and the reference articles at the end.
The optimal amount of protein to support muscle growth and provide other potential health benefits is still being determined. Current guidelines recommend moderate consumption of good quality protein (0.8 g/kg of ideal body weight per day) from a variety of sources for adults ages 19 and older. To put this figure into context, a 150-pound adult would require 54 grams of protein daily. To help make it more understandable, an ounce of lean meat and other plant-based proteins each contain approximately 7 grams of protein per serving and a cup of fat-free or low-fat milk contains 8 grams of protein.
protein’s important role in reducing the risk of sarcopenia, a progressive decline in muscle mass and strength that is an effect of normal aging.
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Protein 101
Protein is the major functional and structural component of all the cells of the body and is comprised of amino acids, the building blocks of protein. An essential (also called indispensable) amino acid is one that cannot be synthesized by the body; and therefore, must be consumed as part of the diet. A non-essential amino acid is one that can be produced by the body and, therefore, is not required to come from the diet.
It is recommended that 10-35 percent of calories come from protein. Healthy adults are encouraged to consume 0.8 grams of protein per day per kilogram of body weight. For example, a person who weighs 160 pounds would need 58 grams of protein per day.
Protein comes from a variety of sources. Beef, poultry, fish, and eggs are animal sources of protein that also provide essential B-vitamins such as folate, zinc, and iron. Dairy products, such as milk, cheese, and yogurt, provide calcium and supply protein in the form of casein and whey. Soybeans and soy protein-based foods, like soy milk and soy-based meat alternatives, are a plant based source of protein, which are low in saturated fat and cholesterol-free, and may play a role in reducing risk of heart disease.
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This article, which focuses on protein and sarcopenia, is the second in a series of articles examining an expanded role for protein and health.
What is Sarcopenia?
Sarcopenia is the progressive decline in muscle mass and strength that occurs as an effect of natural aging. More specifically, it is defined as a three to eight percent reduction in lean muscle mass per decade after the age of 30.
Sarcopenia is the progressive decline in muscle mass and strength that occurs as an effect of natural aging. More specifically, it is defined as a three to eight percent reduction in lean muscle mass per decade after the age of 30.
Scope of Sarcopenia
Sarcopenia is widespread among the elderly, yet surprisingly remains in relative obscurity. It is thought to affect 30 percent of those age 60 years and over, and greater than 50 percent of those older than 80 years of age. Advanced sarcopenia is synonymous with physical frailty and associated with increased likelihood of falls, disability, and the impairment of activities of daily living. With such a high prevalence and potential risk, it comes as no surprise that sarcopenia significantly contributes to the cost of healthcare. In 2000, the estimated direct healthcare cost of sarcopenia in the United States was $18.5 billion, or about 1.5 percent of total healthcare expenditures for that year. With an increasingly aging population, the cost of providing healthcare to older individuals is sure to become even more challenging for public health officials.
Sarcopenia is widespread among the elderly, yet surprisingly remains in relative obscurity. It is thought to affect 30 percent of those age 60 years and over, and greater than 50 percent of those older than 80 years of age. Advanced sarcopenia is synonymous with physical frailty and associated with increased likelihood of falls, disability, and the impairment of activities of daily living. With such a high prevalence and potential risk, it comes as no surprise that sarcopenia significantly contributes to the cost of healthcare. In 2000, the estimated direct healthcare cost of sarcopenia in the United States was $18.5 billion, or about 1.5 percent of total healthcare expenditures for that year. With an increasingly aging population, the cost of providing healthcare to older individuals is sure to become even more challenging for public health officials.
Reduce Risk
Although the onset of sarcopenia may be inevitable for some, it may be avoidable and reversible for others. Researchers have identified two measures that can play a role in the fight against sarcopenia: diet and exercise. The benefits of consuming a well-balanced diet and getting regular physical activity are widespread and diverse. Although difficulties implementing diet and exercise interventions with the elderly are well documented, there is no denying the positive impact both have on sarcopenia. Older people can offset the progression of sarcopenia through regular resistance exercise. Furthermore, the benefits of this type of exercise, including increasing muscle strength and size, may be supported by consuming moderately more than the current daily recommendation for protein.
