I Love Leucine

Jose Antonio

The amazing muscle- and power-building effects of amino acids

 Do you remember HMB? Many years ago it was touted as the true anabolic metabolite derived from the oh-so-pedestrian amino acid leucine. In the past decade the indications have become clearer that leucine probably exerts myriad effects related to protein anabolism. For instance, during exercise, muscle protein synthesis decreases and protein degradation and stimulation of branched-chain amino acid oxidation increase (the BCAAs are leucine, valine and isoleucine). The decrease in protein synthesis is associated with inhibition of protein factors that are regulated by intracellular insulin signaling and leucine concentrations.

In essence, both insulin and leucine are key regulators of muscle protein synthesis.¹ Leucine by itself increases that process.² By combining it with protein and carbohydrate, you get quite an anabolic supereffect.

For example, in one study eight male subjects were randomly assigned to three trials in which they downed drinks containing carbohydrate; carbohydrate and protein; or carbohydrate, protein and free leucine following 45 minutes of resistance exercise. The researchers discovered that plasma insulin response was higher in the leucine group than in the other two. Whole-body protein breakdown rates were lower, and whole-body protein synthesis rates were higher in both groups that got protein. Moreover, the addition of leucine resulted in a lower protein oxidation rate. To top it off, muscle protein synthesis, measured over a six-hour period of postexercise recovery, was significantly greater in the leucine group.³

Okay, this study looked mainly at short-term effects. What happens if you supplement with leucine? A recent study looked at the effects of dietary leucine supplementation on the exercise performance of outrigger canoeists. Thirteen competitive outrigger canoeists, 10 female and three male, underwent testing before and after six-week supplementation with capsules of either L-leucine or a placebo. Testing included anthropometry, 10-second upper-body power and work and a row to exhaustion at 70 to 75 of percent maximal aerobic power. Perceived exertion (RPE), heart rate (HR) and plasma BCAA and tryptophan concentrations were assessed.

What happened? Leucine supplementation resulted in significant increases in plasma leucine and total BCAA concentrations. Upper-body power and work significantly increased in both groups after supplementation, but power was significantly greater after leucine supplementation compared to the placebo. Rowing time significantly increased and average RPE significantly decreased with leucine supplementation, while the variables were unchanged with the placebo. Leucine supplementation had no effect on the plasma tryptophan-to-BCAA ratio, HR or anthropometric variables. Six weeks of dietary leucine supplementation significantly improved endurance performance and upper-body power in the outrigger canoeists without significant change in their plasma ratio of tryptophan to BCAA.⁴

So there you have it. Leucine regulates muscle protein synthesis and improves muscular power and endurance.

References

¹ Norton, L.E., and Layman, D.K. (2006). Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. J Nutr. 136:533S-537S.

² Lang, C.H. (2006). Elevated plasma free fatty acids decrease basal protein synthesis but not the anabolic effect of leucine in skeletal muscle. Am J Physiol Endocrinol Metab. [Epub ahead of print].

³ Koopman, R., et al. (2005). Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects. Am J Physiol Endocrinol Metab. 288:E645-53.

⁴ Crowe, M.J., Weatherson, J.N., and Bowden, B.F. (2005). Effects of dietary leucine supplementation on exercise performance. Eur J Appl Physiol. Published online October 2005. 1-9.

Editor’s note: You can listen to Dr. Jose Antonio and Carla Sanchez on their radio show Performance Nutrition, Web and podcast at www.performancenutritionshow.com.

Craving Crusher

Becky Holman

Research out of the University of Copenhagen shows that dark chocolate may help many people control food cravings. The scientists believe the bitter taste may signal the body to regulate appetite. About two bites after a meal may do it—that’s about 50 extra calories. The researchers also suggested that the steric acid content in dark chocolate slows digestion, so those few bites may help you stay feeling full longer.

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• Oranges have white stuff on them after you peel them, but don’t pick it off. It’s called albedo and contains vitamin C, flavones and soluble fiber.

• Green tea is included in many weight-loss supplements, and for good reason. A study showed that overweight exercisers burned 7 percent more belly fat when they drank green tea instead of another beverage with the same calories.

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A frequent criticism of the popular low-carbohydrate style of dieting is that not taking in enough carbs severely inhibits your exercise capacity. Even the most vocal proponent of low-carb dieting, Robert Atkins, M.D., warned in his first book, Diet Revolution, that athletes may have problems training hard under extreme low-carb conditions because the body can’t convert fat into the glucose, a sugar, rapidly enough to support the requirements of intense training. Anaerobic training, such as typical bodybuilding workouts, is fueled primarily by glycogen stored in muscles and liver, as well as glucose circulating in the blood. Since carbohydrates are the prime fuel for anaerobic training, not eating enough carbs would impede high-intensity training.

The Eat-Clean Diet for Men

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The Eat-Clean Diet for Men is different from other books in its category. For one thing, it’s written by husband and wife Bob Kennedy and Tosca Reno. It’s also printed on heavy glossy paper, every page in glorious color—and one of the authors is tied to hardcore bodybuilding. Bob is the publisher of

Frontal-Lobe Lube

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Research has shown that the B-vitamin choline we get in our diets is converted in the brain to citrocholine, a compound that boosts the firing efficiency of neurons in the frontal lobe, the area responsible for reasoning and memory. Citrocholine supplements are available, as are choline supplements. Foods highest in choline include fish, peanuts, cauliflower and egg yolks.

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