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International Society of Sports Nutrition Position Stand: Protein and Exercise

  • Center for Applied Health Sciences (CAHS)


Position Statement The following seven points related to the intake of protein for healthy, exercising individuals constitute the position stand of the Society. They have been approved by the Research Committee of the Society. 1) Vast research supports the contention that individuals engaged in regular exercise training require more dietary protein than sedentary individuals. 2) Protein intakes of 1.4 – 2.0 g/kg/day for physically active individuals is not only safe, but may improve the training adaptations to exercise training. 3) When part of a balanced, nutrient-dense diet, protein intakes at this level are not detrimental to kidney function or bone metabolism in healthy, active persons. 4) While it is possible for physically active individuals to obtain their daily protein requirements through a varied, regular diet, supplemental protein in various forms are a practical way of ensuring adequate and quality protein intake for athletes. 5) Different types and quality of protein can affect amino acid bioavailability following protein supplementation. The superiority of one protein type over another in terms of optimizing recovery and/or training adaptations remains to be convincingly demonstrated. 6) Appropriately timed protein intake is an important component of an overall exercise training program, essential for proper recovery, immune function, and the growth and maintenance of lean body mass. 7) Under certain circumstances, specific amino acid supplements, such as branched-chain amino acids (BCAA's), may improve exercise performance and recovery from exercise.
BioMed Central
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Journal of the International Society
of Sports Nutrition
Open Access
International Society of Sports Nutrition position stand: protein
and exercise
Bill Campbell
, Richard B Kreider*
, Tim Ziegenfuss
, Paul La Bounty
Mike Roberts
, Darren Burke
, Jamie Landis
, Hector Lopez
Jose Antonio
Exercise and Performance Nutrition Laboratory, Dept. of Physical Education and Exercise Science, University of South Florida, 4202 E.
Fowler Avenue, PED 214, Tampa, FL 33620, USA,
Exercise and Sport Nutrition Laboratory, Dept. of Health, Human Performance, and Recreation,
Baylor University, One Bear Place 97313, Waco, TX 76798-7313, USA,
Ohio Research Group of Exercise Science & Sports Nutrition, Wadsworth
Medical Center, 323 High St, STE 103A, Wadsworth, OH 44281, USA,
Exercise and Sport Nutrition Laboratory, Dept. of Health, Human
Performance, and Recreation, Baylor University, One Bear Place 97313, Waco, TX 76798-7313, USA,
Applied Biochemistry and Molecular
Physiology Laboratory, Department of Health and Exercise Science, University of Oklahoma, 1401 Asp Avenue, Norman, OK 73019, USA,
Exercise Science Laboratory, Dept. of Human Kinetics, St. Francis Xavier University, P.O. Box 5000 Antigonish, Nova Scotia, B2G 2W5, Canada,
Department of Biology, Lakeland Community College, 7700 Clocktower Drive, Kirtland, Ohio 44094-5198, USA,
Northwestern University
Feinberg School of Medicine, Department of Physical Medicine and Rehabilitation, Rehabilitation Institute of Chicago, 345 East Superior Street,
Chicago, IL 60611, USA and
Department of Exercise Science and Health Promotion, Florida Atlantic University, 2912 College Avenue, Davie, FL
33314, USA
Email: Bill Campbell -; Richard B Kreider* -;
Tim Ziegenfuss -; Paul La Bounty -; Mike Roberts -;
Darren Burke -; Jamie Landis -; Hector Lopez -; Jose Antonio -
* Corresponding author
Position Statement: The following seven points related to the intake of protein for healthy,
exercising individuals constitute the position stand of the Society. They have been approved by the
Research Committee of the Society. 1) Vast research supports the contention that individuals
engaged in regular exercise training require more dietary protein than sedentary individuals. 2)
Protein intakes of 1.4 – 2.0 g/kg/day for physically active individuals is not only safe, but may
improve the training adaptations to exercise training. 3) When part of a balanced, nutrient-dense
diet, protein intakes at this level are not detrimental to kidney function or bone metabolism in
healthy, active persons. 4) While it is possible for physically active individuals to obtain their daily
protein requirements through a varied, regular diet, supplemental protein in various forms are a
practical way of ensuring adequate and quality protein intake for athletes. 5) Different types and
quality of protein can affect amino acid bioavailability following protein supplementation. The
superiority of one protein type over another in terms of optimizing recovery and/or training
adaptations remains to be convincingly demonstrated. 6) Appropriately timed protein intake is an
important component of an overall exercise training program, essential for proper recovery,
immune function, and the growth and maintenance of lean body mass. 7) Under certain
circumstances, specific amino acid supplements, such as branched-chain amino acids (BCAA's), may
improve exercise performance and recovery from exercise.
Published: 26 September 2007
Journal of the International Society of Sports Nutrition 2007, 4:8 doi:10.1186/1550-2783-4-
Received: 31 August 2007
Accepted: 26 September 2007
This article is available from:
© 2007 Campbell et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Journal of the International Society of Sports Nutrition 2007, 4:8
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Protein intake recommendations
Controversy has existed over the safety and effectiveness
of protein intake above that currently recommended. Cur-
rently, the RDA for protein in healthy adults is 0.8 g/kg
body weight per day [1]. The purpose of this recommen-
dation was to account for individual differences in protein
metabolism, variations in the biological value of protein,
and nitrogen losses in the urine and feces. Many factors
need to be considered when determining an optimal
amount of dietary protein for exercising individuals.
These factors include protein quality, energy intake, car-
bohydrate intake, mode and intensity of exercise, and the
timing of the protein intake [2]. The current recom-
mended level of protein intake (0.8 g/kg/day) is estimated
to be sufficient to meet the need of nearly all (97.5%)
healthy men and women age 19 years and older. This
amount of protein intake may be appropriate for non-
exercising individuals, but it is likely not sufficient to off-
set the oxidation of protein/amino acids during exercise
(approximately 1–5% of the total energy cost of exercise)
nor is it sufficient to provide substrate for lean tissue
accretion or for the repair of exercise induced muscle dam-
age [3,4].
Protein recommendations are based upon nitrogen bal-
ance assessment and amino acid tracer studies. The nitro-
gen balance technique involves quantifying the total
amount of dietary protein that enters the body and the
total amount of the nitrogen that is excreted [5]. Nitrogen
balance studies may underestimate the amount of protein
required for optimal function because these studies do
not directly relate to exercise performance. Also, it is pos-
sible that protein intake above those levels deemed neces-
sary by nitrogen balance studies may improve exercise
performance by enhancing energy utilization or stimulat-
ing increases in fat-free mass in exercising individuals [2].
Indeed, an abundance of research indicates that those
individuals who engage in physical activity/exercise
require higher levels of protein intake than 0.8 g/kg body
weight per day, regardless of the mode of exercise (i.e.
endurance, resistance, etc.) or training state (i.e. recrea-
tional, moderately or well-trained) [6-13]. Also, there is a
genuine risk in consuming insufficient amounts of pro-
tein, especially in the context of exercise; a negative nitro-
gen balance will likely be created, leading to increased
catabolism and impaired recovery from exercise [14].
