Is a ketogenic diet bad for your gut?

Susan Hunter Digestive Health Leave a Comment

There is a lot being said about the benefits of eating a ketogenic diet. People are discussing their new-found health success with eating a ketogenic diet in facebook health support groups and there are companies online spruiking their keto diet plans and supplements. It’s fair to say keto is hot right now.

What is a ketogenic diet?

So, what does eating a ketogenic diet involve?

A true ketogenic diet means you eat 80-90% dairy based saturated fat and 10-20% protein a day with very few carbohydrates allowed. There are variations of this – the Modified Atkins diet being one of them. The aim is to get the body in ketosis, which means it burns fat and produces ketones rather than burning glucose via glycolysis to produce energy.

The benefits of going keto

Dr Dominic D’Agostino has researched the ketogenic diet for many years and has found that when following a ketogenic diet you see a reduction in reactive oxygen species (ROS – bad guys!), increased production of mitochondria in cells (which is our body’s energy production powerhouse) and a reduction of inflammation and a reduction in inflammatory cytokines being produced meaning a slow down in ageing.

Who is keto for?

The mental clarity, quick weight loss and improved energy experienced when eating a keto diet all sound great when you have been feeling flat, down, foggy in the head, and possibly carrying extra weight.

The data indicates it’s a useful diet for neurological disorders especially seizures. Nutritional ketosis is thought to stabilise and preserve brain energy. Children with hard-to-control epilepsy that is unresponsive to medication have benefited from following a ketogenic diet. Decanoic acid produced when ketones are being formed have been found to reduce seizure activity, hence the use in this distressing and serious condition. Ketogenic diet has also been successfully used in the treatment of amyotrophic lateral sclerosis (ALS).

How ketogenic diets influence gut bacteria

People with digestive issues that stem from an imbalance of gut bacteria/dysbiosis are potentially going to struggle with this type of diet long term.

The effect of eating a high saturated fat diet on bacteria in the large bowel is potentially very negative. Endotoxins and bile acids (deoxycholic acid) are produced by the body in response to a high fat diet. Pathogenic and damaging bugs like Desulfovibrio piger and Bilophyla wadsworthia are bile acid eating bugs and the quickest way to create an overgrowth of these bacteria is to eat a high saturated fat, especially a cow’s milk based diet. A high protein diet does the same thing. These bacteria LOVE saturated fat and animal protein. They gobble it up and thrive and actually begin to take over as the dominant bacteria species in the large bowel.

The problem with these bugs taking over is that they are very inflammatory and particularly toxic to the gut as they produce hydrogen sulphide which damages gut integrity and contain endotoxins such as indoles, amines and ammonia that affect the entire body, knowing no boundaries and crossing the blood brain barrier too.

Overgrowth of these bile acid consuming bacteria also increases your risk of colorectal cancer and inflammatory bowel disease. They are also toxic to colonocytes (gut cells) as they stop those gut cells using buytrate (an important fuel substrate for bacteria) as fuel.

Keto = low fibre

In order to eat a ketogenic diet you have to avoid eating whole grains and legumes. These are very important prebiotic foods that act as fuel for beneficial bacteria in the bowel. Avoiding these foods will only lead to beneficial bacteria being starved and if a ketogenic diet is followed for long enough could result in extinction of some bacteria species.

Important considerations

There is no research done so far looking into the role of ketogenic diets in gut health. Before beginning a keto diet it is important to take into consideration the state of your fatty acid profile, gut microbiome, presence of dairy intolerance, nut and cows milk allergy and whether you have any cholesterol metabolism gene mutations before embarking on the ketogenic diet. Also, you can achieve post-exercise ketone production or intermittent fasting.

You don’t need to eat a high fat diet in order to get the neurological and energy benefits of the ketogenic diet. As nutritional medicine moves in the direction of individualised medicine there is no one-size-fits-all diet. Individualised medicine and dietary advice makes the most sense.


Susan Hunter
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