Protein and Sports
Dietary
Protein
•
Complex chemical
structure containing carbon, hydrogen, oxygen, and nitrogen
•
Made up of a
combination of 20 different amino acids
– 9 essential a.a.
(can’t be made by body)
– 11 non-essential a.a.
•
Proteins are made
when 2 or more a.a. are held
together by peptide bond
– 2 a.a.
denote a dipeptide
– More than 2 a.a.
denote a polypeptide
Is there a difference between animal and plant protein?
•
Animal protein is
regarded to be of higher quality than protein found in plants
– This is because animal protein contains each essential
a.a. in proper proportion to
human needs, whereas plants usually don’t
• Foods containing all essential a.a. are known as complete protein foods (usually in
animal protein)
• Foods lacking one or more essential a.a. are known as incomplete
protein foods (usually in plant protein)
• Foods having essential a.a
but in smaller amounts are known as limited protein foods (usually in plant
protein)
Common Foods of Good Protein Sources
• Milk
and meat groups
• Legumes
(classified within milk & meat group)
– Examples: dry beans (garbanzo, kidney, lima, lentils, peas, etc.)
How much dietary protein is needed for average individual?
•
12-15% of daily
caloric intake
•
Grams of protein
needed per kilogram of body weight vary during lifespan
Dietary Guidelines for Adequate Protein Intake
• Eat
a wide variety of animal and plant foods
• If
eating primarily plant sources, then will most likely need more to satisfy
protein needs (i.e. instead of 56 g of protein from animal sources, will likely
need 65 g of protein from plant sources)
– A 30% animal protein source + 70% protein
source = 100% animal protein source
Protein
Metabolism
• Digestion
of protein takes several hours
– However,
once a.a. enter bloodstream,
they are taken up in 5-10 min
• Most
important metabolic fate is formation of proteins necessary for structure
• Excess
a.a. will be processed in
liver to become sources of CHO and fat
Can protein be formed from CHO and Fats?
• Yes,
but with some limitations
– If
nitrogen is present, by-products of CHO breakdown (pyruvic
acid) and Fat breakdown (acetoacetic acid) can form
non-essential a.a.
Major
Functions of Protein
• Formation
of tissue structure, e.g. contractile muscle protein
• Transport
of substances in the blood, e.g. lipoproteins
• Formation
of enzymes
• Formation
of hormones
• Formation
of immune components, e.g. antibodies
Major
Functions of Protein
• Buffering
of acids and bases in blood to maintain optimal pH
• Exert
osmotic pressure to maintain appropriate fluid balance in body tissues,
particularly the blood
• Provide
a source of energy
• Provide
movement of muscle fibers during contraction
How much protein is used for energy during sport activity?
• Less
than 5% of the total energy cost
• In
latter stages of a prolonged exercise, it could contribute up to 15% of total
energy cost; mimicking a state of starvation
What happens to muscle protein during exercise?
• The
rate of protein synthesis slows down and the rate of protein breakdown speeds
up
– It
appears that exercise activates certain proteolytic
enzymes that degrade muscle fiber structure
• This
occurrence appears to be related to fatigue
– It
appears that 6 different a.a.
are broken down in the muscle and form ammonia, glutamine, and alanine
Outcomes of muscle protein breakdown
• Ammonia
may contribute to fatigue
– Impairs
oxidative processes which decrease energy production in the muscle
– When
it gets into the blood, it will go to liver for processing and also will go to
brain
• It
may impair brain function resulting in “central” fatigue
• Glutamine
– Important
fuel source for immune function
Outcomes of muscle protein breakdown
• Leucine (a branched-chain a.a. – BCAA)
– Can
be converted to pyruvate and then oxidized for energy
in muscle
• Note:
BCAA’s (leucine, isoleucine, valine – constitute a
significant amount of muscle tissue) can also be made in liver and supplied to
muscle for energy during endurance activity
– Can
be converted to Alanine
• Can
be converted to glucose in liver and used as energy by central nervous system or
muscles
Outcomes of muscle protein breakdown
• Magnitude
of muscle protein breakdown during exercise will be dependent upon:
– Intensity
and duration of exercise
– Availability
of other fuels (i.e. glycogen) in the muscle
Does exercise increase protein losses in other ways
• It
causes elevated level of protein in the urine (proteinuria)
– A
greater amount occurs from a higher intensity of exercise; also a very
prolonged endurance activity
• Appears
to be due to a decreased reabsorption by the kidneys
during exercise
• Protein
is lost in the sweat
– The
greater the intensity, the greater the loss
What happens to protein metabolism during recovery?
