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The role of branched-chain amino acids in sport - by Doug Cook
Twenty amino acids are the building blocks of protein and the “construction material” of muscles, vital organs and virtually every other part of your body’s lean mass. Of the twenty, eleven can be made by the body via the recycling of old amino acids and the use of carbohydrate. The other nine are considered essential since they must be supplied from the food we eat and can not be synthesized by the body. Of these nine, three: leucine, isoleucine and valine, called Branched—Chain Amino Acids (BCAAs) serve as a critical source of muscle energy during exercise as well as a source of building blocks for muscle repair post exercise.
In fact, the very fibers that make up muscles are themselves "constructed" of these BCAAs [35% of total protein]. Unlike other amino acids, which are mostly metabolized in the liver, BCAAs are metabolized in the muscle tissue itself. Without a sufficient supply, your muscles begin to feel tired and sore during exercise. In contrast, a plentiful supply of BCAAs makes you feel energized—and helps muscles recover and rebuild much faster. And during and after exertion, two other amino acids, arginine and glutamine, work to synthesize proteins, remove harmful toxins and strengthen the body’s immune system.
There is a lot of research in the sport nutrition field on the beneficial role of BCAAs. A study in the February 2006 issue of the Journal of Nutrition found that giving athletes a drink containing various doses of amino acids, improved athletic performance based on various measurements. The supplement, a mixture of amino acids that included the branched-chain amino acids, and arginine and glutamine, was studied over time at several daily dose levels for extended periods of time (10, 30, and 90 days). Outcome variables included physical measures [maximal muscle load, biopsies etc] of muscle strength, fatigue and muscle damage, and blood indices of muscle damage and oxygen-carrying capacity. One beneficial effect of the amino acid supplement was a quicker recovery from the muscle fatigue that followed eccentric [negative phase of the contraction] exercise training. A dose-response study of the amino acid mixture at 2.2, 4.4, and 6.6 g/day for one month showed that at the highest dose, indices of blood oxygen-carrying capacity were increased and those of muscle damage were decreased at the end of the trial. When the amino acid mixture was given for 90 days to elite rugby players during training at a dose of 7.2 g/d, a blood-component analysis indicated improvements in the oxygen-carrying capacity of the blood.
During strenuous exercise such as long runs, or cycling, the body begins to decompose proteins and consume BCAAs in order to compensate for insufficient energy sources. The post-competition blood level of BCAAs may be decreased by 20% because of intramuscular BCAAs consumption in hard sports such as marathons, triathlons and cross-country skiing. This is due to the fact that strenuous exercise consumes and damages muscle tissues. However, that damage can be reduced with the use of BCAAs as a supplement and inhibit the lowering of muscular strength by replenishing BCAAs timely before or during the sport activity. Supplying BCAAs before and during exercise helps to spare muscle glycogen and fat and therefore helps to ‘stretch’ their supply of energy during exercise and seems to help maintain stamina and endurance for a longer period of time. Replenishing BCAAs immediately after the sport activity helps with recovery to mitigates muscle damage and to prevent delayed muscle soreness. In addition to BCAAs, arginine and glutamine also have positive effects on the body engaged in sport activities.
Arginine is closely related to the secretion of growth hormone. Growth hormone is important both for muscle building and for muscle repairing. Replenishment of arginine is considered to promote the synthesis of muscle proteins. Glutamine, an amino acid distributed abundantly in muscles, helps the synthesis of muscle proteins and inhibits their breakdown, as is the case with leucine. Since continuation of strenuous exercise requires glutamine in many organs, it is important to replenish glutamine when doing sports.
So how does one get enough BCAAs to take advantages of them? There are specific supplements designed to contained those that have been used in research and contain iso-leucine, leucine, valine and glutamine, and arginine such as Amino Vital™ www.aimo-vital.com . Alternatively, many foods naturally contain BCAAs, specifically dairy foods and whey protein [derived from milk], eggs and red meat such as beef. Getting the most of these important amino acids will require using them in their different forms. During strenuous exercise such as running and cycling, consuming a milk-based beverage is not idea due to delayed emptying and because they are too high in whole proteins and fat. Using a sport drink that contains BCAAs and a good source of carbohydrate such as Amino Vital Endurance™, which allow you take get the benefits of the amino acids, a good source of carbohydrate in an easy to drink and tolerate beverage. Immediately post exercise, you could use a milk-based beverage that not only has BCAAs but all the essential amino acids and carbohydrate which will aid in the synthesis of muscle glycogen and muscle proteins. Acceptable choices would be chocolate milk, a meal replacement drink like Boost™ or Ensure™, a couple of containers of yogurt or a homemade smoothie made with yogurt, milk or whey protein.
Doug Cook, RD MHSc CDE is a clinical dietitian and certified diabetes educator working at St Michael’s Hospital in Toronto. Doug at dc_dietitian@hotmail.com or visit his website www.wellnessnutrition.ca