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Dietary Protein and
Strength Athletes
Lonnie Lowery, PhD, James F. Edel, BS, and Isaiah M. McBride, BS
Department of Health, Exercise and Rehabilitative Sciences, Winona State University, Winona, Minnesota
SUMMARY
DIETARY PROTEIN, PARTICULARLY
IN THE AMPLE AMOUNTS USED BY
MANY STRENGTH ATHLETES, HAS
LONG BEEN CONTROVERSIAL, IN
PART BECAUSE OF LACK OF DATA.
THE SAFETY (E.G. RENAL AND
BONE HEALTH) AND EFFICACY
(ENHANCED PROTEIN SYNTHESIS,
MUSCLE ACCRETION, AND FAT
LOSS) OF VARIOUS PROTEINS
HAVE NOW BEEN RESEARCHED
TO VARYING DEGREES, HOWEVER. PROTEIN TYPE, DOSE, PERIEXERCISE TIMING, ENERGY
INTAKE, AND TRAINING STATUS
ARE CONSIDERATIONS. RECOMMENDATIONS SHOULD NOT BE
EXTRAPOLATED FROM OTHER
POPULATIONS. THIS REVIEW
COVERS DATA SPECIFIC TO THE
STRENGTH TRAINING POPULATION AND OFFERS PRACTICAL
ADVICE ON MANIPULATING PROTEIN FOR OPTIMAL BENEFITS.
INTRODUCTION
ssessment of best practices
in sports nutrition typically
involves some form of safety
and efficacy evaluation from the scientific literature. With regards to dietary
protein, practical translation from published findings has been difficult at
times. Meaningful data have not been
available on key issues, which have led
to controversy. Different professions
seem to have adopted different views.
Clinicians and health educators share
messages that are not always in agreement with exercise and nutrition
A
26
scientists on topics such as the safety
of large intakes (27,30,31). Unfortunately, data from nonathletic populations and unsubstantiated professional
opinion have often been used in educational materials (30). Indeed, textbooks
sometimes reference each other rather
than using relevant primary literature
and thus have perpetuated certain
health concerns. Recent strength
athlete–specific data do exist, however.
The efficacy of dietary protein for building and repairing various tissues, providing building blocks for bodily
enzymes, immune proteins, and transporters and for helping to maintain
bodily fluid balance and pH clearly
makes it an essential nutrient. Indeed,
there have been suggestions from scientists to increase "official" governmental
recommendations in coming years
(15,23). Decades of research exist supporting protein’s role in enhanced muscle protein synthesis, both when
considered as daily intake and when
timed close to resistance exercise
(3,34,39,41,42,51,53). Despite this consensus that acute protein synthesis is
increased with purposeful, well-timed
intake, it is less clear scientifically how
much muscle accretion is augmented
over time. This is, in part, due to wide
variation in individual responses to the
resistance training stimulus. Although
enhanced muscle gains are probable,
the hypertrophy would come slowly
(43,48,50). Certainly, protein intake is
not infinitely linear in its relationship
to nitrogen retention or protein synthesis, even for strength athletes. At some
point as dosing escalates, nitrogen excretion becomes substantial (indicating
waste, in a sense). Physiologic limits of
VOLUME 34 | NUMBER 4 | AUGUST 2012
anabolic hormones, for example, determine how far the dietary protein and
resistance exercise stimuli take the athlete. Ample protein intake beyond nitrogen equilibrium does not necessarily
lack value; however, it may offer advantages such as affecting intracellular signaling pathways or offering satiety or
increasing metabolic rate. Finally, variables such as protein type, dose, peri-exercise timing, energy intake, and training
status all affect outcomes in research
and thus affect sports nutrition recommendations for athletes.
PROTEIN SAFETY (LARGE
INTAKES)
It is interesting to note that safety data
specific to healthy persons or certainly to
strength athletes consuming ample protein is quite limited. Scientific examinations of issues commonly mentioned by
clinicians, such as renal “stress,” dehydration, gout, bone catabolism, and an
adverse impact on diet quality (e.g., fiber
or saturated fat intake), have been few.
Pencharz et al. (40) concluded: “the data
on the safe upper limits of amino acid
intake in humans is essentially observational.” These researchers suggest that an
experimental “rational basis” is needed to
define the upper limits of tolerance for
dietary amino acids. We should not rely
on extrapolation or professional opinion,
perhaps even less so from nonscientists
and nonathletes.
