Muscle strengthening, aerobic activities, and good dietary protein may help slow age-related declines in muscle mass and strength.
It takes more than just exercise to avoid losing muscle mass as people age. A study conducted at Tufts Human Nutrition Center found that muscle-strengthening exercise preserves muscle mass when it is combined with adequate dietary protein; aerobic activity also may help. The findings were published online in the British Journal of Nutrition.
Vigorous aerobic activity, not just muscle-strengthening exercise, helps preserve muscle mass during aging, “says Martha Savaria Morris, PhD, a scientist in the Nutritional Epidemiology Program at Tufts. “Muscle-strengthening exercise is associated with low muscle mass unless protein intake is adequate.” Dr. Morris and colleague Paul Jacques, DSc, analyzed data from 2,425 participants over age 50 during a four year period. The data included measures of skeletal muscle mass, protein intake, and exercise patterns in obese and non-obese subjects.
LOW MUSCLE MASS:
Each of the three variables has implications regarding age-related declines in muscle mass and strength. “Low muscle mass (also called sarcopenia) is a cause of poor muscle strength, “ says Morris. “One risk (of sarcopenia) is the inability to carry out activities of daily living and, consequently, a lack of independence. Another risk is falls, which often result in serious injury among older adults.
While current U.S. Dietary Guidelines recommend a daily 46 grams of protein for women and 56 grams of protein for men, this study found that the association between protein intake and muscle mass varied with physical activity level. “Unfortunately, it is not as simple as a number of grams per day”, explains Dr. Morris. “It depends on your body weight (0.8 grams of protein per 2.2 pounds). The range is between 40 and 70 grams per day. For example, a 125 pound woman would need 46 grams of protein per day, while a 175 pound man would need 64 grams per day. Exceeding recommended protein intake was associated with benefits to obese subjects only.
The Tufts study also pointed out the advantage of high quality (complete) protein to people who engage in vigorous aerobic activities. Protein quality refers specifically to amino acid content. High quality protein contains all the essential amino acids (hence, “complete” ). Grains and legumes are good for a variety of reasons, but they are not sources of complete protein. Grains are typically low in the amino acid lysine, and legumes tend to be low in methionine. Meat, poultry, and fish are all animal sources of complete protein. The only vegetable source is soy. If meat is your preferred source of complete protein, make sure it is heart-healthy (low in saturated fat) by choosing lean cuts.
VIGOROUS AEROBIC ACTIVITY:
The muscle mass index of non-obese subjects who performed vigorous aerobic activities was consistently high. The highest muscle mass was achieved by participants who combined high intakes of beef or pork with these types of activities. Examples were running, lap swimming, aerobics classes, and fast bicycling—any activity that lasts for at least 10 minutes and causes heavy sweating or large increases in breathing or heart rate.
Dr. Morris suggests three take-home messages:
Connie W. Bales, PhD,RD, Professor, Department of Medicine Duke, Associate Director,GRECC, Durham VA Medical Center. “Maintain Muscle Mass with Age and Retain Your Independence.” Duke Medicine Health News Volume 13G (2013): pages1-2. Print..
Click below to learn more.Membership
Sign up to receive our Newsletter and Emails