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MCT oil  

 

 

MCT oil is a potentially valuable addition to the ketogenic diet although its use is often misunderstood.

It is important to distinguish between MCT oil, and the MCT oil diet. MCT oil seems to be a "good" thing - the MCT oil diet is much more questionable.

MCT oil

MCT stands for medium chain triglycerides. Most naturally occurring fats are triglycerides - tri meaning that each molecule have three carbon chains. In the medium chain triglycerides each chain has 6 - 12 carbon atoms, and for the medically refined grades of MCT oil each chain has 8 - 10 carbon atoms. MCT oils occur naturally, and the most abundant source is coconut oil. Most MCT oil is refined from coconut oil.

MCT oil is a clear light coloured liquid with no flavour and low viscosity. It is often sold in an emulsified form, which is easier to digest, in this case it looks like a white milky liquid.

MCT oil is interesting because, when it is metabolised in the body, it behaves rather more like a carbohydrate than a fat. The fuel of preference for the body is carbohydrate, and the body will use up its store of carbohydrate before using other fuels. Carbohydrates are quick acting - athletes take glucose tablets to provide energy, the body heats rapidly when we drink alcohol - typically carbohydrates will be used within a few hours of eating, which is why we eat so frequently. By contrast, the primary role of fats is to store energy - animals fatten up to prepare for the rigor of winter. The body normally tries to store the fats we eat, but will use them as fuel if there is not enough available from carbohydrates; first it will use the fats in the food, and if these are insufficient it will start to deplete the fat storage in our body tissue. Fats metabolise more slowly and typically it will take a day or so for the fat content of food to be used. That is why we feel full after a fatty meal, and why it really is a good thing to line to stomach with milk before drinking - the fat slows down the metabolism of the alcohol.

Long chain fats (ie the normal varieties) are converted into chemicals called chylomicrons by the digestive system, and these are then transported around the body by the lymphatic system before entering the circulatory system. This is a relatively slow process, and so fats metabolise more slowly than carbohydrates. Unlike other fats, MCT oil does not go into the lymphatic system; instead it is transported directly to the liver where it is metabolised, so releasing energy quickly, just like a carbohydrate, and creating lots of ketones in the process.

MCT oil can be used as a source of fat in the classical ketogenic diet. It offers a number of advantages:

It also has some disadvantages:

We use MCT oil to increase the overall ketone level, and as a booster when ketones are low.

The MCT oil diet

This was introduced by Huttenlocher in the 1970s. A modified form of the diet was subsequently used in the UK by Schwartz.

A comparison of the diets by weight (Classical at 4:1, MCT oil as emulsion) gives:

Version

%RDA

MCT oil

Other fat

Carbs

Protein

Classical

75

none

80

10

10

MCT

100

63

7

20

10

Modified

100

38

24

25

13

A comparison by calories gives:

Version

%RDA

MCT oil

Other fat

Carbs

Protein

Classical

75

none

90

5

5

MCT

100

60

11

19

10

Modified

100

30

41

19

10

The MCT diet differs from the classical diet in three important ways:

The rationale for the MCT diet is that because the MCT oil is more "ketogenic", it is possible to increase the levels of carbohydrate and protein, and still achieve the basic objective of the diet. The increase in carbohydrates and protein enables a wider range of foods within the diet, and so makes it more "palatable".

Various forms of the MCT oil diet are described in the following sections:

There does not seem to have been very much in the way of comparison between the classical and MCT oil diets. The study usually referenced is by Schwartz, Eaton, Bower and Aynsley-Green. This compared the three diets for a sample of 55 children and 4 adults, over a three month period. It concluded that 81% of the sample showed a better than 50% reduction in fits, and that this was independent of the type of diet used. However, careful reading suggests that the results achieved were not very good for any of the three diets.

We have talked with Ruby Schwartz recently, and her recommendation now is to use the classical diet.

Dr Freeman is also not very complimentary about the MCT diet:

Although the MCT diet has been reported to be equally as effective as the classical ketogenic diet, this has not been our experience at Johns Hopkins. . . Many parents tell us that their child has already been on the ketogenic diet without success. On further questioning, this prior diet usually turns out to have been the MCT diet. We have found some children who continued to have seizures despite tolerating the MCT diet, but who subsequently responded well to the classical ketogenic diet. We have also seen many children and families who could not tolerate the MCT diet, but who did well on the classical ketogenic diet.

So the conclusion must be: MCT oil is a good thing to try, particularly if you have difficulties maintaining ketones, but treat the MCT diet with caution.

Notes on fats

The substance we commonly call fat is actually one of several substances which chemists and nutritionists classify as lipids. Fats are characteristically insoluble in water and dissolve only in certain solvents such as alcohol. Fats are similar in their composition to carbohydrates but provide a higher energy yield per gram. They contain somewhere between two to two and a half times more energy than carbohydrates. Unfortunately, fats are uneconomical in their use of oxygen for metabolism and are, as a result difficult to burn. The body requires fats to keep the skin in a healthy condition and the kidneys functioning normally. They are used in the construction of cell walls and they provide the transport mechanism for fat soluble vitamins (Vitamins A,D,E and K).

There are three classes of fats - triglycerides, cholesterol and phospholipids. Fats and oils found in food tend mainly to be triglycerides.

Triglycerides are composed of glycerol which is an alcohol, and three fatty acids chains. Triglycerides make up the majority of the fats we consume and store in our body. They are classified into three distinct groups - saturated, mono-unsaturated and poly-unsaturated. The classification of fats is linked to their chemical composition. Saturated fatty acids have a closed chemical structure, their carbon atoms being "saturated" with hydrogen, making it impossible for other compounds to link with them. Mono-unsaturated fatty acids have a single double bond and two free carbons to which other chemical bonds of hydrogen can occur. Finally, polyunsaturated fatty acids have two or more double bonds and have a number of free carbons to which links can be made. These double bonds make unsaturated fats more biologically active than the almost inert saturated fats.

The fatty acids which are components of triglycerides are made up of chains of carbon, oxygen, and hydrogen atoms of varying length. The length of the chains of carbon leads to these chains being classifies as short chain, medium chain and long chain triglycerides. Medium chain triglycerides have unique properties which make them more biologically available than other forms of fats. Medium chain triglycerides by-pass the usual route taken by fats which the body uses to make the energy available. Unlike other fats, which require the body to store them before use, Medium chain triglycerides require limited processing and are, as a result quickly available for use in the body's energy systems. Another significant feature of medium chain triglycerides is that the body is unable to store them as body fat no matter how much is consumed.

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(checked: )
(update 3.1: 18 July 2002)
(issue 3: 18 September 1997)