IBS vs Coeliac Disease


IBS vs Coeliac Disease

Symptoms of Irritable Bowel Syndrome (IBS) and symptoms of coeliac disease can be identical and the two are often be confused. However, that’s where the simillarities end. They are both very different conditions with very different treatment and very different risks. So knowing which one you are dealing with is the best way to a) get great results, and b) keep yourself healthy in the long term.

This article will cover:

  • What is IBS
  • What is Coeliac Disease
  • How is IBS diagnosed
  • How is Coeliac Disease diagnosed
  • How to implement a low FODMAP gluten challenge
  • Management

What is IBS?

IBS is a functional condition. This means that it doesn’t cause damage to the body, nor does it involve the immune system. In IBS the body looks healthy, but a person lives with unexplained symptoms including abdominal pain, excessive gas and altered bowel movements (constipation or diarrhoea or alternating between the two). IBS affects approximately10-20% of people worldwide

While these are debilitating and impact significantly on quality of life, it’s not dangerous. At this time, science doesn’t know what causes IBS, but we do know the gut brain axis and the sensitivity of nerves in the gut play a major role. You can read more about IBS here. Because IBS is not dangerous, the goal of managing it is to reduce symptoms and improve quality of life.

At this time, the most well researched and evidenced diet for IBS is a low FODMAP diet. You can read more about FODMAPs here.

What is Coeliac Disease?

Coeliac disease, on the other hand, is an autoimmune condition where the body acts abnormally in response to gluten, the protein found naturally in wheat, barley, rye and oats. Coeliac disease affects approximately 1 in 70 Australians.

When a person with coeliac disease eats food containing gluten, it sets off a chain reaction that results in damage to the lining of the small bowel. The result of this is that the body then has trouble absorbing the nutrition from food. This can result in abdominal symptoms (just like those seen in IBS), iron deficiency anaemia, osteoporosis, fertility problems and even lymphoma. As you can imagine, coeliac disease is a serious condition and if you have it, you want to know about it and you want to manage it to prevent symptoms and long term complications.

At this time, the only treatment for coeliac disease is a strict gluten free diet including care to avoid cross contamination. If you have coeliac disease and follow a gluten free diet, your bowel will repair and any symptoms or complications of coeliac disease will resolve. You can read more about the difference between FODMAPs and Gluten here.

How is IBS diagnosed?

There is no specific test for IBS. If you have gut symptoms, the first step is to see your doctor. Your doctor will order blood tests (including the blood test for coeliac disease – I’ll talk more about this below) and investigate any “red flag” symptoms. These include things like unexplained weight loss, bleeding from the back passage, a family history of bowel cancers or inflammatory bowel conditions, symptom onset after age 50 and nocturnal diarrhoea. If you have any red flag symptoms, your doctor will refer you to a gastroenterologist for further testing. If you do not have any red flag symptoms and the blood test for coeliac disease is negative, your symptoms are compared to ROME IV criteria to diagnose IBS.

ROME IV criteria: Recurrent abdominal pain on average at least 1 day/week in the last 3 months, associated with two or more of the following criteria:

  1. Related to defecation
  2. Associated with a change in frequency of stool
  3. Associated with a change in form (appearance) of stool

A note of breath testing

Breath tests have historically been used as part of an IBS diagnosis by indicating if someone malabsorbs lactose, fructose or sorbitol. In recent times, it has been identified that breath tests are not overly accurate potentially leading to unnecessary over restriction and delaying accurate diagnosis. You can read more about breath testing here. 

How is Coeliac Disease diagnosed?

Coeliac disease is a genetic condition that is environmentally triggered. About 30% of the population are born with genes that predispose them to coeliac disease. The most common genes being HLA DQ2 and HLA DQ8. Just having these genes does not mean you have coeliac disease. In most cases, these genes will remain dormant and the person will not go on to develop coeliac disease. You can find out if you have either of these genes with a simple blood test. If you do not have either of these genes, the chance of you developing coeliac disease is very small. If you do have one or both of these genes, it doesn’t mean that you have coeliac disease, just that you can develop it.

In a small number of people an event can occur that causes the coeliac genes to “wake up” and become active resulting in coeliac disease. If this happens, when the person eats gluten antibodies will be released, triggering a chain of events that results in damage to the lining of the small bowel. These antibodies are known as tTG-IgA and DGP.

