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Protein Consumption and the Elderly: What Is the Optimal Level of Intake?

  • Lee Gil Ya Cancer and Diabetes Institute, Gachon University School of Medicine, Incheon, South Korea


Maintaining independence, quality of life, and health is crucial for elderly adults. One of the major threats to living independently is the loss of muscle mass, strength, and function that progressively occurs with aging, known as sarcopenia. Several studies have identified protein (especially the essential amino acids) as a key nutrient for muscle health in elderly adults. Elderly adults are less responsive to the anabolic stimulus of low doses of amino acid intake compared to younger individuals. However, this lack of responsiveness in elderly adults can be overcome with higher levels of protein (or essential amino acid) consumption. The requirement for a larger dose of protein to generate responses in elderly adults similar to the responses in younger adults provides the support for a beneficial effect of increased protein in older populations. The purpose of this review is to present the current evidence related to dietary protein intake and muscle health in elderly adults.
Protein Consumption and the Elderly: What Is the
Optimal Level of Intake?
Jamie I. Baum 1, *, Il-Young Kim 2and Robert R. Wolfe 2
1Department of Food Science, University of Arkansas, 2650 N. Young Ave, Fayetteville, AR 72704, USA
2Department of Geriatrics, the Center for Translational Research on Aging and Longevity,
Donald W. Reynolds Institute on Aging
, College of Medicine, The University of Arkansas for Medical Sciences,
Little Rock, AR 72205, USA; (I.-Y.K.); (R.R.W.)
*Correspondence:; Tel.: +1-479-575-4474
Received: 26 May 2016; Accepted: 3 June 2016; Published: 8 June 2016
Maintaining independence, quality of life, and health is crucial for elderly adults. One of
the major threats to living independently is the loss of muscle mass, strength, and function that
progressively occurs with aging, known as sarcopenia. Several studies have identified protein
(especially the essential amino acids) as a key nutrient for muscle health in elderly adults. Elderly
adults are less responsive to the anabolic stimulus of low doses of amino acid intake compared to
younger individuals. However, this lack of responsiveness in elderly adults can be overcome with
higher levels of protein (or essential amino acid) consumption. The requirement for a larger dose of
protein to generate responses in elderly adults similar to the responses in younger adults provides the
support for a beneficial effect of increased protein in older populations. The purpose of this review is
to present the current evidence related to dietary protein intake and muscle health in elderly adults.
Keywords: protein; aging; muscle; requirements; anabolic response; protein synthesis; elderly
1. Introduction
The United States is experiencing considerable growth in its elderly adult population. By 2015,
the population aged 65 and over is projected to reach nearly 84 million [
]. Maintaining independence,
quality of life, and health is crucial for elderly adults [
]. One of the major threats to living
independently is the loss of muscle mass, strength, and function that progressively occurs with
aging, known as sarcopenia [
]. A loss or reduction in skeletal muscle function often leads to
increased morbidity and mortality either directly, or indirectly, via the development of secondary
diseases such as cardiovascular disease, diabetes, and obesity [
]. The prevalence of obesity among
elderly adults has also increased over the last several decades. For example, the prevalence of obesity
among men aged 65–74 increased from 31.6% in 1999–2002 to 41.5% in 2007–2010. Between 2007 and
2010, approximately 35% of adults aged 65 and over were obese [
]. One reason for the increase in
obesity could be due to body composition shifts that occur as we age, resulting in a higher percentage
of body fat and decreases in muscle mass with age [
]. Both sarcopenia and obesity act synergistically,
which increases the risk of negative health outcomes and earlier onset of disability [2].
Nutrition plays an essential role in the health and function of elderly adults [
]. Inadequate
nutrition can contribute to the development of both sarcopenia and obesity [
]. As life expectancy
continues to rise, it is important to consider optimal nutritional recommendations that will improve
health outcomes, quality of life, and physical independence in elderly adults [
]. Several studies have
identified protein as a key nutrient for elderly adults (reviewed in [
]). Protein intake greater than
the recommended amounts may improve muscle health, prevent sarcopenia [
], and help maintain
energy balance, weight management [
], and cardiovascular function [
]. Benefits of increased
protein intake include improved muscle function and the prevention onset of chronic diseases, which
Nutrients 2016,8, 359; doi:10.3390/nu8060359
Nutrients 2016,8, 359 2 of 9
can increase quality of life in healthy elderly adults [
]. Therefore, the purpose of this review is to
present the current evidence related to dietary protein intake and muscle health in elderly adults.
2. Optimal Protein Intake for Elderly Adults
2.1. Dietary Protein Recommendations
Traditionally, protein recommendations have been based on studies that estimate the minimum
protein intake necessary to maintain nitrogen balance [
]. However, the problem with relying on
these results is that they do not measure any physiological endpoints relevant to healthy aging,
such as muscle function. The current dietary recommendations for protein intake include the
dietary reference intakes (DRI) for macronutrients, which include an estimated average requirement
(EAR), a recommended dietary allowance (RDA) and an acceptable macronutrient distribution range
(AMDR) [
]. In the case of daily protein intake, the EAR for dietary protein is 0.66 g/kg/day and the
Food and Nutrition Board recommends an RDA of 0.8 g/kg/day for all adults over 18 years of age,
including elderly adults over the age of 65. The RDA for protein was based on all available studies
that estimate the minimum protein intake necessary to avoid a progressive loss of lean body mass as
determined by nitrogen balance [
]. The Food and Nutrition Board recognizes a distinction between
the RDA and the level of protein intake needed for optimal health. Therefore, the recommendation for
the ADMR includes a range of optimal protein intakes in the context of a complete diet (10%–35% of
daily energy intake come from protein [
]), which makes the ADMR more relevant to normal dietary
intake than the RDA [3].
2.2. Protein Requirements for Elderly Adults
Experts in the field of protein and aging recommend a protein intake between 1.2 and 2.0 g/kg/day
or higher for elderly adults [
]. The RDA of 0.8 g/kg/day is well below these recommendations
and reflects a value at the lowest end of the AMDR. It is estimated that 38% of adult men and 41% of
adult women have dietary protein intakes below the RDA [16,17].
