Epilepsy is a disorder in which periodic seizures are caused by abnormal electrical impulses that occur in the brain. In most people, seizures can be controlled with one or more antiepileptic medications, but sometimes after a while these medications stop helping (so-called drug-resistant-epilepsy). People with drug-resistant epilepsy may be prescribed a special diet (the so-called ketogenic diet). Ketogenic diets are high in fat and low in carbohydrates.
The purpose of this review was to study the effects of ketogenic diets on seizure control, cognitive abilities (such as learning, attention, and academic performance in children; learning, attention, and memory in adults), and behavior. We also looked at the side effects of this diet, the number of participants who dropped out of studies, and the reasons for their dropping out.
Characteristics of research
In medical databases, we searched for randomized controlled clinical trials (clinical trials in which people are randomly assigned to one of two or more treatment groups) involving adults or children with epilepsy, in which the ketogenic diet was compared with other treatments. We found 11 randomized controlled clinical trials involving 778 people. The duration of clinical trials ranged from two to 16 months.
Short-term side effects of ketogenic diets included diarrhea, constipation, and vomiting. The long-term effects are not known from these studies.
All studies reported participants dropping out due to a lack of reduction in seizure attacks and poor diet tolerance.
One study reported the effects of a ketogenic diet on quality of life, cognitive ability, and behavior. There were no differences in the quality of life of those who followed a ketogenic diet and in the group receiving treatment as usual, but participants who followed a ketogenic diet were more active, more productive, and less anxious. Further research is needed in this area.
Recently, other, better-tolerated ketogenic diets, such as the modified Atkins diet, have shown similar effects on seizure control, as have stricter (more restrictive) ketogenic diets. However, more research is needed.
Quality of evidence
The studies included in the review were limited to a small number of participants, and 10 of the 11 studies included only children, so we rated the quality of the evidence as low or very low.
There are currently few studies using these diets in adults, so further research in this area is needed.