The ketogenic diet as a treatment for intractable epilepsy

The ketogenic diet is a high-fat, low-carbohydrate diet that was developed in 1921 to treat epilepsy, but the mechanism of protection against seizures still remains vague. The goal of the ketogenic diet is to foster a continual production of ketones in the blood, by forcing the body to burn fat instead of glucose, as its primary source of energy. Ten to twenty percent of children using this diet have their seizures completely controlled, while half of the remaining 80% to 90% will have either a decrease in the frequency of seizures or a reduction in the number of anti-seizure medications.

One drawback to the diet treatment may include delayed growth. Growth is dependent on adequate energy intake, which may be lacking because carbohydrates are omitted and calories may be restricted up to 75% of the recommended energy allowance, to induce ketosis. In addition, vitamin and mineral deficiencies may develop if supplementation is not given on starting the diet. Contradictory findings with respect to growth outcomes have left clinicians with little direction in determining the risk-to-benefit ratio of the diet. Therefore, a group of researchers from Rush University examined changes in growth and seizure reduction and the relationship of these outcomes to urinary ketone thresholds of children, placed on the ketogenic diet.

Fifty-seven subjects, ages 1 to 26 years old, started the ketogenic diet at Rush University Medical Center between August 1995 and December 2001. Thirty-nine subjects stayed on the diet for six months. On referral to the ketogenic diet program, each family was trained in keeping a measured 3-day food diary. Height, length and weight measurements were taken at baseline and compared with those obtained at the 6- and 12-month clinic follow-up visits. The neurologist assessed changes in seizures at every follow-up visit. Percent seizure reduction was recorded for each subject at baseline and at the 12-month follow-up visit. Urinary ketone levels were based on daily records that were bought to clinic visits.

Height-for-age z scores significantly decreased from -0.30 to -0.99 among subjects on the diet for 12 months. Subjects with high ketones experienced a significant decrease in height-for-age z scores from -0.45 to -1.1, whereas subjects with moderate ketosis did not. Observed percent seizure reduction was similar to those of other published studies, with subjects with high ketosis being more likely to have better seizure control on the ketogenic diet at both 6 months and 12 months; this difference was not significant.

Subjects on the ketogenic diet showed a delay in growth. However, because the study had a 40% dropout rate, the findings manifest a serious selection bias. Even with the result of this and previous studies, practitioners and family members may be willing to accept the delayed growth if the ketogenic diet provides relief from daily seizures. More research is needed to evaluate the relationship between ketosis and growth.

Sarah Peterson, Christy Tangney, Erika Pimentel-Zablah, et al. Changes in Growth and Seizure Reduction in Children on the Ketogenic Diet as a Treatment for Intractable Epilepsy. JADA; 105:718-725 (May, 2005). [Correspondence: Sarah Peterson, MS, RD, Department of Clinical Nutrition, Rush University Medical Center, Suite 425, 1700 West Van Buren, Chicago, IL 60612. E-mail: Sarah_J_Peterson@rush.edu]


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