Saturday, August 15, 2009
What is it? Medium Chain triglycerides (MCT's) are a type of lipid (fat). MCT's are different from other lipids because their length and structure differ from long chain fatty acids that are found in the normal diet. MCT's are technically a saturated fat with 8,- • carbon lengths, as opposed to long chain fatty acids which have 16, 18, or more, carbon lengths. MCT's are derived from the fractioning of other oils, usually coconut oil.
MCT's are fats with some unique biological properties from that of other lipids. They were originally designed for use with people with digestive disorders that caused malabsorption of long chain fatty acids.
MCT's are absorbed and utilized more efficiently than other fats. Long chain fatty acids we all know and love to eat must be transported in small fat-containing globs known as chylomicrons and then passed through the lymph system. MCT's, on the other hand, are transported through the small intestine into the portal blood and go directly to the liver to be burned as energy, thus bypassing the normal route for fats. MCT's can also bypass the carnitine shuttle system (see section on carnitine for more info) and can enter the mitochondria directly to be oxidized, or "burned," as energy. This is one of several reasons MCT's are less likely to be stored as body fat than long chain fatty acids.
MCT's may also increase thermogenesis (heat production) and preserve muscle mass during certain catabolic (muscle wasting) states such as cancer, burns, post surgical, HIV, and other ailments where trauma or disease contributes to a loss of muscle mass. MCT oil is often marketed to athletes as a sports nutrition supplement as it is a calorie dense energy source less likely to end up as bodyfat. MCT's are also sold as a weight loss supplement by some companies.
What does the research have to say?
MCT's have demonstrated a wide variety of effects in animals leading to less bodyfat storage and additional energy being lost as heat (i.e. thermogenesis). In both human and animal research MCT's seem to increase the thermic effect of food and increase daily energy expenditure (EE); which means the energy is lost as heat rather than stored as bodyfat. The substantial number of studies with animals would lead one to believe that MCT's may be a great dieting and fat loss aid for people.
There are also studies showing in severe catabolic states, such as burns, certain types of cancer, etc., that MCT's are helpful for maintaining nitrogen balance and muscle mass. A handful of human studies have shown the energy expenditure after eating MCT's is higher than for other types of fat, which would suggest that over time the use of MCT's should help with weight loss. Again, the few studies that have looked directly at the use of MCT's for weight loss are generally disappointing, finding no effects on weight loss.
Why? Some research suggests MCT's have a more pronounced effect on the release of the fat storing hormone insulin than other fats as well as having other effects that might counter its positive influence on fat loss. MCT's may have a sort of biphasic dual effect that cancel each other out.
One review paper on the topic theorized the reasons for this lack of effect. "Findings in support of the opinion (lower energy density, control of satiety, rapid intrahepatic delivery and oxidation rates, poor adipose tissue incorporation) may be invalidated by counteracting data (stimulation of insulin secretion and of anabolicTelated processes, increased de novo fatty acid synthesis, induced hypertriglyceridemia). The balance between these two opposing influences depends on the composition (energy intake, nature of ingredients, MCT/LCT ratio, octanoate/decanoate ratio) and duration of the regimen."
Translated, the positive effects of MCT's (increased burning of fats, decreases in hunger, the reduced likely hood of MCT's being made into bodyfat, etc.) may be offset by some potential negatives. Those negative may be an increased release of the fat storage hormone insulin, an increase in the production of triglycerides, and other factors.
The net effect may be no fat is lost, at least in humans, though more research is needed for definitive answers. MCT's have genuine medical uses where digestion of fats and various liver problems exist, as well as having possible anti catabolic (muscle sparing) effects in hospitalized patients.
MCT's are a supplement that just never took off with people. Athletes have used the products to one extent or another for many years, but MCT's have never been very popular in the sports nutrition arena either. The general feedback is neither very exciting nor very compelling for athletes or people trying lose weight.