High Leucine

 

Intake Not Always Necessary

 

Leucine is a branched-chain amino acid that is vitally important for muscle protein synthesis and exercise performance. It is an important building block for muscle hypertrophy and is a trigger for a biochemical pathway (mTOR) that stimulates protein synthesis. A U.S. Army Research Institute of Environmental Medicine study found no difference in muscle protein synthesis in adults consuming 10 grams of essential amino acids plus 3.5 grams of leucine, compared to people given 10 grams of essential amino acids containing 1.8 grams of leucine. High intake of leucine appears unnecessary when people take sufficient quantities of essential amino acids. Higher leucine intake may be indicated during periods of intense exercise, starvation dieting and aging. (Nutrition Reviews, 69:550-557)

Melatonin

 

Influences Sex Steroids

 

Melatonin is a hormone released by the pineal gland that helps regulate sleep. Many animals reproduce better during periods of greater sunlight because they produce less melatonin. University of California, Berkeley researchers— in a study on birds— found that sex hormones were lower when melatonin levels were higher (during longer periods of darkness). Many bodybuilders take melatonin supplements to promote sleep. If the results of this study apply to humans, overuse of melatonin supplements could depress natural testosterone production. (Endocrinology, published online)

L-Carnitine L-Tartrate

 

Promotes Muscle Recovery in Middle-Aged Adults

 

L-carnitine L-tartrate is a popular supplement in some endurance athletes and bodybuilders. L-carnitine is an important chemical found in the mitochondria— the cells’ energy centers— where it helps break down long-chain fatty acids and promotes oxygen consumption. Intense weight training restricts muscle blood flow and oxygen delivery, which interferes with muscle cell function and damages cell membranes.

In young adults, L-carnitine L-tartrate supplements reduced chemical damage to tissues after exercise and promoted muscle tissue repair and recovery. Several studies found that L-carnitine L-tartrate promoted recovery and prevented free radical tissue damage in intensely training young men. A sophisticated study from the University of Connecticut, Storrs, led by Bill Kraemer, found similar results in middle-aged men. Muscle deterioration with age is a serious problem that decreases physical performance, quality of life, and can lead to premature death.

The study showed that L-carnitine L-tartrate reduced markers of tissue breakdown, free radical formation, and muscle soreness after exercise. The supplement had no effect on physical performance. (Metabolism Clinical and Experimental, in press; published online)