Interest in medium-chain triglycerides (MCT) has grown rapidly over the last few years.
This is partly due to the widely-publicized benefits of coconut oil, a rich source of them.
Many advocates boast that medium-chain triglycerides (MCTs) can aid in weight loss.
In addition, MCT oil has become a popular supplement among athletes and bodybuilders.
Here is everything you need to know about MCTs, including what they are and what health benefits they may have.
MCT stands for medium-chain triglycerides, which are fats found in foods like coconut oil. They are metabolized differently than the long-chain triglycerides (LCT) found in most other foods.
MCT oil is a supplement that contains a lot of these fats, and is claimed to have many health benefits.
Triglyceride is simply the technical term for fat. Triglycerides have two main purposes — they are transported into cells and burned for energy, or stored as body fat.
Triglycerides are named after their chemical structure, more specifically the length of their fatty acid chains. All triglycerides are made up of a glycerol molecule and 3 fatty acids.
The majority of fat in your diet is made up of long-chain fatty acids, which contain 13–21 carbons. Short-chain fatty acids have fewer than 6 carbon atoms.
In contrast, the medium-chain fatty acids in MCTs have 6–12 carbon atoms.
These are the main medium-chain fatty acids:
- C6: Caproic acid or hexanoic acid.
- C8: Caprylic acid or octanoic acid.
- C10: Capric acid or decanoic acid.
- C12: Lauric acid or dodecanoic acid.
Some experts argue that C6, C8 and C10, which are referred to as the "capra fatty acids," reflect the definition of MCT more accurately than C12 (lauric acid) (1).
Bottom Line: Medium-chain triglycerides (MCT) are types of fatty acids containing 6–12 carbons. They include caproic acid (C6), caprylic acid (C8), capric acid (C10) and lauric acid (C12).
Because of the shorter chain length of the fatty acids, MCTs are rapidly broken down and absorbed into the body.
Unlike longer-chain fatty acids, MCTs go straight to the liver.
There they can be used as an instant energy source or turned into ketones, which are substances produced when the liver breaks down large amounts of fat.
Unlike regular fatty acids, ketones can cross from the blood to the brain. This provides an alternative energy source for the brain, which ordinarily uses glucose for fuel.
Because the calories contained in MCTs are more efficiently turned into energy and used by the body, they are less likely to be stored as fat.
Bottom Line: Due to their shorter chain length, medium-chain triglycerides are more rapidly broken down and absorbed into the body. This makes them a fast energy source and less likely to be stored as fat.
There are two main ways to increase the amount of MCT in your diet — through whole food sources or supplements such as MCT oil.
Whole Food Sources
These foods are the richest in medium-chain triglycerides, shown as the percentage of fatty acids that are MCTs (2):
- Coconut oil: Greater than 60%.
- Palm kernel oil: Greater than 50%.
- Dairy products: 10–12%.
Although the sources above are rich in MCTs, their compositions vary. For example, coconut oil contains all four types of MCTs, plus a small amount of LCTs.
However, its MCTs consist of greater amounts of lauric acid (C12) and smaller amounts of the "capra fatty acids" (C6, C8 and C10). In fact, coconut oil is about 50% lauric acid (C12), making it one of the best natural sources of this fatty acid.
Compared to coconut oil, dairy sources tend to have a higher proportion of capra fatty acids (C6, C8 and C10) and a lower proportion of lauric acid (C12).
In milk, capra fatty acids make up 4–12% of all fatty acids, and lauric acid (C12) makes up 2–5% (3).
Bottom Line: Whole food sources of MCTs include coconut oil, palm kernel oil and dairy products. However, their MCT composition varies.
MCT oil is a highly concentrated source of medium-chain triglycerides.
It is man-made, through a process called fractionation. This involves extracting and isolating the MCTs from coconut or palm kernel oil.
MCT oils generally contain either 100% caprylic acid (C8), 100% capric acid (C10) or a combination of the two.
Caproic acid (C6) is not normally included due to its unpleasant taste and smell. Lauric acid (C12) is often missing or present in only small amounts (4).
Given that lauric acid is the main component in coconut oil, be careful of manufacturers who market MCT oils as "liquid coconut oil," which is misleading.
Many people debate whether lauric acid reduces or enhances the quality of MCT oils.
