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The ketogenic diet is a high fat, adequate protein, low carbohydrate diet designed to mimic many of the biochemical changes associated with prolonged starvation. First developed in the early 1900s, and successfully used for the treatment of seizures in children during the 20s and 30s, the ketogenic diet was then gradually forgotten as new anticonvulsant medications were developed. The ketogenic diet has recently been ‘rediscovered’ and is achieving increasingly widespread use. Its modern day role as alternative management for children with difficult-to-control epilepsy is currently being re-defined.
The ketogenic diet is not a ‘fad’ or a ‘quack diet’, but rather is an alternative medical treatment for children with difficult-to-control epilepsy. The ketogenic diet should only be used under the supervision of a physician and a dietician.
Background
Fasting to achieve control of seizures was described in both the Bible and during the Middle Ages, but it was only during the early 1920s that scientific papers first appeared describing the beneficial effects of prolonged fasting for children whose epilepsy could not be controlled by the few medications then available. These papers claimed that starvation, drinking only water for 10 to 20 or more days, could result in control of seizures for prolonged periods of time.
During this era, when the metabolic effects of diabetes were also being studied, it was noted that the biochemical effects of fasting could be mimicked by eating a diet high in fat, but with insufficient carbohydrate to completely ‘burn’ the fats. The resulting ‘ash’ from the incompletely burned fat consisted of ketones in the blood. Multiple clinical papers during the 1920s and 30s reported that approximately a third of children taking this ‘ketogenic diet’ had their seizures largely controlled, a third had a substantial improvement in siezure control and a third received no substantial benefit. The mechanism(s) by which these ketone bodies, principally beta hydroxybutyric acid, decrease, or even, completely control, seizures in children remain(s) unknown even today.
After the discovery of phenytoin in 1938, attention turned from the ketogenic diet to the development of new anticonvulsant drugs. As new drugs were developed, the ketogenic diet was used less frequently, and since fewer dieticians were trained in the subtleties of the diet, it was used less frequently and often less successfully.
In 1994, the successful treatment of a child with difficult-to-control seizures led to widespread media attention and a re-awakening of interest in the diet in the United States.
What is the ketogenic diet?
The ketogenic diet is a high fat, adequate protein, very low carbohydrate diet which is carefully and individually calculated for each child. Calories are restricted and depend on the age and activity of the child. If properly calculated, the child should neither gain nor lose significant weight, but should grow normally for his/her stature and the weight should remain close to the ideal weight for height. If the child is overweight, calories are limited until the ideal body weight is approached. Fluids are also restricted, although for reasons which are less clear. The diet provides approximately 90 per cent of the child’s caloric requirement as fat (cream, butter, mayonnaise), one gram per kilogram of body weight as protein, and minimal carbohydrate intake. The diet must be supplemented with vitamins and calcium.
What does the diet do?
The diet was designed to simulate many of the metabolic effects of starvation. During starvation, the body first uses its store of glucose and glycogen, then begins to burn the stored body fat. When there is not sufficient glucose available, the fats cannot be completely burned and ketone bodies (acetoacetate and beta hydroxy butyrate) are left as the residue of incompletely burned fat. The ketogenic diet provides exogenous fats (fat from outside the body) for the body to burn, but limits the available carbohydrate so that ketone bodies build up. It is the high level of these ketones which appear to suppress seizures.
So what do these children eat?
The children are only permitted to eat the prescribed, carefully calculated meals. While the portions are small, the ketosis suppresses appetite and thirst and after a short period of adjustment children are rarely hungry. While a common reaction to the concept of such a high fat diet both from physicians and others is 'Yuck', well prepared ketogenic meals can be both tasty and appealing.
A typical breakfast might include a mushroom omelet with several slices of bacon and hot chocolate made with 36 per cent cream. Lunch might include celery stalks filled with peanut butter or cream cheese, lettuce with mayonnaise and a slice of tomato, and a caffeine-free diet soda. Dinner might include a weighed portion of hot dog with ketchup or mustard, lettuce and mayonnaise, a whipped cream sundae with a strawberry and a diet soda.
How effective is the diet?
While the effectivess of the diet has been documented in many older studies, it remains equally effective today in children with difficult-to-control seizures, despite the introduction of many new anticonvulsants. A current study from Johns Hopkins (published in Pediatrics, December 1998) evaluated the effectiveness and tolerability of the diet in 150 consecutive children which were outstanding.
It should be noted that 71 per cent of those starting the diet remained on it for more than six months and more than half remained on the diet for one year. If the diet was effective in decreasing the seizures it was, in general, well tolerated, and the most frequent reason for discontinuing the diet was that it was insufficiently effective to warrant the dietary restrictions. The diet was equally effective at different ages and in children with varying seizure types.
Frequently asked questions about the diet
Who should try the diet?
The ketogenic diet is an alternative therapy for children who have difficult-to-control epilepsy. We have defined difficult-to-control epilepsy as having more than two seizures per week despite the appropriate use of more than two anticonvulsant medications. The diet has not been adequately studied in adults or in children under one year of age. Parents who think that the diet may be appropriate for their child should consult with their physician. The diet should never be attempted without medical supervision.
Will my child be able to stop taking anticonvulsant medications?
Our goal is to make all children on the diet both seizure-free and medication-free. Unfortunately this is often not possible. While some patients are able to gradually discontinue medications while on the diet, many do not become seizure-free, and many require some continued medication.
How long must children remain on the diet?
Children whose seizures are completely controlled on this diet often discontinue it after being seizure-free for two years. Others continue the diet as long as they find it useful. If the diet is stopped, or the ratio decreased, and the seizures return, then the diet can either be re-instituted or the person can re-start medications.
How does the diet work?
It appears that the high fat intake combined with carbohydrate and caloric restriction result in ketosis. The current standard of care requires that the urine remains 4+ (160-180mml) for ketones. Recent evidence suggests that the serum ketone levels may be far more critical than those in the urine. While 4+ urine may be necessary for seizure control it may be insufficient for optimum control and calories may need to be further restricted or the ratio of fat to protein and carbohydrate may need to be increased. Studies of serum levels of ketones and their correlation with seizure control are in progress.
How the ketone bodies suppress seizures is unknown, but currently an area of investigations. However, suppression of ketosis by the administration of carbohydrates may quickly result in a recurrence of seizures.
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