The BBC has a 30 minute report on muscle loss that you don't want to miss. It includes interviews with several of the foremost researchers on the subject, which you may also be familiar with as sarcopenia. So pull a chair up next to your computer speakers and get comfortable, your muscles will thank you for it.
[BTW-I couldn't track down a transcript of this broadcast, but if you are unable to access this program from your computer, this older BBC article provides some of the same information, minus the most recent research. The bottom of this page also provides links to the researchers mentioned in the audio program.]
One of the featured scientists, Professor of Clinical Physiology, Faculty of Medicine & Health Sciences at the Univerisity of Nottingham Medical School Mike Rennie, said he was surprised by one of the conclusions from recent research:
Loss of lean muscle (lean muscle is crucial for good health ) is primarily a problem of inadequate protein synthesis.
Why is this surprising?
How Muscle Is Made
Because muscle is constantly being regenerated through a process of tearing down and rebuilding of tissue. Muscles are broken down by the body to harvest amino acids, which are then used, in part, to rebuild these muscles.
The amino acids from muscle may also be used to build hormones, neurotransmitters and other tissues. They perform a host of other functions within the body. When amino acids are adequately supplied through the diet, the carefully balanced give-and-take of protein supports the healthy functioning of all of these systems, as well as the maintenance of muscle.
Exercise can cause muscle tissue breakdown, but this breakdown then signals the body to rebuild muscle and store more amino acids there, resulting in muscle growth.
How Muscle Is Lost
Both aging and illness can make it difficult for the body to maintain this process; muscles grow weaker and smaller as they are depleted of amino acids. Rebuilding muscle tissue slows or stops as the body becomes overwhelmed by the demand.
Exactly how this happens is still a hot research topic - getting hotter, in fact, as the US population ages, because loss of muscle mass affects the immune system, bone health, the ability to fight off and recover from major illness, and can lead to injury and disability.
Scientists simply don't have all of the answers yet. But what they have learned is that it's not so much the breakdown of muscle (sometimes called catabolism) that's the problem. It's when this breakdown is not followed by rebuilding (anabolism).
Headed for a Breakdown
Muscle breakdown in and of itself is not the problem, scientists like Rennie and others have concluded, because this breakdown is normal part of muscle regeneration.
For example, as I mentioned earlier, exercise actually induces muscle breakdown. Findings published in the 2004 Journal of Nutrition even show that exercise specifically induces the breakdown of the branched-chain amino acids (BCAA) in muscle.
When everything is functioning properly, this then triggers repair and rebuilding of muscle. If this doesn't happen, however, muscle is lost.
Over time, this can add up to some serious lean muscle loss, up to one pound each year, and 80 percent over a lifetime.
Why Do You Build Me Up, Buttercup
Branched chain amino acids, it turns out, are really important for muscle building. After exercise, these amino acids have been shown to activate key enzymes that stimulate protein synthesis.
The authors of the 2004 Journal of Nutrition study on exercise-induced BCAA catabolism concluded that "....that the BCAA requirement [may be]increased by exercise. BCAA supplementation before and after exercise has beneficial effects for decreasing exercise-induced muscle damage and promoting muscle-protein synthesis."
So muscle breakdown during exercise can teach us something about how muscles deteriorate, and what may protect them.
But what about age-related muscle loss? Does it happen the same way? Can BCAAs - or anything else, for that matter - help preserve muscle, the way they do after exercise? (pssst...they help when taken before exercise, too, but that's for another post.)
BCAAs and Age-Related Muscle Loss
For one thing, we know that the BCAAs leucine and isoleucine are known to help preserve lean muscle. Moreover, scientists have recently found that BCAAs leucine, isoleucine and valine increased the lifespan of mice by 12 percent, and improved age-related muscle deficits and mitrochondrial biogenisis (think energy) too.
Their study, "Branched-chain amino acid supplementation promotes survival and supports cardiac and skeletal muscle mitochondrial biogenesis in middle-aged mice," is published in Cellular Metabolism. (quiz: what kind of car does a middle-age mouse drive?)
But older adults may have difficulty taking in adequate BCAAs, since they may have difficulty chewing, produce fewer endogenous digestive enzymes and may be less inclined to choose protein foods. In fact, between 15 and 38 percent of adult men and 27 to 41 percent of adult women may not be getting the RDA for protein on a daily basis. Unfortunately, we know that protein intake is directly correlated to how much lean mass is lost with age.
This does mean though, that older adults can take help support their own muscle health by making sure their diet contains enough quality protein. Remember, changes to the diet should never be made without consulting a physician.
Exercise and Aging Muscle
The other good news is that resistance exercise seems to do a good job of maintaining and building muscle, even with age. In fact, Rennie calls the growth response of older adults' muscles to weight bearing exercise "a much bigger response than expected."
While older muscles may respond to exercise more slowly- and perhaps less efficiently- than younger muscles do, they do respond.
Many say muscle wasting is more a disease of inactivity rather than of age.
It may be a combination of both. Scientists are still sorting out the roles of hormones, diet, activity and genes in this puzzle. But the role of exercise is undeniable.
Take a look at this MRI of an 70 year old woman's quadriceps, before and after resistance training, from this study in the Journal of Applied Physiology. Her muscle increased in size by 32 percent over 8 - 12 weeks of daily resistance exercise. Improvements in muscle strength, not just size, were also seen.
Organizations like the National Strength and Conditioning Association provide guidelines for weight-bearing exercise for seniors, but this should only be done under the supervision of a physician or health care provider.
And so, to summarize what we now know about preserving and building lean muscle, the two factors that can make a difference are:
1. Eating and absorbing adequate amounts of high quality protein
2. Stimulating muscles with resistance exercise
Both of these steps should only be done with the guidance of a physician, of course. But science is showing that they may go a long way when it comes to supporting healthy lean muscle.
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