What are the effects of ketogenic diets for people with drug-resistant epilepsy?

Abstract

A ketogenic diet may help reduce the frequency of epilepsy seizures, but all the evidence is of very low to low certainty, and no conclusions can be drawn as to the benefits or harms associated with such diets, or whether any one type of ketogenic diet may be preferable over another.For people with drug‐resistant epilepsy, low‐certainty evidence suggests that the introduction of a ketogenic diet (high fat, adequate protein, low carbohydrate) has little to no effect on the numbers of people achieving seizure freedom, but 35% to 56% of people may experience 50% or greater reduction in seizure frequency with a ketogenic diet versus 0% to 18% with a standard/usual diet (all values on average). Withdrawal from the diet varied considerably across trials, ranging from 8% to 35% with a ketogenic diet and from 0% to 40% with the standard/usual diet. Other outcomes were assessed in too few people to be clinically useful (activity, productivity, anxiety, quality of life, adverse effects; analyses included 57 to 204 people).When researchers compared different ketogenic diets, the proportion of people achieving seizure freedom was greatest with the 3:1 ketogenic diet (35%) and least with the modified Atkins diet (10% to 25%). The proportion of people achieving 50% or greater reduction in seizure frequency was greatest with the 4:1 ketogenic diet (58% to 85%) or the 3:1 ketogenic diet (72%) and least with the modified Atkins diet (42% to 60%) or the classic ketogenic diet (43%). The proportion of people withdrawing was greatest with the classic ketogenic diet (33%) and least with the gradual‐onset ketogenic diet (8%). Researchers reported few differences in terms of adverse effects, but all studies were underpowered. The most frequently reported adverse effects were vomiting and constipation. However, the evidence from which these rates were derived is of very low certainty. No trial reported on activity, productivity, anxiety, or quality of life.