Many advocates market MCT oil as better than coconut oil because caprylic acid (C8) and capric acid (C10) are thought to be more rapidly absorbed and processed for energy than lauric acid (C12).
Since C13 is a long-chain fatty acid and lauric acid (C12) is quite similar in structure, some experts argue that it might act more like a long-chain fat, making it less valuable.
Although evidence supports that lauric acid is more rapidly absorbed in the body than LCTs, one study suggests that lengthening the carbon chain by 2 carbons can slow down the rate of diffusion by 100 times (5, 6, 7).
Therefore, compared to other medium-chain triglycerides, lauric acid may be a slightly less efficient way to obtain energy. However, it also has unique health benefits.
Bottom Line: MCT oil is an easy way to get large concentrations of certain MCTs. It usually contains C8, C10 or a combination of the two.
Which Should You Choose?
The source best for you depends on your goals and the amount of medium-chain triglycerides you want.
It is not clear what dose is needed to obtain potential benefits. In studies, doses range from 5–70 grams (0.17–2.5 oz) of MCT daily.
If your aim is to achieve overall good health, using coconut oil or palm kernel oil in cooking is probably sufficient.
However, for higher doses you might want to consider MCT oil.
One of the good things about MCT oil is that it has virtually no taste or smell. It can be consumed straight from the jar or alternatively mixed into food or drinks.
Bottom Line: Coconut and palm kernel oils are rich sources of medium-chain triglycerides, but MCT oil supplements contain much larger amounts.
There are several ways that MCTs may help with weight loss, including:
- Lower Energy Density: MCTs provide around 10% fewer calories than LCTs, or 8.4 calories per gram for MCTs versus 9.2 calories per gram for LCTs (10).
- Increase Fullness: One study found that compared to LCTs, MCTs resulted in greater increases in peptide YY and leptin, two hormones that help reduce appetite and increase feelings of fullness (11).
- Fat Storage: Given that MCTs are absorbed and used more rapidly than LCTs, they are less likely to be stored as body fat (10).
- Burn Calories: Studies in animals and humans show that MCTs (mainly C8 and C10) may increase the body's ability to burn fat and calories (12, 13, 14, 15, 16, 17, 18).
- Greater Fat Loss: One study found that an MCT-rich diet caused greater fat burning and fat loss than a diet higher in LCTs. However, these effects may disappear after 2–3 weeks once the body has adapted (18).
- Low-carb Diets: Very low-carb or ketogenic diets are a effective ways to lose weight. Given that MCTs produce ketones, adding them to your diet can increase the number of carbs you can eat while staying in ketosis.
Bottom Line: MCTs may aid in weight loss through reduced calorie intake, increased fullness, less fat storage, improved calorie burning and increased ketones on low-carb diets.
While many studies have found positive effects of MCTs on weight loss, other studies have found no effects (19).
In a review of 14 studies, 7 evaluated fullness, 8 measured weight loss and 6 assessed calorie-burning.
Only one study found increases in fullness, while 6 studies found reductions in weight and 4 found increased calorie burning (20).
In another review of 12 animal studies, 7 reported a decrease in weight gain and 5 found no differences. In terms of food intake, 4 detected a decrease, 1 detected an increase and 7 found no differences (21).
In addition, the amount of weight loss caused by MCTs is actually very modest.
A review of 13 studies found that on average the amount of weight lost on a diet high in MCTs was only 1.1 lbs (0.5 kg) over 3 weeks or more when compared to a diet high in LCTs (19).
Another study found that a diet rich in medium-chain triglycerides resulted in a 2-lb (0.9-kg) greater weight loss than a diet rich in LCTs over a 12 week period (22).
Further high-quality studies are needed to determine how effective MCTs are for weight loss and what amounts need to be taken to experience benefits.
Bottom Line: A diet high in medium-chain triglycerides may help with weight loss, although the effect is generally quite modest.
MCTs are thought to increase energy levels during high-intensity exercise and serve as an alternative energy source, sparing glycogen stores.
This may positively affect endurance and have benefits for athletes on low-carb diets.
One animal study found that mice fed a diet rich in medium-chain triglycerides did much better in swimming tests than mice fed a diet rich in LCTs (23).
Additionally, consuming food containing MCTs instead of LCTs for 2 weeks resulted in longer duration of high-intensity exercise among recreational athletes (24).