Although the onset of sarcopenia may be inevitable for some, it may be avoidable and reversible for others. Researchers have identified two measures that can play a role in the fight against sarcopenia: diet and exercise. The benefits of consuming a well-balanced diet and getting regular physical activity are widespread and diverse. Although difficulties implementing diet and exercise interventions with the elderly are well documented, there is no denying the positive impact both have on sarcopenia. Older people can offset the progression of sarcopenia through regular resistance exercise. Furthermore, the benefits of this type of exercise, including increasing muscle strength and size, may be supported by consuming moderately more than the current daily recommendation for protein.
Increase Intake in Older Individuals
Protein is recognized as the key macronutrient responsible for safeguarding against sarcopenia, but there is some debate over the exact amount required. Presently, the daily recommended dietary intake (RDI) for protein is 0.8 grams per kilogram of body weight for adults ages 19 and older, but recent arguments claim this amount may not promote optimal health or protect the elderly population from sarcopenic muscle loss. Unfortunately, many older persons may not be meeting the current RDI standards for protein, with approximately 35 percent consuming less than what is recommended, and about 15 percent consuming less than 75 percent of recommended amounts. Even greater cause for concern is that emerging research points to the need for moderately higher protein recommendations (1-1.3 grams per kilogram of body weight per day) than already exist to reduce the risk of sarcopenia. In other words, although many older individuals lack a sufficient amount of protein in their diet, the true protein deficiency may be even larger than we realize.
Protein is recognized as the key macronutrient responsible for safeguarding against sarcopenia, but there is some debate over the exact amount required. Presently, the daily recommended dietary intake (RDI) for protein is 0.8 grams per kilogram of body weight for adults ages 19 and older, but recent arguments claim this amount may not promote optimal health or protect the elderly population from sarcopenic muscle loss. Unfortunately, many older persons may not be meeting the current RDI standards for protein, with approximately 35 percent consuming less than what is recommended, and about 15 percent consuming less than 75 percent of recommended amounts. Even greater cause for concern is that emerging research points to the need for moderately higher protein recommendations (1-1.3 grams per kilogram of body weight per day) than already exist to reduce the risk of sarcopenia. In other words, although many older individuals lack a sufficient amount of protein in their diet, the true protein deficiency may be even larger than we realize.
Divide and Conquer
As we grow older, the body becomes less efficient in converting amino acids into muscle tissue. However, higher doses of amino acids may be capable of stimulating muscle building to a similar extent as that of the young. In addition to meeting daily protein requirements, research indicates that reaching a specific threshold of protein at each meal may generate a maximum muscle building effect. Thus, assuming adequate total energy intake and normal renal function, placing importance on the distribution of protein across meals is paramount and may be a useful strategy for muscle mass maintenance.
As we grow older, the body becomes less efficient in converting amino acids into muscle tissue. However, higher doses of amino acids may be capable of stimulating muscle building to a similar extent as that of the young. In addition to meeting daily protein requirements, research indicates that reaching a specific threshold of protein at each meal may generate a maximum muscle building effect. Thus, assuming adequate total energy intake and normal renal function, placing importance on the distribution of protein across meals is paramount and may be a useful strategy for muscle mass maintenance.
Build Strong Bones
In addition to aiding muscle development, protein also benefits bone health. Similar to many other body tissues, bones undergo protein turnover and require a steady stream of dietary protein for maintenance. However, just as the current DRI for protein for muscle maintenance may be too low for older individuals; it may also be too low for optimal bone health. In fact, research with this population has identified a positive association between protein intake and change in bone mass density in those with the highest intake of protein that were supplemented with calcium and vitamin D. So, while the role of protein and bone health is important, it should also be complemented with calcium and Vitamin D.
In addition to aiding muscle development, protein also benefits bone health. Similar to many other body tissues, bones undergo protein turnover and require a steady stream of dietary protein for maintenance. However, just as the current DRI for protein for muscle maintenance may be too low for older individuals; it may also be too low for optimal bone health. In fact, research with this population has identified a positive association between protein intake and change in bone mass density in those with the highest intake of protein that were supplemented with calcium and vitamin D. So, while the role of protein and bone health is important, it should also be complemented with calcium and Vitamin D.
Defending against the onset of sarcopenia is a daunting task, particularly when it comes to getting a person to comply with new or unfamiliar lifestyle modifications. Individuals may be challenged to find ways to incorporate more exercise and consume the recommended amounts of protein every day. Advice about how to reduce risk of sarcopenia should take into consideration the many barriers that might prevent someone from taking steps to build strong muscles and bones while improving their quality of life in later years.
Centers for Disease Control and Prevention. Department of Health and Human Services. “Healthy Aging for Older Adults.” http://www.cdc.gov/aging/.