Relative to endurance exercise, recommended protein
intakes range from of 1.0 g/kg to 1.6 g/kg per day
[2,4,7,15] depending on the intensity and duration of the
endurance exercise, as well as the training status of the
individual. For example, an elite endurance athlete
requires a greater level of protein intake approaching the
higher end the aforementioned range (1.0 to 1.6 g/kg/
day). Additionally, as endurance exercise increases in
intensity and duration, there is an increased oxidation of
branched-chain amino acids, which creates a demand
within the body for protein intakes at the upper end of
this range. Strength/power exercise is thought to increase
protein requirements even more than endurance exercise,
particularly during the initial stages of training and/or
sharp increases in volume. Recommendations for
strength/power exercise typically range from 1.6 to 2.0 g/
kg/day [3,11-13,16], although some research suggests that
protein requirements may actually decrease during train-
ing due to biological adaptations that improve net protein
retention [17].
Little research has been conducted on exercise activities
that are intermittent in nature (e.g., soccer, basketball,
mixed martial arts, etc.). In a review focusing on soccer
players, a protein intake of 1.4–1.7 g/kg was recom-
mended [18]. Protein intakes within this range (1.4 to 1.7
g/kg/day) are recommended for those engaging in other
types of intermittent sports.
In summary, it is the position of the International Society
of Sport Nutrition that exercising individuals ingest pro-
tein ranging from 1.4 to 2.0 g/kg/day. Individuals engag-
ing in endurance exercise should ingest levels at the lower
end of this range, individuals engaging in intermittent
activities should ingest levels in the middle of this range,
and those engaging in strength/power exercise should
ingest levels at the upper end of this range.
Safety of protein intakes higher than RDA
It is often erroneously reported by popular media that a
chronically high protein intake is unhealthy and may
result in unnecessary metabolic strain on the kidneys
leading to impaired renal function. Another concern that
is often cited is that high protein diets increase the excre-
tion of calcium thereby increasing the risk for osteoporo-
sis. Both of these concerns are unfounded as there is no
substantive evidence that protein intakes in the ranges
suggested above will have adverse effects in healthy, exer-
cising individuals.
One of the main points of debate relative to protein intake
and kidney function is the belief that habitual protein
consumption in excess of the RDA promotes chronic renal
disease through increased glomerular pressure and hyper-
filtration [19,20]. The majority of scientific evidence cited
by the authors [20] was generated from animal models
and patients with co-existing renal disease. As such, the
extension of this relationship to healthy individuals with
normal renal function is inappropriate [21]. In a well
designed prospective cohort study, it was surmised that
high protein intake was not associated with renal func-
tional decline in women with normally operating kidneys
[22]. Also, it has been reported that there are no statisti-
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cally significant differences in age, sex, weight, and kidney
function between non-vegetarians and vegetarians (a
group demonstrated to have lower dietary protein
intakes) [23,24]. Both the non-vegetarian and vegetarian
groups possessed similar kidney function, and displayed
the same rate of progressive deterioration in renal physi-
ology with age [24]. Preliminary clinical and epidemio-
logical studies have suggested a benefit of relatively high
protein diets on major risk factors for chronic kidney dis-
ease, such as hypertension, diabetes, obesity and meta-
bolic syndrome. Future studies are necessary to further
examine the role of relatively high protein weight loss
diets, dietary protein source (quality) and quantity on the
prevalence and development of kidney disease in at risk
patient populations [25,26]. While it appears that dietary
protein intakes above the RDA are not deleterious for
healthy, exercising individuals, those individuals with
mild renal insufficiency need to closely monitor their pro-
tein intake as observational data from epidemiological
studies provide evidence that dietary protein intake may
be related to the progression of renal disease [21,26].
In addition to renal function, the relationship between
dietary protein intake and bone metabolism has also
served as the cause for some controversy. Specifically,
there is concern that a high intake of dietary protein
results in the leaching of calcium from bones, which may
lead to osteopenia and predispose some individuals to
osteoporosis. This supposition stems from early studies
reporting an increase in urine acidity from increased die-
tary protein that appeared to be linked to drawing calcium
from the bones to buffer the acid load. However, studies
reporting this effect were limited by small sample sizes,
methodological errors, and the use of high doses of puri-
fied forms of protein [27]. It is now known that the phos-
phate content of protein foods (and supplements fortified
with calcium and phosphorous) negates this effect. In
fact, some data suggest that elderly men and women (the
segment of the population most susceptible to osteoporo-
sis) should consume dietary protein above current recom-
mendations (0.8 g/kg/day) to optimize bone mass [28].
In addition, data from stable calcium isotope studies is
emerging, which suggests the main source of the increase
in urinary calcium from a high-protein diet is intestinal
(dietary) and not from bone resorption [29]. Also, given
that exercise training supplies the stimulus for increasing
skeletal muscle protein, levels in the range of 1.4 to 2.0 g/
kg/d are recommended to transform this stimulus into
additional contractile tissue, which is an important pre-
dictor in bone mass accrual during pre-pubertal growth
[30,31]. More research needs to be conducted in adults
and the elderly relative to exercise, skeletal muscle hyper-
trophy and protein intake and their cumulative effects on
bone mass. Overall, there is a lack of scientific evidence
linking higher dietary protein intakes to adverse outcomes
in healthy, exercising individuals. There is, however, a
body of scientific literature which has documented a ben-
efit of protein supplementation to the health of multiple
organ systems. It is therefore the position of the Interna-
tional Society of Sport Nutrition that active elderly indi-
viduals require protein intakes ranging from 1.4 to 2.0 g/
kg/day, and that this level of intake is safe.
Protein quality and common types of protein
To obtain supplemental dietary protein, exercising indi-
viduals often ingest protein powders. Powdered protein is
convenient and, depending on the product, can be cost-
efficient as well [32]. Common sources of protein include
milk, whey, casein, egg, and soy-based powders. Different
protein sources and purification methods may affect the
bioavailability of amino acids. The amino acid bioavaila-
bility of a protein source is best conceptualized as the
amount and variety of amino acids that are digested and
absorbed into the bloodstream after a protein is ingested.
Furthermore, amino acid bioavailability may also be
reflected by the difference between the nitrogen content
from a protein source that is ingested versus the nitrogen
content that is subsequently present in the feces. Consid-
eration of the bioavailability of amino acids into the
blood, as well as their delivery to the target tissue(s), is of
greatest importance when planning a regimen of pre- and
post-exercise protein ingestion. A protein that provides an
adequate circulating pool of amino acids before and after
exercise is readily taken up by skeletal muscle to optimize
nitrogen balance and muscle protein kinetics [33].
