By Mary T. Newport, M.D. June 2017

There is a common misconception that all saturated fats are bad and to be avoided, however, there is a unique group of fatty acids known as medium chain fatty acids that have special properties with significant health benefits that differentiate them from the longer chain saturated fats.  These fatty acids are not found in significant amounts in the typical high carbohydrate, low fat Western diet. 

Medium chain triglycerides (MCTs) have three  medium chain fatty acid molecules linked together by a glycerol molecule.  [JWS1] [o2] The medium chain fatty acids consist of 6- to 12-carbon chains [JWS3] with hydrogen and oxygen atoms bound to them [o4] and the length of the carbon chain affects the various properties of each fatty acid.   All of the medium chain fatty acids are fully saturated fats, meaning that all available docking sites are occupied by hydrogen atoms, but they behave very differently than the longer chain saturated fatty acids.

Abbreviation based on # carbon atoms in chain

Chemical Structure

Common Names

C:6

  CH3(CH2)4COOH

  caproic acid

  hexanoic acid

C:8

  CH3(CH2)6COOH

  caprylic acid

 octanoic acid

C:10

  CH3(CH2)8COOH

  capric acid

  decanoic acid

C:12

  CH3(CH2)10COOH

  lauric acid

  dodecanoic acid

MCTs are only produced in the human in the mammary glands of lactating women, making up 10-17% of the lipids in breast milk.  After weaning, MCTs must come from food, so for the infant, to mimic breast milk, MCTs are added to very many infant formulas as MCT oil, coconut oil and palm kernel oil.  Coconut oil is the richest natural source, containing up to 60% MCTs, followed by palm kernel oil, and is also present in the milk fat of other mammals, such as goats and cows.  On the other hand, there are no MCTs in other commonly used oils, such as olive, soybean, canola, safflower, or fish oil. There is a small amount of MCTs in palm oil, which is different from palm kernel oil.  MCT oil is usually extracted from coconut or palm kernel oil.  Most over-the-counter brands contain a formulation that is primarily C:8 and then C:10 with minimal amounts of C:6 and C:12.  However, it is possible to buy almost pure C:8 and recently other combinations of MCTs have become available.  MCT oil is also available in a powder form.

There are a number of differences between MCTs and the longer chain triglycerides (LCTs) that account for their efficiency in conversion to fuel for immediate use by brain, muscles and other organs and, as a result, provide significant health advantages.  Unlike the LCTs, MCTs do not require digestive enzymes (lipases and bile salts) to be broken apart, or packaging into chylomicrons to be transported from inside the intestine to the blood stream; MCTs are easily absorbed directly from the intestine and taken by way of the portal system to the liver, rather than into the lymphatic system.  Along with this easy absorption, MCTs appear to enhance absorption of other substances such as calcium, magnesium and amino acids, potentially providing a nutritional advantage for those who have an immature bowel, such as premature newborns, and people with impaired fat metabolism and malabsorption syndromes, such as biliary cirrhosis, Crohn’s disease, regional enteritis, celiac disease, or pancreatitis. 

The mitochondria are organelles inside of most cells in which adenosine triphosphate (ATP) is made.  ATP is the basic energy molecule that allows cells to carry out their many different functions.  Unlike LCTs, MCTs do not require carnitine for oxidation and easily pass through the mitochondrial membrane without enzymes or a shuttle system. Once inside the mitochondria, MCTs enter metabolic pathways to produce acetyl-CoA, which is oxidized by way of the tricarboxylic acid cycle or further converted to ketones, thereby leading to production of ATP. 

MCTs provide about 8.3 kcals per gram compared with 9.0 kcal for LCTs and, since they are converted directly to fuel for immediate use, are not stored as fat.  For this reason, MCTs are useful for people who have increased energy needs, such as those recovering from surgery, severe injuries or burns, or dealing with cancer.  MCTs also have been shown to increase physical endurance, and, coupled with the increased immediate energy availability, would be useful to those who desire to enhance their athletic performance, as well as the elderly or frail who, very literally, wish to have more energy.

