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BioMed Central
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Journal of the International Society
of Sports Nutrition
Open Access
Commentary
International Society of Sports Nutrition position stand: protein
and exercise
Bill Campbell
1
, Richard B Kreider*
2
, Tim Ziegenfuss
3
, Paul La Bounty
4
,
Mike Roberts
5
, Darren Burke
6
, Jamie Landis
7
, Hector Lopez
8
and
Jose Antonio
9
Address:
1
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,
2
Exercise and Sport Nutrition Laboratory, Dept. of Health, Human Performance, and Recreation,
Baylor University, One Bear Place 97313, Waco, TX 76798-7313, USA,
3
Ohio Research Group of Exercise Science & Sports Nutrition, Wadsworth
Medical Center, 323 High St, STE 103A, Wadsworth, OH 44281, USA,
4
Exercise and Sport Nutrition Laboratory, Dept. of Health, Human
Performance, and Recreation, Baylor University, One Bear Place 97313, Waco, TX 76798-7313, USA,
5
Applied Biochemistry and Molecular
Physiology Laboratory, Department of Health and Exercise Science, University of Oklahoma, 1401 Asp Avenue, Norman, OK 73019, USA,
6
Exercise Science Laboratory, Dept. of Human Kinetics, St. Francis Xavier University, P.O. Box 5000 Antigonish, Nova Scotia, B2G 2W5, Canada,
7
Department of Biology, Lakeland Community College, 7700 Clocktower Drive, Kirtland, Ohio 44094-5198, USA,
8
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
9
Department of Exercise Science and Health Promotion, Florida Atlantic University, 2912 College Avenue, Davie, FL
33314, USA
Email: Bill Campbell - campbell@coedu.usf.edu; Richard B Kreider* - Richard_Kreider@baylor.edu;
Tim Ziegenfuss - tim@ohioresearchgroup.com; Paul La Bounty - Paul_La_Bounty@baylor.edu; Mike Roberts - Mike_Roberts@ou.edu;
Darren Burke - dburke@stfx.ca; Jamie Landis - jlandis@lakelandcc.edu; Hector Lopez - hlopezmd@gmail.com; Jose Antonio - exphys@aol.com
* Corresponding author
Abstract
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-
8
Received: 31 August 2007
Accepted: 26 September 2007
This article is available from: http://www.jissn.com/content/4/1/8
© 2007 Campbell et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0
),
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 http://www.jissn.com/content/4/1/8
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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
supplements
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
accretion.
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
individual.
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-
formance.
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.
Conclusion
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.
Abbreviations
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-
ests.
References
1. Institute of Medicine of the National Academies: Dietary reference
intakes for energy, carbohydrate, fiber, fat, fatty acids, cho-
lesterol, protein, and amino acids (macronutrients). Wash-
ington, DC , National Academies Press; 2002.
2. Lemon PW: Beyond the zone: protein needs of active individ-
uals. J Am Coll Nutr 2000, 19(5 Suppl):513S-521S.
3. Joint Position Statement: nutrition and athletic perform-
ance. American College of Sports Medicine, American Die-
tetic Association, and Dietitians of Canada. Med Sci Sports
Exerc 2000, 32(12):2130-2145.
4. Tarnopolsky M: Protein requirements for endurance athletes.
Nutrition 2004, 20(7-8):662-668.
5. Rand WM, Pellett PL, Young VR: Meta-analysis of nitrogen bal-
ance studies for estimating protein requirements in healthy
adults. Am J Clin Nutr 2003, 77(1):109-127.
6. Forslund AH, El-Khoury AE, Olsson RM, Sjodin AM, Hambraeus L,
Young VR: Effect of protein intake and physical activity on 24-
h pattern and rate of macronutrient utilization. Am J Physiol
1999, 276(5 Pt 1):E964-76.
7. Meredith CN, Zackin MJ, Frontera WR, Evans WJ: Dietary protein
requirements and body protein metabolism in endurance-
trained men. J Appl Physiol 1989, 66(6):2850-2856.
8. Phillips SM, Atkinson SA, Tarnopolsky MA, MacDougall JD: Gender
differences in leucine kinetics and nitrogen balance in endur-
ance athletes. J Appl Physiol 1993, 75(5):2134-2141.