•
Protein breakdown
is reduced
•
Protein synthesis
is either increased or unchanged; particularly in the exercised muscle groups
– Leucine balance has been shown to return to normal in 24
hours
– With weight training exercise, protein anabolism is
generally high 24-48 hours post-lifting; may be slight protein breakdown
immediately after exercise
– Eccentric exercise tends to cause more protein
breakdown; hence a longer protein balance recovery
How does exercise training affect protein metabolism?
• Trained
individuals, at rest, tend to spare more protein as fat is more readily used as
an energy source
• Aerobic
exercise training tends to increase the formation of more mitochondria and
oxidative enzymes; this increases potential for muscle to use BCAA’s for energy
• Resistance
training promotes more synthesis of contractile proteins
How does exercise training affect protein metabolism?
• Decreases
production and accumulation of ammonia
– Appears
to be incorporated into other a.a.’s
– May
help reduce potential fatigue
• Reduces
potential muscle damage which might normally occur with eccentric exercise
– However,
overtraining seems to be associated with decreased glutamine
Do weight training athletes need more protein in the diet?
• Varying
opinions exist
– National
Research Council suggests that no increment is needed provided enough Calories
are ingested in diet
– Many
investigators believe that a range of 1.1-1.8 grams/kg of body weight is
appropriate, depending upon the type of sport activity
Specific
sport needs of protein
• Strength-type
activities
– Optimal
intake recommendations range from 1.5 to 1.8 g/kg body wt per day
• Some
research suggest higher intakes
• 0.8
g/kg/day may actually limit growth in strength-training individuals
– An additional
200 Calories per day are also recommended; intake should include CHO also
Specific
sport needs of protein
• Endurance-type
activities
– Optimal
intake recommendations range from 1.1 to 1.4 g/kg body wt per day
– Intensive
endurance athletes should consider 1.8 to 2.0 g/kg body wt per day
– Female
athletes may need more dietary protein than “recommendations” since energy
intakes are usually lower than males
– Athletes
attempting to lose wt for competition will likely need a greater protein intake
Specific
sport needs of protein
• Intermittent
high intensity-type activities
– Optimal
intake recommendations range from 1.4 to 1.7 g/kg body wt per day
– Much
more research needs to be done in this area
Specific
sport needs of protein
•
Sports Anemia
– A lack of hemoglobin; reduced O2-carrying
capacity
– Believed to occur in early stages of endurance
training due to increase in protein synthesis for myoglobin,
mitochondria, and other muscle proteins (at the expense of taking the protein
from hemoglobin)
– Cause could also be due to expansion of water volume
in the blood
– 1.25 to 2.0 g/kg body wt is suggested within 1st
month of training to prevent anemia
Protein Need Based Upon Weight Gain Goal
•
Based upon a 70
kg individual who lifts weights
– Background
• 1 pound of muscle = 454 grams
• 70% of muscle is water
• 7% of muscle is lipid (fat)
• 22% of muscle is protein
– Gaining 1 pound of muscle/week (since 454 x .22 = 100;
then 100 ÷ 7 days = ~14 grams per day)
• 14 grams of additional protein/day
• Double this amount to gain 2 lbs/week
Are there certain sports that may need extra protein in
diets?
• Wrestlers
and Gymnasts may need extra protein due to low Calorie intakes
• Young
athletes may need extra protein due to growth and development
• Ultra
endurance athletes may require more protein due to greater potential muscle
damage
Is Timing of Protein Intake Important for Athletes?
•
Protein intake
within 1-3 hours following exercise may stimulate protein synthesis
•
Small, multiple
meals throughout day, with adequate protein, may stimulate protein synthesis
•
Other
considerations in meals
– Adequate CHO helps spare protein
– Adding protein to CHO supplement during recovery
increases glycogen resynthesis
• Protein/CHO supplements shown to elicit hormone responses favorable to muscle
growth
Protein:
Ergogenic Effects
• Are
high protein diets or supplements really necessary?
– Athletes
involved in strenuous, resistance exercise generally require more protein than
the suggested RDA for the average individual
– Protein
supplements of natural sources don’t offer any more benefits than those from
food sources
• May
attain protein requirements from high-protein foods such as powdered milk, skim
milk, eggs, and chicken
Protein:
Ergogenic Effects
• Are
high protein diets or supplements really necessary?
– For
athletes “on the go” commercial supplements may be important to get necessary
protein
• Examples
– Nutrament, Nitrofuel, GatorPro (supplement to balanced diets)
– Spirulina (algae), brewer’s yeast (protein with vitamins
and minerals; not ergogenic)
– Enzymes
and DNA (degraded in digestive tract)
Protein: Ergogenic Effects for
Strength-Type Activities?