KEY WORDS:
protein; protein synthesis; whey; casein;
soy; milk; beef; egg; postworkout; timing;
nutrition; hypertrophy; energy; kcal; supplement; whole food
Copyright Ó National Strength and Conditioning Association
Indirect research and plausibility arguments that generate concern, such as
the “Brenner hypothesis” (increased kidney filtration is damaging), have not been
borne out in limited population-specific
studies. For example, 2 early investigations by Poortmans and Dellalieux (44)
and Brändle et al. (7) found no adverse
effects of high-protein diets—although
both studies compared large male
strength athletes with somewhat dissimilar control groups (27,30). New research
by Lowery et al. (28) more closely
addressed certain control issues and
reported no differences in kidney “damage” (urinary microalbumin) or kidney
function (creatinine clearance) in quasiexperimental designs of strength athletes
consuming very large amounts of protein
(approximately 250 g daily; 3.2 g/kg
body mass; 34% of energy intake) compared with controls on a more typical
diet. Importantly, these designs involved
long-term data, using self-reported
intakes of over a decade (28).
Protein-focused research on bone
resorption and ultimately bone mineral
density (BMD) is similarly uncommon,
with specific data on strength athletes
only becoming available in 2009–11 to
our knowledge. Older data on the calciuria of high-protein (e.g., meat) diets
in nonlifters suggested potentially deleterious effects (17). Concerns and cautionary language on bone loss, based on
these findings, are still present in educational materials offered to college students and by certain personal training
groups (30). This has, however, drawn
critique from the scientific community
because extra calcium in the urine does
not equate to low BMD or increased
fracture risk (14,36). Indeed, Lowery
et al. (32,33) reported no differences,
after correcting for body mass differences, in whole-body or site-specific BMD
when comparing strength athletes who
do or do not habitually seek extra protein in the diet.
Similarly, data on purported dehydration, gout, and poorer diet “quality” have
not been supported by scientific study in
strength athletes (27,28,29). This is not to
say all sports that involve resistance
training will have similarly benign
findings or that very long durations of
intake beyond a decade are completely
without consequence. These are topics
for future research. The current, practical
conclusion that can be made by a review
of the literature is that large protein
intakes in healthy strength athletes, such
as weightlifters, bodybuilders, powerlifters, and strongman athletes can be
wasteful but do not appear harmful—up
to perhaps 3 g/kg daily and over periods
of about 10 years.
PROTEIN TYPES
The concept of dietary variety is a widely
accepted one, ensuring that the individual receives a broad spectrum of
nutrients, does not overconsume any
one nutrient or contaminant, and of
course complies with his training diet.
This section thus explores a variety of
protein food options. There are 5 primary types of dietary protein that will
be discussed: whey, casein, soy, egg,
and beef. These protein types can be
found in a variety of dietary sources.
Whey and casein are milk proteins. Milk
proteins combined with resistance training have been linked to an increase
in protein synthesis and an increase in
muscle strength (16,20,26,50). Egg protein supplements are derived from
chicken egg whites or whole egg sources. There are limited studies linking the
effects of egg protein in response to athletes (24,37,39). Soy protein is found in
the soybean and is generally considered
a complete protein. This nonanimal protein is thus a widely accepted vegetable
protein source. Soy can be used by athletes searching for nonanimal proteins or
by those with lactose intolerance. Beef is
also a high-quality complete protein—
one that also contains zoochemicals,
such as creatine and carnosine, that
may be beneficial to strength athletes.
These 5 proteins come in various forms
and have different physiologic effects.
The milk protein whey is a derivative
of a curd processing technique of milk.
Whey is divided into a few supplemental forms: isolates, concentrates, and
hydrolysates. The differences of these
forms are in the processing method.
Isolated whey proteins, or simply
concentrated forms (less pure in
a sense), are very high-quality proteins
but whey hydrolysates (enzymatically
predigested in part) are also available.
Again, note that whey isolates are considered more specific to the protein
itself, as opposed to whey concentrates
that include greater amounts of other
substances. As noted by Campbell
(10), “The primary differences among
these forms are the method of processing, plus small differences in fat and
lactose content, and amino acid profiles. Whey protein isolate is the most
pure and concentrated form of whey
protein available. It contains 90% or
more protein and very little fat and
lactose. Whey protein concentrate
has anywhere between 25% and 89%
protein depending upon the product.”
Whey hydrolysate supplementation—
arguably the optimal form of whey—
has been shown to increase muscle
protein synthesis greater than soy
and casein postresistance training
(49). Furthermore, studies have found
that hydrolyzed whey isolate can
increase actual gains in lean mass and
strength over 10 weeks compared with
casein (13). It is logical, especially considering further studies on acute protein synthesis and training gains
performed by Phillips et al. (42,43) that
whey proteins, including isolates and
hydrolysates, are the best choice for
muscular gains when consumed postworkout. These facts, along with
whey’s superior solubility to traditional
casein, make it attractive.