The quality of a protein source has previously been deter-
mined by the somewhat outdated protein efficiency ratio
(PER), and the more precise protein digestibility corrected
amino acid score (PDCAAS). The former method was
used to evaluate the quality of a protein source by quanti-
fying the amount of body mass maturing rats accrue when
fed a test protein. The latter method was established by
the Food and Agriculture Organization (FAO 1991) as a
more appropriate scoring method which utilized the
amino acid composition of a test protein relative to a ref-
erence amino acid pattern, which was then corrected for
differences in protein digestibility [34]. The U.S. Dairy
Export Council's Reference Manual for U.S. Whey and
Lactose Products (2003) indicates that milk-derived whey
protein isolate presents the highest PDCAAS out of all of
the common protein sources due to its high content of
essential and branched chain amino acids. Milk-derived
casein, egg white powder, and soy protein isolate are also
classified as high quality protein sources with all of them
scoring a value of unity (1.00) on the PDCAAS scale. In
contrast, lentils score a value of 0.52 while wheat gluten
scores a meager 0.25.
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Commercially, the two most popular types of proteins in
supplemental form are whey and casein. Recent investiga-
tions have detailed the serum amino acid responses to
ingesting different protein types. Using amino acid tracer
methodology, it was demonstrated that whey protein elic-
its a sharp, rapid increase of plasma amino acids follow-
ing ingestion, while the consumption of casein induces a
moderate, prolonged increase in plasma amino acids that
was sustained over a 7-hr postprandial time period [35].
The differences in the digestibility and absorption of these
protein types may indicate that the ingestion of "slow"
(casein) and "fast" (whey) proteins differentially mediate
whole body protein metabolism due to their digestive
properties [35]. Other studies have shown similar differ-
ences in the peak plasma levels of amino acids following
ingestion of whey and casein fractions (i.e., whey fractions
peaking earlier than casein fractions) [36,37].
Applied exercise science research has also demonstrated
the differential effects that ingesting different proteins
exerts on postprandial blood amino acid responses and
muscle protein synthesis after exercise. The data are equiv-
ocal relative to which type of protein increases net protein
status (breakdown minus synthesis) to a greater extent
after exercise. Some research has demonstrated that
despite different patterns of blood amino acid responses,
muscle protein net balance was similar in those ingesting
casein or whey [33]. However, additional research has
indicated that whey protein induced protein gain to a
greater extent than casein [38]. In contrast, several other
studies have shown that casein increased protein deposi-
tion at levels greater than whey proteins [35,37].
The recommendation of the International Society of Sport
Nutrition is that individuals engaging in exercise attempt
to obtain their protein requirements through whole
foods. When supplements are ingested, we recommend
that the protein contain both whey and casein compo-
nents due to their high protein digestibility corrected
amino acid score and ability to increase muscle protein
Protein timing
It is generally recognized that active individuals require
more dietary protein due to an increase in intramuscular
protein oxidation [39] and protein breakdown [40] that
occurs during exercise, as well as the need to further com-
plement intramuscular protein resynthesis and attenuate
proteolytic mechanisms that occur during the post-exer-
cise recovery phases [41-43]. Thus, a strategically planned
protein intake regimen timed around physical activity is
integral in preserving muscle mass or eliciting muscular
hypertrophy, ensuring a proper recovery from exercise,
and perhaps even sustaining optimal immune function.
Previously, high levels of blood amino acids following a
bout of resistance training have been found to be integral
in promoting muscle protein synthesis [44]. Evidence is
accumulating that supports the benefits of the timing of
protein intake and its effect on gains in lean mass during
resistance exercise training [45-49]. Given that much of
the research to date has been conducted on resistance
exercise, more investigations are required to ascertain the
effects of protein timing on other modes of exercise.
Research has also highlighted the positive immune and
health-related effects associated with post-exercise protein
ingestion. A previous investigation utilizing 130 United
States Marine subjects [50] examined the effects of an
ingested supplement (8 g carbohydrate, 10 g protein, 3 g
fat) immediately after exercise on the status of various
health markers. These data were compared to 129 subjects
ingesting a non-protein supplement (8 g carbohydrate, 0
g protein, 3 g fat), and 128 subjects ingesting placebo tab-
lets (0 g carbohydrate, 0 g protein, 0 g fat). Upon the com-
pletion of the 54-d trial, researchers reported that the
subjects ingesting the protein supplement had an average
of 33% fewer total medical visits, including 28% less visits
due to bacterial or viral infections, 37% less orthopedic-
related visits, and 83% less visits due to heat exhaustion.
Moreover, post-exercise muscle soreness was significantly
reduced in subjects ingesting protein when compared to
the control groups. Previous studies using animal models
have demonstrated that whey protein elicits immuno-
enhancing properties, likely due to its high content of
cysteine; an amino acid that is needed for glutathione pro-
duction [51,52]. Hence, previous research has indicated
that ingesting a protein source that is rich in essential
amino acids and is readily digestible immediately before
and following exercise training is beneficial for increasing
muscle mass, recovery following exercise, and sustaining
immune function during high-volume training periods.
While protein ingestion is emphasized in this article, the
concomitant ingestion of protein and carbohydrates prior
to and/or following exercise has also been shown to be
advantageous in increasing muscle protein synthesis; a
result which is likely due to an increase in insulin signal-
ing following the ingestion of carbohydrates.
It is the position of the International Society of Sport
Nutrition that exercising individuals should consume
high quality protein within the time period encompassing
their exercise session (i.e. before, during, and after).
The role of BCAA's in exercise
The branched-chain amino acids (i.e. leucine, isoleucine
and valine) constitute approximately one-third of skeletal
muscle protein [53]. An increasing amount of literature
suggests that of the three BCAAs, leucine appears to play
the most significant role in stimulating protein synthesis
[54]. In this regard, amino acid supplementation (partic-
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ularly the BCAAs) may be advantageous for the exercising
A few studies reported that when BCAAs were infused in
humans at rest, protein balance increases by either
decreasing the rate of protein breakdown, increasing the
rate of protein synthesis or a combination of both [55,56].
Following resistance exercise in males it has been shown
that the addition of free leucine combined with carbohy-
drate and protein led to a greater increase protein synthe-
sis as compared to taking the same amount of
carbohydrate and protein without leucine [57]. However,
the majority of the research relative to leucine ingestion
and protein synthesis has been conducted using animal
models. Similar research needs to be conducted in healthy
individuals engaging in resistance exercise.
