Herbs & Supplements:
Medium-Chain Triglycerides

Supplement Forms / Alternate Names
  • MCTs
Principal Proposed Uses
  • Difficulty Digesting Fat (Especially in AIDS), Performance Enhancement
Other Proposed Uses
  • Weight Loss, Epilepsy

Medium-chain triglycerides (MCTs) are fats with an unusual chemical structure that allows the body to digest them easily. Most fats are broken down in the intestine and remade into a special form that can be transported in the blood. But MCTs are absorbed intact and taken to the liver, where they are used directly for energy. In this sense, they are processed very similarly to carbohydrates.

MCTs are different enough from other fats that they can be used as fat substitutes by people (especially those with AIDS) who need calories but are unable to absorb or metabolize normal fats.

MCTs are popular among athletes as a performance enhancer, but there is no consistent evidence as yet that they are effective.

Sources

There is no dietary requirement for MCTs. Coconut oil, palm oil, and butter contain up to 15% MCTs (plus a lot of other fats). You can also buy MCTs as purified supplements.

Therapeutic Dosages

MCTs can be eaten as salad oil or used in cooking. When taken as an athletic supplement, dosages in the neighborhood of 85 mg daily are common.

Therapeutic Uses

Preliminary evidence suggests that MCTs are a useful fat substitute for those who have trouble digesting fat. This includes people with serious diseases such as AIDS who need to find a way to gain weight.^1,2 It might also be helpful for those who have trouble digesting fatty foods because they lack the proper enzymes (pancreatic insufficiency).³

MCTs are also popular among athletes as a concentrated source of easily utilized energy.^4,5,6

MCTs have also been used for weight loss, but the results of studies have been generally unimpressive.^7-10,29

What Is the Scientific Evidence for Medium-Chain Triglycerides?

Fat Malabsorption

A double-blind placebo-controlled study on 24 men and women with AIDS suggests that MCTs can help improve AIDS-related fat malabsorption.¹¹ In this disorder, fat is not digested; it passes unchanged through the intestines, and the body is deprived of calories as well as fat-soluble vitamins.

The study subjects were split into two groups: One received a liquid diet containing normal fats, whereas the other group received mostly MCTs. After 12 days, the participants on the MCT formula showed significantly less fat in their stool and better fat absorption than the other group.

Another double-blind study found similar results in 24 men with AIDS-related fat malabsorption.¹²

The body depends on enzymes from the pancreas to digest fat. In one study, individuals with inadequate pancreatic function due to chronic pancreatitis appeared to be better able to absorb MCTs than ordinary fatty acids.¹³ However, this didn't turn out to mean much on a practical basis, because without taking extra digestive enzymes they could only just barely absorb the MCTs; whereas, if they took digestive enzymes, they absorbed ordinary fats as well as MCTs without difficulty.

Athletic Performance

MCTs have been proposed as an "ergogenic aid," an energy-boosting supplement to enhance athletic performance. During intense exercise, your body first burns up available energy from the blood (in the form of glucose) and then starts to use energy stored in the form of a larger carbohydrate called glycogen. When the glycogen is depleted, exhaustion begins to set in.

One solution to this is carbo-loading, the practice of taking large doses of carbohydrates prior to exercise in order to increase glycogen stores. Athletes can also sip carbohydrate-loaded drinks during exercise.

MCTs may provide an alternative. Like other fats, they provide more energy per ounce than carbohydrates; but unlike normal fats, this energy can be released rapidly.¹⁴

A number of double-blind trials using MCTs for improving high-intensity or endurance exercise performance have been conducted, but the results have been thoroughly inconsistent.^15–21 This is not surprising, as none of these studies enrolled enough participants to provide trustworthy results.

Larger studies are necessary to discover whether MCTs are really as useful for athletes as its proponents claim.

Weight Loss

Some evidence suggests that MCT consumption might enhance the body's natural tendency to burn fat.^22,23,24 This has led to investigations of MCTs as a weight-loss aid. However, the results of clinical trials thus far have not been impressive.

In a 4-week double-blind placebo-controlled trial, 66 women were put on a very low-carbohydrate diet to induce ketosis.²⁵ Half of the women received a liquid supplement containing ordinary fats; the other half received a similar supplement in which the ordinary fats were replaced by MCTs.

The results indicated that the MCT supplement significantly increased the rate of "fat burning" during the first 2 weeks of the trial and also reduced the loss of muscle mass. However, these benefits declined during the last 2 weeks of the trial, which suggests that the effects of MCTs are temporary.

In other trials, substitution of MCTs for ordinary fats in a standard low-calorie diet failed to enhance weight loss.^26,27,29

Safety Issues

Studies in animals and humans tell us that MCTs are quite safe when consumed at a level of up to 50% of total dietary fat.²⁸ However, some people who consume MCTs, especially on an empty stomach, experience annoying (but not severe) abdominal cramps and bloating.

The maximum safe dosage of MCTs in young children, pregnant or nursing women, or people with serious kidney or liver disease has not been established.

Last reviewed March 2002 by Medical Review Board

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