The Science of MCT Oils

by Mireille Najjar

While medium chain triglyceride (MCT) oils are known to be effective fat substitutes for those with abnormal fat metabolism and absorption, it is unclear whether these fats are effective in increasing energy expenditure and assisting in significant weight loss.

What are MCTs?

Medium chain triglycerides are fats that are naturally found in coconut and palm kernel oil. They have an unusual chemical structure and are easily digestible. Unlike most fats that are broken down in the intestine and remade into a special form that can be transported in the blood, MCTs are absorbed intact and taken to the liver to be used for energy. They are broken down in a manner similar to that of carbohydrates.

One of the unique advantages of MCTs is that they provide about 10% fewer calories than large chain triglycerides (LCTs) – approximately 8.3 calories per gram for MCTs versus 9 calories per gram for LCTs. Additionally, shorter chain length means that MCTs are more quickly metabolized as fuel for immediate use by organs and muscles.

Another advantage of the energy-enhancing properties of MCTs is that, unlike LCTs, they do not require the presence of carnitine, a compound critical in energy production. This results in the production of ketones, which form as a result of fat metabolism. MCTs as a source of ketone bodies make these fats a suitable choice for those with increased energy needs, such as during post-surgery, normal or stunted growth, and for enhanced athletic performance.

Scientific Evidence for MCTs

MCT oils are useful fat substitutes, especially for people with AIDS who need calories but are unable to absorb or metabolize normal fats. For instance, a 1997 double-blind, placebo-controlled study in the Journal of the American Dietetic Association reported that MCTs can help improve AIDS-related fat malabsorption in 24 men and women with AIDS. Another double-blind study in Nutrition found similar results in 24 men with AIDS-related fat malabsorption. Some studies also suggest that MCTs might be helpful for those who have trouble digesting fatty foods because they lack the proper enzymes; however, a 1996 study in the Scandinavian Journal of Gastroenterology found that taking digestive enzymes seems to be more effective.

It has also been reported that MCTs may prevent fat storage. A 2008 paper published in the Asian Pacific Journal of Clinical Nutrition noted that MCTs, particularly when used as cooking oil, might decrease storage of excess calories as fat, since they are immediately burned for energy. Some studies have also found that MCTs might enhance body composition, or the ratio of fat to lean tissue.

The possibility of MCT oil as a valuable energy source during high-intensity physical exercise has also been studied. Since MCTs are more easily digested than other fats, they may quickly produce large amounts of energy after being consumed, which can enhance an athlete’s performance during intense physical activity. Not all scientific data supports this notion, though; the NYU Langone Medical Center reported insufficient evidence to link the effects of MCTs on increased energy expenditure amongst athletes.

MCTs and Weight Loss

Although MCTs have been proposed as a weight loss aid due to their quick digestibility and large energy provision, there have been mixed results linking MCTs and weight loss. According to the NYU Langone Medical Center, studies have generally not supported the use of MCTs for weight loss. Other studies, however, suggest that there is a potential link between MCT consumption and weight loss outcomes. For instance, in a 2008 study in the American Journal of Clinical Nutrition, researchers found that over the four months, overweight subjects that received MCT oil while on a weight-loss plan lost more weight (around four pounds) than those who consumed olive oil and concluded that MCT oil can be useful to enhance weight loss. It is uncertain, though, whether these MCT users would have continued to lose more weight had they continued to consume the oil after the four-month study period. Other small studies that typically lasted one to four months also observed similar results—dieters who used small amounts of MCT oil lost more weight than dieters who used liquid vegetable oil.

In addition to weight loss, scientific studies have suggested that substituting MCTs for other fats in a healthy diet may help to suppress appetite and support healthy weight and body composition. For instance, in a 14-day 1996 study in the International Journal of Obesity and Related Metabolic Disorders, researchers noted that substituting an easily-metabolized fat, such as MCTs, for other fats such as LCTs, in high-fat diets can limit excess weight gain usually produced by energy-dense diets. MCT oil consumption could thus be advantageous for those who want to gain muscle mass and decrease body fat.

What Can We Conclude?

With all of the overlapping evidence, it is difficult to pinpoint the specific functions of MCT oil. While we may not yet know all the benefits of this unconventional fat, what we can extrapolate is that further research with more study subjects is needed to determine how beneficial MCT oil really is for weight loss and increased energy expenditure. It is also apparent that MCT oil can be particularly useful for those who are unable to metabolize and absorb conventional fats.

At this point, we can safely claim that MCT oil can be used as a dietary substitute for salad dressings, sauces, or cooking as a source of beneficial fatty acids.

Mireille Najjar is a first-year NUTCOM student who thoroughly enjoys learning more about the effects of ketosis on weight loss and epilepsy treatment.

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