Although several factors are considered necessary for its efficacy, the diet's exact mechanism of action has not yet been determined. It is known that a high level of ketosis must be reached. Traditionally, ketosis has been monitored by measuring urinary acetoaeetate. Measurement of blood ketones (eg, p-hydroxybutyrate) may give a more accurate picture of ketosis level although this is not feasible for routine outpatient care.
Strict adherence to the diet is essential since only a small variation in dietary intake can affect the maintenance of ketosis and thus seizure control. Food is usually divided into three meals per day. Intake between meals is restricted to those foods that provide little or no carbohydrates. These include sugar-free fruit-llavored drinks made w ith saccharin, sugar-free soda, water, or measured amounts of nuts or olives. The diet must be supplemented with a multivitamin and multimineral supplement as well as additional calcium. The carbohydrate content of all medications must be determined and calculated as part of the total carbohydrate content of the diet.'1
Table 30-1 describes variations of the ketogenic diet. There are two broad categories of ketogenic diets, based on the predominant fat source, either medium chain triglyceride oil or long chain dietary fats (cream, butter, oil. and margarine).
Table 30-1. Ketogenic Diet Variations
MCT Oil Diet
Cream Diet (Traditional Diet)
Introduced in 1971 by Huttenlocher6
Introduced in 1921 by Wilder7
Fat source MCT oil (60% of kcal) Long chain fat
kcal content RDA for age
75-80% of either
RDA or typical intake Restricted
Restricted only if necessary
Initiation of diet After 3 large urinary ketone readings
After 1 large urinary ketone reading
MCT = medium chain triglyceride; RDA = Recommended Dietary Allowance.
Diet initiation is best done in an inpatient setting, due to the real potential for hypoglycemia, dehydration, and acidosis. The child is fasted until urinary ketones, measured as acetoacetic acid on urinary dipsticks, are large (80 to 160 mg/dL). This usually occurs in 24 to 36 hours. Eggnog (composed of heavy cream, pasteurized egg. and artificial sweetener and flavoring) is given for the first 1 to 2 days to allow tolerance to develop to the high fat content of the diet. One-third of the estimated energy needs are given on the first day. and two-thirds on the second day. Once the full amount of calories are reached, either eggnog or real food may be served.
Meal plans are calculated to provide the determined amounts of carbohydrate, protein, and fat per meal according to their individual diet prescription (see instructions on calculating the diet prescription, below). This relationship of grams of fat to grams of protein plus carbohydrates is the ketogenic ratio. A ketogenic diet will typically have a 4:1 or 3:1 ratio. In a 4:1 ratio, there is four times as much fat as protein and carbohydrate. Computer programs are available for calculating meal plans. Table 30-2 illustrates a typical meal plan for a day on the ketogenic diet.
One of the attractions of the ketogenic diet is that its use may allow the reduction or discontinuation of antiepileptic medications, drugs that may have adverse side effects.
Table 30-2. Typical Day's Menu for an 8-Year-Old Boy
Diet: 1885 kcal 62.8 g Fat 8.5 g Protein 7 g Carbohydrate
57 g egg 47 g orange 51 g butter 55 g heavy cream
25 g cheese 72 g broccoli 35 g oil
55 g heavy cream
67 g hot dog 27 g grapes 35 g mayonnaise 50 g heavy cream
Nonetheless, the diet itself may result in a number of short-term and long-term complications for which all patients should be carefully monitored.4-8 y Table 30-3 reviews common possible side effects of ketogenic diet therapy and suggests steps for their prevention or treatment.
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