Comment: The quality of evidence is downgraded by inconsistency (heterogeneity in patients and interventions), imprecise results (few studies for each comparison) and indirectness (short follow-up time, differences in studied patients).
A Cochrane review included 7 studies with a total of 427 children and adolescents and no adults. There was a remarkable portion of co-morbidities, e.g. cerebral palsy and mental retardation, among the patients. A meta-analysis was not possible due to the heterogeneity of the studies. Reported rates of seizure freedom reached as high as 55% in a 4 : 1 ketogenic diet (KD) group after 3 months and reported rates of seizure reduction reached as high as 85% in a 4 : 1 KD group after 3 months. One trial found no significant difference between the fasting-onset and gradual-onset KD for rates of seizure freedom and reported a greater rate of seizure reduction in the gradual-onset KD group. Studies assessing the efficacy of the modified Atkins diet (MAD) reported seizure freedom rates of up to 10% and seizure reduction rates of up to 60%. One study compared the MAD to a 4 : 1 KD, but did not report rates of seizure freedom or seizure reduction. Adverse effects were fairly consistent across different dietary interventions. The most commonly reported adverse effects were gastrointestinal syndromes. It was common that adverse effects were the reason for participants dropping out of trials. Other reasons for drop-out included lack of efficacy and non-acceptance of the diet. Although there was some evidence for greater antiepileptic efficacy for a 4 : 1 KD over lower ratios, the 4 : 1 KD was consistently associated with more adverse effects. No studies assessed the effect of dietary interventions on quality of life, or cognitive or behavioural functioning.
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