The ketogenic diet is gaining in popularity – and has attracted some controversey – so we asked Eimear Forbes, senior dietitian in ketogenic diet therapies in Temple Street Children’s University Hospital, for her expert opinion on the diet we’ve been hearing so much about.

The keto diet and medical conditions – tell us more.

The ketogenic diet is a proven medical therapy for epilepsy in existence since the 1920s, and is a treatment option for use in children with uncontrolled epilepsy. There are many randomised control trials that demonstrate the effectiveness of the ketogenic diet in decreasing seizures in patients with epilepsy.

So what exactly is the ketogenic diet? The ketogenic diet is a very high fat, low carbohydrate diet with adequate amounts of protein. The aim of the diet is to produce ketone bodies, which are normally only produced by the body in energy restriction. Each food in the diet is weighed and each patient is given a prescription for their fat and carbohydrate at each meal.

The diet is very restrictive – in many situations a maximum of 20g carbohydrate is permitted per day (one potato is equal to 10-15g carbohydrate).

As a result, foods such as breads, cereals, pasta, rice and potatoes are essentially eliminated from the diet, as well as yoghurts and milk due to their carbohydrate content.

Most of the energy comes from the fat in the diet with the main sources being butters, oils and creams, together with protein foods such as eggs, meat, fish and cheese weighed each day.

With those restrictions, is it challenging for patients?

It is one of the most challenging and restrictive medical diets, and it must be administered and monitored under the strict supervision of a registered dietitian with the appropriate experience working in partnership with a medical team to ensure safety and efficacy of the diet therapy, and to allow for medication and diet alteration as required.

However, it can be absolutely life-changing for patients with epilepsy when it works and helps to reduce seizure activity.

In epilepsy, blood ketone and blood sugar levels are monitored daily to assess levels of ketosis and guide any required alteration to the diet that may decrease seizure activity if required.

This also ensures that ketone levels do not increase to an unsafe level and make the person feel ill – nausea, lethargy, irritability and, at worst, the patient can become very medically unwell. There is also the risk that blood sugar levels may be too low which can also have severe side effects.

So, who is it suitable for?

The diet is not suitable for all patients and a screening process is undertaken for all referrals. If a person is very underweight, the diet should not be initiated until they are more stable.

The diet can lead to side effects such as vitamin and mineral deficiencies, as well as effects on bone health, growth, constipation, overall gastrointestinal upset, renal stones and hyperlipidaemia.

Therefore close monitoring and dietary alteration is essential to help avoid these side effects or treat them when they occur.

In the last number of years there has been growing interest and research on the use of ketogenic diet in other neurological disorders, but much of the research to date has been based on animal studies.

There are also some animal studies outlining the potential for it to be used as a therapy option alongside conventional treatments of radiotherapy and chemotherapy in some brain tumours, especially where there are tumour-associated seizures or slow growing brain tumours.

However, this is only suggested at present with a small number of individual human case reports and animal studies. Clinical trials, which would influence medical practice, are required to determine if ketogenic diet therapy is an effective and safe therapy option in neuro-oncology.

Eimear Forbes is a member of the Irish Nutrition and Dietetic Institute. It has a free recipe booklet available for cancer patients. Email info@indi.ie. Payment for postage and packing is required.

Separately, University College Cork and Breakthrough Cancer Research have a cookbook , Eating Well with Swallowing Difficulties in Cancer, which is available free of charge to patients in Ireland through their hospital. An ebook is at breakthroughcancerresearch.ie