Dietary Therapy for Epilepsy

Mass General’s Center for Dietary Therapy, part of the comprehensive pediatric epilepsy program, is one of the largest in the United States, with more than 300 children on a low glycemic index diet. Dietary therapy is prescribed most often for people with refractory epilepsy – those whose seizures have not been controlled despite trying multiple antiepileptic drugs.

Low Glycemic Index Diet

Mass General most often prescribes a Low Glycemic Index Treatment, a dietary alteration that induces very stable blood glucose levels while still allowing freedom in the kinds of foods kids can eat. The glycemic index is a measure of a food’s effect on blood glucose. This diet allows up to about 60 grams of carbohydrates per day, but only those with a low glycemic index, such as whole-grain bread. Watermelon is out, but strawberries, with a lower glycemic index, are in. There are no meal plans, and no weighing of foods. “Families can eat out, as long as they understand how to identify what the glycemic index of the food is, and adjust portion size," says Dr. Elizabeth Thiele, Director of the Pediatric Epilepsy Program at Mass General. "There is a lot more flexibility.”

Among the refractory epilepsy patients who arrive at Mass General, Dr. Thiele says, “about a third of that population will become seizure free on the diet, about a third will have greater than a 50% reduction.”

For the many families witnessing the first effective relief from seizures for their child, the diet often feels nothing short of miraculous. Dr. Thiele recalls one patient, "a young girl with severe cerebral palsy and really nasty epilepsy, who had never stood independently. After going on the diet, she walked down the aisle in church to her first communion. She is now a nationally ranked Special Olympics athlete.”

Modified Atkins Diet

The modified Atkins diet was first developed in 2003 as an alternative to the classic ketogenic diet. The modified Atkins diet is also high in fat and low in carbohydrates. Families following this treatment regimen no longer have to weigh and measure foods or follow specific meal plans. Daily carbohydrates are restricted to 10 grams per day for the first month and subsequently liberalized to 15-20 grams per day if 10 grams is too restrictive. This treatment can be started without a hospital stay and does not require an initial fast or any caloric or fluid restriction. Nearly two thirds of patients experience halve their usual number seizures after six months on the diet, and many are able to reduce their medication dosage.

Ketogenic Diet

The classic ketogenic diet was developed in the 1920s and grew from observations that fasting was an effective way to control seizures. When the body fasts, it draws on fat reserves for energy, forming ketone bodies that circulate in the blood. A strict ketogenic diet mimics that effect by reducing daily carbohydrate intake to 10 grams (less than half a slice of bread), while loading up on fats. The diet is effective, but can be difficult to follow: every meal has to be prepared with a gram scale, following specific recipes. That limitation severely restricts foods that kids like to eat and eliminates the possibility of going out to restaurants.

The ketogenic diet consists mostly of fats, with limited carbohydrates and the recommended daily allowance of protein. Dietitians carefully calculate individualized meal plans for patients based on their calorie and protein needs for growth and development, and their ketogenic diet ratio. The prescribed ratio refers to grams of fat to grams of protein and carbohydrates combined. The higher the ratio, the larger the percentage of fat in the diet.

Foods are weighed to the nearest tenth of a gram and are consumed in the prescribed ratio of fat to carbohydrates and proteins. A typical ratio of 4:1 means that the vast majority of calories come from fat, typically in the form of butter, cream, and mayonnaise. Although the diet is high in fat, excessive weight gain is avoided as it can affect the metabolic process of the diet. Dietitians also work to ensure that a patient receives sufficient vitamins and minerals to avoid deficiencies. It is also essential to routinely monitor the blood levels for any side effects from the diet.

As the body metabolizes high-fat foods, it produces chemical compounds called ketone bodies, resulting in a physiologic state known as ketosis. It also increases the acidity of the blood. Experts hypothesize that the presence of ketone bodies may be involved in the reduction of the abnormal brain activity responsible for seizures, but still very little is known as to the actual mechanisms of this process.

The ketogenic diet requires a short hospital stay and may require an initial fasting period under the supervision of a physician familiar with the treatment. Potential side effects of the diet include constipation, acidosis, and elevated serum lipids, as well as kidney stones. All of these are relatively easily mitigated provided the diet is administered properly.