But what of other complete proteins?
Casein, the main protein in common
cow’s milk, is referred to as a “slowdigesting protein” (41) compared with
whey, egg, and soy because it clots in
the stomach. In a number of studies,
casein did not increase protein synthesis like whey protein postexercise
(4,49,53). However, casein prevents
bodily protein breakdown by promoting an anticatabolic effect that is not
found in whey protein (4). Casein
may also be superior for satiety (1).
Although it may not be the single best
choice from a protein synthetic perspective, casein can be an inexpensive
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27
Dietary Protein and Strength Athletes
high-quality protein choice. Indeed,
data does exist, suggesting it may be
similar in efficacy to whey in the long
run. As stated by Tipton et al. (53) and
restated by Phillips et al. (43), “Both
whey and casein protein have recently
been demonstrated to be effective in
supporting a positive leucine and phenylalanine balance following resistance
exercise, with no apparent difference
between the two proteins.” From
a whole-body perspective, the lingering elevation in amino acids seen after
casein ingestion suggests that it may be
beneficial to consume in the evening,
before the overnight fast. This is speculation, however, given the notion of
refractoriness (serum amino acids do
not indefinitely increase muscle protein
synthesis). This is not to say casein is
the only, or even the single best, choice
in the evening. To the authors’ knowledge, evening protein comparisons
have not been reported. An athlete’s
goals and needs can help determine
protein choices. For example, whey
may enhance sleep quality or next
day alertness (35). Yet in the interest
of dietary variety, food preferences,
protein quality, functional food properties, and whole-body protein synthesis,
casein is a valid choice.
Soy protein foods, like whey, have 3
subcategories: soy flour, soy concentrate, and soy isolate. Soy isolate has
the greatest concentration of protein
compared with concentrates and flour
(22). Soy protein can be an inexpensive
adequate option for supplementation.
Much of the lay concern regarding
soy’s estrogenic or feminizing effects
among strength athletes appears overstated. Nevertheless, some hormonal
concerns are indeed present in the scientific literature, and soy does have
a poorer leucine content than whey
(47). Despite its similar protein quality
(protein digestibility–corrected amino
acid score, PDCAAS) and relative
speed of digestion/absorption, soy
does not increase muscle protein synthesis as much as whey protein does
(49). For these reasons, soy is best
suited for those eschewing higherquality animal products, such as whey
or egg. Soy is probably not the preferred protein choice for omnivores,
given the lactose free availability of
physiologically superior and more neutral tasting, versatile dairy proteins
(Table 1).
Egg protein probably gets less attention than whey, casein, or soy but is
a recommended, very high-quality protein. Egg protein is widely known
among nutritionists to be ranked highly
in various measures of protein quality
(protein efficiency ratio, PDCAAS,
etc.), and eggs offer functional food
benefits and nutrients not found to
the same extent in dairy proteins or
meats (2). Indeed, it was egg protein
that was investigated by Moore et al.
(39) when they determined that a 20-g
post-workout dose was close to the
optimal dose for peak protein synthesis.
Eggs may best be consumed as whole
foods because of their nutrient richness,
functional food qualities, and quick
preparation.
Dietary sources of beef protein include
hamburger, beef tips, cubed steak, and
other cuts of meat derived from cows.
Because of its solid nature, beef protein
is a slower-digesting protein. The value
of beef to resistance trainers is established, but studies differ somewhat
with regards to its superiority versus
a lacto-ovo vegetarian type of diet, at
least in older men (11,21). Beef is a rich
source of calories and nutrients, such as
creatine, that may support muscle
gains. Early research by Ingwall (25),
using cultured cells and organs, suggested that creatine was the chemical
signal coupling increased muscular
activity with contractile mass. However, Haub et al. (21) performed a study
focused on the effectiveness of a lactoovo vegetarian type of diet versus
a beef-based diet and found no significant differences in strength, body composition, resting energy expenditure,
and muscle creatine/phosphocreatine.
Beef’s primary advantage may be in its
Table 1
Protein characteristics and practical applications
Practical application
Proteins
Speed of protein
When to consume
Dietary sources
Complete protein
Whey
Fast
30 min before exercise and immediately after
Dairy products
Yes
Casein
Slow
Breakfast, evenings,* during major meals
Dairy products
Yes
Soy
Medium
During major meals at least 2 hours before
or after exercise
Soybeans
Yes
Soy flower
Soy milk
Egg
Fast
Beef
Slow (solid)
(meat)
30 min before exercise and immediately after,
during major meals
Whole egg, egg whites
Yes
During major meals, evenings*
90% lean hamburger,
round steak
Yes
*Speculation based on satiety and/or daily preferences and/or whole-body protein retention.
