Medium-Chain Triglyceride (MCT) Diet

The medium-chain triglyceride (MCT) diet is a form of dietary therapy for epilepsy. Unlike the classic ketogenic diet, it includes a supplement called MCT oil, which contains fatty acids called medium-chain triglycerides. These fatty acids are more “ketogenic” than the fatty acids usually found in butter and oil. This means that children taking the MCT diet can eat a wider range of food, including more carbohydrate, and still be in a state of ketosis.

Benefits of the MCT diet

Although it does not work for every child, the MCT diet has been shown to reduce seizures in many children. In some children, it may eliminate seizures altogether. The MCT diet has been studied in comparison with the classic ketogenic diet, and has been shown to give similar levels of seizure control.

Compared with the classic ketogenic diet, the MCT diet allows more calories, more carbohydrate, larger portion sizes, more fruits and vegetables, and a wider range of food. For these reasons, it can be useful for picky eaters or children with large appetites. The diet is more balanced, so children need fewer vitamin and mineral supplements. Children taking the MCT diet are also less likely to have side effects such as kidney stones, low blood sugar, constipation, low bone density, and poor growth. Their ratio of “good” HDL cholesterol to “bad” LDL cholesterol tends to be better than with the ketogenic diet.

Because it takes time to build up the amount of MCT oil in your child’s diet, it may take a few months to judge whether the diet will be effective. If the MCT diet is successful in controlling seizures, it may be continued for several years under the guidance and monitoring of your child's doctor.

Limitations and side effects of the MCT diet

MCT oil is expensive, which is a barrier for many families. In addition, few dietitians are trained to use MCT oil, so this diet is not widely available.

In some studies, the MCT diet has been associated with side effects such as diarrhea, vomiting, bloating, and cramps. Other studies have found that these side effects can be reduced by increasing the amount of MCT oil in the diet slowly.

The MCT diet should not be used by children who take valproate, as there have been some reports that the combination causes liver failure.

Ask your child's doctor to explain all possible side effects, what you should watch for, and what action you should take for each one.

It is also important for your child to take specific vitamin and mineral supplements. Your child's doctor and dietitian can advise you on these.

Before deciding to try the MCT diet, it is important to note that:

  • More foods are allowed than with the classic ketogenic diet, but the diet is still very restrictive, especially for a child. The diet controls the type of food and the quantity of food. Some children may feel isolated at school because they cannot eat “normal” food.
  • The diet will not work unless it is followed carefully, and some children are unable or unwilling to follow it.
  • It can be time-consuming and tedious to prepare. This usually gets easier as families adapt to the new routine.
  • It might not work for some children, no matter how closely they follow the diet.
  • It is not safe for children with certain metabolic disorders, such as fatty acid oxidation defects.
  • The diet has some potentially serious medical side effects. Children must be followed closely by a doctor during treatment with the diet.

Starting the MCT diet

Before starting the MCT diet, your child will need a full evaluation. This will include a physical examination, with measurement of his height and weight and a number of blood and urine tests. The team will also ask for a diet history for your child, including what he eats at home, what he does and does not like to eat, how much he eats, whether you see any problems feeding him the diet, and whether your family has any cultural or religious food restrictions.

The MCT diet is usually started in the hospital. Your child will be admitted to hospital for a stay of 5 to 8 days. You may be asked to stop allowing any sweets for a week before admission, and to feed him a specific low-carbohydrate menu the day before.

As your child begins the diet, ketones will appear in the blood and urine. These will be measured at regular intervals. Your child's blood sugar will also be measured.

The MCT oil is gradually introduced over several days so your child’s body can get used to the change in food. Your child will be given “ketogenic shakes” containing milk, MCT oil, and protein powder, and then move to solid foods if this goes well. Your child will also take vitamin and mineral supplements.

While in the hospital, your child will be closely monitored with urine and blood tests, and your child will be watched for any side effects such as diarrhea or vomiting.

Learning to use the MCT diet

In the meantime, the team will train you on how to administer the diet. A dietitian will explain how to plan menus, what food to use, how to read nutrition labels, how to prepare the food, quantities, feeding times, and side effects to watch for. She will explain where to buy MCT oil and how to use it. She will give you vitamin and mineral supplements that your child will need, and explain where to buy more. She will also help you with strategies for dealing with problems you may encounter while your child is on the diet, including illness, hunger, refusing food, low blood sugar, and high or low ketones.

A nurse will train you on how to measure your child's blood sugar and urinary ketones and how to keep track of his body weight, fluid intake, and seizure activity.

After about 5 days in the hospital, once the diet is established, there are no complications, and you have been trained on the diet, the child is released from the hospital and you can continue the diet at home. The team will explain what to do if you have any questions.

Using the MCT diet at home

Sticking closely to the diet is very important to ensure your child has given it a proper try and to see if it can control your child's seizures. It will take several weeks or even months on the diet to see if it reduces your child's seizures. However, straying from the diet, for example by having a couple of extra cookies, can have an almost immediate negative effect. If you find the diet too restrictive, speak to your dietitian and doctor to discuss ways to alter it to make it easier to use. Changes to the diet could mean changes to content, quantity, or scheduling.

Children on the MCT diet require frequent monitoring, usually every month for the first few months and then usually every 3 to 6 months. Check-ups will include measurements of weight and height, as well as urine and blood tests.

Between appointments, you will need to keep track of your child's seizure activity, urinary ketone levels, blood sugar levels, fluid intake, and body weight.

Because your child is growing, the diet may need to be adjusted periodically to give him enough energy. As long as there are no side effects, the amount of MCT oil in your child’s diet will be gradually increased for better seizure control.

Some medications, including over-the-counter cough and cold medicines and IV fluids, have sugar (carbohydrates) in them. The dietitian will explain how to avoid using any medications with carbohydrates. Whenever you take your child to the doctor, or get a new prescription, you need to inform them that your child is on the MCT diet.

Discontinuing the MCT diet

After several years of well-controlled seizures, in consultation with your child's doctor and dietitian, the diet may be tapered off. Alternatively, if it is not working or you find it too restrictive, the diet may be tapered off or your child’s doctor may suggest switching to a different diet.

The MCT diet should not be stopped abruptly, as this may trigger seizures. It is usually tapered slowly, by giving 10% less MCT oil every 1 to 3 months and gradually increasing the amount of carbohydrate. Your child may be advised to avoid sweets and junk food even after stopping the diet. Your child's dietitian and doctor will work with you to discontinue the diet.

Elizabeth J. Donner, MD, FRCPC