By Dr. Frank Sabatino

Sarcopenia is the combined loss of skeletal muscle mass, function, and strength that can progress at a rate of almost 1% muscle loss per year after the age of 50. As a result, muscle strength can decline 50 percent in older adults, with as much as a 30 percent loss of muscle mass by age 80, contributing to an increased risk of falls and fractures. (1). One third of people over the age of 65 fall each year, and fall related injuries impact 40% of people over 75 and 80% of people over the age of 80. (2)

Since muscle fibers also contain the greatest number of energy factories (mitochondria), and store the bulk of circulating sugar in glycogen reserves (the storage form of sugar), the loss of muscle mass can promote profound fatigue, elevated blood sugar, and the increased risk of type 2 diabetes, excessive weight and body fat. Muscles also attach to bones and exert mechanical forces that create electric current in the crystalline structure of bones that attracts calcium and increases bone density and regeneration. Therefore, the loss of muscle mass can be a significant cause of osteoporosis. 

This muscle loss of sarcopenia targets fast-twitch muscle fibers, referred to as Type II fibers, that respond to rapid, high intensity activation and are responsible for quick movements and precise fine motor control rather than the slow-twitch fibers responsible for slower, repetitive movements and postural control. Since fall prevention requires quick muscle action, strong muscle response and finite control of foot placement, you can understand how this type of muscle loss increases the risk of falls.

Resistance exercise with weight training specifically targets fast-twitch muscle fibers and has the greatest potential to increase muscle cell growth and muscle mass. In this case, a mechanical force is translated into the biological responses of protein synthesis and muscle growth. When a muscle encounters tension, the tension is translated from the surface of muscle cells deep into the nucleus of the cell that contains the DNA that codes for protein and activates the process of muscle protein synthesis for muscle growth. 

Two of the most important controls for muscle growth are tension, and the action of the enzyme mTOR, which is activated by the amount, quality and availability of protein intake. The elongating, eccentric phase of muscle action (e.g. when you are returning the weight back to the starting position after a bicep curl) provides more that 20-50% more tension in muscle fibers than the concentric action of the curl itself, for optimal  activation of protein synthesis in the nuclei of muscle cells to increase muscle growth.     

The response of biological entities to low levels of minimally threatening or damaging stressors is called hormesis and improves their adaptability to environmental challenges. The high tension of mechanical stress in weight training creates the hormetic effects of inflammation and disruption of calcium homeostasis in muscles that trigger repair and growth of muscle cells. This inflammation is felt as a delayed onset of muscle soreness (DOMS) that can be felt a day or two after your workout. An ideal dose of DOMS and the eccentric action of resistance training activates special satellite cells that live on the periphery of muscles and are a major player in muscle growth. Large, long muscles of the body have many nuclei for protein synthesis all along their extensive length. When satellite cells are activated, they fuse with muscle cells and donate extra nuclei to the muscles in a process called myonuclear accretion that gives muscle a greater capacity for protein synthesis and growth. 

 Adequate protein intake, combined with weight resistance training can significantly prevent the loss of muscle mass. The cellular enzyme mTOR exerts the greatest control over protein synthesis for muscle growth and is activated by tension and the amount and availability of protein in your diet. Certain amino acids are the biggest stimulators of mTOR, and the essential branched-chain amino acid, leucine, is the most important signal molecule for this enzyme. The recommended dietary allowances (RDA) for protein is 0.8 grams of protein per kilogram of body weight per day (0.36 grams per pound of body weight) to meet the needs of most of the adult population. For people ranging from 100-200 pounds, 36-72 grams of protein would meet their daily protein requirement.

However, it is important to recognize that your protein requirement may be altered as you get older. Older adults may be consuming less food as a result of decreased appetite, dental problems, impaired taste, swallowing issues, financial problems, and acute and chronic disease, which combined with decreased digestive efficiency and utilization of protein, tend to increase the requirement of protein intake of the elderly compared to more active younger adults. (3,4)

An evaluation of more than 11,000 adults ranging in age from 51-70+ suggested that dietary protein intake was significantly lower in older age groups and that 46 percent of these older adults were not meeting the RDA of daily protein intake. An even more significant decrease was seen in older adults with acute and chronic illness. (5) 

A growing body of evidence has suggested that the RDA in older adults should actually be increased from the typical RDA of 0.36 grams per pound of body weight to 0.45-0.68, which would increase recommended protein intake to 67-100 grams for a 150 pound person.(6) 

Elder adults consuming 92 grams of protein a day had a 30 percent lower risk of loss of functional integrity associated with gait, speed, and grip strength, and significantly lower risk of falls, fractures, and frailty.(7) These benefits were particularly more evident in women than men. An international group suggested that older people need 0.45-0.54 grams of protein per pound of body weight to make up for age-related changes in protein metabolism, organ assimilation, and declining repair responses to ingested protein. (8) It should be noted that people of any age, especially older people with kidney damage or disease, should limit their protein intake.

In a study done over a three-year period, older men and women, ages 70-79, consuming 91 grams of protein daily lost 40 percent less lean mass than those eating 50-60 grams a day. (9) Evaluating over 72,000 older adults in a Framingham cohort study, when protein intake was increased from the typical RDA levels to 76 grams daily in women and 80 grams daily in men, there was a significant increase in the mass and strength of the quadriceps muscle (thigh muscle that extends the lower leg). (10) In a national nutritional survey of over 24,000 older adults, highest protein intake was associated with the lowest body mass index and waist circumference, significant risk factors for obesity, diabetes, and heart disease. (11) In addition, those who had higher protein consumption had higher levels of HDL cholesterol and an improvement in cardio-metabolic health.