Most published results, based on data from either epidemiological or short-term studies, indicate
a potential beneficial effect of increasing protein intake in elderly adults. These data demonstrate that
elderly adults, compared with younger adults, are less responsive to low doses of amino acid intake [
However, this lack of responsiveness in healthy older adults can usually be overcome with higher
levels of essential amino acid (EAA) consumption [
]. This is also reflected in studies comparing
varying levels of protein consumption [
], suggesting that the lack of muscle responsiveness to
lower doses of protein intake in elderly adults can be overcome with a higher level of protein intake.
The requirement for a larger dose of protein to generate responses in elderly adults similar to the
responses in younger adults provides the support for a beneficial effect of increased protein in older
populations [8].
The mechanism by which dietary protein affects muscle is through the stimulation of muscle
protein synthesis and/or suppression of protein breakdown by the absorbed amino acids consumed
in the diet [
]. There appears to be an EAA threshold when it comes to stimulating muscle
protein synthesis. Ingestion of relatively small amounts of EAA (2.5, 5 or 10 g) appears to increase
myofibrillar protein synthesis in a dose-dependent manner [
]. However, a larger dose of EAA
(20–40 g) fail to elicit an additional effect on protein synthesis in young and older subjects. Similar
results were observed after the ingestion of either 113 or 340 g of lean beef containing 10 or 30 g
EAA, respectively [
]. Despite a threefold increase in EAA content, there was no further increase
in protein synthesis in either young or older subjects following consumption of 340 g versus 113 g
of protein. There are fewer data regarding the response of protein breakdown to different levels of
protein or amino acid intake. The balance between protein synthesis and breakdown is discussed in
more detail below.
Nutrients 2016,8, 359 3 of 9
2.3. Essential Amino Acid Requirements for Aging Adults
Essential amino acids, especially the branched-chain amino acid leucine, are potent stimulators
of muscle protein synthesis. Studies have focused on the stimulation of muscle protein synthesis
via the protein kinase mTORC1 (mechanistic target of rapamycin complex 1) [
], but the
in vivo
significance of this mechanism as a regulator of the rate of protein synthesis in human subjects is
not yet proven. Several studies demonstrate that maximal stimulation of muscle protein synthesis is
possible with 15 g of EAA (reviewed in [
]). This translates to ~35 g of high quality protein per meal
delivering ~15 g of EAA. A larger amount of lower quality protein, which contains a lower content
of EAA, would be required to achieve the same functional benefits. The addition of nonessential
amino acids to a supplement containing EAA does not result in additional stimulation of muscle
protein synthesis [
], indicating that the quality of the protein, or its amino acid profile, is a key
determinant of the functional potential of protein in muscle health. This is supported by several
studies demonstrating that the ingestion of milk proteins, compared with the ingestion of soy protein
stimulates muscle protein synthesis to a greater extent after resistance exercise, owing to the higher
content of EAA in milk protein [
]. The data from the Health, Aging and Body Composition study
support these findings [31], showing that intake of animal protein (with greater content of EAA), but
not plant protein, was significantly associated with the preservation of lean body mass over three years
in older adults [
]. In that study, individuals in the highest quintile of protein intake had 40% less
loss in lean body mass than those in the lowest quintile of protein intake [31].
2.4. The Importance of Protein Quality
When considering protein intake, it is also important to consider total energy intake. Age is
associated with a progressive decline in basal metabolic rate (BMR) at a rate of 1%–2% per decade
after 20 years of age [
]. This reduction in BMR is closely associated with the loss in fat-free
mass, including muscle, and the gain of less metabolically active fat [
] that occurs as we age [
In fact, studies suggest that BMR adjusted for the change in fat-free mass is 5% lower in elderly adults
compared to younger adults [
]. This implies that aging adults require a lower daily energy intake.
However, the extent to which BMR may increase or decrease with age depends on the balance between
weight gain with age, tending to increase BMR, and aging, which decreases BMR [35].
Although older adults typically eat less than younger adults, including less protein [
], it is
important for aging adults to consider total caloric intake when choosing a protein source to incorporate
in the diet. The discrepancies in quality between animal and plant protein sources go beyond the
amino acid profiles. When the energy content of the protein source is accounted for, the caloric intake
needed to meet the EAA requirements from plant sources of protein is considerably higher than the
caloric intake from animal sources of protein [
]. This is important to consider since obesity, especially
with aging, is a major public health concern. Obesity is the most predominant factor limiting mobility
in the elderly [37].
2.5. Dietary Protein and Muscle Anabolic Response in Elderly Adults
There is abundant evidence that muscle plays a central role in the prevention of many chronic
diseases, including diabetes and obesity [
]. In addition, evidence that optimal health for elderly
adults is dependent on maintaining muscle mass is emerging [
]. EAAs are the primary nutrients
responsible for the maintenance of muscle mass and function, but elderly individuals have reduced
anabolic sensitivity to amino acids (termed anabolic resistance). An increasing amount of evidence
suggests that a minimum threshold of EAA needs to be reached to elicit an anabolic muscle response,
and older individuals require a higher concentration of amino acids compared to younger individuals.
Optimal protein intake per meal can be defined as the minimal dose of protein intake that results
in the maximal anabolic response and thus can help maintain or improve muscle mass (reflected
as lean body mass) and function over time. It has been reported that the optimal dose of dietary
Nutrients 2016,8, 359 4 of 9
protein consumption in a meal that results in a near maximal anabolic response is ~35 g/meal [
] or
0.40 g/kg/meal of high-quality protein in elderly adults [
], translatable to 1.2 g/kg/day or 96 g/day
for an 80 kg elderly adults. The optimum amount for elderly adults (0.24 g/kg/meal) is approximately
70% greater than that for young adults (0.8 g/kg/day) [
], indicating an age-associated anabolic
resistance to dietary protein. It is likely that elderly individuals need more protein intake to achieve
a maximal anabolic response per meal considering the varying degrees of quality of protein eaten
in the real world. In a typical American diet, the consumption of the majority of total daily protein
intake skews toward dinner (~50% of total amount; ~40–60 g protein) [
] that clearly exceeds
the “optimal” protein dose (i.e., ~35 g protein/meal) without extra stimulation of anabolic response.
