Dietary Therapy in Epilepsy
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Direct answer
The classic ketogenic diet is a high-fat, low-carbohydrate, adequate-protein prescription, computed as a ketogenic ratio of fat to protein-plus-carbohydrate of 3:1 or 4:1, that controls seizures in a substantial minority of drug-resistant children — roughly half achieve greater than 50 per cent seizure reduction — and it is the therapy of choice, ahead of any drug, in glucose transporter type 1 deficiency and pyruvate dehydrogenase deficiency. Practical variants have widened access: the medium-chain triglyceride diet, the modified Atkins diet with carbohydrates around 10 to 20 g per day, and the low glycaemic index treatment, the last two tolerable without hospitalisation. Screen before starting, because beta-oxidation defects, pyruvate carboxylase deficiency and porphyria are absolute contraindications in which the diet can be lethal.
What you must remember
- Ketogenic ratio 3:1 or 4:1 (grams of fat to grams of protein plus carbohydrate); 4:1 is more ketogenic but harder to tolerate, and infants often do well at 3:1 or 2:1 with added medium-chain triglyceride.
- Diet-of-choice indications: GLUT1 deficiency (seizures plus movement disorder, acquired microcephaly, low CSF glucose with low CSF lactate) and pyruvate dehydrogenase deficiency — where ketones bypass the blocked glycolytic pathway.
- Strong-syndrome indications: Dravet, Lennox-Gastaut, West syndrome refractory to hormones, myoclonic-astatic epilepsy (Doose), tuberous sclerosis-related epilepsy and febrile infection-related epilepsy syndrome.
- Efficacy benchmarks worth quoting: about half of treated children reach over 50 per cent seizure reduction, a minority become seizure-free, and response usually declares itself within one to three months.
- Contraindications: fatty acid beta-oxidation defects such as MCAD deficiency, carnitine palmitoyltransferase deficiencies, pyruvate carboxylase deficiency and porphyria; a history suggestive of these demands a metabolic screen before starting.
- Complications: early hypoglycaemia and acidosis, later constipation, growth faltering in the youngest, nephrolithiasis in roughly 5 to 7 per cent, dyslipidaemia, and selenium and zinc deficiency — the diet mandates micronutrient, calcium, vitamin D and often carnitine supplementation.
- Medication housekeeping: carbohydrate-laden syrups and suspensions break ketosis, so swap to sugar-free formulations — a detail examiners relish — and watch valproate-related carnitine depletion.
- Wean antiseizure drugs rather than celebrate the diet in isolation: the usual plan is diet initiation, seizure confirmation of response, then staged drug withdrawal.
Starting the diet, step by step
A four-year-old with Lennox-Gastaut on three drugs and weekly falls reaches the diet clinic. Step one is the pre-diet evaluation: seizure and medication review, growth assessment and a dietitian-led food history — in Indian kitchens the dietitian rebuilds meals around ghee, cream, oils, paneer and eggs, with coconut oil and medium-chain triglyceride supplements for vegetarian families. Step two is screening: basic metabolic panel including glucose, calcium, electrolytes, liver and renal profiles, lipid profile, urine for ketones and any suspicion-driven metabolic studies to exclude beta-oxidation disease. Step three, choose the format — for a school-aged child, many centres now start the modified Atkins diet at home, carbohydrate-limited to about 10 g per day initially and liberalised later, reserving classical 4:1 admission-based initiation for infants, tube-fed children or refractory status. Step four, teach ketone monitoring — urine dipsticks or capillary beta-hydroxybutyrate — with target ketosis and a sick-day plan, since illness, hidden sugars and vomiting disrupt it. Step five, audit at one and three months: seizure diary, growth, ketone readings, and the medication review for sugary syrups to be exchanged for tablets. Step six, set expectations — a three-month trial if tolerated, drug taper on response, and gradual liberalisation after about two years of control, with continued growth and bone surveillance.
Where students slip
The classic slip is treating the diet as a last resort of fringe value — its evidence in Dravet, Doose and GLUT1 deficiency is stronger than that of most add-on drugs, and in GLUT1 deficiency the diet outranks drugs entirely. The second is skipping the contraindication screen: a child who deteriorates into hypoketotic hypoglycaemia on the diet has a beta-oxidation defect, and the exam answer is to stop the diet and investigate, not to push the ratio higher. The third is forgetting that the diet is a calculated medical prescription — "just avoid sugar" is not the ketogenic diet, and pharmacists swapping a sugar-free formulation is part of its management.
Frequently asked questions
What is the ketogenic ratio?
The ratio of grams of fat to grams of protein plus carbohydrate, classically 3:1 or 4:1, individually adjusted for tolerance and age.
In which two disorders is the ketogenic diet the treatment of choice?
Glucose transporter type 1 deficiency and pyruvate dehydrogenase deficiency, where ketones bypass the defective energy pathway.
What are the absolute contraindications to the diet?
Fatty acid beta-oxidation defects, pyruvate carboxylase deficiency and porphyria — the diet can precipitate severe metabolic decompensation.
How does the modified Atkins diet differ?
It restricts carbohydrates to about 10 to 20 g per day with fat encouraged freely and protein unrestricted, needing no admission, fasting or strict weighing.
Which complication occurs in 5 to 7 per cent of children on the diet?
Kidney stones, warranting hydration counsel and monitoring alongside growth, lipids and micronutrient status.