Leucine

One of the most frightening things about getting older is the seemingly unavoidable loss of strength, muscle and power. From age 25 to 50 the average male and female lose 10 percent of muscle and after 50, 1 to 1.4 percent every year.¹ Do those statistics apply, though, to masters bodybuilders and strength athletes? Do they have different nutritional needs for optimizing growth from what they needed when they were in their 20s?

A great deal of our research concerns why people lose muscle tissue after the age of 50 at an accelerated rate, how you can prevent that loss and, most important for the readers of IRON MAN, how older athletes respond to training. What we and others have found is that a blunted muscle-building response to the amino acid leucine plays a prominent role in muscle loss with age. That leads to practical info you can use to reverse the muscle-tissue aging process.

50-Year-Old Athletes and Resistance Training

Before delving into the central issue of amino acid supplementation for masters athletes, we want to address common questions: “I’m getting older, so is bodybuilding still for me? Can I still get results in the gym?” The answer is absolutely yes.

For example, studies indicate that men and women aged 50 to 100 can achieve 50 to 60 percent increases in muscle cell size,^2,3 60 to 260 percent elevations in isometric (handgrip) and dynamic (free weights and machines) strength^2,3 and 30 percent increases in power in short periods of time—12 to 16 weeks.⁴ If building muscle and changing your body are your goals, then those studies enable us to boldly declare that bodybuilding and strength training are for you, regardless of your age.

Nevertheless, studies indicate that the overall growth response to training is blunted compared to what young people experience.⁵ The reason may lie in how older athletes respond to the anabolic properties of their meals.⁶

Amino Acids—the Key to Muscle Tissue Growth

Every time you eat a meal containing carbohydrates, proteins and fats, you send out triggering signals that tell muscle tissue to build new proteins. The process of building new proteins is called protein synthesis. More than 80 percent of muscle-growth stimulation is actually triggered by the protein and amino acids in that meal.⁸ Proteins are made up of 20 amino acids, nine of which are termed essential because they cannot be produced in the body and therefore must be obtained through diet.

Only the nine essential amino acids are responsible for stimulating the building of new muscle from a meal. For example, one study found that six grams of essential aminos stimulated twice the protein synthesis that a dose of three grams of nonessential amino acids and three grams of essential amino acids did. Additional studies have shown that 15 grams of pure essential amino acids stimulated twice as much protein synthesis as 15 grams of a whole protein source, even though the calories were the same.⁹ That’s because whole proteins are a natural mixture of both essential and nonessential amino acids in roughly equal proportion.

Leucine, the Critical Element

The word anabolism is synonymous with growth. Clearly, essential amino acids are anabolic, but scientists have found that after the age of 50 people become resistant to their effects. Dr. Katsanos and his fellow scientists found that seven grams of essential amino acids stimulated protein synthesis in young people but completely failed to do so in older people. Does that mean that older people have lost the capacity to respond to amino acids? If so, then the muscle loss and the blunted response we see to resistance training are an inevitable consequence of aging. Fortunately, that is not the case. Senior trainees simply need a higher dose of critical elements in an essential-amino mixture.

Leucine appears to be the main essential amino acid responsible for protein synthesis.¹¹ It’s the only amino acid that can stimulate protein synthesis alone.¹² Because older people are resistant to the anabolic effects of amino acids, researchers investigated what would happen if they bumped up the leucine content from the original 1.7 grams to 2.8 grams in a seven-gram mixture.¹³ They found that the older people could stimulate protein synthesis to the same extent as young people. Research also shows that there are no differences in the building of muscle tissue between younger and older people at a dose of 15 grams of essential aminos.¹⁰

That implies that masters athletes can respond the way young athletes do, given a higher dose of amino acids.

Practical Implications

We commonly see people eating just oatmeal for breakfast or older athletes buying a “healthy” breakfast that contains about seven grams of protein, only half of which provide essential amino acids. Such eating patterns help explain much of the muscle loss and the blunted response to exercise that occur with age. Masters athletes should be taking in an amino acid mixture or whole protein that contains a minimum of 2.5 to three grams of leucine per serving. Some scientists say that it should be higher—3.2 to 4.3 grams¹⁴—as lesser amounts may result in no muscle growth. The higher leucine content brings them gains similar to those of their younger counterparts.

At a recent meeting of the International Society of Sports Nutrition, our colleague Layne Norton explained that you should be aware of the leucine content in various proteins. Beef, egg, casein, chicken, pork and fish are approximately 8 to 9 percent leucine, and whey protein is 12 percent leucine. For calorie efficiency a masters athlete can also take 15 grams of essential amino acids.

