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If you’re like most of my IBS nutrition clients you’ve done your research on the best diets for IBS. You might have looked into a vegan diet, intermittent fasting, or keto and the carnivore diet. 

Are the ketogenic and carnivore diets suitable for IBS?

The ketogenic diet has gained popularity in recent years in some communities. Some people notice a benefit of weight loss and blood sugar regulation.

The carnivore diet is one step more extreme, eliminating nearly all foods except animal products. But are these diets suitable if you’ve got irritable bowel syndrome (IBS)?

In this article, I’ll help you understand the science behind these diets, their potential benefits, and the risks they pose, particularly for those with IBS.

Close up of flat lay of food in small glass bowls including eggs, some raw salmon, a cooked egg cut in half, some nuts and spinach in foreground

What is the ketogenic diet?

The ketogenic diet (or keto) is a very low-carbohydrate, high-fat diet. By restricting carbohydrates to as little as 20 to 50 grams per day, the body is forced to switch from using glucose as its primary energy source to using ketones.

Ketones are molecules produced by the liver from fats. They can serve as an alternative fuel for the brain and other cells. This process, known as ketosis, typically begins within three days of starting the diet.

Originally developed to help children with epilepsy manage their symptoms, the ketogenic diet has since become widely adopted for weight loss and other potential health benefits.

It’s similar in principle to older diets like the Atkins diet but focuses more heavily on maintaining ketosis.

Why some people with IBS may feel better on keto

Some people with IBS might notice initial improvements in their symptoms when following a ketogenic diet. This is largely because the diet cuts out many high-FODMAP foods—fermentable carbohydrates that can trigger symptoms like bloating and diarrhoea.

When you reduce vegetables, fruits, grains, and legumes, you may experience less fermentation in the gut. This could lead to a reduction in bloating and gas.

Additionally, some people report steadier energy levels on a high-fat diet. Unlike glucose, which can cause blood sugar spikes and dips, fats provide a slower, more consistent release of energy.

Some people say they have more energy on a keto diet.

The risks of the ketogenic diet for IBS

While the ketogenic diet may seem promising at first, it comes with significant risks, especially for those with IBS.

High fat and cholesterol risks

The diet’s reliance on high-fat foods can lead to increased levels of low-density lipoproteins (LDL), or “bad” cholesterol. Elevated LDL is strongly associated with a higher risk of cardiovascular disease, and this risk is not something to be ignored.

Research consistently shows that diets high in saturated fats are likely to raise LDL levels, potentially leading to long-term health complications. 

You won’t know you’ve got high cholesterol unless you get tested. 

Digestive motility issues

High-fat meals naturally slow digestion, which can worsen constipation for people with IBS. On the other hand, some individuals may experience urgency and diarrhoea if their bodies struggle to process fats properly.

Removing fibre from your diet long term can affect your gut motility. 

Increased intestinal permeability

Research also suggests that very low-carbohydrate diets like keto can increase intestinal permeability, sometimes referred to as “leaky gut.”

A 2023 study in individuals with obesity found that those following a ketogenic diet had higher levels of intestinal permeability markers, such as the lactulose-to-mannitol ratio.

Over time, increased permeability can exacerbate gut inflammation, potentially worsening IBS symptoms and contributing to broader health issues.

Flat lay of raw meat against a dark grey marble surface. Includes a raw burger, chicken, two steaks and a liver. Words Drawbacks to a keto or carnivore diet.

What is the carnivore diet?

The carnivore diet takes the principles of the ketogenic diet to an extreme. It involves consuming only animal products such as meat, fish, eggs, and butter. You’d completely remove all vegetables, fruits, grains, and legumes from your diet.

While advocates claim it can improve certain health conditions, there is no scientific evidence to support its use, particularly for IBS.

The dangers of the carnivore diet for IBS

Gut microbiome changes

One of the most concerning aspects of the carnivore diet is its impact on the gut microbiome. A healthy gut microbiome thrives on a diverse diet that includes fibre-rich plant foods.

Fibre is essential for producing short-chain fatty acids (SCFAs), which have anti-inflammatory properties and serve as fuel for the cells lining the colon.

A 2014 study on healthy men found that switching to an animal-only diet for just five days significantly altered the gut microbiome. Participants experienced an increase in inflammatory bacteria, such as Bilophila wadsworthia, which has been linked to conditions like Crohn’s disease and ulcerative colitis. At the same time, they had a decrease in beneficial SCFAs, potentially increasing gut inflammation and irritation.

Loss of fibre’s protective benefits

The complete removal of fibre from the diet can have far-reaching consequences. Fibre not only supports gut motility and regular bowel movements but also interacts with the immune system and maintains the gut lining’s protective mucus layer.

Without adequate fibre, the gut may become more susceptible to irritation, inflammation, and infection.

Increased bile salts

Another potential issue is the increase in secondary bile salts, which are produced when fats are broken down. These compounds can irritate the colon, especially in individuals with bile acid malabsorption (a common but underdiagnosed condition in IBS-D).

Increased bile salt production may lead to diarrhoea and other uncomfortable symptoms.

 

 

5 non-food strategies for managing IBS

Tips for IBS that don't involve changing your diet

Better alternatives for managing IBS symptoms

While the ketogenic and carnivore diets may offer some short-term relief by eliminating high-FODMAP foods, their long-term risks far outweigh the benefits.

Instead, consider these alternative approaches to managing IBS:

1 Low FODMAP diet

The low FODMAP diet is a scientifically validated approach for reducing IBS symptoms. By identifying and eliminating specific trigger foods, you can achieve symptom relief without the risks associated with extreme diets. It’s not something you should follow for a long time, but it’s a dietary intervention to help you identify triggers.

You can try my self study course if you want to follow a clear method for the low FODMAP diet with recipes and guideance.

2 Focus on balanced nutrition

A diet that includes a variety of different fibres from fruits, vegetables, and grains. Also include lean proteins, and healthy fats ensures you get essential nutrients while supporting your gut microbiome.

3 Lifestyle changes

Sometimes IBS isn’t driven by food. You can make improvements to your symptoms by working on stress management, exercise and breathing exercises. These things seem like they aren’t enough at first, but can have a huge impact on your digestion over time. 

4 Personalised advice

Work with a qualified nutritional therapist to develop a tailored plan based on your specific symptoms, triggers, and health goals. IBS is a highly individual condition, and a one-size-fits-all approach rarely works.

The ketogenic and carnivore diets may seem like tempting options for managing your IBS due to their initial symptom relief.

However, their long-term risks, including negative impacts on gut health, cardiovascular health, and the gut microbiome, make them unsuitable for most people with IBS.

Instead, a balanced, high fibre diet combined with personalised advice offers a safer and more effective way to manage symptoms while supporting overall health.

Next steps

If you want help figuring out your IBS triggers, start your Gut Reset with me over 3 months to find a diet that works for you. Just set up a free call to discuss what you need some help with. Email info@goodnessme-nutrition.com

 

IBS Nutritionist

Hi, I'm Anna Mapson, registered Nutritional Therapist.

I help people with IBS and SIBO get control of unpredictable gut symptoms to find long term relief from painful and embarrassing IBS without restrictive dieting.

I can help you to:

  • understand your digestion better, so you recognise your triggers
  • eat a well balanced diet, with tasty meals that are simple to prepare
  • reintroduce your trigger foods so you can get back to enjoying food again

Find more about my 3 month 1:1 Gut Reset programme. 

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