This led to an interesting hypothesis that spreading daily protein intake evenly throughout the day can
result in a greater cumulative anabolic response than the skewed pattern of protein intake [
]. If this
is the case, elderly adults can gain benefits regarding improvement in muscle mass and strength, and
related functions, simply by adopting even distribution pattern of equal amounts of protein intake [
However, the rationale behind this hypothesis is largely incorrect, as the hypothesis was solely based
on data on muscle protein synthesis (MPS), which is only one half of the equation determining net
anabolic response (i.e., net anabolic response = protein synthesis minus protein breakdown).
The significance of simultaneous measurement of both protein synthesis and breakdown is
dependent on a number of catabolic conditions (i.e., loss of muscle mass over time) such as type I
diabetes, cancer cachexia, and burn injury, in which the rate of protein synthesis is typically not blunted
but actually normal or often increased [
], due largely to the increased availability of amino acids
secondary to an accelerated rate of protein breakdown. This issue is important when quantifying the
net anabolic response to dietary protein intake. Furthermore, although net anabolic response at the
muscle level is the most relevant physiological response, the whole body is potentially involved in
the anabolic response to protein ingestion, as approximately half of the total body protein turnover
occurs at non-muscle tissues, particularly gut tissue [
]. Thus, determination at the muscle level could
underestimate total anabolic response. For example, a large portion of the amino acids absorbed from
a meal is retained in gut proteins that turn over rapidly [
], particularly following a mixed meal,
due largely to a systemic insulin response [
]. Those amino acids can, in turn, be released into the
blood over time as a result of a protein breakdown and be used for incorporation into new proteins in
muscle. This is of particular importance in situations where older adults consume a protein intake
greater than the amount that stimulates a maximal MPS.
Consistent with this notion, our recent findings showed that similar MPS responses were achieved
by two doses of protein intake (40 g vs. 70 g), while a greater net protein synthesis at whole-body
level was achieved with a meal containing 70 g of protein due to the suppression of breakdown
amplifying the anabolic effect of the stimulation of synthesis [
]. Furthermore, we have directly tested
the “distribution” hypothesis at two protein levels (0.8 g or 1.5 g protein/kg/day) in mixed meals
and found no beneficial effects of an even distribution pattern of protein intake on net anabolic
response at whole-body level and MPS [
]. Instead, we found the higher protein intake (i.e.,
1.5 g/kg/day) resulted in a greater anabolic response at whole-body level and MPS. Strikingly, the
positive anabolic response achieved with both levels of protein intake was largely due to reductions
in protein breakdown, indicating the importance of simultaneous determination of both protein
synthesis and breakdown, as protein synthesis actually declined with 0.8 g protein/kg/day, regardless
of the distribution patterns. Furthermore, the same study [
] showed that whole body anabolic
response increased linearly with increasing amount of protein intake (dose range: ~6.4–91.7 g), without
evidence of plateau in older adults [
]. These results extended previous findings shown by the Deutz
group [
], indicating that the amount of total protein, but not the pattern of protein intake, is
of importance with respect to maximizing anabolic response. Importantly, the linear relationship
between the amount of protein intake and anabolic response has been recognized for more than half
a century, as determined by a nitrogen balance technique, although the anabolic response beyond RDA
Nutrients 2016,8, 359 5 of 9
for protein (i.e., 0.8 g protein/kg/day) has been ignored [48]. Therefore, data indicate that there is no
practical limit to the anabolic response in increasing amount of dietary protein intake.
Taken together, the data do not support the notion that a maximal anabolic response is stimulated
with ~35 g of high quality protein per meal [
] or 0.4 g/kg/meal (1.2 g/kg/day) for older
adults [
]. The “even distribution hypothesis” was based on this limit of anabolic response [
but that hypothesis ignored many important factors in determining true net anabolic response.
These factors include the quality of protein consumed, the contribution of protein breakdown to
the net anabolic response, and the potential involvement of whole body response, all of which result
in the considerable underestimation of the maximal anabolic response. It is therefore unreasonable
to base recommendations for the optimal level of protein intake in elderly adults on the idea that the
maximal effective dose of protein is ~35 g per meal. If the goal of the optimal level of protein intake is
considered to be the amount needed to maximally stimulate protein anabolism (i.e., synthesis minus
breakdown), then consumption of dietary protein in accord with the higher end of the AMDR (35% of
total calories) is reasonable. Unfortunately, long-term studies assessing the effect of this level of dietary
protein consumption on functional outcomes in elderly adults have not been performed.
2.6. Dietary Protein and Anabolic Signaling in Muscle of Elderly Adults
Signaling through mTORC1 is involved in the regulation of several anabolic processes in the body
including protein synthesis [
]. In skeletal muscle, amino acids signal through mTORC1 to
initiate the process of protein synthesis [
]. The translation initiation factors 4E-BP1 (eukaryotic
initiation factor 4E binding protein 1) and p70S6K (ribosomal protein S6 kinase) are downstream targets
of mTORC1 [
]. Signals provided by EAA, especially leucine, are required for full activation of
this pathway [
]. Muscle becomes resistant to the normal stimulatory effects of postprandial
leucine concentrations with increasing age [
], which may result in the reduced stimulation of the
mTORC1 pathway and reduced activation of translation initiation and subsequent MPS. This could be
due to a reduced sensitivity to leucine with age, to less efficient absorption of leucine from the gut, or
to the fact that the dietary protein intake tends to decrease with age [8,55,56].
