The ketogenic diet (KD) is a high-fat, low-carbohydrate, and low-protein diet that is widely used to treat epilepsy in children. Although the KD has been shown to be efficacious in the treatment of childhood epilepsy, the long-term effects of the KD on brain development are not clear. The objective of this study was to examine the long-term effects of the KD on visual-spatial memory, activity level, and emotionality in immature rats after status epilepticus (SE). Weanling rats were subjected to lithium/pilocarpine-induced SE or saline injections and were then randomized to either the KD or regular rat diet, both fed ad libitum. One month later, rats were evaluated for visual-spatial memory in the water maze, activity level in the open field test, and emotionality with the handling test. Spontaneous recurrent seizures were measured using videotaping, and seizure susceptibility was tested with flurothyl inhalation. Brains were weighed and examined for mossy fiber sprouting and cell loss. Although rats treated with the KD were active and seemed healthy, their weight gain was substantially lower than that in rats that received regular rat diet. The KD reduced the number of spontaneous seizures but had no discernible effect on flurothyl seizure susceptibility. KD-fed rats, with or without SE, had significantly impaired visual-spatial learning and memory compared with rats that were fed regular diet. The KD had minimal effects on activity level and emotionality. Rats that were treated with the KD had significantly impaired brain growth. No differences in pathology scores between the KD and regular diet groups were seen after SE. Despite reducing the number of spontaneous seizures after SE, the KD resulted in severe impairment in visual-spatial memory and decreased brain growth, with no effect on mossy fiber sprouting. This study raises concerns about the long-term effects of the KD on brain development.
Abbreviations: BHB, β-hydroxybutyrate, KD, ketogenic diet, NoSE-Cont, no status epilepticus, control diet group, NoSE-KD, no status epilepticus, ketogenic diet group, P, postnatal day, SE, status epilepticus, SE-Cont, status epilepticus, control diet group, SE-KD, status epilepticus, ketogenic diet group
The ketogenic diet (KD) is a high-fat, low-carbohydrate, and low-protein diet that is now widely used to treat epilepsy (1-4). Although the diet has not undergone the rigorous evaluation process required for marketing of antiepileptic drugs, there is now a considerable body of evidence indicating that the KD is efficacious in the treatment of epilepsy (1, 2, 5, 6).
Despite the use of the KD over several decades, the long-term effects of the KD on cognition are not yet known. Anecdotal reports suggest improvements in alertness, cognitive function, and behavior (2), although impairments in patients have also been reported (7). In a prospective study on the effects of the KD, Pulsifer et al.(8) found that developmental quotients in children on the diet improved after 1 y. One of the difficulties in evaluating cognitive effects of the KD in children is that the diet is rarely continued in children who do not respond with a reduction in seizure frequency (5, 9). The improvement in cognitive function therefore may represent the effects of reduced seizures, a positive cognitive effect of the diet, or a combination of these factors. Because the KD is not administered to healthy children, it is unlikely that clinical studies will provide definitive answers about the effects of the KD on cognitive function.
In this regard, experimental animal models may provide insight into the effects of the KD on cognitive function. The KD is well tolerated by rats and has been shown by most authors to suppress seizures in some rodent models of seizures (10-17). In this study, we examined the cognitive and behavioral effects of the KD when administered to immature rats with and without a history of status epilepticus (SE). We report that KD treatment is associated with serious adverse effects on spatial learning and memory.