28
VOLUME 34 | NUMBER 4 | AUGUST 2012
culinary versatility and attractiveness to
many strength trainers.
PROTEIN TIMING AND DOSE
The timing of ingested protein in relation
to a bout of resistance exercise is perhaps
the most promulgated aspect of sports
nutrition because the post-exercise “carbohydrate window” concept was popularized in the 1980s and 1990s. Earlier
protein synthesis work by researchers,
such as Tarnopolsky, has been continually expanded upon by these investigators and their colleagues such as Tipton
and Phillips. Importantly, these researchers and others have shown that the stimulus of resistance exercise opens a muscle
protein synthetic “window of opportunity” that is additive or synergistic with
the provision of other stimulatory factors,
such as the amino acid leucine (of which
whey protein is richest), insulin release
from eating, and amino acid building
blocks in general. The net effect between
the immediate post-exercise period and
perhaps 36 hours later appears to be
greater activation of the mammalian
target of rapamycin pathway within
muscle cells, positively affecting protein
synthesis (34).
As discussed in the “Protein Types” section of this article, whey protein may be
the ideal source of rapidly accessible
amino acids to pair with the resistance
exercise stimulus (42,43). Indeed, a recent
quote from Phillips’ group is summative:
“There is mounting evidence that the
timing of ingestion and the protein
source during recovery independently
regulate the protein synthetic response
and influence the extent of muscle
hypertrophy” (8).
The optimal single dose of peri-workout
protein appears to be 10–20 g, although
different types of protein may differ to
some extent (39,45,48,54). Earlier data
(48,54) suggest that approximately
6–40 g of protein (and/or indispensable
amino acids) is effective at increasing
protein synthesis post-workout. In the
context of an entire day, this is not a large
amount (a few eggs or 1–2 scoops of
protein powder), and resistance trainers
routinely consume double this amount
in peri-exercise drinks and meals. It is
interesting to note that an optimal leucine dose is contained in a typical serving
of whey protein (the richest source of
this stimulatory amino acid). With consideration for metabolic effects beyond
protein synthesis, from satiety to a high
thermic effect to potential for psychological and immune support during hard
training, substantial daily protein intakes
approximating the traditional “one gram
per pound” are not unreasonable for
healthy athletes (31,52).
ENERGY INTAKE AND TRAINING
STATUS
Daily energy intake affects protein
needs. As stated by Butterfield (9):
“. when energy balance is negative,
an intake of protein as high as 2 g 3 kg
body weight21 3 d21 may be inadequate to maintain N equilibrium.”
That is, on a low calorie intake, even
fairly large amounts of protein may
not be enough. Butterfield (9) also
demonstrated that as one adds more
and more daily kilocalories above his
requirement, he tends to experience
better and better nitrogen retention.
This is not a new concept. Data from
Chiang and Huang (12) illustrated
that for each 15% increase in kilocalories intake, nitrogen retention progressively increased. Specifically, at a fixed
protein intake of 1.2 g/kg daily, there
were incremental increases in nitrogen
retention with greater kilocalories
consumption. At maintenance energy
intake, 15% above maintenance
energy and at 30% above, nitrogen balance increased from 7.2 to 23.8 to 33.3
mg N 3 kg21 3 d21 in the ascending
calorie series and decreased from 27.8
to 17.6 to 4.8 mg N 3 kg21 3 d21 in the
descending series. These classic data
are corroborated by overfeeding studies by Roberts et al. (46) and Bouchard
and Tremblay (6), in which nonlifters
exhibited a body protein deposition of
13–33% of 1,000 kcal daily surpluses.
Note that these are nonathletes.
Although energy surplus alone is not
sufficient for optimized muscle protein
synthesis, this is a practical point of
which coaches and athletes should
stay cognizant. Many athletes undereat
or skip meals (31), a fact that would
hamper muscular gains.