Age-related muscle loss may involve a decreased response to EAA due to decreased
phosphorylation of mTORC1 and p70S6K [
]. In response to 10 g of EAA, mTORC1 phosphorylation,
or activation, while significantly increased in skeletal muscle of elderly adults, is still significantly
lower in younger adults [
]. Guillet et al. [
] found that p70S6K phosphorylation is not stimulated
in older adults after infusion with leucine. These findings are supported by Fry et al. [
] who found
that elderly adults, compared with young adults, have significantly reduced phosphorylation of
mTORC1 and translation initiation factors after a bout of resistance exercise. Gene expression of
proteins associated with muscle protein synthesis and satellite cell function also differ between young
and elderly adults in response to exercise and supplementation with EAA [
]. While no difference
was found between young and elderly in the fasted state, there was a significant decrease in protein
(REDD1, TSC1, TSC2, and IGF1 receptor) expression six hours post-exercise and EAA intervention in
elderly adults versus young adults [
]. In addition, after only seven days of bed rest, elderly adults had
a reduced response to EAA ingestion resulting in no increase in MPS, activation of translation initiation
factors (4E-BP1 and p70S6K), and no increase in amino acid transporters [
]. Elderly adults also had
decreased LAT1 (L-type amino acid transporter) and SNAT2 (sodium-coupled neutral amino acid
transporter 2) following seven days of bed rest [
]. These findings are further supported in a study by
Tanner et al.
], who found that, after five days of bed rest, elderly adults (but not younger adults)
had reduced amino acid-induced anabolic sensitivity, resulting in decreased muscle protein synthesis.
In this study, elderly adults had increased MURF1 gene expression at baseline and increased AMPK
phosphorylation after bed rest, which is suggestive of increased muscle protein breakdown [
]. These
data are important because they demonstrate how quickly an injury or hospital stay could decrease
skeletal muscle function. While all of these data suggest a potential role of changes in sensitivity of
mTORC1 and related factors in the anabolic response as well as anabolic resistance in elderly adults, it
Nutrients 2016,8, 359 6 of 9
must also be acknowledged that the nature of the data is correlational and thus does not definitively
prove a cause–effect relationship. To this end, it has recently been shown that consumption of a very
small dose of EAA (3 g) can stimulate muscle protein anabolism equivalently to 20 g of whey protein
in the absence of any time-coincident changes in initiation factor activity [62].
3. Conclusions
Elderly adults are less responsive to the anabolic stimulus of low doses of amino acid intake
compared to younger adults [
]. However, this lack of responsiveness in elderly adults can be
overcome with higher levels of protein consumption [
]. This is also reflected in studies comparing
varying levels of protein intake [
]. This suggests that the lack of muscle responsiveness to lower
doses of protein in older adults can be overcome with a higher level of protein intake. The requirement
for a larger dose of protein to generate responses in elderly adults similar to the responses in younger
adults provides the support for a beneficial effect of increased protein in elderly populations [
The consumption of dietary protein consistent with the upper end of the AMDRs (as much as 30%–35%
of total caloric intake) may prove to be beneficial, although practical limitations may make this level of
dietary protein intake difficult. The consumption of high-quality proteins that are easily digestible and
contain a high proportion of EAAs lessens the urgency of consuming diets with an extremely high
protein content.
The authors were supported by the Claude D. Pepper Center for Older Americans in Little
Rock, AR. Baum and Kim were supported by a Pepper Center Pilot Study Award P30 AG028718. Wolfe has
received honoraria for talks or consulting from the National Cattleman’s Beef Association, PepsiCo, and Pronutria.
Wolfe has also received research grants for the Abbott Nutrition and National Cattleman’s Beef Association.
Baum has received grants from the Egg Nutrition Center/American Egg Board.
Author Contributions: The authors wrote and reviewed the material together.
Conflicts of Interest: The authors declare no conflict of interest.
The following abbreviations are used in this manuscript:
4E-BP1 eukaryotic initiation factor 4E-binding protein 1
AMDR acceptable macronutrient distribution range
AMPK AMP-activated protein kinase
BMR basal metabolic rate
DRI dietary reference intake
EAA essential amino acids
EAR estimated average requirement
LAT1 L-type amino acid transporter
MPS muscle protein synthesis
mTORC1 mechanistic target of rapamycin
MURF1 muscle RING-finger protein-1
p70S6K ribosomal protein S6 kinase
RDA recommended dietary allowance
REDD1 regulated in development and DNA damage responses 1
SNAT2 sodium-coupled neutral amino acid transporter 2
TSC1 tuberous sclerosis 1
TSC2 tuberous sclerosis 2
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2016 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access
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... Over the past decade, a number of experts and scientific advisory groups have evaluated the adequacy of protein intake recommendations for adults over the age of 60-65 [10][11][12][13][14]. In the US, for adults over the age of 60, the Recommended Dietary Allowance for protein intake established by the Food and Nutrition Board of the National Academy of Medicine is 0.8 g protein/kg body weight/d, which is the same as for younger adults [15]. ...
... The PROT-AGE Study Group, a consortium of the European Union Geriatric Medicine Society (EUGMS), in cooperation with other scientific organizations, recommends an intake of 1-1.2 g protein/g body weight/d for adults over age 65 [10]. Additional insights developed in recent years have prompted independent experts to recommend a protein intake of at least 1.2 g protein/kg body weight for adults age >65 [11,[16][17][18]. While there is a range of protein intake recommendations by authoritative sources from 0.8 to 1.2 g protein intake/kg body weight/d, the higher daily intake target is associated with more favorable conditions for maximal protein synthesis in older adults (e.g., [18]). ...