BCAA ingestion has been shown to be beneficial during
aerobic exercise. When BCAAs are taken during aerobic
exercise the net rate of protein degradation has been
shown to decrease [58]. Equally important, BCAA admin-
istration given before and during exhaustive aerobic exer-
cise to individuals with reduced muscle glycogen stores
may also delay muscle glycogen depletion [59]. When
BCAAs were given to runners during a marathon it
improved the performance of "slower" runners (those
who completed the race in 3.05 h-3.30 h) as compared to
"faster" runners (those who completed the race in less
than 3.05 h) [60]. Although there are numerous reported
metabolic causes of fatigue such as glycogen depletion,
proton accumulation, decreases in phosphocreatine lev-
els, hypoglycemia, and increased free tryptophan/BCAA
ratio, it is the increase in the free tryptophan/BCAA ratio
that may be attenuated with BCAA supplementation. Dur-
ing prolonged aerobic exercise, the concentration of free
tryptophan increases and the uptake of tryptophan into
the brain increases. When this occurs, 5-hydroxytryp-
tamine (a.k.a. serotonin), which is thought to play a role
in the subjective feelings of fatigue, is produced. Similarly,
BCAAs are transported into the brain by the same carrier
system as tryptophan and thus "compete" with tryp-
tophan to be transported into the brain. Therefore, it is
believed that when certain amino acids such as BCAAs are
present in the plasma in sufficient amounts, it theoreti-
cally may decrease the uptake of tryptophan in the brain
and ultimately decrease the feelings of fatigue [61,62].
Furthermore, there is also research to suggest that BCAA
administration taken during prolonged endurance events
may help with mental performance in addition to the
aforementioned performance benefits [60]. However, not
all research investigating BCAA supplementation has
reported improvements in exercise performance. One
such study [63] reported that leucine ingestion taken
before and during anaerobic running to exhaustion (200
mg/kg of body weight) and during a strength training ses-
sion (100 mg/kg of body weight) did not improve exercise
performance. Reasons for discrepant results are not clear
at this time, but at the very minimum, it seems apparent
that supplementation with BCAAs does not impair per-
Because BCAAs have been shown to aid in recovery proc-
esses from exercise such as stimulating protein synthesis,
aiding in glycogen resynthesis, as well as delaying the
onset of fatigue and helping maintain mental function in
aerobic-based exercise, we suggest consuming BCAAs (in
addition to carbohydrates) before, during, and following
an exercise bout. It has been suggested that the RDA for
leucine alone should be 45 mg/kg/day for sedentary indi-
viduals, and even higher for active individuals [53]. How-
ever, while more research is indicated, because BCAAs
occur in nature (i.e. animal protein) in a 2:1:1 ratio (leu-
cine: isoleucine: valine), one may consider ingesting 45
mg/kg/day of leucine along with approximately 22.5
mg/kg/day of both isoleucine and valine in a 24 hour time
frame in order to optimize overall training adaptations.
This will ensure the 2:1:1 ratio that appears often in ani-
mal protein [64]. It should not be overlooked that com-
plete proteins in whole foods, as well as most quality
protein powders, contain approximately 25% BCAAs. Any
deficiency in BCAA intake from whole foods can easily be
remedied by consuming whey protein during the time
frame encompassing the exercise session; however, an
attempt should be made to obtain all recommended
BCAAs from whole food protein sources.
It is the position of the International Society of Sports
Nutrition that exercising individuals need approximately
1.4 to 2.0 grams of protein per kilogram of bodyweight
per day. The amount is dependent upon the mode and
intensity of the exercise, the quality of the protein
ingested, and the status of the energy and carbohydrate
intake of the individual. Concerns that protein intake
within this range is unhealthy are unfounded in healthy,
exercising individuals. An attempt should be made to
obtain protein requirements from whole foods, but sup-
plemental protein is a safe and convenient method of
ingesting high quality dietary protein. The timing of pro-
tein intake in the time period encompassing the exercise
session has several benefits including improved recovery
and greater gains in fat free mass. Protein residues such as
branched chain amino acids have been shown to be ben-
eficial for the exercising individual, including increasing
the rates of protein synthesis, decreasing the rate of pro-
tein degradation, and possibly aiding in recovery from
exercise. In summary, exercising individuals need more
dietary protein than their sedentary counterparts, which
can be obtained from whole foods as well as from high
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quality supplemental protein sources such as whey and
casein protein.
g/kg/d = grams per kilogram of bodyweight per day
BCAAs = branched-chain amino acids
Competing interests
The author(s) declare that they have no competing inter-
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... A previous study showed that a protein intake of 1.4-2.0 g/kg body weight could improve body adaptability for intensive physical activities (53). Adequate protein intake is critical in the overall exercise training program, required for proper and speedy recovery from injury including bolstering immune function, growth, and maintenance of lean body mass (53). ...
... g/kg body weight could improve body adaptability for intensive physical activities (53). Adequate protein intake is critical in the overall exercise training program, required for proper and speedy recovery from injury including bolstering immune function, growth, and maintenance of lean body mass (53). ...
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Background: Optimum dietary intake and adequate nutritional knowledge have been recognized as the key factors that play a critical role in improving the athlete's health and nutrition status. This study aimed to measure the association of nutritional knowledge, practice, supplement use, and nutrient intake with strength performance among Nepalese Taekwondo players. Methods: Between August 2019 and January 2020, a cross-sectional study was conducted among 293 Taekwondo students in Kathmandu Metropolitan City (mean age, 18 years; 63.1% male, 36.9% female). Face-to-face interviews were conducted using semi-structured questionnaires. Anthropometric measures, nutritional intake, nutrition knowledge, and practice were all recorded. The handgrip strength was measured using a handgrip dynamometer as a proxy for strength performance. Univariate and bivariate analyses were used to find out the association between predictor and outcome variables. Results: More than half of the participants had poor nutrition knowledge [54.3% (159/293)], and poor nutrition practice [55.3% (162/293)] scores. Daily mean energy, carbohydrate, protein and fat intake were 48.0, 8.6, 1.6, and 1.5, respectively among Taekwondo players. Daily total energy and carbohydrate intake were 48.2 and 8.7, respectively among male players which is higher than female players. However, daily protein and fat intake were higher in female players (1.7 and 1.6 , respectively). Both calcium (375.3 mg) and iron (9 mg) intake among Taekwondo players were significantly lower than current sports nutrition guidelines. Nutritional knowledge score (r=0.117), height (r=0.538), weight (r=0.651), body mass index (r=0.347), fat (r=0.075), and energy (r=0.127) intake showed significant positive correlation with strength performance of athletes. The strength performance was positively associated with training hours per day (β=0.41, 95% CI: 0.09-0.91), body mass index (β=0.35, 95% CI: 0.09-0.61), nutrition knowledge score (β=0.13, 95% CI: 0.01-0.25), and energy intake (β=0.13, 95% CI: 0.12-0.14). Conclusions: The nutritional knowledge and practice both were suboptimal among Taekwondo athletes. Height, weight, body mass index, nutritional knowledge, energy, and fat intake showed a positive correlation with strength performance. Future studies can build on the premise of this study to identify the robust relationship between nutritional knowledge, practice, different supplement use, and nutrient intake among other athletes too.
... The balance between the rates of protein synthesis and breakdown determines muscle mass maintenance, which is greatly influenced by dietary protein intake [1][2]. Adequate dietary protein intake is particularly desirable for athletes and athletic enthusiasts to improve their performance, or for the elderly who possess a high risk of sarcopenia and frailty [3][4][5][6][7][8]. ...
