16 Dietary Therapies
The ketogenic diet and related diets used for epilepsy are medical treatments, not lifestyle diets. They change how the body makes energy, and they need the same careful supervision as a seizure medication. Please do not start one on your own. Your epilepsy team, including a dietitian trained in these diets, should guide every step.
16.1 What are dietary therapies?
Dietary therapies are carefully planned ways of eating that can reduce seizures in some patients with epilepsy. The best known is the ketogenic diet, which was developed about a century ago and is still in use today1. Over the years several versions have been created, ranging from very strict to more flexible. Together they are often called ketogenic diet therapies2.
These diets are usually considered for people with drug-resistant epilepsy, epilepsy that has not been controlled after trying at least two appropriate seizure medications3. For a few specific conditions, described later in this chapter, a ketogenic diet is the first and most important treatment rather than a later option.
Most people on a dietary therapy keep taking their seizure medications. The diet is added to their treatment rather than replacing it, although medications can sometimes be reduced later under the team’s guidance4.
16.2 How do they work?
Normally, the body runs mainly on sugar (glucose), which comes from carbohydrates such as bread, pasta, rice, fruit, and sweets. When carbohydrates are cut back sharply and fat is increased, the body switches to burning fat for energy instead. As it does this, the liver makes substances called ketones, which the brain can use as fuel. This state is called ketosis1.
Being in ketosis seems to make seizures less likely through several changes in the brain, including shifts in brain chemistry, in how brain cells use energy, and in the signals that pass between nerve cells. Researchers still do not fully understand every step of how this works1,5.
16.3 The different types of diets
All ketogenic diet therapies are high in fat and very low in carbohydrates. They differ in how strict they are and how much measuring they require. Your team will help you choose the one that fits your child’s age, medical needs, and family life2.
16.3.1 The classic ketogenic diet
The classic ketogenic diet is the strictest version. It is built on a ratio of fat to everything else. In a 4:1 diet, for every 4 grams of fat your child eats, they eat only 1 gram of protein and carbohydrate combined. A 3:1 ratio is a little less strict. About 90% of the calories in a classic 4:1 diet come from fat2.
Every meal and snack is planned by a dietitian, and food is weighed on a gram scale. This precision is a lot of work, but it gives the team close control over the diet. The classic diet is often used for infants, for children fed by a feeding tube, and for children who need the strongest possible effect; it is also the preferred form for children under two years of age2,6. Ready-made ketogenic formulas make the diet easier for babies and tube-fed children.
16.3.2 The medium-chain triglyceride (MCT) diet
Medium-chain triglycerides (MCTs) are a type of fat, usually given as an oil or emulsion, that the body turns into ketones especially easily. Because MCT fat produces ketones so efficiently, the MCT diet allows a bit more carbohydrate and protein than the classic diet2. The classic and MCT diets appear to work about equally well7. MCT oil can cause stomach cramps or diarrhea, so it is usually introduced slowly.
16.3.3 The modified Atkins diet
The modified Atkins diet is a more flexible option, with roughly 65% of calories from fat, 25% from protein, and 10% from carbohydrate8. Instead of weighing every food, families count the grams of carbohydrate eaten each day, usually starting at about 10 to 20 grams a day for children. Fat is encouraged at every meal, but there is no strict ratio, and protein and calories are not limited2.
Because it is easier to follow, the modified Atkins diet is a common choice for older children, teenagers, and adults2,9.
