Preventing Age-Related Muscle Loss
Most of us lose muscle as we agea loss of 1 to 2 percent a year after age 50, on average, or about 30 percent between age 50 and 70. In particular, arms and legs weaken and look thinner or flabbier. It becomes harder to lift packages. Loss of muscle in the legs increases the risk of falls. This steady loss of muscle mass and strength tends to accompany many of the things we associate with aging:
- becoming less active,
- eating less healthfully,
- developing chronic diseases,
- becoming frail.
When the muscle loss becomes relatively severe, it’s called sarcopenia. (Similarly, when age-related bone loss goes beyond a certain point it’s called osteopenia and then, if it gets worse, osteoporosis.) But sarcopenia prevention is possible.
Muscle: Use It or Lose It
There’s no standard way to define or diagnose sarcopenia, since age-related muscle loss occurs over a continuum (as does bone loss). It isn’t just a matter of measuring loss of muscle size, but also of evaluating changes in muscle quality and functional abilities. Thus, there are varying estimates about how many people have sarcopeniaanywhere from 10 to 50 percent of those over age 70.
Many factors besides age-related lifestyle changes contribute to sarcopenia. Metabolic changes result in more protein breakdown in muscles and reduced muscle synthesis. Declining hormone levels also come into play, as do pro-inflammatory compounds and cell-damaging free radicals, which can promote muscle wasting and affect muscle fibers. Rapid weight loss (from dieting or illness) as well as prolonged bed rest can accelerate muscle loss.
Never Too Late to Improve Muscle Strength
Countless studies have shown that older people who do resistance training can significantly improve their muscle strength and performance, even after just a couple of months of trainingand even if they are frail and over age 80. Any strength training can help prevent or treat sarcopenia. Strenuous workouts are most effective, according to a 2010 analysis in Aging Research Reviews, which included data from 47 studies, though that would be challenging for many older sedentary people, who need to start gradually.
Protein and Muscle Loss
Most Americanseven vegetarians and athletesget more than enough protein from food. Older people are often exceptions, however. Sometimes it’s because they simply eat less or have trouble chewing protein sources such as meat.
The recommended dietary allowance (RDA) for adults is 0.8 grams of protein a day for each kilogram (2.2 pounds) of body weight. That’s 56 grams of protein for someone weighing 154 pounds.
It’s estimated that 40 percent of people over 70 don’t consume that much protein. And some researchers believe that older people should aim higherat least 1.3 grams per kilogram, or 91 grams of protein for a 154-pounder.
Still, few studies have looked at the effect of higher protein intakes on sarcopenia, and results have been inconsistent. The amount of muscle protein synthesis may depend in part on the protein source (whey protein is better than soy, for instance). The timing of your protein intake could make a difference, too, but there’s debate about the optimal schedule. Some research suggests that eating most of your protein at midday is best for muscle metabolism. Other research indicates that consuming about 25 to 30 grams of protein at each meal is better.
Protein & Exercise
Moreover, eating some protein in the hour after moderately intense strength training seems to boost muscle synthesis during the next several hours. A Danish study in the Journal of Physiology, for example, found that men in their mid-seventies who consumed protein immediately after resistance training developed more muscle after 12 weeks, compared to men who had the protein two hours after exercising. Similarly, a recent Dutch study found that older men (also in their mid-seventies) had greater muscle synthesis when they exercised before consuming protein (20 grams) than when they didn’t exercise before consuming it.
To help prevent (or treat) sarcopenia, do strength training regularly and make sure you eat adequate proteinsome of it perhaps shortly after your workouts. Dairy products as well as fruits and vegetables supply nutrients and other compounds that help protect aging muscles.
But don’t go overboard with protein. Many older people have impaired kidney function, and excessive protein intake can make matters worse. If you do increase your protein intake, talk to your doctor, who may want to test your kidney function, especially if you are over 65 or have diabetes or high blood pressure.
Final thought: Consider taking 800 to 1,000 IU of vitamin D a dayor more if your doctor says your blood levels are low. Population studies have linked low D levels to increased risk of sarcopenia.
How much protein do you consume? Meat, chicken and fish have 6 to 8 grams per ounce. Milk has 8 grams per cup; yogurt, 10 to 13 per cup; an egg, 6 grams; an ounce of peanuts, 8 grams. Cooked beans have 7 grams per half cup; a slice of bread or half cup of pasta, 3 grams. Grain products are often overlooked as protein sources—they supply nearly one-fifth of our total protein intake. Even vegetables contain protein, albeit smaller amounts (a half cup of broccoli or asparagus has 2 grams).
For younger people, it isn’t hard to have a moderately high protein intake, but older people may have to make an effort. Four ounces of lean meat, a cup of beans, two cups of milk, a cup of pasta and a cup of yogurt would supply about 75 grams of protein. Add in the small amounts of protein in the other foods you’re eating, and you’ll reach 90 grams or more. If you consume 2,000 calories a day, about 18 percent of your daily calories will then be coming from protein, which is considered a moderately high-protein diet. If you’re older and lack appetite, high-protein “nutritional drinks” such as Ensure or Boost are an option.
If you want to figure out how much protein you’re eating, fill out the food questionnaire on the USDA’s site www.mypyramidtracker.gov. You can also consult a registered dietitian to work out an appropriate eating plan.
Adapted from The University of California, Berkeley Wellness Letter (January 2012)