In addition, compared to LCTs, MCTs are relatively thermogenic, meaning that they increase the metabolic rate and therefore more calories are burned over 24 hours.  A number of studies in animals and people have shown that much less fat is deposited by those consuming the high MCT oil diet compared to an equivalent amount of LCTs or when a high-fat diet or compared to eating a low fat diet.  Also, studies show that MCTs appear to suppress appetite, resulting in fewer calories consumed.  The net result is that a diet rich in MCTs could be useful as a weight loss or weight maintenance strategy, so long as they are substituted for other fats and/or carbohydrate in the diet and not simply added to the existing diet.[JWS5] [o6] 

Another unique property of MCTs is that they significantly increase the utilization of glucose that is mediated by insulin both in diabetics and non-diabetics, thereby potentially providing improved glucose control in the diabetic person and in people with other conditions that are complicated by insulin resistance. 

This leads back to further discussion of the idea of using MCTs, and the resultant ketones from their metabolism, as alternative fuels for the brain, skeletal and cardiac muscle, and other organs.  Ketones can readily be used as an alternative fuel, bypassing the initial steps in glucose metabolism and entering the tricarboxylic acid cycle to produce acetyl-CoA and ultimately ATP. When glucose is not readily available to burn as fuel, such as when glucose stores are used up during prolonged fasting or running a marathon, ketones can readily be used as an alternative fuel.  Ketones can also provide alternative fuel when glucose is ineffectively transported across the cell membrane, as in cells that are insulin resistant, since insulin is required for glucose to enter cells.  For the diabetic, this could provide some protection from the eventual organ deterioration that often occurs, affecting the eyes, kidneys, skin and other organs.

In recent years, MCT oil and coconut oil have come into popular use for people with Alzheimer’s disease, other dementias, Parkinson’s disease, ALS, and other neurodegenerative diseases in which there is decreased glucose metabolism in the affected areas of the brain and/or peripheral nervous system.  The idea here is that dietary ketosis through consumption of MCTs may effectively bypass the problem of insulin resistance and result in improved function and survival of the affected cells.  Relatively small studies of MCT oil in Alzheimer’s disease and mild cognitive impairment have shown improved memory and cognitive performance in nearly half of people who are given MCT oil, and several larger studies of MCT oil and also a pilot study of a coconut and MCT oil combination are currently underway.  In addition, MCT oil has been shown to protect cognition in brittle type 1 insulin-dependent diabetics during severe hypoglycemic episodes.

There are other properties of MCTs that appear to be beneficial to health.  As just one example, lauric acid (C:12) is known to have anti-microbial effects for various bacteria, such as h. pylori, the bacteria that causes ulcers, yeast, protozoa, and has even been shown to dissolve the lipid capsule of the herpes and HIV viruses.  It is one of the components of breast milk that is believed to protect the newborn from infection.  On the other hand, lauric acid supports the growth of normal gut flora.   When used for this reason, coconut oil, which is roughly 50% lauric acid, may be preferable to MCT oil.

In summary, the many unique properties of MCTs make a strong case for incorporating coconut oil, MCT oil, and other sources of MCTs in the diet on a daily basis.


 [JWS1]I’m not sure about MCTs but triglycerides in general can have different length and differently saturated fatty acid chains linked to glycerol.

 [o2]Okay, then to be safe should probably change it to take out “of the same” and make molecules plural.

 [JWS3]I changed what I wrote to 6-12 but newer papers for some reason say 6-10 and that lauric acid is only sometimes counted for some reason

 [o4]I have also seen only C:8-12 in other papers!

 [JWS5]I’m not sure we need to add this. Several studies show the satiating effects of MCTs and that when added to the diet people self-restrict calories in a dose dependent manner. This statement might put somebody off from trying it if they think they’ll have to cut out something else.  They will eat less without thinking about it.

 [o6]Unfortunately I have had a number of people tell me they added it to their diet and gained weight rather quickly and this discouraged them from continuing.  This actually happened to Steve - + 12 pounds over several months until we began to cut other sources of calories.  Now he is minus 15 pounds from his starting weight, but that took a couple of years.