... Additionally, muscle protein synthesis (MPS) induced after protein intake is proportional to the amount of protein ingested [3], but the amount of protein required to induce muscle synthesis increases with age; therefore, higher protein intake is required in the elderly [3][4][5][6]. Dietary protein intake for muscle maintenance and weight gain should consider not only the quantity but also the quality and timing of intake [2,[9][10][11][12]. The branched-chain amino acids (BCAAs) content in essential amino acids (EAAs) is important for protein quality, and leucine has been reported to promote MPS, in particular, by stimulating the mammalian rapamycin complex 1 (mTORC1) signaling pathway [13,14]. ...
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Background: The rate of protein digestion and amino acid (AA) absorption determines the postprandial rise in circulating AA and modulates postprandial muscle protein synthesis (MPS) rates. Furthermore, it is necessary to consider the timing of protein ingestion, along with its quantity and quality, to regulate the blood AA concentration. Chicken breasts are a popular food among athletes as they are a good source of animal protein, containing sufficient essential amino acids (EAAs) and branched-chain amino acids (BCAAs). Low-molecular-weight chicken peptides (Cpep), a novel protein supplement, were isolated from chicken breasts. Blood AA dynamics, which have a significant influence on MPS rates, were observed and compared with commercially available whey- and soy-derived protein supplements.Objectives: We evaluated blood AA dynamics after Cpep intake compared with whey protein (WP), and soy protein (SP).Methods: Three groups of six healthy adult men volunteers (age 39 ± 10 years) ingested 0.3 g/kg (protein/body weight) of Cpep, WP, and SP. The concentrations of AA in the plasma were measured before and after the ingestion period and their kinetics were compared.Results: Cpep comprises free amino acids or peptides, and their average molecular weights are lower than those of WP and SP. The absorption dynamics of AA in the plasma were evaluated. After Cpep intake, EAA and BCAA concentrations peaked at 30 min and levels of EAA and BCAA were higher than those after WP and SP ingestion at 15 and 30 min, respectively. Conversely, the levels of total AA, EAA, and BCAA decreased 45 min after Cpep intake compared with WP and SP intakes. In contrast, WP and SP showed similar blood AA dynamics with a peak at 60 min.Conclusions: Cpep is absorbed significantly faster than WP and SP, making it a useful option for efficient protein intake to maintain and increase muscle mass.Keywords: chicken-derived peptides, blood amino acid dynamics, branched-chain amino acid, muscle protein synthesis
... Meanwhile, neither the Chinese nor the US apps offered any nutrition advice specific to before, during, or after exercise. According to the International Society of Sports Nutrition, proper nutritional intake before, during, and after exercise would significantly enhance exercise capacity and maintenance of normal physical function (50). We propose that app developers highlight the efficient combination of diet and exercise to promote maternal and fetal health. ...
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Background Mobile applications (apps) are becoming increasingly prevalent as tools for improving maternal health behaviors. However, the recently updated content and quality of these apps remain unknown. This research investigated the fundamental characteristics, functional modules, and overall quality of maternal apps available in the United States and China to reveal critical nutrition and physical activity gaps. Methods A systematic search was performed in Android and iOS app stores (China and the United States). Apps were eligible if they targeted pregnant or postpartum women, focused on nutrition or physical activity, and had interfaces in English or Chinese. The basic characteristics, functional modules, and overall quality of the apps were evaluated, and differences between apps available in China or the United States were determined using analysis of variance and chi-square tests. Pearson correlations were utilized to investigate links between objective quality and user rating. Results A total of 65 maternity-related nutrition and physical activity apps (34 from China and 31 from the United States) were eligible. Among them, 68% (21/31) of US apps and 56% (19/34) of Chinese apps did not provide supporting evidence for their content. A greater number of Chinese apps provided app-based general education modules, namely food nutrition knowledge ( n = 0, 0% in the United States vs. n = 30, 88.2% in China). Meanwhile, a greater number of US apps provided exercise modules, namely pregnancy yoga ( n = 21, 67.7% in the United States vs. n = 2, 5.9% in China). The overall app quality rating in the United States was lower than it was in China (mean: 3.5, SD: 0.6 in China vs. mean: 3.4, SD: 0.7 in the United States). There was no relationship between the overall app quality rating and the user rating in either country (rho = 0.11 in China and rho = –0.13 in the United States). Conclusion The characteristics and functional modules of in-store apps for maternal nutrition and physical activity differed between the United States and China. Both countries’ apps, especially Chinese apps, lacked evidence-based information, and there was no correlation between app quality and user rating. The results therefore suggest that user ratings cannot be used as an objective indicator of app quality and that it is necessary to improve the empirical basis and credibility of apps in both countries.
... These reports have highlighted a number of potential factors, including proliferation of the satellite cells, as well as IGF-1 and androgen receptor expression in high compared to low-responders (Petrella et al. 2008;Mobley et al. 2018). Moreover, intrinsic (e.g., biomolecular signaling pathways and body composition) and extrinsic (e.g., protein intake and dietary habits) factors have been explored between high and low-responders (Campbell et al. 2007). However, as noted in the able-bodied literature (Petrella et al. 2008;Mobley et al. 2018), some individuals with SCI have a more favorable hypertrophy response to NMES-RT compared to others. ...
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The purpose of the study was to identify potential predictors of muscle hypertrophy responsiveness following neuromuscular electrical stimulation resistance training (NMES-RT) in persons with chronic spinal cord injury (SCI). Data for twenty individuals with motor complete SCI who completed twice weekly NMES-RT lasting 12–16 weeks as part of their participation in one of two separate clinical trials were pooled and retrospectively analyzed. Magnetic resonance imaging (MRI) was used to measure muscle cross-sectional area (CSA) of the whole thigh and knee extensor muscle before and after NMES-RT. Muscle biopsies and fasting biomarkers were also measured. Following the completion of the respective NMES-RT trials, participants were classified into either high-responders (n = 8; muscle CSA > 20%) or low-responders (n = 12; muscle CSA < 20%) based on whole thigh muscle CSA hypertrophy. Whole thigh muscle and knee extensors CSAs were significantly greater (P < 0.0001) in high-responders (29 ± 7% and 47 ± 15%, respectively) compared to low-responders (12 ± 3% and 19 ± 6%, respectively). There were no differences in total caloric intake or macronutrient intake between groups. Extensor spasticity was lower in the high-responders compared to the low-responders as was the dosage of baclofen. Prior to the intervention, the high-responders had greater body mass compared to the low-responders with SCI (87.8 ± 13.7 vs. 70.4 ± 15.8 kg; P = 0.012), body mass index (BMI: 27.6 ± 2.7 vs. 22.9 ± 6.0 kg/m²; P = 0.04), as well as greater percentage in whole body and regional fat mass (P < 0.05). Furthermore, high-responders had a 69% greater increase (P = 0.086) in total Akt protein expression than low-responders. High-responders also exhibited reduced circulating IGF-1 with a concomitant increase in IGFBP-3. Exploratory analyses revealed upregulation of mRNAs for muscle hypertrophy markers [IRS-1, Akt, mTOR] and downregulation of protein degradation markers [myostatin, MurF-1, and PDK4] in the high-responders compared to low-responders. The findings indicate that body composition, spasticity, baclofen usage, and multiple signaling pathways (anabolic and catabolic) are involved in the differential muscle hypertrophy response to NMES-RT in persons with chronic SCI.