16.3.4 The low glycemic index treatment
The low glycemic index treatment (LGIT) is the most flexible of these diets. The glycemic index measures how quickly a food raises blood sugar. With LGIT, carbohydrates are limited to roughly 40 to 60 grams a day, and the carbohydrates eaten come from low-glycemic-index foods, generally those with a glycemic index below 50, such as most vegetables, whole grains, and some fruits1,2. It produces only mild ketosis, but many children still see a good reduction in seizures10. It is not recommended for GLUT1 or pyruvate dehydrogenase deficiency, where stronger ketosis is needed2.
| Diet | How strict? | What is measured | Often used for |
|---|---|---|---|
| Classic ketogenic diet | Most strict | All food weighed to a fat ratio | Infants, children under 2, tube-fed children, specific conditions |
| MCT diet | Strict | Food weighed, MCT oil added | Children who need more carbohydrate or protein, or more palatability |
| Modified Atkins diet | Moderate | Daily carbohydrate grams | Older children, teens, adults |
| Low glycemic index treatment | Least strict | Daily carbohydrate grams and food type | People who cannot manage stricter diets |
16.4 Who might benefit?
Dietary therapy can be tried for almost any type of drug-resistant epilepsy. Experts recommend offering it once two or three appropriate seizure medications have failed, rather than saving it as a last resort2.
For two rare metabolic conditions, a ketogenic diet is the treatment of choice. In glucose transporter type 1 deficiency (GLUT1 deficiency), sugar cannot get into the brain properly, and ketones give the brain the fuel it is missing11,12. In pyruvate dehydrogenase deficiency (PDH deficiency), the body cannot use sugar efficiently for energy, and ketones offer a way around the problem because they enter the Krebs cycle without needing pyruvate dehydrogenase13,14. If your child has one of these conditions, your team will likely recommend starting a ketogenic diet early15. These conditions are sometimes found through genetic testing.
Experts also consider dietary therapy especially worth trying in several other conditions where it often works well, including infantile spasms, Dravet syndrome, epilepsy with myoclonic-atonic seizures (Doose syndrome), tuberous sclerosis complex, Angelman syndrome, certain mitochondrial disorders, super-refractory status epilepticus, and children fed by a feeding tube2,16.
16.4.1 Who should not use a ketogenic diet?
A small number of rare conditions make a ketogenic diet unsafe. These are mostly inherited problems with how the body breaks down fat, such as fatty acid oxidation disorders, primary carnitine deficiency and related carnitine transport disorders, pyruvate carboxylase deficiency, and porphyria2,17. Before starting, your team will review your child’s history and may order blood and urine tests to make sure none of these is present.
16.5 How well do they work?
Dietary therapies clearly help many people with drug-resistant epilepsy, but they do not help everyone, and it is hard to predict in advance who will respond. In a landmark UK randomized trial, 38% of children on the ketogenic diet had their seizures cut by more than half after three months, compared with 6% of children who continued usual care18.
A Cochrane review that combined 13 randomized trials found that children on ketogenic diets were about three times more likely to become seizure-free and up to six times more likely to have a 50% or greater reduction in seizures than children on usual care, although most studies were small and the overall certainty of the evidence was low7. A network meta-analysis reached a similar conclusion, finding that the classic ketogenic diet, the modified Atkins diet, and LGIT each reduced seizures significantly compared with usual care, with no clear winner among them19.
Some children become seizure-free on the diet, but this is not the most common outcome. A more typical good result is fewer, shorter, or less severe seizures. Many families also notice their child seems more alert or better able to concentrate, sometimes because seizure medications can later be reduced under the team’s guidance.
Because the diet takes time to work, experts recommend a fair trial of about three months before deciding whether it is helping, though when the diet does work, improvement often appears within the first few weeks4.
16.6 Starting the diet
Before starting, you will meet with the epilepsy team, which usually includes a neurologist and a specialized dietitian, and often a nurse and social worker. They will check your child’s growth, review their medications, and order baseline blood and urine tests20. The dietitian will teach you how to prepare meals, read food labels, and plan for school, holidays, and eating out.
Some centres start the classic ketogenic diet in hospital over a few days so that your child can be watched closely while their body adjusts; others start it at home with frequent check-ins. More flexible diets such as the modified Atkins diet are almost always started at home20. In the past, children were asked to fast before starting, but a gradual start is just as effective and better tolerated, so fasting is no longer considered necessary4.