9. Lamont LS, Patel DG, Kalhan SC: Leucine kinetics in endurance-
trained humans. J Appl Physiol 1990, 69(1):1-6.
10. Friedman JE, Lemon PW: Effect of chronic endurance exercise
on retention of dietary protein. Int J Sports Med 1989,
10(2):118-123.
11. Tarnopolsky MA, Atkinson SA, MacDougall JD, Chesley A, Phillips S,
Schwarcz HP: Evaluation of protein requirements for trained
strength athletes. J Appl Physiol 1992, 73(5):1986-1995.
12. Lemon PW, Tarnopolsky MA, MacDougall JD, Atkinson SA: Protein
requirements and muscle mass/strength changes during
intensive training in novice bodybuilders. J Appl Physiol 1992,
73(2):767-775.
13. Lemon PW: Protein and amino acid needs of the strength ath-
lete. Int J Sport Nutr 1991, 1(2):127-145.
14. Kreider RB, Almada AL, Antonio J, Broeder C, Earnest C, Green-
wood M, Incledon T, Kalman DS, Kleiner SM, Leutholtz B, Lowery
LM, Mendel R, Stout JR, Willoughby DS, Ziegenfuss TN: ISSN Exer-
cise and Sport Nutrition Review: Research and Recommen-
dations. Journal of the International Society of Sports Nutrition 2004,
1(1):1-44.
15. Gaine PC, Pikosky MA, Martin WF, Bolster DR, Maresh CM, Rod-
riguez NR: Level of dietary protein impacts whole body pro-
tein turnover in trained males at rest. Metabolism 2006,
55(4):501-507.
16. Antonio J, Stout JR: Sports Supplements. Philadelphia, PA , Lippin-
cott Williams & Wilkins; 2001.
17. Rennie MJ, Tipton KD: Protein and amino acid metabolism dur-
ing and after exercise and the effects of nutrition. Annu Rev
Nutr 2000, 20:457-483.
18. Lemon PW: Protein requirements of soccer. J Sports Sci 1994,
12 Spec No:S17-22.
19. Metges CC, Barth CA: Metabolic consequences of a high die-
tary-protein intake in adulthood: assessment of the available
evidence. J Nutr 2000, 130(4):886-889.
20. Brenner BM, Meyer TW, Hostetter TH: Dietary protein intake
and the progressive nature of kidney disease: the role of
hemodynamically mediated glomerular injury in the patho-
genesis of progressive glomerular sclerosis in aging, renal
ablation, and intrinsic renal disease. N Engl J Med 1982,
307(11):652-659.
21. Martin WF, Armstrong LE, Rodriguez NR: Dietary protein intake
and renal function. Nutr Metab (Lond) 2005, 2:25.
22. Knight EL, Stampfer MJ, Hankinson SE, Spiegelman D, Curhan GC:
The impact of protein intake on renal function decline in
women with normal renal function or mild renal insuffi-
ciency. Ann Intern Med 2003, 138(6):460-467.
23. Bedford JL, Barr SI: Diets and selected lifestyle practices of self-
defined adult vegetarians from a population-based sample
suggest they are more 'health conscious'. Int J Behav Nutr Phys
Act 2005, 2(1):4.
24. Blum M, Averbuch M, Wolman Y, Aviram A: Protein intake and
kidney function in humans: its effect on 'normal aging'. Arch
Intern Med 1989, 149(1):211-212.
25. Pecoits-Filho R: Dietary protein intake and kidney disease in
Western diet. Contrib Nephrol 2007, 155:102-112.
26. Lentine K, Wrone EM: New insights into protein intake and
progression of renal disease. Curr Opin Nephrol Hypertens 2004,
13(3):333-336.
27. Ginty F: Dietary protein and bone health. Proc Nutr Soc 2003,
62(4):867-876.
28. Dawson-Hughes B, Harris SS, Rasmussen H, Song L, Dallal GE: Effect
of dietary protein supplements on calcium excretion in
healthy older men and women. J Clin Endocrinol Metab 2004,
89(3):1169-1173.
29. Kerstetter JE, O'Brien KO, Caseria DM, Wall DE, Insogna KL: The
impact of dietary protein on calcium absorption and kinetic
measures of bone turnover in women. J Clin Endocrinol Metab
2005, 90(1):26-31.