... The reduction in muscle damage may be one reason for the improved endurance sports performance [4,6,7]. In general, ingesting 20-40 g of high-quality protein can increase muscle protein synthesis rate and reduce muscle damage [26][27][28]. However, consuming protein during longdistance exercise may increase protein oxidation, meaning that intake of protein may become fuel during exercise [29,30]. ...
Full-text available
Background: The purpose of this study is to explore the effect of carbohydrate only or carbohydrate plus protein supplementation on endurance capacity and muscle damage. Methods: Ten recreationally active male runners (VO2max: 53.61 ± 3.86 ml/kg·min) completed run-to-exhaustion test three times with different intakes of intervention drinks. There was a 7-day wash-out period between tests. Each test started with 60 minutes of running at 70% VO2max (phase 1), followed by an endurance capacity test: time-to-exhaustion running at 80% VO2max (phase 2). Participants randomly ingested either 1) 0.4 g/kg BM carbohydrate before phase 1 and before phase 2 (CHO+CHO), 2) 0.4 g/kg BM protein before phase 1 and 0.4 g/kg BM carbohydrate before phase 2 (PRO+CHO), or 3) 0.4 g/kg BM carbohydrate before phase 1 and 0.4 g/kg BM protein before phase 2 (CHO+PRO). All subjects ingested carbohydrate (CHO) 1.2 g/kg BM during phase 1, and blood samples were obtained before, immediately, and 24 h after exercise for measurements of alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatine kinase (CK), and myoglobin (MB). Results: There was no significant difference in time to exhaustion between the three supplement strategies (CHO+CHO: 432 ± 225 s; PRO+CHO: 463 ± 227 s; CHO+PRO: 461 ± 248 s). However, ALT and AST were significantly lower in PRO+CHO than in CHO+CHO 24 h after exercise (ALT: 16.80 ± 6.31 vs. 24.39 ± 2.54 U/L; AST: 24.06 ± 4.77 vs. 31.51 ± 7.53 U/L, p < 0.05). MB was significantly lower in PRO+CHO and CHO+PRO than in CHO+CHO 24 h after exercise (40.7 ± 15.2; 38.1 ± 14.3; 64.3 ± 28.9 ng/mL, respectively, p < 0.05). CK increased less in PRO+CHO compared to CHO+CHO 24 h after exercise (404.22 ± 75.31 VS. 642.33 ± 68.57 U/L, p < 0.05). Conclusion: Carbohydrate and protein supplement strategies can reduce muscle damage caused by endurance exercise, but they do not improve endurance exercise capacity.
... In fact, numerous athletes ingest more than 2.0 g/kg/day of protein on a daily basis [21]. The International Society of Sports Nutrition claims that the ingestion of 1.4 to 2.0 g/kg/day of protein by physically active people is not only safe, but may even enhance training adaptations to exercise [22]. This level is also within the Institute of Medicine's Acceptable Macronutrient Distribution Range (AMDR) of 10-35 percent protein [23] For optimal anabolic impact, 0.4 g/kg/meal should be taken over a total of 4 meals to reach 1.6 g/kg/day (with a maximum daily consumption of 2.2 g/kg/day) [24]. ...
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Whey protein is best recognized as a nutritional supplement that has been increasingly popular among gym users as the primary sports nutrition product used by athletes to improve exercise performance, body composition, and muscle growth. The types of supplements utilized can have a big impact on how athletes are treated medically. Two goals guide this work. To begin with, assess athletes' protein consumption. Second, we want to see if whey protein supplements alter the function of athletes' livers and kidneys. This is an analytical cross-sectional study conducted on 105 healthy male gym attendants in Al Nasiriyah city, Thi-Qar, Provence, south of Iraq, from June to November 2021. They were divided into two groups of athletes: group 1 (non-protein group) and group 2 (protein supplements group) with age of Mean ±SD of (27.56 ±8.31 years) and (29.26 ±7.35 years) respectively. The results indicate that athletes consume protein at a higher rate than the RDA for the general population, whether or not they utilize supplements. In terms of liver and renal function biomarkers, the results demonstrate no significant difference between the protein supplement group and the non-protein supplement group.
Bu çalışma, elit karate branşı sporcularının ulusal ve uluslararası 2 farklı müsabaka öncesi beslenme durumlarını saptamak ve karşılaştırmak amacı ile yapılmıştır. Çalışmaya Türkiye Olimpiyat Hazırlık Merkezi (TOHM) bünyesinde olup karate dalında yarışan 18 yaş üstü tüm elit sporcular (6 erkek,8 kadın; toplam 14 kişi) katılmıştır. Sporculara ait veriler sporcuların genel özellikleri, antropometrik ölçümler ile vücut kompozisyonları, beslenme durumları ve hidrasyon durumlarının belirlenmesi şeklinde 4 ana kısımdan oluşmaktadır. Araştırmaya katılan kadın sporcuların ulusal şampiyona öncesi diyetle aldıkları enerji 2338,5±638.0 kkal iken; uluslararası şampiyona öncesi 1884.4±738.31 kkal olarak saptanmıştır. Erkek sporcuların ise ulusal şampiyona öncesi diyetle aldıkları enerji 2490.2±1056.02 kkal iken; uluslararası şampiyona öncesi 2421.8±416.31kkal olarak saptanmıştır. Ulusal şampiyona öncesi kadınların karbonhidrat, protein ve yağ alımları sırasıyla 3.5±1.34 g/kg, 2.1±0.67 g/kg ve 2.0±0.71g/kg olarak belirlenirken; erkek karate sporcularında ise karbonhidrat, protein ve yağ alımları sırasıyla 3.1±1.74 g/kg; 1.9±0.73 g/kg ve 1.6±0.77 g/kg olarak saptanmıştır. Erkek karate sporcularında ise kadınların karbonhidrat, protein ve yağ alımları sırasıyla 3.1±1.74 g/kg; 1.9±0.73 g/kg ve 1.6±0.77 g/kg olarak saptanmıştır. Karate sporcularında uluslararası şampiyonası öncesindeki beslenme durumları incelendiğinde kadınların karbonhidrat, protein ve yağ alımları sırasıyla 3.4±1.63 g/kg 1.5±0.52 g/kg ve 1.3±0.53 g/kg; erkek karate sporcularının ise sırasıyla 3.1±0.46 g/kg 1.5±0.29 g/kg ve 1.5±0.29 g/kg olarak belirlenmiştir. Araştırmaya katılan karate oyuncularının ulusal ve uluslararası müsabaka öncesinde alınan besin tüketim kaydına göre toplam enerjilerinin karbonhidrattan gelen oranları ve sıvı alımları arasındaki fark istatistiksel olarak önemli bulunmuştur.
