Angelman syndrome is a complex neurological disorder characterized by delayed mental and physical development, speech impediments, frequent burst of unexplainable laughter, and seizures that usually start in children between 18 months and 2 years old.
To help control seizures, two types of diet are normally prescribed to Angelman patients: a ketogenic diet and a low glycemic index diet.
The ketogenic diet
A ketogenic diet is a high-fat, low-carbohydrate diet that can be helpful in controlling epileptic seizures. The classic ketogenic diet provides 3 to 4 grams of fat for every gram of carbohydrate. The body of a person on a ketogenic diet starts using fat bodies called ketones (hence the name ‘ketogenic’) as its primary fuel source instead of carbohydrates.
The ratio of fat to total carbohydrate and protein is carefully measured by a dietitian and monitored by a neurologist. Patients on a ketogenic diet also continue to take seizure medications.
The ketogenic diet has been shown to be beneficial in reducing seizures, but side effects such as the formation of kidney stones, high cholesterol levels, and constipation can occur. It is important that the patient’s blood and urine are monitored periodically for any signs of such problems.
Low glycemic index diet
The glycemic index (GI) of a food refers to the amount of blood sugar that the food raises compared to a standard reference. Foods with a GI of less than 55 are digested and absorbed slowly, whereas those with a GI above 70 are readily absorbed and rapidly raise blood sugar levels. Low GI food suggestions can be found here.
A low glycemic index (LGI) diet is similar to a ketogenic diet, and not only includes a high fat content but also carbohydrates (40-60 grams per day) with a low GI. Unlike the ketogenic diet, the LGI diet formula is only an approximation of food quantities, not measured as thoroughly as in the ketogenic diet.
An LGI diet is flexible as long as the carbohydrates used adhere to the low GI requirement. It is especially useful in individuals with low-intensity seizures. Regular follow-ups and blood tests are required to ensure that no side effects occur.
Other dietary formulations
A classic ketogenic diet is very strict in terms of fat-to-carbohydrate and protein ratios. Based on the severity of a person’s symptoms, the dietitian and the neurologist might prescribe certain diet modifications to allow for more carbohydrate and protein intake. Common modifications to the classic ketogenic diet include the modified Atkins diet (MAD) and the medium-chain triglyceride (MCT) diet.
In MAD, there is no fluid, carbohydrate, or protein restriction. The formulation of the diet is not weighed and measured, although it encourages a higher fat content with an approximate fat-to-carbohydrate and protein ratio of 1:1.
An MCT diet is a variation of the classic ketogenic diet, wherein oils made of medium-chain fatty acids are used instead of long-chain triglyceride (LCT) fatty acids. The MCT diet forms ketones much more easily than an LCT-heavy diet and, as a result, allows for additional carbohydrate and protein intake.
Clinical trials
An efficacy and tolerability study found that an LGI diet was effective in reducing seizures by more than 80% in five of six children with Angelman syndrome-related epilepsy.
Another clinical study (NCT03644693) also assessed the safety and tolerability of a nutritional formula supplemented with ketones in up to 15 children with Angelman syndrome and treatment-resistant seizures, ages 4 to 11. Results are not yet available.
Last updated: September 6, 2019
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