A diverse use of whole plant foods will provide adequate protein for muscle growth. A consistent use of plant foods high in leucine, including legumes, seeds, nuts, whole grains, and soy proteins, are especially important. Beans and lentils (14-18 grams per cup), nuts and seeds (4-12 grams per ounce), oatmeal (8 grams per cup), and quinoa (which provides complete protein containing all the essential amino acids at 8 grams per cup) are valuable sources of plant protein. Data from United States Department of Agriculture also makes it clear that a variety of deep greens and veggies provide additional sources of protein with the added benefit of low calorie density to your diet. A pound of broccoli provides 158 calories and 10.8 grams of protein; a pound of kale provides 128 calories and 8.6 grams of protein; and a pound of spinach provides 104 calories and 12 grams of protein; whereas a pound of beef sirloin contains 1000 calories and 132 grams of protein. 

Use of Protein Powders

The NHA strongly advocates whole plant food sources of protein. However, since injury  and complications of aging may increase the need for more protein intake, it can sometimes be difficult to satisfy an increased protein requirement from daily food intake alone. Under these conditions, the use of protein powder supplementation may have some limited value. Unfortunately many commercial protein powders can also contain added sugars, calories, artificial flavorings, thickeners and even toxic chemicals that may increase digestive distress, weight gain and other disease risks. (12) 

A group called The Clean Label Project screened a variety of protein powders for 130 different toxins and discovered that many protein powders contain heavy metals (lead, arsenic, cadmium and mercury), bisphenol A (BPA), which is used to make plastics and the metal casings of canned food, and pesticides that are linked to a variety of cancers and other disease conditions. (13) If you decide to add additional protein to your diet with protein powder, use protein powder made from organic plant protein without any added sugar, salt, preservatives or toxic additives.  

Timing of Protein Intake and Body Mass Index

The timing of protein consumption may be important for health, muscle mass, and function as you get older. (14) Spreading protein consumption out across the day may provide increased benefits for older adults. Since older adults are less efficient in processing protein, they may need larger amounts, as much as 20-25 grams, per meal. If the amount of protein you eat at a meal is too small, you may not adequately stimulate the uptake of amino acids into skeletal muscles. Muscle protein synthesis was 25% higher when the same daily quantity of protein was consumed across the meals of the day instead of large quantities at any one meal. (15) The more traditional heavy protein dinner should be replaced by a more even intake of protein throughout the day, especially starting with the first meal of your day.

The great news is that sarcopenia can be modified, prevented and reversed by weight training the major muscle groups of the body several times a week and consuming substantial protein from whole plant food. 

References

1. Trombetti A et al. Age-associated declines in muscle mass, strength, power and physical performance: impact of fear of falling and quality of life. Osteoporosis Int 2016;27(2):463-471.

2. Rodrigues F et al. A review of aging, sarcopenia, falls, and resistance trainingin community-dwelling older adults. International Journal of Environmental Research and Public Health. 2022; 19(2):874.

3. Volpi E et al. Is the optimal level of protein intake for older adults greater than the recommended daily allowance. J Gerontol A Biol Sci Med Sci. 2013; 68(6):677-680.

4. Young VP. Amino acids and protein in relation to the nutrition of elderly people. Age Ageing 1990, July; 19(4):S10-S24.

5. Krok-Schoen JL et al. Low dietary protein intakes and associated patterns and functional limitations in an aging population: a NHANES analysis. J Nutr Health and Aging (2019); 23:338-347

6. Paddor-Jones D et al. Protein and healthy aging. Am J Clin Nutr. June, 2015;101(6):1339S-1345S.

7. Hruby A et al. Protein intake and functional integrity in aging: The Framingham Heart Study Offspring. J Gerontol Series, Jan 2020; 75(1):123-130.

8. Bauer J et al. Evidence-based recommendations for optimal dietary protein intake in older people: A position paper from PROT-AGE study group. JAMDA. Aug, 2013;14(8):542-559.

9. Houston D et al. Dietary protein intake is associated with lean muscle mass change in older community-dwelling adults: the healthy aging and body composition (Health ABC) study. Am J Clin Nutr. 2008 Jan; 87(1):150-155.

10. Sahni S et al. Higher protein intake associated with higher mass and quadricep muscle strength in adult men and women. J Nutr. 2015 July; 145(7):1569-1575.

11. Pasiakos S. Higher-Protein diets are associated with higher HDL-cholesterol and lower BMI and waist circumference in US adults. J Nutr. 2015 March; 145(3):605-614.

12. The hidden dangers of protein powders. Harvard Health Publishing, Harvard Medical School, August 15, 2022.

13. op cit.

14. Gerald J and Dorothy R Friedman School of Nutrition Science and Policy. Rethinking protein needs for older adults. Tufts Health and Nutrition Newsletter, updated September 17, 2019.

15. Paddor-Jones D et al. Protein and healthy aging. Am J Clin Nutr. June, 2015;101(6):1339S-1345S.