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Seaweeds attract substantial interest as novel sources of sustainable food protein, as they are established sources of industrial hydrocolloids with reasonable protein content. In this study, we investigate the protein composition and nutritional quality of a seaweed protein extract (SPE) from Gigartina sp. The SPE displayed low (<2%), but pH-dependent, aqueous solubility likely due to the harsh conditions employed during extraction. Solubility improved using alkaline buffering and detergent addition to facilitate proteomic characterization by quantitative LC-MS/MS. Proteomics analysis revealed that SPE was dominated by proteins related to light harvest and particularly phycobiliproteins (44%), where phycoerythrin was most abundant (28%). Based on subcellular localization, the extraction method was evaluated as good for release of cellular protein. SPE was rich in essential amino acids (36-41%) and particularly branched chain amino acids (22-24%), and thereby a potential source of nutritional food protein. Using bioinformatic prediction and structural modelling, we found abundant SPE proteins contained novel peptides with the amphiphilic properties required to stabilize an oil/water interface, and thereby high probability of being potent emulsifiers. Based on this study, Gigartina sp. could serve a good candidate for extraction of sustainable, nutritious food protein, with the possibility of further processing into hydrolysates with strong emulsifying properties for use as natural food ingredients.
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Advanced nutritional interventions are one of the key components of elite sports performance in general. Combat sports require a high percentage of muscle mass with minimum body weight to generate the maximum power possible. An adequate level of nutrition knowledge, particularly with respect to identifying energy needs while avoiding confusion over dietary supplements and false perceptions of steroid requirement, which may compromise the health condition, is of crucial importance. In this context, the aim of our work is to highlight nutritional require-ments/nutritional assessment, the importance of daily dietary intake in combat players, which increasingly includes a broad range of sports nutrition supplements, and the roles of vitamins, minerals and proteins, combined with antioxidants and strength training, in muscular performance. The main nutrients required in the daily diet of combat players, the mechanisms of action, the main outcomes and possible side effects are summarized. Special attention is paid to natural supplements and their importance and advantages over synthetic ones, along with future trends of development.
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Many athletic populations report poor sleep, especially during intensive training and competition periods. Recently, diet has been shown to significantly affect sleep in general populations; however, little is known about the effect diet has on the sleep of athletically trained populations. With sleep critical for optimal recovery and sports performance, this systematic review aimed to evaluate the evidence demonstrating that dietary factors influence the sleep of athletically trained populations. Four electronic databases were searched from inception to May 2022, with primary research articles included if they contained a dietary factor(s), an outcome measure of sleep or sleepiness, and participants could be identified as ‘athletically trained’. Thirty-five studies were included, with 21 studies assessed as positive quality, 13 as neutral, and one as negative. Sleep or sleepiness was measured objectively in 46% of studies (n = 16). The review showed that evening (≥5 p.m.) caffeine intakes >2 mg·kg−1 body mass decreased sleep duration and sleep efficiency, and increased sleep latency and wake after sleep onset. Evening consumption of high glycaemic index carbohydrates and protein high in tryptophan may reduce sleep latency. Although promising, more research is required before the impact of probiotics, cherry juice, and beetroot juice on the sleep of athletes can be resolved. Athletic populations experiencing sleep difficulties should be screened for caffeine use and trial dietary strategies (e.g., evening consumption of high GI carbohydrates) to improve sleep.
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Abstract Sport nutrition is a constantly evolving field with literally thousands of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper presents a well-referenced overview of the current state of the science related to how to optimize training through nutrition. More specifically, this article discusses: 1.) how to evaluate the scientific merit of nutritional supplements; 2.) general nutritional strategies to optimize performance and enhance recovery; and, 3.) our current understanding of the available science behind weight gain, weight loss, and performance enhancement supplements. Our hope is that ISSN members find this review useful in their daily practice and consultation with their clients.
Conference Paper
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There has been debate among athletes and nutritionists regarding dietary protein needs for centuries. Although contrary to traditional belief, recent scientific information collected on physically active individuals tends to indicate that regular exercise increases daily protein requirements; however, the precise details remain to be worked out. Based on laboratory measures, daily protein requirements are increased by perhaps as much as 100% vs. recommendations for sedentary individuals (1.6-1.8 vs. 0.8 g/kg). Yet even these intakes are much less than those reported by most athletes. This may mean that actual requirements are below what is needed to optimize athletic performance, and so the debate continues. Numerous interacting factors including energy intake, carbohydrate availability, exercise intensity, duration and type, dietary protein quality, training history, gender, age, timing of nutrient intake and the like make this topic extremely complex. Many questions remain to be resolved. At the present time, substantial data indicate that the current recommended protein intake should be adjusted upward for those who are physically active, especially in populations whose needs are elevated for other reasons, e.g., growing individuals, dieters, vegetarians, individuals with muscle disease-induced weakness and the elderly. For these latter groups, specific supplementation may be appropriate, but for most North Americans who consume a varied diet, including complete protein foods (meat, eggs, fish and dairy products), and sufficient energy the increased protein needs induced by a regular exercise program can be met in one's diet.
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The speed of absorption of dietary amino acids by the gut varies according to the type of ingested dietary protein. This could affect postprandial protein synthesis, breakdown, and deposition. To test this hypothesis, two intrinsically 13C-leucine-labeled milk proteins, casein (CAS) and whey protein (WP), of different physicochemical properties were ingested as one single meal by healthy adults. Postprandial whole body leucine kinetics were assessed by using a dual tracer methodology. WP induced a dramatic but short increase of plasma amino acids. CAS induced a prolonged plateau of moderate hyperaminoacidemia, probably because of a slow gastric emptying. Whole body protein breakdown was inhibited by 34% after CAS ingestion but not after WP ingestion. Postprandial protein synthesis was stimulated by 68% with the WP meal and to a lesser extent (+31%) with the CAS meal. Postprandial whole body leucine oxidation over 7 h was lower with CAS (272 ± 91 μmol⋅kg−1) than with WP (373 ± 56 μmol⋅kg−1). Leucine intake was identical in both meals (380 μmol⋅kg−1). Therefore, net leucine balance over the 7 h after the meal was more positive with CAS than with WP (P < 0.05, WP vs. CAS). In conclusion, the speed of protein digestion and amino acid absorption from the gut has a major effect on whole body protein anabolism after one single meal. By analogy with carbohydrate metabolism, slow and fast proteins modulate the postprandial metabolic response, a concept to be applied to wasting situations.
