What is gluten – and where do we find it?

Gluten is the main protein found in the following grains:
  • Wheat (also known as spelt, semolina and durum)
  • Rye
  • Barley
  • Triticale
  • Oats*

When mixed with water, gluten forms a tough, rubbery and elastic substance and a web of fine strands, which stretch and rise, creating the structure and texture seen in bread, cakes, biscuits and other baked goods.

Hidden Gluten: In addition to the obvious gluten-containing foods, several products contain gluten in thickening agents and flavourings, such as sausages and stock powders. Coeliac New Zealand is an excellent source of current advice and resources to help you identify gluten-free foods.

*Oats are grown next to wheat fields, which contaminates them with gluten. They also contain a type of gluten (‘avenin’), so are not considered ‘gluten free’. However, studies have shown that some individuals with Coeliac Disease or gluten intolerance can tolerate limited amounts of uncontaminated oats. Coeliac NZ advises that people with a new coeliac diagnosis should avoid oats, even if uncontaminated, and only add them to their diet under medical supervision.

What is coeliac disease?

Coeliac disease involves an immune response to gluten. It develops in genetically predisposed people as a result of eating gluten, causing damage to the small intestine’s villi, reducing their ability to absorb nutrients from food. Symptoms can include bloating, diarrhoea, fatigue, and weight loss, as well as longer term conditions such as anaemia and osteoporosis.

For people with coeliac disease, even trace amounts of gluten can cause a reaction and following a lifelong, strict gluten-free diet is the only current treatment.

Dermatitis herpetiformis, also known as DH or Duhring’s disease, is an uncommon chronic, intensely itchy, blistering skin condition caused by an immune reaction to ingesting gluten. Everyone with DH also has coeliac disease.

(Picture credits: Coeliac New Zealand website (2023))

(Picture credits: Coeliac New Zealand website (2023))

What is gluten intolerance?

Non-coeliac gluten intolerance – known as gluten intolerance / sensitivity – happens when people develop a variety of unpleasant symptoms when they eat gluten-containing foods. Removing gluten from their diet often helps these symptoms. People with gluten intolerance may tolerate small amounts of gluten without experiencing symptoms – with amounts varying between individuals, and depending on how much they eat and how sensitive they are.

Note that it is important for people to know if they have coeliac disease or not BEFORE starting a gluten-free diet (see Diagnosis).

Other causes of similar symptoms:

In addition to gluten, there are several other causes of uncomfortable gut symptoms, including intolerances to other substances (e.g. amines, salicylates, sulphites) or a group of short-chain carbohydrates termed FODMAPS (fermentable, oligosaccharides, disaccharides, monosaccharides and polyols) that may not be absorbed in the small intestine.

People suffering from Irritable Bowel Syndrome (IBS) can experience similar gastrointestinal symptoms including abdominal pain, bloating, wind and diarrhoea often feel better on a gluten-free diet. IBS sufferers can often tolerate some gluten-containing foods without triggering their symptoms – and these can be discovered by working with a dietitian.

Physical factors – like the amount you eat (stretching your stomach) and chewing gum (swallowing air) – and stress can also affect the severity of symptoms.

You may only have a problem with one or two foods, and the trick is determining which one(s). Consult your doctor or dietitian to get an accurate diagnosis and help you do this.


The results for coeliac disease testing won’t be accurate if you are already following a gluten-free diet – so it’s important to exclude other possible diagnoses before excluding gluten-containing foods.

Diagnosis of coeliac disease is made through a combination of blood tests, duodenal (small bowel) biopsy and, in some cases, gene testing. There is no specific gluten intolerance test – so it is important to work with your doctor to eliminate coeliac disease and determine your individual management plan.

Is a gluten-free diet a healthier choice?

Many people believe that a gluten-free diet is healthier, but there is no reason to avoid this protein UNLESS you have been diagnosed with coeliac disease, gluten intolerance, or another condition affected by gluten. As with any eating pattern there are pros and cons to excluding gluten.

Depending on your food choices to start, removing gluten-containing foods may cause you to improve your diet quality (leaving you feeling better with or without gluten). For example:

  • You might eat less processed foods e.g., cakes, pastries and biscuits (with gluten) or
  • Choose more whole foods e.g., fruits and vegetables

Drawbacks to following a gluten-free diet unnecessarily include:

  • Specialised gluten-free products (e.g., biscuits and cakes) 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 protein, aren’t very filling, and can lack beneficial whole grains.
  • Poorly managed gluten-free diets can be lacking in fibre, calcium, iron and B vitamins (Vici et al., 2016).
  • Gluten-free products are more expensive than their traditional counterparts.

Healthy gluten-free options

It is possible to eat well on a gluten-free diet, though it may take some planning. Choose high-fibre, high protein grains that are naturally gluten-free such as quinoa, buckwheat, and millet. Legume-based pastas are also a great alternative.

Fruits, vegetables, dairy products, legumes, nuts, seeds, fish and meat are all naturally gluten-free. Eating a range of foods from all the food groups will ensure that you are meeting your nutrition needs.

Get professional support

Following a gluten-free diet should only be done on the advice of a doctor or dietitian who will help you get an accurate diagnosis and then determine what foods you can enjoy – and what you should avoid. In some cases, they will guide you on an elimination diet, where all suspect foods are removed for a set time, then gradually reintroduced to find which 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.

Resources and more information:

Last reviewed: 02/05/2023

Last modified: May 23, 2023