Intractable epilepsy – of which Lennox-Gastaut is a prime example – refers to a type of epilepsy that doesn't respond to anti-epilepsy medication. In children who suffer from Lennox-Gastaut epilepsy, the use of the ketogenic diet is often the last resort to keep the child from suffering multiple seizures every day.
But the diet can be both dangerous and difficult to maintain.
What does the diet entail?
The ketogenic diet involves inducing a state of ketosis in the child by reducing carbohydrate intake drastically and increasing the intake of fats and proteins to compensate for the lack of carbohydrates.
The diet forces the body to burn fats for energy (nearly 80% of the diet's energy is derived from fat) – a process which produces chemicals called ketones.
For some reason that is not yet fully understood, the ketones that circulate in the body help to suppress epileptic seizures (Krause, 2000; Epilepsy Foundation, 2007). It's possible that ketones act like inhibitors of neurotransmission that prevents seizures (Krause, 2000).
However, the diet is not successful in all cases. About 30% of children with severe seizures will respond fully to the ketogenic diet, while 30% will experience a decrease in seizures, and 30% will not respond. We also don't yet know why the diet works for some children and not for others (Krause, 2000).
Initial ketosis is induced in children by starvation for 24 to 72 hours. During this period the child is usually hospitalised. Once a satisfactory state of ketosis has been achieved, the child is given the high-fat, high-protein diet.
There are two versions of the ketogenic diet: the older version, which reduces carbohydrate intake to a minimum, and a more recent version that makes use of medium-chain triglycerides (MCTs) to provide the high fat intake.
The latter diet is probably easier to apply because it allows small quantities of fruit and vegetables and doesn't require such strict attention to liquid intake. When the older ketogenic diet is used, the child must be partially dehydrated to ensure that the circulating ketones are not diluted. With the MCT diet, liquid restriction is less severe (Krause, 2000).
Important things to remember
The following vital points must be kept in mind when considering or applying the ketogenic diet:
- Don't ever put your child or yourself on a ketogenic diet without consulting a medical team that consists of an epilepsy specialist and a dietician.
- Don't stop your child's anti-epileptic medication without consulting the doctor who is treating him or her.
- The ketogenic diet will not work in all cases of intractable epilepsy.
- The ketogenic diet is difficult to apply and you're going to need the guidance of a dietician to help you work out how much food your child is going to eat. Generally, the energy content of the diet is reduced to compensate for the high fat levels. It's also important for the child to take a multivitamin and mineral supplement to ensure that he does not develop nutritional deficiencies. All these aspects will be addressed by your dietician. (Krause, 2000; Epilepsy Foundation, 2007)
Side effects of the ketogenic diet
The ketogenic diet can have a variety of side effects, including:
- Dehydration – this needs to be monitored very carefully as a certain degree of dehydration is necessary to make the diet effective, but excessive dehydration can have serious consequences.
- Constipation – this is due to the lack of dietary fibre in the diet caused by omitting fruit, vegetables, grains and cereals. The epilepsy specialist will have to prescribe a suitable, gentle laxative.
- Kidney or gallstones may develop because of the high fat content of the diet. Children need to be monitored regularly to check if they're developing kidney or gallstones.
- Vitamin deficiencies induced by omitting fruits, vegetables and grains. As mentioned before, the child needs to take a vitamin and mineral supplement.
- Increased blood cholesterol levels, particularly in children with an inborn defect in terms of cholesterol metabolism. This can have serious consequences and the medical team will monitor your child throughout her use of the diet.
- Refusal by the child to follow such a diet. The ketogenic diet is unpalatable and may make children feel marginalised because they cannot eat 'normal' foods. Behavioural counselling may be necessary to help the child manage her diet.
- Difficulty in applying the diet. Foods for each meal have to be carefully weighed and the volume of liquid the child drinks each day must be carefully controlled. Some parents may find it impossible to adhere to such a strict regimen, particularly if they work or are away from home often.
- Short duration. The ketogenic diet can generally not be applied for longer than two years. (Krause, 2000; Epilepsy Foundation, 2007)
Some tips to keep in mind
- The following foods are rich sources of fat: butter, cream, eggs and mayonnaise.
- Check all medications (and even toothpaste) to see if they contain sugar or carbohydrates, as even a small amount of additional carbohydrate can derail the diet.
- Encourage your child if she manages to stick to the diet and give her special ketogenic treats (e.g. ice cream made with cream and sweetened with artificial sweeteners).
- Get as much help as possible from the medical team.
- To find a dietician, visit the Association for Dietetics in SA website and click on "Find a Dietician".
- Visit the website of the American Epilepsy Foundation and search "ketogenic diet" to find more information on this subject.
The ketogenic diet has been around for more than 80 years and in some cases of intractable epilepsy, particularly in young children, it can work wonders. But it's not a diet that should be self-applied under any circumstances.
Text copyright: Dr I.V. van Heerden, DietDoc
12 November 2007
(Krause's Food, Nutrition, & Diet Therapy, 10th Ed. Eds. L K Mahan & S Escott-Stump, 2000. WB Saunders Co, Philadelphia; www.epilepsyfoundation.org/ 2007)
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