Dietary fats – friend or foe for IBS?

The low FODMAP diet is a well-established method of successfully managing IBS symptoms in many people.  
In addition to FODMAPs, there are other dietary factors that may worsen IBS symptoms.  

Some of these commonly include alcohol, caffeine and dietary fats. While not everyone reacts to the same foods or responds to the same dietary treatment, some are more common or effective than others.

Dietary Fats and IBS

Dietary fat intake is associated with worsening IBS symptoms in some patients.  This is particularly common for those with Diarrhoea Predominant IBS (IBS-D).

One reason for this is that fat impacts our gut motor activity. This means that fat can affect the rate and efficiency of digestion in some people. Many patients with IBS are extra sensitive to this.

We each have different tolerance levels for certain nutrients such as carbohydrates (e.g FODMAPs) and fat.  So the more sensitive you are to dietary fat, the lower your fat tolerance level will be.

This fat sensitivity can contribute to various symptoms such as cramps, bloating, gas, and diarrhoea.  Some people who experience these symptoms may have other underlying reasons for not tolerating fat well.  It appears Bile Acid Malabsorption (BAM) is quite common in patients suffering from IBS-D and may contribute to a low-fat tolerance.  

Now let’s take a lot at what BAM actually is…

Bile Acid Malabsorption (BAM)

Bile acids are a substance that our liver forms from cholesterol. Our liver releases bile acids after eating, especially high-fat meals. This is because their main role is to help with fat digestion. Normally, bile acids help digest food as it moves along your digestive tract, until the end of the small bowel. In the small bowel, most of the bile acids are reabsorbed. They then travel back to the liver and hang there until our next meal.

This re-absorption of bile acids does not occur sufficiently in some people, causing malabsorption. Malabsorption causes bile acids to flow through to the colon, rather than back to the liver. When too much bile acid ends up in the colon it draws in more fluid, causing diarrhoea. BAM causes similar symptoms to fat sensitivity.

What causes BAM?

Like with IBS, the exact cause of BAM is often unknown.  Research suggests that up to 20-30% of patients with IBS-D may have BAM, but often goes undiagnosed.  BAM can also result from inflammatory bowel conditions such as Crohn’s Disease, some types of bowel surgery, and some gastrointestinal diseases.  Diagnosis of BAM is usually done via a particular scan and is a treatable condition. If you have IBS-D and experience problematic fat sensitivity, it is best to seek advice from your GP.

What type of fat is best for IBS management?

There is no evidence to suggest which specific types of fat are better or worse for managing symptoms of fat sensitivity.  

For good health, it is recommended less than 10% of our total fat intake is from saturated fat, as high saturated fat intake can increase the risk of heart disease. Saturated fat is high in animal products such as dairy and meat, coconut/coconut products, palm oil, and various packaged products.

We should aim to receive the majority of our fat intake from unsaturated fat sources, which help reduce our risk of heart disease. This includes polyunsaturated fats such as omega-3 fats (high in oily fish) and omega-6 fats (high in soybean oil, safflower oil, and certain nuts).  

This also includes monounsaturated fat which is found in avocado, canola oil, olive oil, and some nuts.

How much fat will worsen IBS symptoms?

Only some individuals with IBS will experience fat sensitivity, whereas others may have a high-fat tolerance.  Fat is more commonly a trigger for those with IBS-D, and a high intake can worsen symptoms.  There is no set amount of fat for managing IBS, so it is best to modify fat intake according to your individual tolerance levels.

For healthy individuals, fat should make up between 20-35% of total energy intake. Sometimes a low-fat diet can help with symptom management of IBS, particularly IBS-D.  This is best done with the supervision of an Accredited Practising Dietitian, to ensure nutrient requirements are being met.

Need help with the low FODMAP diet? Our FREE dietitian developed program will guide you through it, step-by-step. Includes a low FODMAP food guide. Sign up now.

If you are experiencing gut symptoms and have not been recommended a low FODMAP diet by a health professional, get started with the manage your gut symptoms program.

Reviewed by the healthylife Advisory Board March 2022