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Abstract Recent trends in weight loss diets have led to a substantial increase in protein intake by individuals. As a result, the safety of habitually consuming dietary protein in excess of recommended intakes has been questioned. In particular, there is concern that high protein intake may promote renal damage by chronically increasing glomerular pressure and hyperfiltration. There is, however, a serious question as to whether there is significant evidence to support this relationship in healthy individuals. In fact, some studies suggest that hyperfiltration, the purported mechanism for renal damage, is a normal adaptative mechanism that occurs in response to several physiological conditions. This paper reviews the available evidence that increased dietary protein intake is a health concern in terms of the potential to initiate or promote renal disease. While protein restriction may be appropriate for treatment of existing kidney disease, we find no significant evidence for a detrimental effect of high protein intakes on kidney function in healthy persons after centuries of a high protein Western diet.
The public is often advised to limit their consumption of animal proteins because of the concern about increased calcium loss associated with high protein intake. Unfortunately, this advice is primarily based on studies that found hypercalciuric effects of purified proteins. Attempts to test common sources of protein have suffered from significant design and methodological limitations; epidemiologic studies of the effects of protein on bone health have yielded mixed results. Findings from three recent, carefully controlled feeding studies, summarised below, show that a moderately high intake of animal protein does not adversely affect calcium retention and may even be beneficial for bone health. Several milk/dairy supplementation trials also indicate that a concomitant increase in calcium and protein intake (along with other nutrients present in these foods), favourably affects bone health at various stages of the life cycle. Nonetheless, the effects of animal protein on bone health remain unclear. Carefully controlled feeding studies are needed to better understand the effects of dairy proteins per se, as well as milk and milk products as whole foods, on calcium homeostasis and bone health.
• The effect of dietary protein on kidney function expressed by creatinine clearance was studied in healthy subjects following a "normal" unrestricted protein diet and compared with a group of vegetarians maintained on a long-term low-protein diet. Both groups had similar kidney function and displayed the same rate of progressive deterioration in renal function with age. These results suggest that, in contrast with the important therapeutic effect of low-protein intake on the progressive deterioration of kidney function in diseased kidneys, such a diet does not significantly affect kidney function with "normal aging" in healthy subjects.(Arch Intern Med 1989;149:211-212)
J Physiol 2001 August 15: 535(1): 301–11(1) Age-associated loss of skeletal muscle mass and strength can partly be counteracted by resistance training, causing a net synthesis of muscular proteins. Protein synthesis is influenced synergistically by post-exercise amino acid supplementation, but the importance of the timing of protein intake remains unresolved. (2) The study investigated the importance of immediate (P0) or delayed (P2) intake of an oral protein supplement upon muscle hypertrophy and strength over a period of resistance training in elderly males. (3) Thirteen men (age 74 ± 1 years; body mass index (BMI), 25 ± 1 kg m- 2 (means ± SEM)) completed a 12-week resistance training program (three times per week) receiving oral protein in liquid form (10 g protein, 7 g carbohydrate, 3 g fat) immediately after (P0) or 2 h after (P2) each training session. Muscle hypertrophy was evaluated by magnetic resonance imaging (MRI) and from muscle biopsies and muscle strength was determined using dynamic and isokinetic strength measurements. Body composition was determined from dual-energy X-ray absorptiometry (DEXA) and food records were obtained over 4 days. The plasma insulin response to protein supplementation was also determined. (4) In response to training, the cross-sectional area of m. quadriceps femoris (54.6 ± 0.5–58.3 ± 0.5 cm2) and mean fiber area (4047 ± 320–5019 ± 615 μ m2) increased in the P0 group, whereas no significant increase was observed in P2. For P0 both dynamic and isokinetic strength increased, by 46 and 15%, respectively (P P
• The performance of an athlete can be impaired significantly by a faulty or inadequate diet, even before clinical signs of a deficiency are manifest. But the manipulation of an already adequate diet does not enhance performance. The composition of a meal preceding single-effort events like the high jump has little effect on performance, but performance in tests involving prolonged muscular work is enhanced if carbohydrate stores are replete at the beginning of the test. Obesity is a mechanical handicap in most, though not in all, forms of athletics. The average corporeal density of athletes is higher than that assumed for the general population; therefore the usual height-weight tables give the misleading impression that an athlete of given height is too heavy and presumably obese. Placing him on a reducing diet would be a mistake. Ordinarily he will spontaneously ingest food in amounts sufficient to maintain his weight. Performance is generally influenced by motivation, skill, and other neuromuscular and psychological factors. The training table provides the athlete with the foods on which he has learned he can rely; it also provides some of the sense of security generally obtainable by the practice of rituals. The best diet for him is a balanced one consisting of a variety of the foods he enjoys, in amounts that maintain his weight at an optimum level.
Components of the diet related to changes in eating habits that characterize the modern Western world are important factors in the increasingly high prevalence of chronic disease, including obesity, diabetes, hypertension and as a consequence, chronic kidney disease. The healthy diets recommended for the general population to promote longevity (such as the Mediterranean diet), are defined based on epidemiological and intervention studies and are usually characterized by a relatively higher amount of protein than the usual Western diet. Unfortunately, very few clinical studies focused on diet-based strategies of prevention of kidney disorders. Furthermore, this review will propose that the concept that protein restricted diets decrease the risk of developing kidney disease in the general population is not supported by the scientific literature. Indeed, preliminary studies showing a positive effect of relatively high protein diets on risk factors for chronic kidney disease (particularly on obesity, hypertension and diabetes) point to the need for future studies addressing diets that could prevent the increasingly high prevalence of kidney disease in the Western world. On the other hand, there is a potential role for protein restriction in patients with established kidney disease, particularly in patients with significant decrease in glomerular filtration rate. The exact protective action of protein restriction in patients with established renal disease needs further analysis, taking into account the more broad effects of protein restriction (lower phosphate, acidosis, uric acid) and a more current definition of malnutrition.
There are at least 5 metabolic causes of fatigue, a decrease in the phosphocreatine level in muscle, proton accumulation in muscle, depletion of the glycogen store in muscle, hypoglycaemia and an increase in the plasma concentration ratio of free tryptophan/branched-chain amino acids. Proton accumulation may be a common cause of fatigue in most forms of exercise and may be an important factor in fatigue in those persons who are chronically physically inactive and also in the elderly: thus, the aerobic capacity markedly decreases under these conditions, so that ATP must be synthesized by the much less efficient anaerobic system. A marked increase in the plasma fatty acid level, which may occur when liver glycogen store is depleted and when hypoglycaemia results, or during intermittent exercise when the rate of fatty acid oxidation may not match the mobilisation of fatty acids, could be involved indirectly in fatigue. This is because such an increase in the plasma level of fatty acids raises the free plasma concentration of tryptophan, which can increase the entry of tryptophan into the brain, which will increase the brain level of 5-hydroxytryptamine: there is evidence that the latter may be involved in central fatigue. In this case, provision of branched-chain amino acids in order to maintain the resting plasma concentration ratio of free tryptophan/branched-chain amino acids should delay fatigue--there is prima facie evidence in support of this hypothesis. This hypothesis may have considerable clinical importance.