triglycerides

Perhaps the perfect dietary fat for endurance athletes has finally been found. 'Medium-chain triglycerides' (aka MCTs) are unique fats which are absorbed from the digestive system more quickly than regular lipids, and scientific studies have linked MCTs with an increased metabolism of body fat, preservation of muscle tissue, and significant increases in metabolic rate. To make themselves look more attractive to finicky humans, MCTs don't allow themselves to be stored very easily as body fat, and some research has indicated that MCTs are not likely to end up in the fatty deposits which tend to clog the inside walls of your coronary arteries.

To make matters even more interesting, exercise scientists have long speculated that MCTs might promote improved endurance performances, primarily because MCTs can slip into the 'mitochondria' inside muscle cells much more readily than regular fats. Since muscles create most of the energy they need by breaking down fat and carbohydrate inside their mitochondria, MCTs' ability to enter the mitochondria quickly should increase energy production and help to conserve muscles' most precious fuel - glycogen.


They work when combined with carbo
Until now, however, MCTs' capacity to enhance exercise was speculative, but a new study at the University of Cape Town demonstrates that MCTs can indeed improve performances in certain situations. In the South African study, six experienced cyclists performed the same exercise test on three separate days. The test consisted of two hours of easy pedaling at just 60% V02max (about 73 per cent of maximal heart rate), closely followed by a 40-kilometre time trial completed as quickly as possible. During the three tests, the athletes consumed either a 10-per cent carbohydrate solution, a 4.3-per cent MCT beverage, or a drink which contained both 10-per cent carbos AND 4.3-per cent MCTs. In all cases, the subjects consumed 400 ml (14 ounces) of drink at the beginning of the test and then 100 ml (3.4 ounces, or three to four normal swallows) every 10 minutes thereafter.

The carbohydrate PLUS MCT drink produced the best performances during the 40-K time trial. With carbo plus MCT, cyclists needed just 65 minutes to complete the ride, versus 66:45 with carbohydrate alone and a sluggish 72:08 with only MCTs.

Why did adding MCT to the carbohydrate sports drink enhance performance? Basically, MCTs decreased glycogen depletion in the cyclists' leg muscles during the first two hours of the tests; the MCTs simply replaced glycogen as an energy source during those first two hours. As a result, when the cyclists pedaled along furiously during the 40-K trial, carbo-MCT athletes had more glycogen available to sustain their intense efforts.

It's important to bear in mind that the MCTs had to be ADDED to carbohydrate in order to shore up performance; the MCT-only drink produced terrible results. The trouble with using MCT alone is that it can conserve glycogen, but it can't replace the carbohydrate that is already metabolised - only the carbohydrate in a sports drink can do that. Thus, sports drinks with carbohydrates and MCTs have a double effect: they decrease the 'burn' rates for glycogen and replace used-up glycogen. Beverages with just MCTs can only minimise burn rates.

However, don't get too excited about MCTs just yet, because the blessed things won't heighten all of your endurance performances. For one thing, the main fuel used by your muscles during competitions and strenuous workouts lasting less than three hours is carbohydrate, not fat. Thus, taking in MCTs would yield no, or very small, performance gains during such efforts, since your muscles would be 'tuned' to carbohydrate. It's only when your exercise lasts for more than three hours that MCTs can begin to really kick in.

The bottom line is that if you're going to be cycling, walking, skiing, swimming, or running for over three hours, MCTs can increase your endurance and upgrade your rate of speed, especially toward the tail end of your exertion. No one yet knows the optimal amount of MCTs to ingest during long-duration exercise, but a 4.3-per cent solution (along with the 6-10 per cent carbohydrate content), as utilized in the Cape Town study, may prove to be very effective. True, MCTs are found in 'bad' foods like coconut oil, but their use during competitions should do no harm to your health, and you can buy MCTs in pure form at your local health-food store. If you're a relatively slow marathoner or an ultra-distance competitor, using MCTs may improve your performances rather dramatically.

('Effects of Medium-Chain Triglyceride Ingestion on Carbohydrate Metabolism and Cycling Performance, ' Biochemistry of Exercise Ninth International Conference Abstracts, #38, p. 30, 1994)