MCT: the new fuel for athletes?

I spent several years of my life (a while ago) investigating a potential role of MCT for athletes and because there appears to be a renewed interest in it, I want to discuss what evidence is available today.

MCT performance sport science exercise nutrition

Background

Medium chain triglycerides or MCT are sold as a supplement. It is usually a synthesized fat that is made from coconut oil. Often it is used to replace other fats in the diet because it is argued that MCT are not stored in the body. Therefore MCT could help athletes to loose body fat. It has been a reasonably popular supplement among body builders and other athletes have also become interested in it. There was a lot of talk about MCT in the early 1990s but some of this seems to have returned. MCT is also used as an extra energy source in various energy bars. This blog will discuss what MCT is and what is true and isn’t true about its use.

Benefits of MCT performance sport science exercise nutrition

What is MCT?

MCT is normally present in our diet in very small quantities and there are few natural sources that contain MCT. Most fats are long chain triglycerides (LCT). MCT is usually synthesized from coconut oil. MCT consists of a glycerol backbone with three medium chain fatty acids (MCFA) attached to it.


MCFA contain 8 to 10 carbons, whereas long chain fatty acids contain 12 or more carbons. Unlike most LCT, MCT are liquid at room temperature. This is in part the result of the small molecular size of MCT. MCT are more soluble in water. This greater water solubility and smaller molecular size have consequences for its metabolism.


MCT is normally present in our diet in very small quantities and there are few natural sources that contain MCT

Effects of MCT

Here are some of the possible advantages of MCT:

  • MCT do not slow down gastric emptying. Whereas most fats are knows to keep food in the stomach longer and therefore delay delivery of nutrients, MCT do not seem to have this effect.

  • MCT are also rapidly absorbed in contrast to most other fats.

  • When long chain fatty acids reach the blood stream they are incorporated into large particles called chylomicrons. These chylomicrons travel through the body and deliver fatty acids to the tissues. This process is very slow and it is believed that these chyomicrons are not a great energy source for the muscle. When medium chain fatty acids reach the blood stream they do this as medium chain fatty acids and are transported very rapidly to the muscle. Some of the medium chain fatty acids are converted to ketones in the liver and ketones are then used as a fuel by the muscle.

  • MCT are rapidly used as a fuel. Within minutes after ingestion it is possible to see that the MCT has been oxidized in the muscle.


Carbohydrate plus MCT

When we started to look into MCT we wanted to see if MCT could be an additional energy source during exercise. Carbohydrate intake was important but could we add MCT to provide more energy and perhaps increase fat metabolism and spare muscle glycogen?