Also known as: Medium chain triglycerides, C8, Caprylic acid, C10, Capric acid, MCT powder
Fat MetabolismGood evidence
Fats with shorter carbon chains that are absorbed and used differently from ordinary dietary fat. The C8 and C10 distinction matters, and coconut oil is not a substitute despite what the marketing implies.
Typical dose
10.0–30.0 g per day
With or between meals; build the dose up gradually
What it is
Medium chain triglycerides are fats with 6 to 12 carbon atoms, against the 16 to 18 typical of most dietary fat. That shorter chain changes how they are handled entirely.
Four exist: C6 caproic, C8 caprylic, C10 capric and C12 lauric. C8 converts to ketones fastest and is the premium option. C10 is slower and cheaper. C6 is present in small amounts and causes most of the digestive trouble and the unpleasant taste.
C12 lauric acid is the important catch. Coconut oil is roughly half lauric acid, which is technically medium chain but behaves metabolically much more like ordinary long chain fat. A coconut oil product sold as an MCT is not delivering what a C8 product delivers, and the label word MCT does a lot of work in that gap.
How it works
Long chain fats require bile and pancreatic enzymes, are packaged into chylomicrons and enter the lymphatic system before reaching the bloodstream. Medium chain fats bypass all of that, absorbing directly into the portal vein and travelling straight to the liver.
In the liver they are readily converted to ketones, which is why MCT raises blood ketones within an hour or two regardless of whether you are eating carbohydrate. That is the basis of their use in ketogenic contexts.
They also enter mitochondria without needing carnitine transport, making them a quickly available fuel. This is a genuine metabolic distinction rather than a marketing one, though what it delivers in practice is more modest than the enthusiasm suggests.
What the evidence shows
The ketone elevation is well demonstrated and reproducible. If raising blood ketones is your goal, MCT does that reliably, and C8 does it fastest.
Body composition evidence is more modest. Meta-analyses have reported small reductions in body weight and fat mass when MCT replaces other fats in the diet, typically under a kilogram, alongside modest increases in energy expenditure and satiety.
Exercise performance findings are largely unimpressive, with most trials showing no meaningful benefit and several showing digestive problems that made performance worse. MCT is a useful fuel and a poor ergogenic.
Dosing
Start at 5 to 10 g and build up. Typical use is 10 to 30 g daily, split across servings.
Building up is not optional advice. Going straight to a large dose reliably produces cramping and urgent diarrhoea, and this is the single most common reason people abandon MCT oil. Tolerance improves considerably over one to two weeks.
Check the C8 and C10 breakdown. A product that says only MCT oil may be substantially C12, which is cheaper and does not do the same job. MCT powder is easier on digestion and usually bound to a carrier such as acacia fibre, so the actual oil content is lower than the scoop weight suggests.
With or between meals; build the dose up gradually
Competition status
Permitted — not on the WADA Prohibited List
Category
Fat Metabolism
Safety and side effects
MCT oil is a food fat and is safe. The dominant issue is digestive: cramping, nausea and diarrhoea, which are dose-related and almost entirely a matter of how quickly you built up.
Taking it on an empty stomach makes this worse. With food and built up gradually, most people tolerate it well.
It is calorie dense at around 8 calories per gram, which is worth accounting for if you are tracking intake. Anyone who has been told their liver is not working normally should speak to their doctor first, since MCT is processed there.
Who should avoid it
Build the dose up gradually to avoid significant digestive upset. Speak to your doctor before use if you have been told your liver is not working normally, since MCT is processed there. Account for the calories if tracking intake. Speak to your doctor if you take regular medication.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