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Insufficient protein intake is a common challenge among older adults, leading to loss of muscle mass, decreased function and reduced quality of life. A protein intake of 0.4 g/kg body weight/meal is recommended to help prevent muscle loss. The purpose of this study was to assess whether the protein intake of 0.4 g/kg body weight/meal could be achieved with typical foods and whether culinary spices could enhance protein intake. A lunch meal test was conducted in 100 community-dwelling volunteers; 50 were served a meat entrée and 50 were served a vegetarian entrée with or without added culinary spices. Food consumption, liking and perceived flavor intensity were assessed using a randomized, two-period, within subjects crossover design. Within the meat or vegetarian treatments, there were no differences in entrée or meal intakes between spiced and non-spiced meals. Participants fed meat consumed 0.41 g protein/kg body weight/meal, while the vegetarian intake was 0.25 g protein/kg body weight/meal. The addition of spice to the vegetarian entrée significantly increased liking and flavor intensity of both the entrée and the entire meal, while spice addition only increased flavor for the meat offering. Culinary spices may be a useful tool to improve the liking and flavor of high-quality protein sources among older adults, especially when used with plant-based foods, although improving liking and flavor alone are insufficient to increase protein intake.
... Most of the reviewed articles included in this integrative review recommend a high protein diet (from 1.6 to 3 g/kg/day) with 20-30 g of leucine-rich protein (≈3 g) per meal throughout the day (including pre-sleep intake). This dosage per meal (0.3 g of protein per kg per meal) has been shown to be effective in increasing MPS in young [19] and older adults [82]. It needs to be noted that a uniform distribution of proteins over a 24-h period is more favorable than when quantities are distributed unevenly [83]. ...
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It is estimated that three to five million sports injuries occur worldwide each year. The highest incidence is reported during competition periods with mainly affectation of the musculo-skeletal tissue. For appropriate nutritional management and correct use of nutritional supplements, it is important to individualize based on clinical effects and know the adaptive response during the rehabilitation phase after a sports injury in athletes. Therefore, the aim of this PRISMA in Exercise, Rehabilitation, Sport Medicine and Sports Science PERSiST-based systematic integrative review was to perform an update on nutritional strategies during the rehabilitation phase of musculoskeletal injuries in elite athletes. After searching the following databases: PubMed/Medline, Scopus, PEDro, and Google Scholar, a total of 18 studies met the inclusion criteria (Price Index: 66.6%). The risk of bias assessment for randomized controlled trials was performed using the RoB 2.0 tool while review articles were evaluated using the AMSTAR 2.0 items. Based on the main findings of the selected studies, nutritional strategies that benefit the rehabilitation process in injured athletes include balanced energy intake, and a high-protein and carbohydrate-rich diet. Supportive supervision should be provided to avoid low energy availability. The potential of supplementation with collagen, creatine monohydrate, omega-3 (fish oils), and vitamin D requires further research although the effects are quite promising. It is worth noting the lack of clinical research in injured athletes and the higher number of reviews in the last 10 years. After analyzing the current quantitative and non-quantitative evidence, we encourage researchers to conduct further clinical research studies evaluating doses of the discussed nutrients during the rehabilitation process to confirm findings, but also follow international guidelines at the time to review scientific literature.
... Pharmacological approaches for ameliorating LPF in the elderly have not been successful due to multiple comorbidities associated with age and side effects of drugs [5]. In some cases, exercise training has improved the functional performances of older peoples with LPF [6,7], but not in all [8,9]. ...
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In a recent randomized, double-blind, placebo-controlled trial, we were able to demonstrate the superiority of a dietary supplement composed of essential amino acids (EAAs) over whey protein, in older adults with low physical function. In this paper, we describe the comparative plasma protein expression in the same subject groups of EAAs vs whey. The plasma proteomics data was generated using SOMA scan assay. A total of twenty proteins were found to be differentially expressed in both groups with a 1.5-fold change. Notably, five proteins showed a significantly higher fold change expression in the EAA group which included adenylate kinase isoenzyme 1, casein kinase II 2-alpha, Nascent polypeptide-associated complex subunit alpha, peroxiredoxin-1, and peroxiredoxin-6. These five proteins might have played a significant role in providing energy for the improved cardiac and muscle strength of older adults with LPF. On the other hand, fifteen proteins showed slightly lower fold change expression in the EAA group. Some of these 15 proteins regulate metabolism and were found to be associated with inflammation or other comorbidities. Gene Ontology (GO) enrichment analysis showed the association of these proteins with several biological processes. Furthermore, protein-protein interaction network analysis also showed distinct networks between upregulated and downregulated proteins. In conclusion, the important biological roles of the upregulated proteins plus better physical function of participants in the EAAs vs whey group demonstrated that EAAs have the potential to improve muscle strength and physical function in older adults. This study was registered with NCT03424265 "Nutritional interventions in heart failure."
... Potential explanations, apart from the difference in plant protein source, for these discrepant outcomes, may be the higher dosage of the protein that was used (42 gr/day versus 25 gr/day [23]) and the younger age of study participants (<40 years versus >60 years) [15,23] in previous work compared to our study. Older adults are less responsive to the anabolic stimulus of a low dose of amino acid intake than younger individuals [24]. Moreover, the digestibility of protein is also age-dependent, with poorer digestibility rates at older ages [25][26][27][28]. ...
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Background: Adequate animal-based protein intake can attenuate exercise induced-muscle damage (EIMD) in young adults. We examined the effects of 13 days plant-based (pea) protein supplementation compared to whey protein and placebo on EIMD in active older adults. Methods: 47 Physically active older adults (60+ years) were randomly allocated to the following groups: (I) whey protein (25 g/day), (II) pea protein (25 g/day) or (III) iso-caloric placebo. Blood concentrations of creatine kinase (CK) and lactate dehydrogenase (LDH), and skeletal muscle mass, muscle strength and muscle soreness were measured prior to and 24 h, 48 h and 72 h after a long-distance walking bout (20–30 km). Results: Participants walked 20–30 km and 2 dropped out, leaving n = 15 per subgroup. The whey group showed a significant attenuation of the increase in EIMD at 24 h post-exercise compared to the pea and placebo group (CK concentration: 175 ± 90 versus 300 ± 309 versus 330 ± 165, p = p < 0.001). No differences in LDH levels, muscle strength, skeletal muscle mass and muscle soreness were observed across groups (all p-values > 0.05). Conclusions: Thirteen days of pea protein supplementation (25 g/day) does not attenuate EIMD in older adults following a single bout of prolonged walking exercise, whereas the whey protein supplementation group showed significantly lower post-exercise CK concentrations.
