Muscle strength is one of the keys to healthy aging, yet after we achieve peak mass in our early 40s, it’s pretty much downhill from there. Most people begin to lose modest amounts of muscle at that point and experience progressive deterioration as the years go by, especially if they are sedentary.
Now, with a growing population of aging baby boomers, experts are turning their attention to interventions to help stem the loss of muscle mass, quality and strength, known as sarcopenia. It is caused by a number of complex factors that are not entirely understood, including decreasing amounts of testosterone in men. Muscle decline often goes hand in hand with frailty, a decline of physical function that leads to falls, hospitalization and the need for nursing-home care.
Researchers are looking at promising treatments including inhibiting a naturally occurring protein called myostatin that curbs muscle growth. Pharmaceutical companies already have drugs in the pipeline that act by blocking myostatin or blocking the sites where it is detected in the body, potentially rebuilding muscle.
For now, however, the best medicine available to maintain muscle mass and strength is less complicated and costly—namely, exercise and a healthy diet. Yet about 60% of people over 65 are insufficiently active or overtly inactive, and many have poor nutrition, says Nathan LeBrasseur, a researcher who directs the Muscle Performance and Physical Function Laboratory and the Healthy Aging and Independent Living Initiative at Mayo Clinic in Rochester, Minn. Dr. LeBrasseur estimates that most people will lose approximately 30% of muscle mass over their lifetime, and as much as 50% by the time they reach their 80s or 90s.
Keep Your Motor Running. Muscle is also central to metabolism, or the rate at which fat and calories are burned, and can help improve resiliency to the stressors of aging, Dr. LeBrasseur says. By simply stepping up activity like walking, gardening and household tasks, “we can slow the loss and prevent crossing that critical threshold that leads to functional limitations and metabolic issues.”
Chronic diseases such as diabetes, which inhibits the metabolism of nutrients in the body, are believed to contribute to age-related muscle loss, and older obese individuals with decreased muscle mass or strength are at special risk for adverse outcomes, according to research funded by the National institute on Aging. Related conditions include cachexia, a state of general physical decline and malnutrition associated with chronic disease and cancer, and wasting disorders that can be associated with nerve disease or injury.
More Protein. In addition to the mounting evidence of the benefits of physical activity in stemming decline, Dr. Walston says there is an emerging body of research that suggests older people should eat more protein, with a focus on leaner sources.
According to guidelines published in 2010 by the Society on Sarcopenia, Cachexia and Wasting Disorders, a nonprofit group, as many as 41% of women and 35% of men age 50-plus ingest less than the recommended daily allowance of 0.8 grams of protein per kilogram of body weight (0.36 grams per pound). The group recommends that total protein should be higher in that age range, or 1 to 1.5 grams per kilogram per day (0.45 to 0.68 grams per pound), spread equally through three meals.
The group also says low vitamin D levels are associated with low muscle strength, and supplementing it in those cases has been shown to increase strength and function and reduce falls. But it’s best to talk to a physician before starting any supplements such as protein or vitamin D.
As for exercise, the group notes that resistance exercises can improve strength, while aerobic exercise can improve overall health and quality of life. The group recommends a combination of the two for 20 to 30 minutes three times a week.
Building Up Reserves. Evidence continues to show the benefits of exercise at any age. Last month, a study in the Journal of the American Medical Association found that an exercise program reduced the onset of major disability for at-risk older adults by 18% over about 2½ years.
Roger Fielding, a co-author of the study and director of the Nutrition, Exercise Physiology and Sarcopenia Laboratory at Tufts University, says the study shows that “even as we advance into very old age, physical activity can help preserve independence.”
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