A study from Australia showed that leucine helps athletes exercise longer (European Journal of Applied Physiology, August 2006), so now athletes are lining up to waste their money on supplements that are no more effective than any other source of sugar.

Leucine is a branched chain amino acid that the liver readily converts to sugar. Your body needs extra sugar during endurance exercise, and it doesn't care where it gets it. Your brain gets more than 95 percent of its energy from sugar in your bloodstream. It cannot store extra fuel in its cells. However, there is only enough sugar in your bloodstream to last three minutes. To prevent blood-sugar levels from dropping, your liver constantly releases sugar from its cells into your bloodstream. There is only enough sugar in your liver to last up to 12 hours at rest, and you run out of liver sugar much faster than that when you exercise.

Your liver then makes sugar out of certain protein building blocks called branched chain amino acids in a process called gluconeogenesis. So taking leucine, a branched chain amino acid, helps to maintain blood sugar levels, but so will eating any source of carbohydrates. Athletes buy special concentrated sugar gels, mineral-sugar drinks, and all sorts of expensive exercise foods. None are any more effective in prolonging endurance than ordinary food sources of carbohydrates such as a soda, an orange or banana, a peanut butter and jelly sandwich, a bagel, cookies or whatever you like.

Checked 9/29/08

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