Focusing too much on protein is not
optimal, as illustrated by some of the
math involved. With approximately
2,800 surplus kcal (and just 72 g of protein) necessary to build a pound of new
muscle tissue (6,18,55), regular meals
should always be addressed when working with athletes. A typical college male
needs approximately 3,000 kcal per day
(5), so it is not unheard of for a collegiate
athlete to need upward of 4,500 kcal
daily—not easily done with healthful
dietary variety, given daily schedules
and demands. In fact, protein’s high
satiety value could interfere with athletes’ attempts to gain weight. It is suggested that, when an athlete asks
whether s/he should seek extra protein,
a coach replies with his or her own
question: “That depends; how many
calories are you consuming?” More specifically, athletes differ nutritionally and
in their training, so a coach should consider the overall diet when screening the
need for seeking extra protein. If an athlete is not skipping meals and consumes
multiple servings of foods—including
complete proteins of animal origin—at
each of 4 or more meals and snacks, just
one or perhaps 2 scoops (approximately
20–40 g) of whey protein post-workout
is likely enough.
Training status also appears to play
a role. Research by Hartman et al.
(19) suggested that dietary requirements for protein in novice resistance-trained athletes are not higher,
but lower, after 12 weeks of resistance
training. It is interesting that more
experienced lifters (those who are adapted to resistance training) may actually
need less protein, provided energy is
adequate. This is not to say that ample
protein intake is unimportant for this
population. Although data by Hartman
et al. (19) suggest well-adapted lifters,
consuming plenty of calories may
have lower protein requirements;
official protein needs (i.e., the recommended dietary allowance) do not
technically differ between novice and
advanced resistance trainers. Further,
seeking ample protein intake at any
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29
Dietary Protein and Strength Athletes
Table 2
Supplemental and whole-food protein pros and cons: practical applications
Pros
Cons
Supplemental proteins
Fast preparation
Easy to overdose/overconcentrate
(gastrointestinal osmotic distress)
Low spoilage risk (dry powders, bars)
Cost of specialty formulas
Quickly corrects inadequate intakes
Liquids are less-filling (pro or con)*
Liquids facilitate surplus intake
(pro or con)*
Whole food sources of protein
Specialized diets (soy for vegetarians)
Lactose intolerant (some milk protein
foods)
Large variety of foods
Incomplete proteins (vegetable
source)
Physical properties in recipes
Fat and cholesterol content (pro or
con)
Personal preferences/compliance
Solids may reduce surplus intake
(filling)*
Filling/satisfying (pro or con)*
Preservative content (e.g., nitrites)
Additional nutrients
*Liquids have faster gastric emptying and may be helpful for repeat intake and weight gain.
state of training has a favorable benefit-to-risk ratio. Physique gains and
other health benefits (31) appear
probable without risks for healthy persons. (Again note: One should stay
cognizant that energy intake is often
inadequate in hard training athletes
and should be screened.)
But what of other potential benefits,
other than nitrogen retention, during
novice through advanced training?
“Functional food” proteins, such as
whey, may play a role in such things
as antioxidant defenses, body fat control, and reduced overtraining risks
(31,38). More research is needed in
these areas.
SUMMARY
Dietary protein interventions are a safe
and effective tool for strength athletes
in their pursuit of muscular gains
and potentially enhanced performance
over time. Although strength athletes
30
absorbable iron that dairy products
do not contain. Individuals also have
different taste preferences. Further,
the various proteins exhibit different
physical properties that are useful
in preparing certain recipes. Finally,
portability of proteins without spoilage
(i.e., dry meats and powders) is also of
practical benefit during busy schedules
(Table 2).
Lonnie Lowery
is an assistant
professor of
Nutrition and
Exercise Physiology in the
Department of
Health, Exercise and Rehabilitative
Sciences at Winona State University, and
the President of N.E.W. Associates, Ltd.
James F. Edel is
an undergraduate research
assistant in the
Department of
Health, Exercise
and Rehabilitative Sciences at Winona State University.
often overconsume protein, perhaps in
response to marketing by the food and
supplement industry, the now common
practice of consuming perhaps 20 g of
(usually dairy) proteins after resistance
exercise is recommended.
From a practical perspective, the principle of dietary variety should be
applied. Protein-rich foods are more
than just vehicles for specific proteins
or amino acids, and protein is a nutrient
that is essential for reasons beyond just
muscle mass. Protein foods offer a variety of nutrients and benefits to the
hard training strength athlete. Dairy
foods and/or supplements offer whey,
casein, minerals (notably calcium and
potassium), and hard-to-get vitamins
like vitamin D. Eggs are rich sources
of carotenoids like lutein and zeaxanthin, as well as choline (2). Soy foods
may contain fiber and provide an adequate protein source for vegans. Meats
contain zoochemicals and readily
VOLUME 34 | NUMBER 4 | AUGUST 2012
Isaiah M.
McBride is an
undergraduate
research assistant
in the Department of Health,
Exercise and
Rehabilitative
Sciences at
Winona State
University.
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