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The ketogenic diet (KD) is a high-fat diet used in the management of childhood epilepsy. It was determined in the early part of last century that starvation could have a beneficial effect on seizure control.1–3 Realising that this was not practical, Wilder in 1921 suggested that designing a diet that may mimic the effects of starvation – namely with fat as the main source of energy that is metabolised to ketones – could consequently have a similar effect on epileptic seizures.4 Subsequently, a colleague confirmed the beneficial effect of the then so-called ‘classic ketogenic diet’.5 Following this, its use became widespread, but with the advent of anticonvulsant medication, in particular phenytoin in the 1930s, its use became less favoured. However, in time it became evident that medication was not the solution for all and there was a resurgence in the popularity of the KD.
The original diet was composed of predominantly long-chain fats and was based on the ratio of fat to carbohydrate and protein (3:1 or 4:1), the so-called classic KD. Over the years it became evident that there was some concern about tolerability. In 1971 Huttenlocher reported on the use of an alternative fat – medium-chain triglyceride (MCT), which is more ketogenic per calorie than long-chain fat – as a supplement, and the MCT diet was born.6 However, of note this diet still remained low in carbohydrate. Subsequent use of the KD has been variable, with consideration in management dependent on the experience of individual professionals. However, the evidence base is now increasing as regards benefits of the diet in drug-resistant epilepsies of childhood and, more specifically, particular epilepsy syndromes.
Many open-label retrospective and prospective studies have reported on the use of the diet in the treatment of childhood epilepsy. However, the quality of such studies has been variable. In 2000 a systematic review reported on studies evaluating the KD and its use in childhood epilepsy.7 Of note was the fact that only 11 studies fulfilled the criteria for the review. All 11 were observational, only two had been carried out on a prospective basis and nine out of the 11 were from a single institution.