IBS Diet: What You Should Know

April is IBS Awareness Month, so I’d like to take this opportunity to share some key information that’s worth knowing and considering if you’re living with irritable bowel syndrome.

What is the IBS Diet?

If you’ve received a correct diagnosis of IBS, the next step is appropriate treatment. Diet plays a central role in managing IBS—though it’s important to remember that stress often contributes to symptom flare-ups, so we’ll also look at other treatment strategies later.

First-Line Treatment: What Does It Involve?

We begin by looking at dietary patterns and common triggers—specifically, foods you’ve noticed may bring on symptoms. Many people don’t realise how much the following factors can impact their symptoms:

1. Meal Regularity

Are you eating regular meals, or skipping them and eating at irregular times? Skipping meals can stress the body, raising cortisol levels and worsening IBS symptoms. Skipping also increases the risk of overeating later, which puts strain on a sensitive gut and may trigger pain, bloating, excess wind, or altered bowel movements.

2. Eating Habits

How you eat matters just as much as what you eat. Rushing through meals or not chewing properly can make symptoms worse.

3. Fibre Intake

Many people with IBS don’t eat enough fibre, while others make drastic overnight changes and increase fibre too quickly. Fibre adds bulk to stools, feeds our gut bacteria, and supports gut motility. Various plants derived from plant foods, such as olive oil, but typically found in higher amounts in brightly colored fruit and veg, also providing polyphenols, which seem to have an ability to stop the growth of some ‘unwanted’ bacteria and enhance the growth of the beneficial ones, as studies suggest. 

The recommendation is to consume 30g of fibre per day. You can achieve this by:

• Eating five portions of fruit and vegetables daily (80g per portion)
  
• Choosing wholegrain over white carbohydrates
  
• Including plant-based proteins like beans, pulses, lentils, nuts, and seeds
  

Important: Fibre works best when paired with adequate fluid, so aim for 1.5–2 litres of fluid daily.

4. Hydration

Some of us drink too little, others too much. The right balance helps fibre support digestion and prevents both constipation and dehydration caused by diarrhoea. Include water, squash, herbal teas, and decaffeinated drinks in your daily intake.

5. Caffeine

Caffeine can stimulate the gut and increase acid production in some individuals, which may worsen symptoms. It’s not just in coffee, tea, cola, and energy drinks also contain caffeine. Ask yourself how many of these you drink daily, and when you have them (e.g. on an empty stomach?).

6. Alcohol

Alcohol is also a stimulant, and it can impair the integrity of the gut wall, leading to increased sensitivity and inflammation, and a reduction in important microbial numbers. NHS guidance recommends limiting alcohol to no more than 14 units per week and having at least two alcohol-free days. Avoid binge drinking.

7. Spicy Foods

Capsaicin, the active compound in chilli, speeds up gut transit time and can trigger abdominal discomfort or burning. If you have IBS, reduce your intake of spicy foods.

8. High-Fat Foods

Fat takes longer to digest—up to nine hours—and this can increase bloating, discomfort, and fullness in those with a hypersensitive gut. Limit foods like fried meals, takeaways, sausages, creamy cakes, and crisps. These may not be the sole cause of symptoms, but reducing them can lead to noticeable improvement.

If First-Line Measures Aren’t Enough…

If symptoms persist despite addressing the common triggers above, your dietitian may recommend the Low FODMAP Diet—a second-line dietary approach.

What is the Low FODMAP Diet?

The Low FODMAP diet is a short-term, evidence-based treatment for IBS that can significantly improve symptoms in about 3 out of 4 people. It aims to reduce pain, bloating, and bowel irregularity by eliminating certain poorly absorbed carbohydrates (FODMAPs):

• Fermentable
  
• Oligosaccharides ( so fructans & galacto-oligosaccharides)
• Disaccharides (eg, lactose)
• Monosaccharides 

and

• Polyols -sugar alcohols, labeled on some products as  “sugar-free,” including hard candies, cookies, chewing gums, soft drinks and throat lozenges; but also some fruit such as apples and vegetables.  

Important: You should only start the Low FODMAP diet under the guidance of a Registered Dietitian (RD) trained in IBS management. The diet is restrictive and, without proper support, could lead to nutritional deficiencies.

Note: The Low FODMAP diet is not suitable for individuals with current or past eating disorders.

How It Works

The diet has three phases:

1. Elimination – Temporarily remove high-FODMAP foods (usually 4 weeks but may be longer)
2. Reintroduction – Gradually bring foods back to assess tolerance (up to 10 weeks)
3. Personalisation – Tailor your long-term diet to your needs and symptoms (long-term management of the diet)

This process usually takes over 18 weeks, so it’s essential to consider the time required. What may help to handle this concern is however planning ahead your low FODMAP meals- dietitian can help you to do that too. 

Foods temporarily excluded may include:

• Wheat and wheat family grains as well as products made from them- and it’s not because of gluten as many patients believe, but more so because of the high content of fructan, which is a type of fermentable naturally occurring sugar in some grains, fruits and vegetables. 
• Certain dairy products (which contain lactose- a type of fermentable sugar)
• A wide range of fruit and vegetables (e.g. garlic, onions, broccoli- those are high gas-producing ones) but also fruit and vegetables with a high concentration of other earlier mentioned fermentable types of sugars. 

Avoid using unverified online resources or apps to guide you through this process. The Monash University FODMAP app is reliable, but even then, evidence shows that following this diet with a dietitian leads to far better outcomes.

Need Help?

If you think you may benefit from dietary support, get in touch. I can guide you through your IBS management with a tailored approach that fits your lifestyle.

A Quick Reminder: What is IBS?

IBS affects around 4–11% of people globally, with a higher rate (up to 1 in 5) in the UK, especially in those aged 50 and under. It’s not life-threatening, but symptoms can severely affect quality of life, including work and social functioning.

IBS is diagnosed based on:

• Abdominal pain at least once a week for the past 3 months
  
• Two or more of the following:
  
  • A change in stool frequency
    
  • A change in stool appearance (constipation, diarrhoea, or both; presence of mucus)
    
  • Bloating or discomfort
    

Additional symptoms like incomplete evacuation, bladder symptoms, urgency to open bowels, nausea (feeling sick), backache, and fatigue are common.

Don’t Self-Diagnose

Always seek a proper diagnosis. Keep a symptom diary to help your GP or specialist determine which tests you may need. These may include:

• Faecal calprotectin – to check for inflammation
  
• FIT test – if you’ve noticed blood in your stool
  
• Faecal elastase – if stools are greasy or foul-smelling
  
• Coeliac screening
  
• Blood tests – to rule out anaemia and raised inflammatory markers
  

What Causes IBS?

There’s no single cause. IBS is classified as a neurogastrointestinal disorder due to the interaction between the brain and gut, known as the gut-brain axis. Disruptions in this system can lead to visceral hypersensitivity, where the gut overreacts to food, hormones, and stress.

Other contributing factors may include:

• Food poisoning or traveller’s diarrhoea
  
• Chronic stress
  
• Anxiety or depression
  
• Genetic predisposition
  
• Female sex (more common in women)
  
• Emerging research also points to environmental factors (e.g. pollution) affecting gut microbiota.