Back in the 1980s one of the most popular bodybuilding supplements was medium-chain triglycerides. Just about every top bodybuilder was ingesting MCTs. And their rationale made perfect sense. Before we get into that, however, it’s important to understand precisely what this stuff is to understand any bodybuilding advantages it may offer.
As the name implies, medium-chain triglycerides consist of a medium chain of carbons that vary from six to 10 in length, as opposed to short-chain triglycerides, which contain two to four carbons, and long-chain fatty triglycerides, which have 14 or more carbons. Long-chain triglycerides are by far the most common, with 97 percent of fats being found in that form. A familiar type of LCT is fish oil.
So what’s the big deal about how long a carbon chain is in a fat source? It has to do with absorption properties. LCT absorption involves a complex process. All triglycerides consist of fatty acids attached to a glycerol backbone. With LCTs, the triglycerides must first be separated from the glycerol backbone through the actions of a gut enzyme called lipase. The resulting free fatty acids form micelles, which are absorbed and then reattached to glycerol.
From there they travel through the lymphatic system to the bloodstream. In contrast up to 30 percent of ingested MCTs are absorbed intact across the intestine and go straight to the portal system and into the liver. Thus, MCTs are an express-route type of fat.
While LCTs require the presence of carnitine to be shuttled into the mitochondria, the portion of cells where fat burning occurs, MCTs do not. That equals much more rapid absorption and energy release from MCTs than LCTs. MCT are often called “the fatless fat,” since their rapid absorption into the body resembles that of carbohydrates more than fat.
MCTs easy uptake led to their medical use for treating fat malabsorption diseases, such as cystic fibrosis. In these diseases normal sources of fat cause gastrointestinal distress. So patients got MCTs in place of other fats in order to get needed calories. MCTs contain 8.3 calories per gram, compared to the nine per gram of other fats, about a 10 percent difference.
A tablespoon of MCT oil contains 110 calories and 14 grams of fat. MCTs are also used therapeutically with AIDS patients to stave off excess weight loss, since rapid weight loss is considered a harbinger of impending death in that disease. The same is true for cancer patients. In fact, MCT have been shown to lower levels of tumor necrosis factor-alpha in cancer patients, which is significant because high levels of TNF-a lead to excess muscle catabolism. Indeed, higher levels of this cytokine are also thought to play a role in the loss of muscle that occurs with age.
Besides their use in clinical medicine, MCTs have been extensively researched for application in both exercise and weight loss. From the standpoint of exercise, MCT supplements were suggested as a way to delay and extend the use of glycogen in the body.
Glycogen is a form of stored carbohydrate, and the glycogen that is stored in muscle serves as the primary fuel powering anaerobic exercise and sports, including weight training. The problem is that there is only a limited amount of muscle glycogen available, and once that is depleted, performance drops and fatigue sets in.
In endurance sports, when muscle glycogen depletion sets in, you “hit the wall,” with the muscles just ceasing to work properly. It’s akin to trying to run a car without gas. Since MCTs are rapidly absorbed and provide concentrated fuel, the idea was that taking MCT oil would spare limited muscle glycogen stores and thereby prevent premature energy lags in exercise as well as various sports, particularly endurance events.
While the theory was sound, the real-world testing of MCT oil for sports use proved disappointing. For one thing, the effective dose was found to be 85 grams, but taking that much without building up a tolerance led to extreme gastrointestinal distress—the mother of all stomach aches. Later studies showed that if you lower the dose of MCTs and combine them with carbohydrate, not only were most of the side effects eliminated, but the carbs seemed to work faster as well. The problem was that MCTs didn’t seem to spare glycogen stores as much as expected.
Taking MCTs with carbs also led to a greater use of MCTs for energy—in fact, the energy supplied by MCTs more than doubled when taken with a carb source. Still, their overall usefulness as an ergogenic aid didn’t live up to expectations.
The use of MCTs as a diet aid is another matter. That was the main reason they were taken by bodybuilders in the ’80s. They knew that MCT oil didn’t qualify as a source of essential fatty acids, since MCTs don’t contain any. What intrigued them was the fact that MCTs were so rapidly and smoothly absorbed, providing a readily available source of quickly burned calories with little or no chance of being converted into fat, unlike what happened with LCTs.
MCT oil offered a few other advantages not found in other fat sources. For one thing, it tended to boost thermogenesis, the conversion of calories into heat, which tended to boost resting energy expenditure, providing a metabolic boost. That’s a huge advantage when you’re on a diet.
MCTs also appeared to increase feelings of fullness, another potent plus for folks who are restricting calories. How they did that was somewhat of a mystery, since MCTs don’t affect the gut hormones that interact with the brain to control appetite. They did it is by boosting ketones.
Ketones are by-products of fat metabolism. They are metabolic acids, and because of that when produced in abundance, they can cause a type of metabolic acidosis that can be dangerous. Many diet books advise against going on very low-carb diets because of the increased ketone production that results. In fact, the chances of producing sufficient ketones to cause health problems while on a low-carb diet are remote. The type of acidosis that results from excess ketones usually occurs only with uncontrolled diabetes. From a bodybuilding standpoint ketones are advantageous for a number of reasons.
Ketones serve as an energy substrate stand-in for most tissues of the body, including muscle and brain. In muscles, ketones prevent catabolic effects that may otherwise result from restricting carbs. Some recent studies even suggest that the brain works better on ketones than it does on its usual primary fuel, glucose.
Ketones are also known to blunt appetite, making it easier to stay on a diet. It’s likely for that reason that head-to-head comparisons of high-carb to low-carb diets show that low-carb diets are more effective for fat loss and easier to adhere to. While restricting carbs alone will boost ketone production in the body, adding supplemental MCTs will boost it even more. In addition, the calories and rapid energy properties of MCTs will make low-carb dieting easier and also provide more energy for training.
Concerning the safety aspects of MCTs, the body can tolerate up to one gram per kilogram of bodyweight; however, taking a large dose of an MCT supplement before you are accustomed to it can result in severe stomach pains. It’s best to start with a smaller dose, about one-quarter tablespoon, then gradually increase the dose if you feel okay.
MCT oil isn’t good for cooking purposes as cooking changes the structure, resulting in a vile taste. It is a saturated fat, and some studies show that ingesting large amounts can adversely affect blood lipids, such as boosting low-density lipoprotein, a.k.a. the bad cholesterol. Still, the relationship of saturated fats to cardiovascular disease is a matter of controversy. Indeed, saturated fat also boosts high-density-lipoprotein cholesterol, which protects against cardiovascular.
In recent years, a combination of MCTs and LCTs, called “structured lipids,” has been suggested. The presence of LCTs prevents the rise of blood fats. Another possibility would be to take fish oil, an LCT that has established cardiovascular-disease-prevention effects. People who have liver disease should probably avoid using MCT oil, however, since it travels rapidly to the liver, and could add to liver stress.
So while MCT supplements don’t get the publicity that they did in the ’80s, they can still prove valuable for dieting purposes, especially for those on a lower carb plan. The lower the carbs, the more benefits you will get from supplementing with MCTs. Just don’t go overboard at the start.
Note that MCTs have made a recent comeback in a way, as coconut oil is being touted for all sorts of health benefits. MCT oil is largely derived from coconut oil and is the active ingredient in coconut oil, along with a fatty acid called lauric acid.