IBS and IBD: Insights from a Dietitian with Crohn's Disease

Written by Eloise Turner, APD & IBD Dietitian

Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) are two common digestive conditions that are often confused or used interchangeably. While their symptoms and ability to affect quality of life can overlap, their management strategies are quite different.

As an Accredited Practising Dietitian living with Crohn’s Disease, Eloise Turner dives into how these conditions differ and offers practical nutrition strategies for managing both.

What is IBS?

IBS is a functional gastrointestinal disorder, meaning that it impacts how your gut functions rather than causing any structural damage or inflammation. It affects 1 in 7 people and is more common in women.

People with IBS often experience symptoms like abdominal pain, bloating, gas, and changes in bowel habits—whether it’s diarrhea, constipation, or a mix of the two.

What is IBD?

IBD includes conditions like Crohn’s Disease and Ulcerative Colitis, which are chronic diseases that cause inflammation in the digestive tract. In Crohn’s Disease, inflammation can occur anywhere from the mouth to the anus, while Ulcerative Colitis is confined to the colon. Affecting approximately 1 in 250 people, IBD is an autoimmune condition, meaning the immune system mistakenly attacks the body’s own cells.

Like IBS, people with IBD often experience symptoms like abdominal pain, bloating, gas, and changes in bowel habits but they may also have blood or mucus in the stool and extreme fatigue. During a flare (a period when symptoms worsen due to active inflammation), they may also unintentionally lose weight and/or become malnourished due to the inability to properly digest food and absorb nutrients.

How are they Diagnosed and Managed?

While both IBS and IBD affect the digestive system, the way they’re diagnosed and managed differs. 

IBS is diagnosed based on symptoms and elimination of other causes. Unlike IBD, IBS cannot be confirmed by visual examination, though your doctor may use imaging, blood and/or stool tests to rule out other causes (like IBD, coealiac disease or endometriosis). If you’re diagnosed with IBS, you will likely be recommended dietary and lifestyle changes to manage symptoms.

On the other hand, diagnosing IBD typically involves more invasive testing, such as a
colonoscopy, endoscopy, and/or diagnostic imaging. These tests help confirm the presence of inflammation, determine its location and severity. If you're diagnosed with IBD, you will likely need ongoing monitoring and medication to manage both symptoms and inflammation.

Can You Have Both?

Interestingly, it’s not uncommon for people with IBD to also experience IBS symptoms, even during periods of remission (when symptoms subside and inflammation is controlled). Studies suggest that up to 42% of Crohn’s Disease patients and one-third of those with Ulcerative Colitis experience IBS symptoms. The good news is that both IBS and IBD can benefit from dietary interventions.

The Role Of Nutrition

Managing what you eat is an essential part of living with IBS and/or IBD, but the dietary
strategies can differ based on which is at play.

For IBS, a low FODMAP diet is effective in alleviating symptoms in around 75% of sufferers. It's important to work with a Monash FODMAP-trained dietitian to identify your individual food triggers and create a personalised plan so that your diet doesn’t become unnecessarily restrictive.

For IBD, the focus shifts to ensuring nutritional adequacy, addressing nutritional deficiencies, and reducing inflammatory patterns. During a flare, a modified fibre and/or texture diet may be recommended to minimise gut irritation. In contrast, during remission, a diverse and balanced diet rich in fibre, antioxidants, protein, and healthy fats is essential to reduce the risk of future flares and support overall health. Again, working with an IBD-trained dietitian ensures effective symptom management while meeting nutritional needs.

Key Takeaways

● IBS is characterised by functional disturbances in the gut but it doesn’t cause chronic
inflammation or structural damage like IBD.

● While IBS and IBD share some overlapping symptoms, their management strategies
differ significantly.

● Diet plays a key role in managing both IBS and IBD. For IBS, a low FODMAP diet is
often recommended, while medical nutrition therapy for IBD depends on the stage and
severity of the disease.

Important Note

If you experience any abnormal symptoms, please seek guidance from a qualified health
professional — no matter how healthy you think you may be.