•
Earlier, less
controlled studies suggested body weight gains from extra protein
•
Recent,
well-designed studies do not show any additional gain in muscle mass or
strength when comparing 2.6 g/kg to 1.35 g/kg of protein intake
•
Recommendation:
Do not take in more than 2 g/kg since there is no additional benefit to body
composition or performance
Protein: Ergogenic Effects for
Endurance -Type Activities?
• No
studies have shown that endurance athletes can gain any benefit from additional
protein intake above the RDA of 0.8 grams/kg of body wt.; however, it does
appear to be safe to consume 1.1 to 1.4 grams/kg of protein, just in case
• More
studies are necessary
Protein:
Ergogenic Effects
• What
about a.a. supplements?
– Arginine, lysine, & ornithine
• Arginine, lysine, & ornithine
can stimulate release of human growth hormone (HGH) and insulin; 2 anabolic
hormones
• Arginine can cause dilation of blood vessels and stimulate
epinephrine release
– No
sound evidence to suggest that supplementation with arginine,
lysine, or ornithine enhance muscle development or
increase endurance
Protein:
Ergogenic Effects
• What
about a.a. supplements?
– Tryptophan
• Tryptophan may stimulate release of HGH but also may form 2
neurotransmitters in brain (serotonin & 5-hydroxytrptamine) that may
decrease perception of pain; suggest greater pain tolerance and resistance to
fatigue
– Tryptophan does not appear to be effective in enhancing
performance for either short- or long-term exercise tasks
Protein:
Ergogenic Effects
• What
about a.a. supplements?
– Branched-Chain
Amino Acids (BCAA)
• Thought
to enhance performance by:
– Fuel
for exercise to prevent adverse changes in neuromuscular function
– Spare
use of muscle glycogen
– Prevent
or decrease rate of protein degradation
• Potential
effectiveness resides with Central Fatigue Hypothesis
– High
levels of serum free-tryptophan in conjunction with
low BCAA may result in significant serotonin production; serotonin depresses
brain function
Protein:
Ergogenic Effects
• BCAA
supplementation
– If BCAA’s decrease with prolonged exercise, then this might be
a good reason to take supplements
• Muscle
can use BCAA’s for energy
– BCAA
supplementation and mental performance
• Some
studies have shown more alertness in games or lessened perception of fatigue in
moderate to intense endurance events
• Overall,
no significant benefits proven
Protein:
Ergogenic Effects
– BCAA
supplementation and physical performance
• Taking
dosages ranging from 5-20 grams/day on an acute or chronic basis (several
weeks)
– No
significant benefit to trained endurance athletes
– May
be effective with less trained individuals in endurance events
– Overall,
BCAA supplementation has not been proven to be effective in improving
performance of endurance athletes
Protein:
Ergogenic Effects
• BCAA
supplementation and body composition
– May
slow muscle protein breakdown during exercise while body breaks down fat as an
energy source
• This
could result in maintenance of muscle and loss of body fat
• More
studies need to be done in this area
Protein:
Ergogenic Effects
• What
about a.a. supplements?
– Glutamine
• Made
in muscle
• Functions
– Removal
of excess amino groups from the muscle
– Stimulate
protein synthesis through increasing HGH levels
– Helps
rebuild glucose and glycogen
• Important
for rebuilding CHO in recovery from exercise
– Fuel
for lymphocytes and macrophages (immune cells)
• May
help in preventing “overtraining”
• May
help in treatment of burn patients
Protein:
Ergogenic Effects
• Glutamine
supplementation
– Not been
proven to lessen overtraining symptoms
– Not
conclusive in reducing incidence of infection
Protein:
Ergogenic Effects
• What
about a.a. supplements?
– Aspartates (non-essential)
• May
enhance fat metabolism and spare glycogen
• May
reduce accumulation of ammonia in muscle
• May
improve psychological motivation
– Aspartate supplements (10 grams doses)
• No
significant benefits to anaerobic performance
• May
have beneficial effect on endurance performance; more studies necessary
Protein:
Ergogenic Effects
• What
about a.a. supplements?
– Glycine (non-essential)
• Involved
in formation of creatine, hence PCr
• Gelatin
contains ~ 25% glycine
– Glycine supplementation
• Not
been shown to be any benefit to performance
Protein:
Ergogenic Effects
•
What about other
protein supplements?
– Chondroitin and Glucosamine
• Protein derived from connective tissue for use in
promoting healthy joints
• Both may be synthesized from a.a. and are found in human cartilage
– Chondroitin gives cartilage its resiliency
– Glucosamine helps for cartilage structure
• These supplements have been shown to prevent
osteoarthritis from getting worse, particularly in older athletes
• No data yet to suggest that it prevents development of
joint pain in young, healthy athletes
• Reasonable intake: 1,200 mg chondroitin
and 1,500 mg glucosamine for 2-4 months; check for
pain symptoms
– Safety issues
• May cause bloating or diarrhea
• May cause insulin resistance in diabetics
Protein:
Ergogenic Effects
• What
about other protein supplements?
