Reviews various general matters relating to the ketogenic diet, and provides references.
Diabetic foods are generally not allowed (with the exception of sugar-free drinks), as they make a significant energy contribution to the diet. Diabetic chocolate can be allowed very occasionally (e.g. Christmas, Easter, birthday) provided that only a small amount (30g) is consumed on any one day. Sugar-free diabetic fruit gums can be used occasionally.
Party suggestions include eclairs (without chocolate topping) filled with cream, sugar-free plain cake (sponge cake recipe omitting the sugar), jelly made with sugar-free squash and gelatine.
If food taken on a special occasion exceeds the dietary allowances, it must be counterbalanced by the addition of extra cream or MCT.
Ketogenic enteral feeds
Enteral feeds should be based on the same total and percentage nutrient content as the oral diet.
On the classical diet double cream or Calogen will form the basis of the feed; on regimens containing MCT, Liquigen will be used. Protein and carbohydrate can either be added using skimmed or whole milk, or separate protein and carbohydrate modules (eg Maxipro and glucose polymer). It is important that a complete vitamin, mineral and trace element supplement (eg Paediatric Seravit is included in the feed.
Give frequent drinks of carbohydrate-free liquids (e.g. sugar-free lemonade) for 24 - 48 hours. If the child is ill for more than 24 hours then medical advice should be sought.
It is important that intravenous dextrose is not given unless absolutely essential, as it can provoke convulsions. A low blood sugar in itself is not an indication for intravenous dextrose.
It is usually necessary to stop the fat and / or the MCT for a short period of time, particularly if the child is vomiting. If the child is unwell but is able to eat, then use exchanges with smaller bulk. If the child is unable to eat, give drinks such as milk or unsweetened fruit juice but avoid concentrated sugary drinks, while remaining within exchanges.
Slowly restart protein and carbohydrate or calorie exchanges after 24 hours, beginning with one quarter of the normal allowances. Exchanges can be increased over the next four days. At the same time reintroduce fat/MCT. If Liquigen is used a half strength dilution should be given initially, building up to full strength over 2-3 days. Where diarrhoea is a problem it may be necessary to begin with one quarter strength and build up over 4 - 5 days.
The diet is monitored by regular testing of urinary ketone levels, the overall aim being to produce a ketone level in the region of 3.9 - 7.8mmol/1. If an initial starvation period is not instigated prior to the commencement of the diet then testing for ketones should not be carried out until the diet has been followed for at least 10 days.
Testings should be undertaken twice a day; variations are usually seen with trace to small readings (1.5 mmol/l) in the morning and moderate (3.9 mmol/l) to large (7.8-15.7mmol/1) in the afternoon. In babies where a specimen cannot be collected the test can be done on a wet nappy, although the result is less accurate. A record of ketone levels should be kept as they can be correlated with seizure patterns. A sudden fall in urinary ketones is often an indication of illness or the initial stages of an infection; ketones will reappear on recovery.
If ketone levels are low or absent then the following points need to be checked:
That diet is being strictly adhered to - i.e. the prescribed number of foods is not exceeded, sweet or sugary foods are not being consumed, sugar containing drugs have not been prescribed.
The last intake of fat and/or MCT should not be consumed too early in the day - fat and MCT should be spread throughout the day; it may be necessary to give fat/MCT immediately before sleep to achieve a positive morning result.
Excess fluid should not be consumed - it may be necessary to impose a daily restriction of 1000 ml total.
If none of these factors apply the diet needs to be adjusted and the carbohydrate content reduced, either by reducing carbohydrate or calorie exchanges.
Duration and discontinuation of the diet
The diet should be followed for a minimum of three months, although insurmountable problems may result in its earlier cessation.
The diet is designed for children with intractable epilepsy and should not be considered a diet for life. The optimum duration of the diet is unknown and often the duration will be self-determined by the level of compliance. Research has shown any period between six months and four years as being of benefit to the child.
If the diet is continued for more than a few months it is necessary to re-evaluate energy and nutrient requirements regularly (six monthly) and to adjust the diet accordingly. Anti convulsant therapy may have been reduced during the period of the diet and the family may be reluctant to relax the diet.
When the decision is made to discontinue it is imperative that the dietary restrictions be released slowly over a 5-10 day period; the length of time taken should be determined by the length of time the child has been on the diet. A sudden increase in dietary carbohydrate or a drop in ketone levels can precipitate seizures and this is potentially dangerous.
The following steps to relax the diet are suggested:
reduce fat by 5g 10ml emulsion) each day until normal levels are reached
increase protein until normal size portions are reached
introduce unrestricted cows' milk after seven days
introduce increased quantities of carbohydrate foods after seven days, avoiding concentrated sugars
If at any stage the seizures reappear or become more severe, food consumption should revert to a stage where control was acceptable. Once the child is stable the relaxation of the diet should be resumed at a slower rate.
Ketogenic diets have a valuable role to play in the control of seizures in children with intractable epilepsy. They are however, complex diets to institute and follow and must only be contemplated where close medical and dietetic supervision is available.
Wilder RM The effects of ketonuria on the course of epilepsy. Mayo Cling Bull, 1921, 2 307.
Schwartz R Aynsley-Green A, Bower BD Clinical and metabolic aspects of ketogenic diets. Res Cling Forums 1980, 2(2) 63-74.
Schwartz Ruby M, Boyes S, Aynsley-Green A Metabolic effects of three ketogenic diets in the treatment of severe epilepsy. Developmental Med Child Meurol, 1989, 31 152 160.
Bower BD et al. The use of ketogenic diets in the treatment of epilepsy. Topics in Perinatal Medicine. London: Pitman, 1982
Schwartz RH et al. Ketogenic diets in the treatment of epilepsy; short term clinical effects. Developmental Med Child Neurol, 1989, 31 145 - 151.
Eaton I Epilepsy. In: Thomas B (ed.) Manual of Dietetic Practice. Oxford: Blackwell Scientific Publications, 1988: 489-497.
Livingston S. Dietary treatment in epilepsy. In: Comprehensive Management of Epilepsy in Infancy, Childhood and Adolescence. Springfield: Charles C Thomas, 1977: 111
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