Maintaining muscle mass may help prolong your life

Recent research suggests that the more muscle mass older Americans have, the less likely they are to die prematurely. The findings add to the growing evidence that overall body composition--and not the widely used body mass index, or BMI--is a better predictor of all-cause mortality.

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The study, published online Feb. 20, 2014 in the American Journal of Medicine, is the culmination of previous UCLA research led by Preethi Srikanthan, MD, MS, assistant clinical professor in the endocrinology division at the David Geffen School of Medicine at UCLA, that found that building muscle mass is important in decreasing metabolic risk.

Muscle mass more important than BMI. "As

there is no gold-standard measure of body composition, several studies have addressed this question using different measurement techniques and have obtained different results," Dr. Srikanthan says. "So many studies on the mortality impact of obesity focus on BMI. Our study indicates that clinicians need to be focusing on ways to improve body composition, rather than on BMI alone, when counseling older adults on preventative health behaviors."

The researchers analyzed data collected by the National Health and Nutrition Examination Survey (NHANES) III, conducted between 1988 and 1994. They focused on a group of 3,659 individuals that included men who were 55 or older and women who were 65 or older at the time of the survey. The authors then determined how many of those individuals had died horn natural causes based on a follow-up survey done in 2004.

The body composition of the study subjects was measured using bioelectrical impedance, which involves running an electrical current through the body. Muscle allows the current to pass more easily than fat does, due to muscle's water content. In this way, the researchers could determine a muscle mass index (the amount of muscle relative to height) similar to a body mass index. They looked at how this muscle mass index was related to the risk of death and found that all-cause mortality was significantly lower in the fourth quartile of muscle mass index compared with the first quartile.

"In other words, the greater your muscle mass, the lower your risk of death," says Arun Karlamangla, MD, MS, an associate professor in the geriatrics division at the Geffen School and the study's co-author. "Thus, rather than worrying about weight or body mass index, we should be trying to maximize and maintain muscle mass."

This study does have some limitations. For instance, one cannot definitively establish a cause-and-effect relationship between muscle mass and survival using a cohort study such as NHANES III. "But we can say that muscle mass seems to be an important predictor of risk of death," Dr. Srikanthan says.

"Despite these limitations, this study establishes the independent survival prediction ability of muscle mass as measured by bioelectrical impedance in older adults, using data from a large, nationally representative cohort," Drs. Srikanthan and Karlamangla wrote, adding that BMI's association with mortality in older adults has proven inconsistent. "We conclude that measurement of muscle mass relative to body height should be added to the toolbox of clinicians caring for older adults. Future research should determine the type and duration of exercise interventions that improve muscle mass and potentially increase survival in (healthy), older adults."

Contributors to muscle mass. There are several factors that may affect muscle mass throughout your life. Some of the most notable are:

Protein intake--Consuming protein increases the amount of amino acids that are available for muscle formation in your body. The recommended daily protein intake for women is 0.8 to 1.0 grams per 1 kilogram (about .03 ounces per 2.2 pounds) of body weight. Foods highest in protein include meat, poultry, fish, and dairy foods, along with plant sources such as lentils, beans, and peas. When it comes to muscle mass, it's better to eat more plant proteins and fewer animal proteins.

Vitamin D--The "sunshine" vitamin appears to be critical in the preservation of muscle mass and function. You can get vitamin D from foods and exposure to sunlight. However, few foods contain natural vitamin D (some fish, shellfish, and eggs), and too much sunlight exposure raises the risk of skin cancer, so taking supplements is often advised. Discuss your vitamin D level and possible need for supplementation with your doctor.

Dietary acidity--The acidity of your overall diet appears to affect muscle mass. A diet that contains excess acid-producing nutrients, like meat and dairy, and too few alkaline-producing plant foods, may have negative effects on bone and muscle.

Vitamin B12 and folic acid--Low intakes of vitamin B12 and folic acid, or folate, have been linked with elevated levels of the amino acid homocysteine, and high homocysteine is associated with declines in physical function and muscle strength.

For all adults, the daily Recommended Dietary Allowance (RDA) of vitamin B12 is 2.4 micro grams (meg), and 400 meg of folate.

Vitamin B12 is found in clams, trout, salmon, tuna, beef, haddock, milk, yogurt, and cheese. Folate sources include spinach, black-eyed peas, asparagus, Brussels sprouts, lettuce, avocado, broccoli, and green peas. Many ready-to-eat breakfast cereals, breads, and other products made from grains are fortified with vitamin B12 and/or folic acid.

If you're concerned about getting an adequate amounts of vitamins and other nutrients, talk to your doctor.

Resistance Training Exercises to Try at Home

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Chair squat Stand in front of a chair, bend your knees as if sitting down, and hover above the seat for as long as is comfortable before pushing slowly back up. Do three sets of three repetitions.

Images: Alayna Paquette

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Hip strengthener Sit comfortably, with your legs and feet together, and tie a resistance band around your thighs. Part your legs at the knees while keeping your heels together. Do three sets of 10 repetitions.

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Overhead triceps extension Sit in a chair with a pillow at your lower back. Using 2 lb dumbbells, start behind your neck, slowly reach up, and hold for two seconds. Do three sets of 10 repetitions.

WHAT YOU CAN DO

* Before exercising, warm up for five minutes by doing an easy walk or jog while swinging your arms.

* Work your way up to eight to 12 repetitions of an exercise before increasing weight or adjusting a band's resistance upward; the last two repetitions of the set should feel difficult (but not impossible) to do.

* Alternate body parts--for example, follow a leg exercise with an arm exercise.

* Eat a balance diet, with plenty of fruits and vegetable, to help preserve muscle mass.

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