Athletic performance declines as a result, and even the ability to perform everyday activities such as carrying grocery bags diminishes.
Even worse, as muscle mass decreases, body fat mass does the opposite. Consequently, sarcopenia is also associated with body fat-related diseases and conditions including heart disease and diabetes.
In fact, research has found that muscle volume and strength are excellent predictors of mortality in older adults. As a general rule, the more muscle mass and strength you have in your golden years, the longer you'll live. Muscle may well be the fountain of youth -- or at least one of the streams that feeds it.
The causes of sarcopenia are still somewhat mysterious, although scientists are making rapid progress in shedding new light on them. One key finding is that body stores of the amino acid cysteine decline with age more than those of any other amino acid. Cysteine plays a key role in the regulation of whole-body protein metabolism, which results in changes in body composition.
Another finding is that levels of certain cytokines (immune system messenger cells) increase with age, indicating a state of low-level whole-body inflammation that may also contribute to sarcopenia. But several other factors are probably involved, as well.
Slowing muscle loss
The good news is that sarcopenia can be slowed and, to a certain degree reversed, by two factors: protein consumption and resistance exercise. The most important factor is resistance exercise (weightlifting, calisthenics, etc.). In a recent study from Manchester Metropolitan University in England, a group of 70-year-old men increased their muscle size by 12 percent and their muscle strength by 20 percent over the course of a yearlong resistance-training program.
Other studies have shown that men and women who engage in consistent resistance training throughout their adulthood are able to significantly delay and slow sarcopenia compared to those who don't. So if you think that weightlifting is only for bodybuilders interested in becoming as huge as possible, think again.
Everyone interested in living a long, productive life and in maintaining a high level of performance in sports and everyday activities in their golden years should sustain a moderate resistance exercise program. It doesn't take much: just two half-hour session per week will suffice.
Protein-rich diet: Whey protein
Resistance exercise is most effective when combined with a protein-rich diet. The timing of protein intake and the types of proteins consumed are also important. The benefits of resistance exercise are fully maximized when a protein-rich diet is supplemented with consumption of high-quality proteins immediately before and after resistance workouts.
The highest-quality protein of all is whey protein, which is actually a collection of three proteins found in cow's milk. Whey is isolated from milk in the standard cheese-making process. Whey proteins are distilled from whey into a powder containing little or no fat and lactose (milk sugar, which some people have trouble digesting) and used in a variety of protein supplements.
Whey protein is a complete protein that contains all 20 amino acids and all nine essential amino acids (i.e. amino acids that must be obtained in the diet because the body cannot make them using other amino acids). Its protein digestibility corrected amino acid score, or PDCAAS, (a commonly used scientific measure of protein quality) is 1.14, as compared to 0.94 for beef protein, and its biological value (another measure of protein quality) is an astronomical 149, compared to 100 for eggs.
In addition, whey protein empties from the stomach and is absorbed into the bloodstream from the intestine faster than other proteins. Moreover, whey contains especially high concentrations of amino acids that are metabolized at high rates during exercise -- most notably glutamine and leucine.
Due in part to its fast absorption, whey protein consumption results in a higher peak amino acid concentration in the blood than other proteins. This is important because blood amino acid levels are a key regulator of muscle protein synthesis. The higher the blood amino acid is, the faster muscle protein synthesis occurs.
Indeed, whey protein consumption has been shown to result in faster muscle protein synthesis as compared to other proteins. This makes whey protein more effective than other proteins for repairing exercise-related muscle damage and building bigger, stronger muscles.
Whey protein is also the richest source of the essential branched-chain amino acids (BCAA) leucine, isoleucine, and valine. As much as 30 percent of the amino acids in whey protein are BCAA. Unlike other amino acids, BCAA can be oxidized directly by the muscle cells, so they're used at a high rate during exercise. The BCAA have also been shown to have the greatest positive effect on muscle protein synthesis among all of the amino acids.
Finally, whey protein contains three to four times more bioavailable cysteine (i.e. cysteine in a form the body can readily use) than other proteins including casein and soy. The amino acid cysteine plays a key role in regulating protein metabolism, which results in changes in body composition.
A recent report written for a U.S. government agency noted that "supplementing the diet with whey proteins, particularly in combination with activities such as resistance training, represents a research-based, non-pharmaceutical strategy that can easily be incorporated into the lifestyles of adults to help maintain valuable muscle mass that preserves health throughout the aging process."
We're all looking to turn back, or at least slow down, the clock -- to feel young and function youthfully regardless of our actual age. Building and maintain strong muscles is one of the most effective ways to do so. And the formula for strong muscles couldn't be simpler: resistance exercise plus protein.
Matt Fitzgerald is the author of several books on endurance sports training and nutrition, including Runner's World Performance Nutrition for Runners (Rodale, 2005).