Although the evidence seems positive, there are not enough studies available to confirm this benefit, and the overall link is weak (25).
Bottom Line: The link between MCTs and improved exercise performance is weak and more studies are needed to confirm these claims.
The use of medium-chain triglycerides and MCT oil has been associated with several other health benefits.
MCTs have been linked to lower cholesterol levels in both animal and human studies.
For example, calves consuming MCT-rich milk had lower cholesterol than calves fed LCT-rich milk (26).
A study in 40 women found that consuming coconut oil along with a low-calorie diet reduced LDL cholesterol and increased HDL cholesterol, compared to women consuming soybean oil (29).
Improvements in cholesterol and antioxidant levels may lead to a reduced risk of heart disease over the long term.
One study in 14 healthy men reported that MCT supplements negatively affected cholesterol, increasing total cholesterol and LDL cholesterol (31).
Bottom Line: Diets high in MCT-rich foods like coconut oil may have benefits for cholesterol levels. However, the evidence is mixed.
MCTs may also help lower blood sugar levels. In one study, diets rich in MCTs increased insulin sensitivity in adults with type 2 diabetes (32).
Another study in 40 overweight individuals with type 2 diabetes found that supplementing with MCTs improved diabetes risk factors. It reduced body weight, waist circumference and insulin resistance (33).
However, evidence for the use of medium-chain triglycerides in diabetes is limited. More research is needed to determine its full effects.
Bottom Line: MCTs may help lower blood sugar levels by reducing insulin resistance. However, more research is needed to confirm this benefit.
MCTs produce ketones, which act as an alternative energy source for the brain and can therefore improve brain function.
Recently there has been more interest in the use of MCTs to treat or prevent brain disorders like Alzheimer's disease and dementia (34).
One major study found that MCTs improved learning, memory and brain processing in people with mild to moderate Alzheimer's disease. However, this was only effective in people containing a particular gene, the APOE4 gene (35).
Overall, the evidence is limited to short studies with small sample sizes, so more research is needed.
Bottom Line: MCTs may improve brain function in people with Alzheimer's disease who have a particular genetic make-up. More research is needed.
Other Medical Conditions
Because MCTs are an easily absorbed and digested energy source, they've been used for years to treat malnutrition and disorders that hinder nutrient absorption.
Conditions that benefit from medium-chain triglyceride supplements include diarrhea, steatorrhea (fat indigestion) and liver disease. Patients undergoing bowel or stomach surgery may also benefit.
Evidence also supports the use of MCTs in ketogenic diets treating epilepsy (36).
Bottom Line: MCTs are effective at treating a number of clinical conditions including malnutrition, malabsorption disorders and epilepsy.
MCT oil appears to be safe for most people.
It is not clear what dose is needed to obtain potential health benefits, but many supplement labels suggest 1–3 tablespoons daily.
There are currently no reported adverse interactions with medications or other serious side effects.
However, some minor side effects have been reported and include nausea, vomiting, diarrhea and an upset stomach.
These can be avoided by starting with small doses, such as 1 teaspoon, and increasing intake slowly. Once tolerated, MCT oil can be taken by the tablespoon.
Type 1 Diabetes and MCTs
Some sources discourage people with type 1 diabetes from taking medium-chain triglycerides due to the accompanying production of ketones.
It is thought that high levels of ketones in the blood may increase the risk of ketoacidosis, a very serious condition that can occur in type 1 diabetics.
However, the nutritional ketosis caused by a low-carb diet is completely different than diabetic ketoacidosis, a very serious condition caused by a lack of insulin.
In people with well-controlled diabetes and healthy blood sugar levels, the amount of ketones remain within a safe range even during ketosis.
There are limited studies available that explore the use of MCTs in type 1 diabetes. However, some have been conducted with no harmful effects (38).
Bottom Line: MCT oil is safe for most people, but there are no clear dosage guidelines. Start with small doses and gradually increase your intake.
Medium-chain triglycerides have many potential health benefits.
While they are not a ticket to dramatic weight loss, they may provide a modest benefit. The same can be said for their role in endurance exercise.
For these reasons, adding MCT oil to your diet may be worth a try.
However, remember that whole food sources like coconut oil and grass-fed dairy have additional benefits that are not found in supplements.
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