16.7 Living with the diet
16.7.1 Checking ketones
Your team will ask you to check ketone levels regularly, either with urine strips or with a finger-prick blood test, much like the blood sugar checks used in diabetes. Ketone levels help show whether the diet is being followed and whether changes are needed. Keeping a record of ketone levels alongside seizures helps the team see what is working.
16.7.3 Supplements
Because these diets limit many everyday foods, your child will need supplements to stay healthy. Most children take a carbohydrate-free multivitamin with minerals, along with extra calcium and vitamin D4,9. Some children need other supplements, such as carnitine, based on their blood tests.
16.8 Side effects
Most side effects of dietary therapy are manageable, especially when caught early, and most are temporary22. In the first weeks, the most common problems are constipation, vomiting, low energy, and hunger7. Your child’s team will check in often during this period to help.
Over months to years, the team will watch for other possible effects7,20,22:
- kidney stones
- high cholesterol or other blood fats
- slower growth in height or weight
- weaker bones
- acidosis, a buildup of acid in the blood that can cause tiredness, fast breathing, or vomiting
- low levels of certain vitamins or minerals
This is why regular clinic visits and blood and urine tests are an essential part of the diet. Drinking plenty of fluids helps lower the risk of kidney stones, and giving a medication called potassium citrate to all children at the start of the diet has been shown to reduce kidney stones23. If your child also takes a seizure medication such as topiramate (Topamax) or zonisamide (Zonegran), the team may watch for stones and acidosis more closely17. Do not stop or change any medication without first speaking with your epilepsy team.
Call your team if your child is vomiting, cannot keep food or fluids down, is unusually sleepy or hard to wake, is breathing fast, or has signs of a kidney stone such as blood in the urine or severe pain in the side or back. Illness can quickly throw off the balance of the diet, so ask your team for a sick-day plan before you need one.
16.9 Dietary therapy for adults
Dietary therapies are not only for children. Teenagers and adults with drug-resistant epilepsy can also benefit, and international recommendations for managing adults on these diets were published in 20219. In a randomized trial in people aged 10 to 55, 26% on the modified Atkins diet had a greater-than-50% reduction in seizures at six months, compared with 2.5% in the control group8. Adults usually use the modified Atkins diet or LGIT because these are easier to follow at work and in social settings. Success depends heavily on motivation and good support at home. Adults should also have their cholesterol and bone health checked regularly while on the diet9.
16.10 How long does the diet last?
If the diet is helping, children commonly stay on it for about two years before the team discusses whether to try stopping4. Some children, including those with GLUT1 deficiency, PDH deficiency, or tuberous sclerosis complex, stay on it much longer because their condition continues to depend on it4.
Many children who have done well keep their improvement in seizure control after the diet is stopped, although some have a return or worsening of seizures during or after weaning, so the team monitors closely throughout24. When it is time to stop, the diet is usually weaned slowly over one to three months (and sometimes longer) by gradually adding carbohydrates back, while the team watches closely for any return of seizures4,24. Never stop the diet suddenly unless your team tells you to, because an abrupt change can trigger seizures.
16.11 Is this the same as the popular “keto” diet?
Not quite. The keto diets popular for weight loss are based on the same idea, but they are much less precise and are not designed to control seizures. A medical ketogenic diet is carefully calculated for each person, uses specific supplements, and is monitored with regular tests25. Following a popular keto plan from a book or website is not a safe substitute and should not be tried as a seizure treatment without your epilepsy team.
16.12 Questions to ask your epilepsy team
If you are thinking about dietary therapy, these questions can help guide your conversation:
- Is my child a good candidate for dietary therapy?
- Which type of diet would you recommend, and why?
- Will the diet be started in hospital or at home?
- How often will we need clinic visits and blood tests?
- Which of my child’s current medications or products contain carbohydrates?
- What should we do if my child gets sick while on the diet?
- How will we know if the diet is working, and when will we decide?