x
It’s inevitable. We lose muscle mass and strength as we get older. Once age-related muscle loss becomes severe the condition is labeled sarcopenia. About 30% of people become sarcopenic as they age. Although not technically accurate, sarcopenia has become more of an umbrella term for the general loss of muscle with aging. Once someone has lost a significant amount of muscle, the functions of daily living are severely affected. Adverse health consequences can result from even a modest loss of muscle.
Despite the widespread recognition that muscle mass and strength are lost with aging, the physiological significance of this loss is often underappreciated. It is well recognized that you can’t run as fast or hit the golf ball as far when you get older. If the loss of muscle strength becomes severe, basic activities of daily living can be affected, with significant adverse effects on quality of life, as well as much broader health implications.
Recent research has made clear that a significant loss of muscle mass and/or strength increases your risk of cardiovascular events and decreases your likelihood of survival from various diseases, including cancer and chronic obstructive lung disease. Muscle loss also adversely impacts recovery from major surgery and bone health.
Muscle is at the core of each of these health conditions because it is the amino acid supply line for other tissues and organs in your body. When tissues and organs need an increased supply of amino acids for various stressors—to battle infection, repair wounds, control vascular function, balance metabolic processes, and more—amino acids from muscle are mobilized. Muscle also plays a role in maintaining a healthy energy balance.
Quite often, people don’t recognize that they have lost muscle mass and function until they are 70 years old or older. This oversight is particularly the case with people who don’t participate in any organized recreational activities. They don’t experience a quantitative feedback on performance. The reason that it is not easy to recognize the problems caused by the loss of muscle mass and function is a phenomenon we call a “threshold effect.”
Here’s how it works: The loss of muscle starts in some people as early as age 30. By age 50, almost everyone is starting to lose a significant amount of muscle. However, you may not notice this because your body weight doesn’t change (or may even go up due to increased fat), and you can still comfortably perform the activities of daily living.
As the loss of muscle progresses, basic function may still be maintained, often until the onset of (an inevitable) health setback. The loss of muscle occurs even faster when there is serious illness, injury, or surgery. When the normal age-related rate of muscle loss is coupled with the accelerated loss that occurs in response to a health crisis, function may all of a sudden be affected to the point where you suddenly notice a problem—the “threshold” has been reached.
Exercise is key to maintaining muscle mass as you age. However, after you have lost a significant amount of muscle, you become limited in the amount of exercise you are able to perform. Secondly, since the muscle has been depleted, there are metabolic changes that make it less receptive to the beneficial effects of essential amino acids. This is called anabolic resistance.
The metabolic basis for the loss of muscle with aging is that, over time, the rate of muscle protein breakdown exceeds the rate of muscle protein synthesis. What’s particularly interesting is that in the post-absorptive state (between meals), the rates of muscle protein synthesis and breakdown do not change with aging. But, when dietary protein is consumed there is a diminished increase in protein synthesis. In other words, normal protein nutrition is not as effective in the elderly as it is in younger people. The same amount of dietary protein elicits twice the stimulation of muscle protein synthesis in young individuals as it does in older, healthy individuals.
This dampened response is termed anabolic resistance and it is the principle reason why we lose muscle as we age. The situation is even more pronounced if an older person has some kind of physical stress. Even a case of the flu will make anabolic resistance worse, and more serious diseases like cancer take even more of a toil.
The hormonal changes that occur with aging play a role in accelerated muscle loss. This is particularly true for men. Testosterone is the primary anabolic hormone in men, and the concentration of testosterone in the blood decreases with age.
Growth hormone secretion is also virtually completely shut off in both men and women. Although there is a debate, some (but not all) evidence indicates that the decrease in growth hormone plays a role in causing muscle loss with aging. As a result, testosterone therapy (for men) and growth hormone therapy (for both men and women) is used by some to counteract the loss of muscle mass and strength with aging. While they can be effective, hormone therapy needs to be closely monitored, as adverse side effects are possible.
Dietary supplementation has been marketed and used as therapy in older individuals, mostly with protein-enhanced beverages. The general idea is to provide some high-quality protein like whey protein since the typical diet is lacking in sufficient protein. However, intact protein supplements have not proven to be consistently helpful in reversing muscle loss in older individuals. The problem, as referred to above, is anabolic resistance. The normal action of dietary protein to stimulate muscle protein synthesis is diminished in the elderly. Consequently, loss of muscle mass and function will not be reversed.
In the case of the anabolic resistance and muscle loss that occurs with aging, the profile of essential amino acids (EAAs) in even a high-quality protein is ineffective. That’s because the optimal profile of EAAs to maximally stimulate muscle protein synthesis in the circumstance of anabolic resistance differs from the profile of EAAs in any naturally occurring protein.
Essential amino acids make for exceptional dietary supplements because you can precisely formulate EAAs to be optimal for specific circumstances. Daily supplementation with a complete formulation of EAAs has been shown to reverse loss of muscle mass and function with aging more effectively than hormonal therapy, and there is no risk of adverse side effects, as EAAs are natural (and essential) components of the diet. EAAs can effectively help protect against age-related muscle loss, even without exercise, and will also amplify the beneficial effects of exercise and the beneficial effects of hormonal therapy.
#DrRobertWolfe