Diagnosing Coeliac Disease is a two-step process:

  1. A blood test to screen for the likelihood of coeliac disease. This blood test looks for the presence of tTG-IgA and DGP antibodies.
  2. If the blood test is positive a gastroscopy is performed and a biopsy taken from the small bowel. This biopsy is examined under a microscope to assess for damage.

Since both of these tests are looking for either the presence of antibodies or the damage caused when someone with coeliac disease eats gluten, it is important for gluten to be present in the diet to get an accurate test result. If you are already on a gluten free diet, the blood test and the biopsy will be negative regardless of if you have coeliac ideas or not.

What if I am already on a gluten free diet?

If you are already on a gluten free diet, it is recommended to reintroduce approx. 3-5g of gluten per day for 6 weeks prior to a blood test or gastroscopy to assess for coeliac disease. Now if you have had great results on a gluten free diet, this can sound scary!

First off, gluten is the protein in wheat, barley and rye. FODMAPs are the carbohydrate in wheat, barley and rye. These are different molecules that are often in the same foods. This is why they can be confused so easily.

The good news is that at this time, the research shows that if a person has IBS gluten can be reintroduced without symptoms worsening as long as the gluten is low FODMAP. If you’re now wondering how you do a gluten challenge while on a low FODMAP diet? Well, you’re in the right place!


Low FODMAP gluten challenge:

According to the Royal Australian College of GPs (RACGPs) and Coeliac Australia, to meet the recommendations of gluten intake for a gluten challenge you need to include the equivalent of 2-4 slices of wheat bread per day for 6 weeks. Each item on the following list is equal to 1 slice of wheat bread and is low FODMAP as per Monash FODMAP:

  • 1 slice of regular wheat bread
  • 1 slice of FODMAP certified bread e.g. Bakers Delight lowFOD loaf (most are low FODMAP at 2 slices per serve)
  • ½ cup wheat pasta
  • 1 tsp vital wheat gluten mixed into a smoothie or made into seitan


NB: you can have multiple low FODMAP serves per day as long as you have a few hours gap between serves.


A low FODMAP example of a gluten challenge day could look like:

Breakfast at 7am: 2 slices of Alpine or Bakers Delight bread
Lunch at 1pm: 1 slice of wheat bread
Dinner at 7pm: ½ cup wheat pasta


If you are feeling hesitant about your gluten challenge or concerned about symptoms, we are here to help. Everyday Nutrition dietitians know it can be scary. We can provided personalised guidance and even modify your gluten challenge to help make it “doable”. We want to work at your pace to achieve the best possible outcome.  


Managing diet

Once you know if you have coeliac disease or IBS, you can then go about getting a plan to manage yours symptoms and your health and get great results.


If you have IBS, your dietitian can assess you and advise on if a low FODMAP diet, a food low chemical diet, gut directed hypnotherapy or other proven techniques to manage IBS are most suitable for you.


If you have coeliac disease, your dietitian can work with you to transition to a gluten free diet and advise on any monitoring you may need going forward to maintain health and wellbeing 


Regardless of your diagnosis, its likely you will feel a bit overwhelmed and maybe even go through a period of grieving. This is totally normal. All of a sudden foods you have enjoyed may be off the menu and you are second guessing yourself every time you eat. At Everyday Nutrition we are gut health experts, we know that change doesn’t happen overnight. We are here to support you and guide you through the step by step changes to help you eat for your body and your needs.


Everyday Nutrition dietitians are experts who can help you identify if gluten is in fact a trigger for your symptoms and what level of restriction is necessary for you.


At Everyday Nutrition we can help with:

  • What you need to know about IBS and coeliac disease including how they are managed
  • Discussing what testing you need now and in the future
  • Identifying what you can and can’t eat to get best results
  • If you need to worry about cross contamination or not, and if so how to manage it
  • Label reading and grocery shopping
  • Support strategies for meal planning, recipe ideas, eating out and travelling


If you’re ready to resolve digestive issues and make peace with food book in with one of our specialist dietitians here.




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Meet Joanna


Joanna is a passionate advocate, communicator and educator in the fields of gut health, nutrition and wellness.