Preventing and treating sarcopenia, age-related muscle deterioration
What is sarcopenia?
The definition of sarcopenia is evolving. Initially, sarcopenia was defined as age-related deterioration of muscle mass. In recent years, however, expert panels have argued that diagnosing sarcopenia based on muscle mass alone is of limited clinical value [1,2] and suggest that a diagnosis of sarcopenia is appropriate when an individual has both low muscle mass and functionality, measured as strength or performance [1,2].
The effects of sarcopenia extend beyond the obvious loss of strength. Muscle is a metabolic reservoir and produces substances required for survival after a traumatic event. Ageing populations affected by sarcopenia have decreased ability to regain full function after illness, major surgery, or other traumatic accidents as they lack muscle and, thus, metabolic reserves to bolster their immune and other related systems responsible for recovery [3,4]. Furthermore, sarcopenia is related to increased fall risk , metabolic disorders , and reliance on assisted living . Over a two year period, sarcopenic individuals are at least three times as likely to fall versus those without sarcopenia, regardless of other confounding factors .
Sarcopenia is debilitative; the greater the muscle loss, the more one is to suffer fatality from an injury or disease . In line with this is research demonstrating that, in the elderly, muscle mass predicts survival [10,11].
Who does sarcopenia affect?
After the age of 40, healthy adults lose 8% of their muscle mass every 10 years. This rate of loss increases to 15% per 10 years beyond the age of 70 . Sarcopenia affects 1 – 29% of individuals living in the community, 14 – 33% in a long-term assisted living situation, and 10% in acute hospital care . As far as age distribution, sarcopenia is estimated to affect 30% of individuals over 65 years of age and 50% of those over 80 years of age .
Sarcopenia is primarily observed in sedentary, malnourished (lack of dietary protein and calories) populations  but can also affect those whom are physically active and well-nourished throughout life . Therefore, ageing, physical inactivity, and nutritional status are not the only factors contributing to sarcopenia. Rather, the onset of sarcopenia also involves a decline in muscle regenerative capacity, age-related hormonal changes, inflammatory processes, and a host of other disorders .
Fighting sarcopenia with exercise and nutrition
Exercise and nutrition are key preventative measures and treatments for sarcopenia. Currently, there are no approved drugs to treat sarcopenia. Furthermore, studies investigating the efficacy of treatment with anabolic hormones, hormones that stimulate protein synthesis, have not found a clinically beneficial effect .
A review of seven studies revealed that exercise regimes in frail, sedentary older adults generally improve muscle strength and physical performance, but there was limited data showing increases in muscle mass . The authors of the review suggested that combining various types of exercise (i.e., resistance training, aerobic exercise) may be more beneficial for combatting muscle deterioration than a single exercise regime. Resistance exercise, specifically, is recommended as the most effective approach to improve muscle mass and performance .
Dietary factors associated with increased risk of sarcopenia include low protein and caloric intake. The link between protein intake and muscle anabolism (synthesis) is well established. Generally, the typical American is thought to consume adequate or excessive amounts of protein. However, as we age, our bodies do not use protein as efficiently and, as such, the elderly require greater amounts [20,21]; this is referred to as “anabolic resistance” and is thought to result from dysregulated muscle signaling.
The current recommended protein intake for older adults with sarcopenia is greater than 1.2 grams per kilogram of body weight, with an exception for those with significant kidney issues [13,22]. For an individual weighing 150 pounds, this translates to more than 82 grams, or 2.9 ounces, of protein per day. To illustrate this: 3 ounces of chicken or meat are approximately the size of a standard deck of playing cards. As mentioned, however, anabolic resistance may be a consequence of dysregulated muscle signaling. As such, increasing daily intake of dietary protein may not be effective in combating anabolic resistance and sarcopenia in older age as the extra amino acids (building blocks of protein) may not be effectively utilized .
Beyond protein intake, numerous other individual dietary ingredients have been shown to slow the progression of sarcopenia. Of specific interest is a recent study that combined many of these – whey protein, creatine, vitamin D, Calcium, and fish oil derived (omega-3) fatty acids – in an “all-in-one” supplement and tested if daily consumption would increase muscle mass and functionality versus a placebo . Men of at least 70 years of age consumed the supplement or a placebo over an extended period of time. After 6 weeks of daily consumption, a resistance and high-intensity interval training exercise program was introduced in addition to continual supplement consumption. In the first 6 weeks of the trial, the supplement resulted in muscle mass gains that equated to the amount the men would normally lose in one years’ time. When the men began exercising twice weekly, strength gains were enhanced. However, both groups of men (consuming all-in-one supplement or placebo) improved physical function, aerobic capacity, and metabolic health to a similar extent when the exercise regimes were introduced.
Research suggests a limited role for protein supplementation alone in treating sarcopenia. Resistance exercise is the most effective intervention for maintaining muscle mass [19,25] and emerging research, outlined above, indicates that incorporating dietary alterations in combination with exercise may optimize sarcopenia prevention and treatment.
Any exercise is better than none. However, it is worth stating that all forms of exercise are not created equally. Aerobic exercise (running, walking, elliptical) is key for cardiovascular health and weight loss but does not build muscle mass and is only mildly effective at preserving any mass one already has. Resistance training (weight bearing exercise) effectively increases and preserves muscle mass and functionality.
My advice? If you are approaching or have exceeded the age of 40, ensure you are consuming high-quality protein and adequate calories from different sources. Add supplements, such as whey protein, creatine, vitamin D, Calcium, and fish oil, as needed. Exercise regularly (3 times per week minimum) with an emphasis on resistance training. Official guidelines for physical activity in older adults, as developed by the American College of Sports Medicine and American Heart Association, call for “muscle-strengthening activity” (resistance exercise) to be performed at least non-consecutive 2 days per week . These recommendations are to be used as a minimum. There is evidence that the response to resistance training is dose-specific. In other words, each incremental increase in the intensity of exercise reflects a greater increase in respective strength outcome .
I did not discuss the hormonal factor in-depth here but will mention that research findings are inconsistent as to whether hormone replacement is effective in maintaining or increasing muscle mass.
Merritt Drewery is a native of Baytown, Texas. She holds a Bachelors of Science and Masters of Science in Animal Science, with a focus in Ruminant Nutrition, from Texas A&M University. Merritt recently received her PhD in Molecular and Clinical Nutrition from Louisiana State University. Her research interests include the role of perinatal nutrition in optimizing fetal and infant development, especially in infants born to women with adverse metabolic conditions. In her free time, she is probably playing with her very scruffy, disobedient dog or showing pictures of her nephews to anybody who will feign interest.
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