... As we age, we need to consume more dietary protein to maintain muscle mass and function, but increasing our protein intake is often a challenge due to declining appetite and the poor palatability of high-protein foods (118,119) . There is a need for high-protein foods that are more palatable and less satiating. ...
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The rates of dietary protein digestion and absorption can be significantly increased or decreased by food processing treatments like heating, gelling and enzymatic hydrolysis, with subsequent metabolic impacts e.g. on muscle synthesis and glucose homeostasis. This review examines in vivo evidence that industrial and domestic food processing modify the kinetics of amino acid release and absorption following a protein-rich meal. It focuses on studies that used compositionally-matched test meals processed in different ways. Food processing at extremely high temperature at alkaline pH and/or in the presence of reducing sugars can modify amino acid sidechains, leading to loss of bioavailability. Some protein-rich food ingredients are deliberately aggregated, gelled or hydrolysed during manufacture. Hydrolysis accelerates protein digestion/absorption and increases splanchnic utilisation. Aggregation and gelation may slow or accelerate proteolysis in the gut, depending on aggregate/gel microstructure. Milk, beef and eggs are heat-processed prior to consumption to eliminate pathogens and improve palatability. The temperature and time of heating affect protein digestion and absorption rates, and effects are sometimes nonlinear. In light of a dietary transition away from animal proteins, more research is needed on how food processing affects digestion and absorption of non-animal proteins. Food processing modifies the microstructure of protein-rich foods, and thereby alters protein digestion and absorption kinetics in the stomach and small intestine. Exploiting this principle to optimise metabolic outcomes requires more human clinical trials in which amino acid absorption rates are measured and food microstructure is explicitly considered, measured and manipulated.
During aging total energy expenditure (TEE) decreases by 6% per decade in women, parallel to the reduction in physical activity. Resting metabolic rate (RMR) decreases 1–2% per decade and increases from 50 years (3% per decade). There is a change in fat mass (FM) not associated with the reduction in RMR or loss of fat-free mass (FFM). This increase in FM is higher in women than in men and does not always imply a change in body weight or body mass index (BMI). As caloric intake requirements decrease with aging, the right quality of food and adequate portions become more important. Energy imbalances complicate health and quality of life in both malnutrition and overweight. The ninth edition of the Dietary Guidelines for the USA published in 2020 and incorporating MyPlate are available resources to advise people and help improve nutrition, serving as a guide for adults and older active women also. Adequate calorie intake should be matched to the physical activity level in each, providing the required amount of macronutrients, vitamins, and minerals, and possible food supplements for active women to achieve proper weight control, energy balance, and heath.
This chapter contains information on differences in macro- and micro-nutrient requirements for older people compared to younger adults. Adequacy and quality of dietary intake among older people, detection of risk or presence of malnutrition, and nutritional interventions, including use of appetite stimulants and artificial nutrition modalities, are discussed. A review of nutrition as a whole is beyond the scope of this chapter; however, background on terminology and dietary guidelines is included to provide clarity to topics in the chapter. Much of the data are from the United States, although information from other industrialized nations (e.g., Europe, Australia, New Zealand) are also incorporated since similar concerns exist with dietary quality, risk of malnutrition, and the aging population among most industrialized countries.
Increased life expectancy is posing unprecedented challenges to healthcare systems worldwide. These include a sharp increase in the prevalence of chronic kidney disease (CKD) and of impaired nutritional status with malnutrition-protein-energy wasting (PEW) that portends worse clinical outcomes, including reduced survival. In older adults with CKD, a nutritional dilemma occurs when indications from geriatric nutritional guidelines to maintain the protein intake above 1.0 g/kg/day to prevent malnutrition need to be adapted to the indications from nephrology guidelines, to reduce protein intake in order to prevent or slow CKD progression and improve metabolic abnormalities. To address these issues, the European Society for Clinical Nutrition and Metabolism (ESPEN) and the European Renal Nutrition group of the European Renal Association (ERN-ERA) have prepared this conjoint critical review paper, whose objective is to summarize key concepts related to prevention and treatment of both CKD progression and impaired nutritional status using dietary approaches, and to provide guidance on how to define optimal protein and energy intake in older adults with differing severity of CKD. Overall, the authors support careful assessment to identify the most urgent clinical challenge and the consequent treatment priority. The presence of malnutrition-protein-energy wasting (PEW) suggests the need to avoid or postpone protein restriction, particularly in the presence of stable kidney function and considering the patient's preferences and quality of life. CKD progression and advanced CKD stage support prioritization of protein restriction in the presence of a good nutritional status. Individual risk-benefit assessment and appropriate nutritional monitoring should guide the decision-making process. Higher awareness of the challenges of nutritional care in older adult patients with CKD is needed to improve care and outcomes. Research is advocated to support evidence-based recommendations, which we still lack for this increasingly large patient subgroup.
This systematic review aims, however, to determine which intervention is more effective. The skeletal muscle index (SMI), handgrip, and gait speed were used as indicators of improvement, and these effects were compared across six subgroups: combined intervention versus exercise; nutrition or control group; exercise versus nutrition; and exercise or nutrition versus control group. Out of 1,596 articles, 32 studies (3,063 older adults) were selected and meta-analyzed. Comparing the combined intervention with a control group, the WMD was 0.20kg/m2, 1.56kg, and 0.08m/s for SMI, handgrip, and gait speed, respectively, all of which showed a statistically significant improvement. When a combined intervention was compared with exercise and nutrition, the former resulted in improvements in handgrip (WMD 0.38kg) and gait speed (WMD 0.12m/s). On comparing exercise and nutrition, there was an improvement in gait speed (0.12m/s) with exercise alone. On comparing exercise with a control group, only handgrip (WMD 1.74kg) and gait speed (WMD 0.11m/s) showed improvement, whereas in the nutrition versus the control group, only the handgrip (WMD 0.90kg) improved. Although exercise and nutritional therapy together demonstrated improved muscle strength, exercise is recommended for the improvement of physical performance.