30. Vicente-Rodriguez G: How does exercise affect bone develop-
ment during growth? Sports Med 2006, 36(7):561-569.
31. Vicente-Rodriguez G, Ara I, Perez-Gomez J, Dorado C, Calbet JA:
Muscular development and physical activity as major deter-
minants of femoral bone mass acquisition during growth. Br
J Sports Med 2005, 39(9):611-616.
32. Tipton KD, Wolfe RR: Protein and amino acids for athletes. J
Sports Sci 2004, 22(1):65-79.
33. Tipton KD, Elliott TA, Cree MG, Wolf SE, Sanford AP, Wolfe RR:
Ingestion of casein and whey proteins result in muscle anab-
olism after resistance exercise. Med Sci Sports Exerc 2004,
36(12):2073-2081.
34. Darragh AJ, Hodgkinson SM: Quantifying the digestibility of die-
tary protein. J Nutr 2000, 130(7):1850S-6S.
35. Boirie Y, Dangin M, Gachon P, Vasson MP, Maubois JL, Beaufrere B:
Slow and fast dietary proteins differently modulate post-
prandial protein accretion. Proc Natl Acad Sci U S A 1997,
94(26):14930-14935.
36. Bos C, Metges CC, Gaudichon C, Petzke KJ, Pueyo ME, Morens C,
Everwand J, Benamouzig R, Tome D: Postprandial kinetics of die-
tary amino acids are the main determinant of their metabo-
lism after soy or milk protein ingestion in humans. J Nutr
2003, 133(5):1308-1315.
37. Dangin M, Boirie Y, Garcia-Rodenas C, Gachon P, Fauquant J, Callier
P, Ballevre O, Beaufrere B: The digestion rate of protein is an
independent regulating factor of postprandial protein reten-
tion. Am J Physiol Endocrinol Metab 2001, 280(2):E340-8.
38. Dangin M, Guillet C, Garcia-Rodenas C, Gachon P, Bouteloup-
Demange C, Reiffers-Magnani K, Fauquant J, Ballevre O, Beaufrere B:
The rate of protein digestion affects protein gain differently
during aging in humans. J Physiol 2003, 549(Pt 2):635-644.
39. Rodriguez NR, Vislocky LM, Gaine PC: Dietary protein, endur-
ance exercise, and human skeletal-muscle protein turnover.
Curr Opin Clin Nutr Metab Care 2007, 10(1):40-45.
40. Phillips SM, Parise G, Roy BD, Tipton KD, Wolfe RR, Tamopolsky
MA: Resistance-training-induced adaptations in skeletal mus-
cle protein turnover in the fed state. Can J Physiol Pharmacol
2002, 80(11):1045-1053.
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Page 7 of 7
(page number not for citation purposes)
41. Rennie MJ, Bohe J, Smith K, Wackerhage H, Greenhaff P: Branched-
chain amino acids as fuels and anabolic signals in human
muscle. J Nutr 2006, 136(1 Suppl):264S-8S.
42. Yang Y, Jemiolo B, Trappe S: Proteolytic mRNA expression in
response to acute resistance exercise in human single skele-
tal muscle fibers. J Appl Physiol 2006, 101(5):1442-1450.
43. Biolo G, Maggi SP, Williams BD, Tipton KD, Wolfe RR: Increased
rates of muscle protein turnover and amino acid transport
after resistance exercise in humans. Am J Physiol 1995, 268(3 Pt
1):E514-20.
44. Biolo G, Tipton KD, Klein S, Wolfe RR: An abundant supply of
amino acids enhances the metabolic effect of exercise on
muscle protein. Am J Physiol 1997, 273(1 Pt 1):E122-9.
45. Willoughby DS, Stout JR, Wilborn CD: Effects of resistance train-
ing and protein plus amino acid supplementation on muscle
anabolism, mass, and strength. Amino Acids 2007,
32(4):467-477.
46. Cribb PJ, Williams AD, Stathis CG, Carey MF, Hayes A: Effects of
whey isolate, creatine, and resistance training on muscle
hypertrophy. Med Sci Sports Exerc 2007, 39(2):298-307.