– Creatine
• Found
primarily in meat products, but can be made in kidney and liver from certain a.a.’s and delivered to muscle
• Theory
is that extra creatine would bolster PCr, so
that a drop in power output during high intensity effort would
not occur.
• Supplementation
has shown increase in muscle content
Protein:
Ergogenic Effects
• What
about other protein supplements?
– Creatine Supplementation protocol
– Average
individual needs to replace ~ 2 grams of creatine per
day; 1 gram of which can be obtained from red meat
– One
supplementation strategy
• Total
of 20-30 grams of creatine (pure creatine
monohydrate)
• Taken
in 4 equal doses (5-7 grams per dose) over the course of day
• Combining
creatine with simple CHO will help in transport into
muscle; e.g. 5 grams of creatine with 90 grams CHO
(per dose)
Protein:
Ergogenic Effects
• Creatine Supplementation Effects on Performance
– Improvement
in total and max force in repetitive isometric muscle contractions
– Improvement
in muscle strength and endurance in isotonic strength test, e.g. 1 RM
– Improvement
in muscle force/torque and endurance in isokinetic
strength tests
– Improvement
in cycle ergometer performance in max efforts of 6 to
30 seconds
Protein:
Ergogenic Effects
•
Other creatine supplementation benefits
– Some evidence suggests a benefit to high intensity
efforts of 30-150 seconds (400-800 meter track events); more research needed
– Not likely to improve VO2 max or exercise
events of long duration
– Increase in body mass likely to occur in 1st
week of supplementation; primarily due to water retention; may make it
difficult to lose wt for competition since creatine
tends to stay in muscle for several weeks before disappearing
– Creatine improves ability to do repeated contractions during
training
Protein:
Ergogenic Effects
• Creatine supplementation + caffeine
– Caffeine
may negate benefit of creatine since it could block
PC resynthesis during recovery from exercise
Protein:
Ergogenic Effects
• Safety
of Creatine supplementation
– No
apparent significant adverse effects with 12 weeks of use in healthy
individuals
– Individuals
with kidney problems should avoid creatine
supplementation; extra load on kidney metabolism
– May
cause some gastrointestinal problems particularly if taken immediately prior to
event
– Suggested
to result in muscle cramps due to dilution of electrolytes
Protein:
Ergogenic Effects
•
Summary of Creatine Supplementation
– ACSM Statement
• Apparent absence of health risks does not mean that creatine is safe
– Creatine appears to enhance performance in events where the
amount of PCr may be a limiting factor
• i.e. If PCr levels in muscle are increased with creatine
supplementation, then performance may be enhanced
• Benefit does not appear to be due to greater PCr resynthesis during exercise
recovery
Protein:
Ergogenic Effects
•
HMB (Beta-Hydroxy-Beta-Methylbutyrate) Supplementation
– A by-product of leucine
metabolism (made by body)
– Theory is that it inhibits breakdown of muscle tissue
during strenuous exercise
• Also, theorized to ↑
lean muscle mass, ↓ body fat, and ↑
muscle strength and power
– Supplementation results (1-3 grams/day)
• May slow rate of muscle breakdown in untrained
resistance-training individuals (initial 3 weeks)
• Does not benefit resistance-trained individuals; no
additional benefit if combined with creatine or
CHO/protein supplement
• 8 weeks of HMB supplementation had no adverse effects
on health
Protein:
Ergogenic Effects
•
Choline Supplementation
– An amine found in lecithin (found in egg yolks liver,
nuts, wheat germ, cauliflower, soybeans)
– Helps in formation of acetylcholine, a
neurotransmitter in CNS
– Theory
• Since plasma choline levels
are reduced with long duration, exhaustive exercise, this may lead to fatigue
• Choline supplementation may lessen chance of fatigue
– Supplementation results
• Shown to ↓
run time and improve mood in some studies but no change in others; results are
equivocal
Protein:
Ergogenic Effects
•
Inosine Supplementation
– Not an a.a.
but is a nucleoside that helps form purines (nonprotein nitrogen compounds); i.e. associated with ATP
– Theory
• Improves ATP production in muscle so may benefit
strength-type athletes and aerobic athletes
– Supplementation results (1-10 g/day doses)
• Not shown to enhance performance, and likely to hamper
performance (lessened effort on supramaximal cycling
test)
• Should not be taken by individuals predisposed to gout
due to potential for uric acid formation
Protein Supplementation: Ergogenic
or Health Effects
• At
present time, there is inadequate scientific data to support ergogenic or health benefits to individual amino acid
supplementation in healthy individuals