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Malnutrition is a highly prevalent condition in older adults. It is associated with low muscle mass and function and increased occurrence of health problems. Maintaining an adequate nutritional status as well as a sufficient nutrient intake in older people is therefore essential to address this public health problem. For this purpose, protein supplementation is known to prevent the loss of muscle mass during aging, and the consumption of various pomegranate extracts induces numerous health benefits, mainly through their antioxidant properties. However, to our knowledge, no study has to date investigated the impact of their combination on the level of malnutrition in older people. The objective of this preliminary study was thus to evaluate the safety of a combination of protein and a pomegranate extract in healthy subjects aged 65 years or more during a 21-day supplementation period. Thirty older participants were randomly assigned to receive protein and a pomegranate extract (Test group) or protein and maltodextrin (Control group) during a 21-day intervention period. The primary outcomes were the safety and tolerability of the supplementation defined as the occurrence of adverse events, and additional secondary outcomes included physical examination and hematological and biochemical parameters. No serious adverse events were reported in any group. Changes in physical, hematological, and biochemical parameters between the initial screening and the end of the study were equivalent in both groups, except for glutamate-pyruvate transaminase (GPT) and prealbumin, for which a decrease was observed only in the Test group. Our initial findings support the safety of the combination of protein and a pomegranate extract in healthy elderly people. Future clinical trials on a larger sample and a longer period are needed to determine the efficacy of this combination.
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Skeletal muscle mass and function are progressively lost with age, a condition referred to as sarcopenia. By the age of 60, many older adults begin to be affected by muscle loss. There is a link between decreased muscle mass and strength and adverse health outcomes such as obesity, diabetes and cardiovascular disease. Data suggest that increasing dietary protein intake at meals may counterbalance muscle loss in older individuals due to the increased availability of amino acids, which stimulate muscle protein synthesis by activating the mammalian target of rapamycin (mTORC1). Increased muscle protein synthesis can lead to increased muscle mass, strength and function over time. This review aims to address the current recommended dietary allowance (RDA) for protein and whether or not this value meets the needs for older adults based upon current scientific evidence. The current RDA for protein is 0.8 g/kg body weight/day. However, literature suggests that consuming protein in amounts greater than the RDA can improve muscle mass, strength and function in older adults.
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One of the many threats to independent life is the age-related loss of muscle mass and muscle function commonly referred to as sarcopenia. Another important health risk in old age leading to functional decline is obesity. Obesity prevalence in older persons is increasing, and like sarcopenia, severe obesity has been consistently associated with several negative health outcomes, disabilities, falls, and mobility limitations. Both sarcopenia and obesity pose a health risk for older persons per se, but in combination, they synergistically increase the risk for negative health outcomes and an earlier onset of disability. This combination of sarcopenia and obesity is commonly referred to as sarcopenic obesity. The present narrative review reports the current knowledge on the effects of complex interventions containing nutrition and exercise interventions in community-dwelling older persons with sarcopenic obesity. To date, several complex interventions with different outcomes have been conducted and have shown promise in counteracting either sarcopenia or obesity, but only a few studies have addressed the complex syndrome of sarcopenic obesity. Strong evidence exists on exercise interventions in sarcopenia, especially on strength training, and for obese older persons, strength exercise in combination with a dietary weight loss intervention demonstrated positive effects on muscle function and body fat. The differences in study protocols and target populations make it impossible at the moment to extract data for a meta-analysis or give state-of-the-art recommendations based on reliable evidence. A conclusion that can be drawn from this narrative review is that more exercise programs containing strength and aerobic exercise in combination with dietary interventions including a supervised weight loss program and/or protein supplements should be conducted in order to investigate possible positive effects on sarcopenic obesity.
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Dietary guidelines suggest consuming a mixed-protein diet, consisting of high-quality animal, dairy, and plant-based foods. However, current data on the distribution and the food sources of protein intake in a free-living, representative sample of US adults are not available. Data from the National Health and Nutrition Examination Survey (NHANES), 2007-2010, were used in these analyses (n = 10,977, age ≥ 19 years). Several US Department of Agriculture (USDA) databases were used to partition the composition of foods consumed into animal, dairy, or plant components. Mean ± SE animal, dairy, and plant protein intakes were determined and deciles of usual intakes were estimated. The percentages of total protein intake derived from animal, dairy, and plant protein were 46%, 16%, and 30%, respectively; 8% of intake could not be classified. Chicken and beef were the primary food sources of animal protein intake. Cheese, reduced-fat milk, and ice cream/dairy desserts were primary sources of dairy protein intake. Yeast breads, rolls/buns, and nuts/seeds were primary sources of plant protein intake. This study provides baseline data for assessing the effectiveness of public health interventions designed to alter the composition of protein foods consumed by the American public.
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Declines in skeletal muscle mass and strength are major contributors to increased mortality, morbidity and reduced quality of life in older people. Recommended Dietary Allowances/Intakes have failed to adequately consider the protein requirements of the elderly with respect to function. The aim of this paper was to review definitions of optimal protein status and the evidence base for optimal dietary protein. Current recommended protein intakes for older people do not account for the compensatory loss of muscle mass that occurs on lower protein intakes. Older people have lower rates of protein synthesis and whole-body proteolysis in response to an anabolic stimulus (food or resistance exercise). Recommendations for the level of adequate dietary intake of protein for older people should be informed by evidence derived from functional outcomes. Randomized controlled trials report a clear benefit of increased dietary protein on lean mass gain and leg strength, particularly when combined with resistance exercise. There is good consistent evidence (level III-2 to IV) that consumption of 1.0 to 1.3 g/kg/day dietary protein combined with twice-weekly progressive resistance exercise reduces age-related muscle mass loss. Older people appear to require 1.0 to 1.3 g/kg/day dietary protein to optimize physical function, particularly whilst undertaking resistance exercise recommendations.
