten free diet and nutrient deficiencies: A review. Clinical Nutrition, 35(6), 1236-1241.

Last reviewed: 21/06/2022

Last modified: July 20, 2022