The next question is whether masters athletes should take leucine supplements. The answer is that while leucine increases protein synthesis by itself, it acts much faster when combined with other amino acids—25 minutes compared to 120.¹⁵ Leucine, isoleucine and valine are collectively called the branched-

chain amino acids. Taking leucine triggers the enzyme responsible for breaking down the other two BCAAs, and when their concentration is lowered, protein synthesis goes down as well. That’s why we advise taking either an entire essential amino acids mixture or a mixture of the BCAAs with leucine at a 2-to-1 ratio to each of the other BCAAs.

Based on the above studies, we recommend the following for masters athletes:

1) Eat four to five meals per day of animal-based whole protein sources. If that comes from meats, the leucine content will generally be 8 to 9 percent, and you’ll need about 40 grams to get three grams of leucine. If you use a whey protein supplement as well, you’ll need only 25 to 30 grams of whole protein.

2) Between meals we recommend two to three servings of either BCAAs with a minimum of three grams of leucine or 15 grams of essential amino acids with the same leucine content. The reason we recommend taking the supplements between meals is that they’re an extremely calorie-efficient way to add muscle without adding unnecessary fat.⁹ That’s particularly important for masters athletes, whose metabolisms may be lower than those of younger athletes.

The beauty of science is that it directly asks the difficult questions and then answers them with solid data. As researchers in the lab we can tell you that bodybuilding is a timeless sport, but only when you give your body adequate nutrients to support your hard work in the gym. Clearly the nutrient threshold shifts with age, but by countering that shift with adequate servings of essential amino acids, particularly leucine, you’ll recover as if you were 30 years younger.

Editor’s note: Gabriel Wilson is completing his Ph.D. in nutrition, with an emphasis on optimal protein requirements for muscle growth, and is a researcher in the Division of Nutritional Sciences, University of Illinois, Urbana. He is vice president of the Web site ABCBodybuilding
.com. Jacob Wilson is a skeletal-muscle physiologist and researcher in the Department of Nutrition, Food, and Exercise Science, Florida State University, Tallahassee. He is president of the Web site ABC
Bodybuilding.com.

References

¹ Larsson, L., et al. (1979). Muscle strength and speed of movement in relation to age and muscle morphology. J Appl Physiol. 46(3):451-456.

² Pyka, G., et al. (1994). Muscle strength and fiber adaptations to a year-long resistance-training program in elderly men and women. J Gerontol. 49(1):M22-27.

³ Singh, M.A., et al. (1999). Insulin-like growth factor I in skeletal muscle after weight-lifting exercise in frail elders. Am J Physiol. 277(1 Pt 1):E135-143.

⁴ Hakkinen, K., et al. (1998). Changes in muscle morphology, electromyographic activity, and force production characteristics during progressive strength training in young and older men. J Gerontol A Biol Sci Med Sci. 3(6):B415-423.

⁵ Kosek, D.J., et al. (2006). Efficacy of 3 days/wk resistance training on myofiber hypertrophy and myogenic mechanisms in young vs. older adults. J Appl Physiol. 101(2):531-544.

⁶ Katsanos, C.S., et al. (2005). Aging is associated with diminished accretion of muscle proteins after the ingestion of a small bolus of essential amino acids. Am J Clin Nutr. 82(5):1065-1073.

⁷ Moffatt, R.J., et al. (2008). Nutrition for resistance training in middle-aged adults. In Nutrition for Middle-Aged Adults (vol 1). In press.

⁸ Rennie, M.J., et al. (2002). Latency, duration and dose response relationships of amino acid effects on human muscle protein synthesis. J Nutr. 132(10):3225S-3227S.

⁹ Paddon-Jones, D., et al. (2006). Differential stimulation of muscle protein synthesis in elderly humans following isocaloric ingestion of amino acids or whey protein. Exp Gerontol. 41(2):215-219.

¹⁰ Paddon-Jones, D., et al. (2004). Amino acid ingestion improves muscle protein synthesis in the young and elderly. Am J Physiol Endocrinol Metab. 286(3):E321-328.

¹¹ Norton, L.E., and Layman, D.K. (2006). Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. J Nutr. 136(2):533S-537S.

¹² Garlick, P.J. (2005). The role of leucine in the regulation of protein metabolism. J Nutr. 135(6 Suppl):1553S-1556S.

¹³ Katsanos, C.S., et al. (2006). A high proportion of leucine is required for optimal stimulation of the rate of muscle protein synthesis by essential amino acids in the elderly. Am J Physiol Endocrinol Metab. 291(2):E381-387.

¹⁴ Norton, L. (2008). Optimal protein intake and meal frequency to support maximal protein synthesis and muscle mass. JISSN. 3(5):S4.

¹⁵ Kobayashi, H., et al. (2006). Modulations of muscle protein metabolism by branched-chain amino acids in normal and muscle-atrophying rats. J Nutr. 136(1 Suppl):234S-236S.  IM