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The amount of dietary protein needed to prevent deficiency in most individuals is defined in the United States and Canada by the Recommended Dietary Allowance and is currently set at 0.8 g protein · kg(-1) · d(-1) for adults. To meet this protein recommendation, the intake of a variety of protein food sources is advised. The goal of this article is to show that commonly consumed food sources of protein are more than just protein but also significant sources of essential nutrients. Commonly consumed sources of dietary protein frequently contribute substantially to intakes of nutrients such as calcium, vitamin D, potassium, dietary fiber, iron, and folate, which have been identified as nutrients of "concern" (i.e., intakes are often lower than recommended). Despite this, dietary recommendations to reduce intakes of saturated fat and solid fats may result in dietary guidance to reduce intakes of commonly consumed food sources of protein, in particular animal-based protein. We propose that following such dietary guidance would make it difficult to meet recommended intakes for a number of nutrients, at least without marked changes in dietary consumption patterns. These apparently conflicting pieces of dietary guidance are hard to reconcile; however, we view it as prudent to advise the intake of high-quality dietary protein to ensure adequate intakes of a number of nutrients, particularly nutrients of concern. © 2015 American Society for Nutrition.
A novel method has been developed to determine protein requirements, which is called indicator amino acid oxidation (IAAO). This technique has been validated by comparison with the "gold standard" nitrogen balance. Using IAAO we have shown that minimum protein requirements have been underestimated by 30%-50%. The National Academy of Sciences has for macro-nutrients proposed "Acceptable Macronutrient Distribution Ranges", which for protein is 10% to 35% of total energy. In practice, we suggest 1.5-2.2 g/(kg·day) of a variety of high-quality proteins.
We have determined whole body protein kinetics i.e., protein synthesis (PS), breakdown (PB), and net balance (NB) in human subjects in the fasted state and following ingestion of ~40g (moderate protein, or MP) that has been reported to maximize the protein synthetic response or ~70g (higher protein, HP) protein, more representative of the amount of protein in the dinner of an average American diet. Twenty three healthy young men who had performed prior resistance exercise (X-MP or X-HP) or time-matched resting (R-MP or R-HP) were studied during a primed continuous infusion of L-[2H5]phenylalanine and L-[2H2]tyrosine. Subjects were randomly assigned into an exercise (X, n=12) or resting (R, n=11) group, and each group was studied at the two levels of dietary protein intake in random order. PS, PB, and NB were expressed as increases above the basal, fasting values (mg/kg LBM/min). Exercise did not significantly affect protein kinetics and blood chemistry. Feeding resulted in positive NB at both levels of protein intake: NB was greater in response to the meal containing HP (p<0.00001). The greater NB with HP was achieved primarily through a greater reduction in PB and to a lesser extent stimulation of protein synthesis (for all, p<0.0001). HP resulted in greater plasma EAA responses (p<0.01) vs. MP, with no differences in insulin and glucose responses. In conclusion, whole body net protein balance improves with greater protein intake above that previously suggested to maximally stimulating muscle protein synthesis because of a simultaneous reduction in protein breakdown.
Bed rest-induced muscle loss and impaired muscle recovery may contribute to age-related sarcopenia. It is unknown if there are age-related differences in muscle mass and muscle anabolic and catabolic responses to bed rest. A secondary objective was to determine if rehabilitation could reverse bed rest responses. Nine older and fourteen young adults participated in a 5-day bed rest challenge. This was followed by 8-weeks of high intensity resistance exercise (REHAB). Leg lean mass (DXA) and strength were determined. Muscle biopsies were collected during a constant stable isotope infusion in the postabsorptive state and after EAA ingestion on three occasions: before (PRE), after bed rest (BEDREST) and after REHAB. Samples were assessed for protein synthesis, mTORC1 signaling, REDD1/2 expression and molecular markers related to muscle proteolysis (MURF1, MAFBX, AMPKα, LC3II/I, Beclin1). We found that leg lean mass and strength decreased in older but not younger adults after BEDREST (P<0.05) and was restored after REHAB. EAA-induced mTORC1 signaling and protein synthesis increased at PRE in both age-groups (P<0.05). Although both groups had blunted mTORC1 signaling, increased REDD2 and MURF1 mRNA after BEDREST, only older adults had reduced EAA-induced protein synthesis rates and increased MAFBX mRNA, p-AMPKα and the LC3II/I ratio (P<0.05). We conclude that older adults are more susceptible than young persons to muscle loss after short-term bed rest. This may be partially explained by a combined suppression of protein synthesis and a marginal increase in proteolytic markers. Finally, rehabilitation restored bed rest-induced deficits in lean mass and strength in older adults. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
Objective. —To review published and presented data on the relationship between dietary protein and blood pressure in humans and animals. Data Sources. —Bibliographies from review articles and books on diet and blood pressure that had references to dietary protein. The bibliographies were supplemented with computerized MEDLINE search restricted to English language and abstracts presented at epidemiologic meetings. Study Selection. —Observational and intervention studies in humans and experimental studies in animals. Data Extraction. —In human studies, systolic or diastolic blood pressure were outcome measures, and dietary protein was measured by dietary assessment methods or by urine collections. In animal studies, blood pressure and related physiological effects were outcome measures, and experimental treatment included protein or amino acids. Data Synthesis. —Historically, dietary protein has been thought to raise blood pressure; however, studies conducted in Japan raised the possibility of an inverse relationship. Data analyses from subsequent observational studies in the United States and elsewhere have provided evidence of an inverse relationship between protein and blood pressure. However, intervention studies have mostly found no significant effects of protein on blood pressure. Few animal studies have specifically examined the effects of increased dietary protein on blood pressure. Conclusions. —Because of insufficient data and limitations in previous investigations, better controlled and adequately powered human studies are needed to assess the effect of dietary protein on blood pressure. In addition, more research using animal models, in which experimental conditions are highly controlled and detailed mechanistic studies can be performed, is needed to help provide experimental support for or against the protein—blood pressure hypothesis.(JAMA. 1996;275:1598-1603)