- Published14 Aug 2018
- Reviewed14 Aug 2018
Diets aren’t just for weight loss. What, how much, and even when we eat all affect the way our brains work. For people with epilepsy, diet can reduce the likelihood of seizures. Mackenzie Cervenka, a neurologist and director of the Adult Epilepsy Diet Center at Johns Hopkins Hospital, explains what the ketogenic diet is and how it can benefit people with epilepsy.
What is a ketogenic diet?
A ketogenic diet is a very high-fat low-carbohydrate diet that is designed to induce fat metabolism. When the body is depleted of glucose stores, it shifts to metabolizing fat and fatty acids, which produces compounds called ketones. Ketones cross through the blood-brain barrier and enter the brain, where they’re used as an alternative energy source.
The classic ketogenic diet used as far back as the 1920s is a four to one ratio (in grams) of fat to carbohydrates plus protein. That’s about 90 percent of calories coming from fat. We typically teach our patients a modified Atkins diet, which limits the net carbohydrate intake to 20 grams per day without any limitations on the amount of protein and fat they eat. Typically, about 60 to 70 percent of their daily calorie intake comes from fat. (That’s more than double what the USDA Dietary Guidelines recommend.)
Why do doctors recommend this kind of diet for people with epilepsy?
The ketogenic diet can reduce the frequency of seizures. In clinical trials of people with treatment-resistant epilepsy — meaning they’ve tried a number of antiepileptic medications and continued to experience seizures — the ketogenic diet typically reduces the number of seizures by 50 percent or more in half of patients. The number of patients that will go on to become seizure-free after adopting a ketogenic diet is much smaller — some studies say it’s as low as 0 percent of patients and in others it’s closer to 20 percent.
How does the diet reduce seizures?
During a seizure, networks of neurons fire when they are not supposed to. This can happen because the brain cells are more excitable and are releasing lots of excitatory neurotransmitters, like glutamate. Or it could be that neighboring brain cells aren’t able to suppress the spread of excitability like they normally would using inhibitory neurotransmitters like gamma-aminobutyric acid, or GABA.
The ketogenic diet reduces the amount of glutamate in the brain and enhances the synthesis of GABA, making it less likely for a seizure to occur. The diet can also reduce inflammation in the brain, and inflammation due to infections like meningitis, encephalitis, or autoimmune disorders can trigger seizures.
There have also been a couple of really interesting studies recently that examined how the ketogenic diet can alter the gut microbiome, the trillions of microorganisms inhabiting the digestive tract. These studies found the ketogenic diet can increase certain bacteria species that promote an increased proportion of GABA to glutamate in the brain.
Why do you think lifestyle modifications like the ketogenic diet can be important for people with epilepsy?
For patients with treatment-resistant epilepsy, the dose of a drug or combination of drugs necessary to stop seizures can sometimes cause significant sedation. I’ve seen instances where patients have been able to control their seizures, but their quality of life is really impacted by side effects.
In talking with my patients, a major part of epilepsy they struggle with most is the lack of control. They worry about going out in public and suddenly having a seizure — there’s just no predictability to it whatsoever, and I think that causes major anxiety. A diet is something in their environment they can control. They can be in control of their treatment and seizures, and I think that empowers them.
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