Aging adults and seniors make up a significant portion of the US population. According to 2019 US Census figures, nearly one third (30%) of Americans are now age 55 or older. For this group, maintaining quality of life, functionality and independence for as long as possible is a primary goal. To this end, the critical importance of minimizing age-related loss of muscle mass (sarcopenia) and its associated risks, such as bone loss/breakage and impaired cardiovascular function, can not be overstated.
Protein and essential amino acids (EAA), notably leucine, are widely recognized as key nutrients for building and maintaining muscle mass in people of all ages. A 2016 review paper investigating optimal levels of protein intake for elderly people noted larger doses of protein are required for older adults, compared to younger adults, in order to achieve the same degree of muscle protein synthesis.
The established protein RDA of 0.8 grams/kg body weight for “all” adults age 18 and up is insufficient for seniors. In fact, protein requirements for older adults generally range from 1.2 to 2 grams/kg body weight—possibly higher in some cases! This means the minimum EAA threshold needed to produce an anabolic response is approximately 70% greater in older adults than in young adults. The “age-associated anabolic resistance” to dietary protein is due, in part, to increased protein catabolism in older individuals, necessitating higher intakes to achieve amino acid balance in the body.
In addition to a minimum EAA threshold, there also appears to be a maximum EAA threshold beyond which larger intake fails to elicit additional impacts on muscle gain. This threshold was determined to be 15 grams of EAA or about 35 grams of quality protein per meal (the amount supplied by about 5 oz of lean beef, for example.) Quality protein in this instance refers to animal protein, which alone furnishes a full complement of essential amino acids. Plant proteins tend to be deficient in one of two essential amino acids. A three-year study comparing animal and plant protein found that only animal protein was significantly associated with the preservation of lean body mass in older adults, due to its higher, more complete EAA content. The effort to meet EAA requirements from plant sources also requires a considerably higher caloric intake, potentially setting the stage for inadvertent weight gain in older populations, since basal metabolic rates decline by 1%-2% per decade after age 20, significantly decreasing caloric needs over time.
As with low EAA intakes, low activity levels also decrease the ability to build and maintain muscle mass in older populations. In two separate studies, elderly adults showed a reduced response to EAA ingestion and decreased muscle protein synthesis after five and seven days of bed rest, suggesting how quickly injury or illness can decrease skeletal muscle function and subsequently impact quality of life.
While elderly inactive adults may be less responsive to the anabolic stimulus of low dose amino acid intake than younger people, increased consumption of quality protein or EAA can help reverse this trend. In general, consuming 35 grams of protein, two to three times per day is a baseline recommendation. Protein shakes or specially formulated drinks containing free-form amino acids may be a convenient way to help meet requirements or increase EAA consumption while keeping caloric intake down. Recently, advances in scientific amino acid formulation have led to achieving large gains with small doses; for example, 3 g of an EAA blend high in leucine was shown to stimulate muscle protein anabolism equivalently to 20 g of whey protein.
One such highly researched blend of essential amino acids, trademarked under the name Reginator®, has been shown in more than 20 clinical trials to effectively stimulate muscle protein synthesis at low doses in adult subjects of various ages and activity levels, such as seniors at rest. Reginator® is offered in an exclusive selection of Moss Nutrition Products including our new SarcoSelect® EAA with added leucine, launching in September 2020.
By Diana Allen, MS, CNS, Product Development Manager
Baum JI, et al. Protein Consumption and the Elderly: What is the Optimal Level of Intake? Nutrients. 2016 Jun 8;8(6):359