47. Tipton KD, Borsheim E, Wolf SE, Sanford AP, Wolfe RR: Acute
response of net muscle protein balance reflects 24-h balance
after exercise and amino acid ingestion. Am J Physiol Endocrinol
Metab 2003, 284(1):E76-89.
48. Esmarck B, Andersen JL, Olsen S, Richter EA, Mizuno M, Kjaer M:
Timing of postexercise protein intake is important for mus-
cle hypertrophy with resistance training in elderly humans. J
Physiol 2001, 535(Pt 1):301-311.
49. Tipton KD, Ferrando AA, Phillips SM, Doyle D Jr., Wolfe RR: Pos-
texercise net protein synthesis in human muscle from orally
administered amino acids. Am J Physiol 1999, 276(4 Pt
1):E628-34.
50. Flakoll PJ, Judy T, Flinn K, Carr C, Flinn S: Postexercise protein
supplementation improves health and muscle soreness dur-
ing basic military training in Marine recruits. J Appl Physiol
2004, 96(3):951-956.
51. Bounous G, Batist G, Gold P: Immunoenhancing property of die-
tary whey protein in mice: role of glutathione. Clin Invest Med
1989, 12(3):154-161.
52. Bounous G, Kongshavn PA, Gold P: The immunoenhancing prop-
erty of dietary whey protein concentrate. Clin Invest Med 1988,
11(4):271-278.
53. Mero A: Leucine supplementation and intensive training.
Sports Med 1999, 27(6):347-358.
54. Kimball SR, Jefferson LS: Signaling pathways and molecular
mechanisms through which branched-chain amino acids
mediate translational control of protein synthesis. J Nutr
2006, 136(1 Suppl):227S-31S.
55. Louard RJ, Barrett EJ, Gelfand RA: Effect of infused branched-
chain amino acids on muscle and whole-body amino acid
metabolism in man. Clin Sci (Lond) 1990, 79(5):457-466.
56. Blomstrand E, Eliasson J, Karlsson HK, Kohnke R: Branched-chain
amino acids activate key enzymes in protein synthesis after
physical exercise. J Nutr 2006, 136(1 Suppl):269S-73S.
57. Koopman R, Wagenmakers AJ, Manders RJ, Zorenc AH, Senden JM,
Gorselink M, Keizer HA, van Loon LJ: Combined ingestion of pro-
tein and free leucine with carbohydrate increases postexer-
cise muscle protein synthesis in vivo in male subjects. Am J
Physiol Endocrinol Metab 2005, 288(4):E645-53.
58. Blomstrand E, Newsholme EA: Effect of branched-chain amino
acid supplementation on the exercise-induced change in aro-
matic amino acid concentration in human muscle. Acta Physiol
Scand 1992, 146(3):293-298.
59. Blomstrand E, Ek S, Newsholme EA: Influence of ingesting a solu-
tion of branched-chain amino acids on plasma and muscle
concentrations of amino acids during prolonged submaximal
exercise. Nutrition 1996, 12(7-8):485-490.
60. Blomstrand E, Hassmen P, Ekblom B, Newsholme EA: Administra-
tion of branched-chain amino acids during sustained exer-
cise--effects on performance and on plasma concentration of
some amino acids. Eur J Appl Physiol Occup Physiol 1991,
63(2):83-88.
61. Blomstrand E: A role for branched-chain amino acids in reduc-
ing central fatigue. J Nutr 2006, 136(2):544S-547S.
62. Newsholme EA, Blomstrand E, Ekblom B: Physical and mental
fatigue: metabolic mechanisms and importance of plasma
amino acids. Br Med Bull 1992, 48(3):477-495.
63. Pitkanen HT, Oja SS, Rusko H, Nummela A, Komi PV, Saransaari P,
Takala T, Mero AA: Leucine supplementation does not
enhance acute strength or running performance but affects
serum amino acid concentration. Amino Acids 2003,
25(1):85-94.
64. Shimomura Y, Murakami T, Nakai N, Nagasaki M, Harris RA: Exer-
cise promotes BCAA catabolism: effects of BCAA supple-
mentation on skeletal muscle during exercise. J Nutr 2004,
134(6 Suppl):1583S-1587S.
