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JUNE 5, 2011 * Nutrition
Nutrition Edge - Vol 3


Of the 21 amino acids, leucine has a special place in endurance exercise. Although amino acids are the building blocks of protein, leucine, in its free state, has a major impact on endurance as well as muscle recovery. Leucine belongs to a class called branched chain amino acids (BCAAs).  The other members of this group are valine and isoleucine.  In total, BCAAs compose about one-third of muscle protein. At one time, researchers believed that carbohydrate and fat were the only sources of muscle energy. However, in the mid ‘80s it was discovered that when exercise exceeds 40 minutes, BCCAs become an important fuel source, supplying up to 20% of muscle energy needs. Among the three BCCAs, leucine has a special role in this regard, being far more readily converted to energy than the other two.
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The muscles of endurance athletes really take a beating. During workouts, muscle cells are damaged by the strain of repetitive, intense contractions. The cell membranes are disrupted by free radicals produced through aerobic metabolism. Muscle proteins are broken down for use as fuel. And so on.
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The concept of diet quality gets surprisingly little attention. Much more attention is paid to things like the macronutrient composition of different diets (i.e. the proportions of carbs, fats, and proteins), the glycemic index of different diets, and restrictions such as meat and gluten avoidance. But research has clearly shown that the relative quality of one’s diet is the only thing that really matters. The typical vegetarian diet is only healthier than the typical omnivorous diet, for example, because it’s a higher-quality diet. But a high-quality omnivorous diet is just as healthy as a typical vegetarian diet.
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