MCT fats have ketogenic properties
The term "MCT" covers fats with medium-chain fatty acids. These fatty acids consist of a chain length between six and twelve carbon atoms. They are digested and metabolized differently from long-chain fats (LCT). For the most part, they are already digested in the mouth and then in the stomach. Because MCT fats are also water soluble, there is no micelle formation as with LCT fats, therefore MCT fats do not require bile to emulsify micelles or pancreatic lipase to split fats. MCT fats are transported as free fatty acids directly through the small intestine cells into the blood to the liver and mitochondria. Again, the fatty acids do not require carnitine as a transporter like long-chain fatty acids. Because of these properties, medium-chain fatty acids reach the liver much more quickly, where most of them are converted to ketone bodies. Thus, MCT fats have a higher ketogenicity than LCT fats, i.e. for the same amount of fat, more ketone bodies are formed and thus ketosis is increased.
Ketogenic effect of MCT fats is increased by coffee consumption, fasting, and emulsification of MCTs with beverages, whereas carbohydrate-rich meals can significantly reduce the ketogenic effect of MCT fats.
Due to the special properties (fast and direct transport to the liver) of MCTs, it is particularly important that their dosage is increased slowly. The intake of a large amount at once (> 15g) and without habituation can lead to gastrointestinal symptoms such as nausea or upset stomach. Therefore, it is recommended to increase the amount consumed slowly.
Practical tips for the dosage of MCT fats
- Start with a low amount (5 ml or 6g)
- If this dosage is well tolerated, the amount can be increased to 15 - 20 g
- Generally, 1 g MCT/kg body weight is well tolerated
- Emulsifying MCT fats (e.g., with a blender) can increase the absorption rate and reduce gastrointestinal distress
Source
Lin, T. Y., Liu, H. W., & Hung, T. M. (2021). The ketogenic effect of medium-chain triacylglycerides. Frontiers in nutrition, 8, 747284. https://doi.org/10.3389/fnut.2021.747284