Sarcopenia was named by the CDC as one of the top five health risks for older adults over a decade ago. And yet awareness of the condition has been slow-growing, until now.
Boom!
Enter the baby boomers.This generation is 40 million strong, and expected to live longer than any previous generation. Many have watched their parents age, become frail, or lose their independence due to a chronic disease or broken hip. Boomers are looking for ways to help aging parents and safeguard their own healthy futures.
Their needs, and ongoing research into the physiological mechanisms behind sarcopenia, have finally driven the issue of age-related muscle loss into the spotlight. It couldn't be more timely.
Muscle loss can begin as young as age 30, when men and women can lose much as a half-pound of muscle each year. And for every half-pound of lean muscle lost, most are gaining twice as much fat. This can make muscle loss an insidious process because this additional fat means that the lost lean tissue may not register on the scale. A person's weight may not change drastically even when their ratio of muscle to fat does. (See a New York Times illustration of what this looks like).
Research shows that after age 50, this process significantly accelerates. A 20 to 40 percent loss of lean muscle mass is possible by the time a person has reached 70.
Most baby boomers have already turned 65 as of this year.
So why is this muscle loss such a big deal?
Turns out that our muscles do more than just help us move. Our muscles are an integral part of a healthy immune system and metabolism. Lack of lean muscle is even associated with higher mortality rates in men.
Muscles secrete hormones that fight inflammation. They play an important role in the immune system, and serve as a reserve of amino acids needed for tissue repair during illness and injury. Lack of muscle is a known risk factor for those debilitating hip fractures we so want to avoid. A lack of healthy lean muscle can also affect insulin functioning and mineral metabolism, and therefore influences several chronic diseases.
In fact, inadequate muscle mass can impact:
Immune response
Chronic diseases such as diabetes and osteoporosis
Survival rates from critical illness such as cardiovascular disease and cancer
Ability to recover from injury and surgery.
Given the importance of lean muscle mass, older adults need solutions for muscle health now.
The logical place to begin is by understanding why muscle loss happens in the first place.
Motor Neurons
One obvious culprit is lack of use. Take a look at a neuromuscular junction, the place in the body where muscle fibers connect with the nerve cells that stimulate them. Moving muscles - walking, gardening, running the elliptical, aka exercise- gets these nerves firing (a good thing). This, in turn, signals more nutrients to be sent into the muscle, and encourages muscle cells to make repairs and reproduce.
When all is quiet on the western front - aka sitting on the couch watching House marathons - aka inactivity- this process slows dramatically. Atrophy occurs. A classic case of use it or lose it.
...Easy enough to remedy if you are forty and can schedule some exercise into your day. Not so easy as you get older, deal with injuries and disabilities, or struggle with painful diseases like osteoarthritis. And making things even more difficult - even when older adults can exercise, it seems that the motor nerve endings weaken and fray, their ability to relay messages to muscle fibers decreases considerably.
Molecular Changes
Other contributors to the problem of muscle loss include hormonal and molecular changes that occur with age. Hormone levels may decrease. Hormone receptors and uptake of hormones may be diminished, which can alter metabolic processes such as insulin sensitivity and fat distribution. Expression of microRNA in skeletal muscle (a topic I will explore further in an upcoming post) slows and becomes disregulated. MicroRNA helps to instruct muscle cells on how to grow and function, so when it goes awry, the growth cycle of muscle cells, and consequently protein synthesis, can be affected.
Dietary Protein
Finally, scientists have shown that dietary protein plays a role in lean muscle maintenance.
Many older adults do not take in Recommended Daily Allowance for protein - between 15 and 38 percent of adult men and 27 to 41 percent of adult women, according to an analysis reported in the American Journal of Clinical Nutrition.
What's more, not all of the protein older adults do get is necessarily utilized by the body. Protein can only be absorbed by the body for a certain amount of time after ingestion. And as we age our bodies produce fewer digestive enzymes, making it more difficult to break down and absorb protein. The undigested protein can create uncomfortable gastrointestinal symptoms like gas, bloating, and constipation, and people may decrease the protein in their diet in order to avoid this discomfort.
The body also becomes less efficient at using the amino acids it does get from protein. Since these amino acids are important in such a wide range of physiological functions, from building hormones and neurotransmitters to tissue repair and immune response, the lack of protein can have far-reaching consequences.
Solutions
As the population ages, scientists are looking for ways to combat sarcopenic muscle loss on all three of these fronts.
Physical activity is thought to improve and help preserve motor neuron function, although the ability of some older adults to remain active may be limited, as discussed above. Generally speaking, exercise (under the supervision of a health care provider) is encouraged, and shown to be beneficial at almost every age.
Researchers are working on ways to affect change through hormonal, molecular and genetic pathways, although it may be a long time before this research translates into available treatments. (Interesting to note, however, is the discovery that one way genes may be turned on, off, or modified, is through good old-fashioned diet and exercise!)
Improving dietary protein intake and utilization is one part of the solution that is practical and obtainable for many people. Simply becoming aware of protein intake, choosing quality digestible proteins, and addressing digestion issues with a health care provider may all be important steps that can make a difference.
