Transcript Athletic Performance and Protein Intake

Athletic Performance and
Protein Intake
Protein Basics
• Proteins are molecules have many
enzymatic and structural functions related
to the growth, maintenance and repair.
– The goal of dietary protein intake is to
contribute the amino acids necessary to
assimilate proteins for skeletal structures and
hormones, function as cell membrane
receptors and maintain fluid balance.
Protein needs are estimated by measuring nitrogen
balance...
Nitrogen balance=
in (protein intake) – out (sweat, urine and feces)
H
O
R
Protein Degradation: catabolism
Protein Synthesis: anabolism
H2N - C - C
Amine
Protein Turnover 200g-400g daily
OH
carboxyl
These two mechanisms employ
different pathways. Both pathways
are always “on”. Nitrogen balance
reflects the net protein degradation
or synthesis at the whole body level.
Protein Synthesis
• For athletes in training their goal is to
maintain or increase lean body mass (FFM)
– An increase in muscle size and thus mass is
caused by an increase in protein synthesis.
• Increased protein synthesis is reflected by an
positive nitrogen balance... Anabolic environment.
– Muscle mass maintenance (endurance
athletes) is sustained by discouraging protein
degradation.
• Protein degradation is reflected in a negative
nitrogen balance... Catabolic environment.
Dietary Protein Requirements
• The RDA for protein in normal sedentary
individuals is 0.8g/kgBW (1kg=2.2lbs)
– For a 130lbs person=(130/2.2)*0.8 = 47g
– For a 180lbs person=(180/2.2)*0.8 = 65g
• Athletes have increased protein needs
compared to sedentary people but there is
some debate about how much protein
athletes really need...
Protein and Athletes
• General belief:
– Endurance performance = CHO intake
– Strength/Power performance = protein intake
• But this is not true. All athletes have an
increased need over sedentary people for
dietary protein.
– Goal of endurance athletes: provide amino acids
for energy , maintain FFM
– Goal of resistance athletes: gain/maintain FFM
Protein Needs in Athletes
• Endurance Athletes:
– Protein oxidation occurs as an energy source
– After prolonged or high intensity exercise a negative
net protein balance is seen
– Training seems to have a protein sparing effect,
protein oxidation during exercise decreases with
training
• Recommendations, agreed upon by most
researchers:
– 1.2-1.8g/kgBW
• For 130lbs person (1.5g/kgBW)= 88g
• For 180lbs person (1.5g/kgBW)= 122g
Meeting dietary protein needs in
Athletes...
• Endurance:
– Ex: Tour de France. Athletes have difficulty
maintaining energy balance but are in nitrogen
balance. Research has shown a linear relationship
between energy intake and protein intake. When they
consumed 12% protein of 6500kcal, easily met
requirements.
When energy intake matches output in endurance
exercise athletes don’t need to supplement with extra
protein.
Protein Needs in Athletes
• Resistance Training/Strength Athletes:
numerous research studies but no clarity about
how much “extra” protein a strength athlete
needs.
• The goal of the resistance trained athlete is to
increase FFM (must be in positive protein
balance after exercise, promote muscle
synthesis)
– The general consensus is that a general increase in
dietary protein intake will promote muscle growth
Strength Athletes
• Research has shown:
– Tarnopolsky et al. recommended that athletes
involved in high intensity sports & resistance training
consume 1.76g/kg/BW of protein to maintain a
positive nitrogen balance.
• 130lb person = 104g
• 180lb person = 144g
– They also showed that 1.0g/kgBW maintained
nitrogen balance while 2.77g/kgBW attained a
positive balance that was twice that of the lower
group.
• Also evidence that body-builders require
only 0.82g/kgBW to maintain balance...
• Surprisingly one study found that athletes
couldn’t maintain nitrogen balance with an
intake of 2.0g/kgBW.
Conflicting results in dietary protein
recommendations are due to problems with
methods used and intensity of the training.
• Lemon et al. adds to the body of literature
suggesting that strength and power athletes
need between 1.5-2.0g/kgBW
Evidence has shown:
– protein needs in strength athletes increase with
changes in intensity and volume to their training
– This need for “extra” protein is negated after 12 days
of training. (temporary in response to a training
stimulus)
– With further increases in training loads, protein
requirements are also increasing to promote
synthesis.
Meeting dietary protein needs in
Athletes...
• If athletes consume 15% of their calories as
protein are they getting enough to promote an
increase in FFM?
– Let’s do the math for a male involved in a moderate
intensity resistance training program (160lbs=72.7kg):
PROTEIN CONSUMED:
TDEE = 3000kcal
15% of 3000kcal= 450kcal/4kcal/gPRO = 112g PRO =
112/72.7 = 1.45 g/kg BW/day
Meeting dietary protein needs in
Athletes...
• What about 20%?
3000kcal *20%= 569kcal/4kcal/gPRO=140g
PRO = 1.9 g/kg/day
Is simply increasing dietary protein intake
sufficient to maintain or increase FFM?
After exercise the environment of the body is
catabolic (favors protein breakdown).
• Feeding promotes protein synthesis:
1) Increases amino acid pool
2) Elevated plasma insulin reduces protein
breakdown
What should I eat?
A mixed meal is recommended with at least
1g of CHO/kg BW and 0.5g PRO/kg BW
after an intense training session.
180lbs (81.8kg) = 82g CHO and 41g PRO
Protein Intake and Protein
Synthesis
Rasmussen et al. (2000)
– After a bout of resistance exercise subjects
were fed 6g of a.a. plus 35g sucrose
– Plasma a.a. increased 3-fold, insulin
increased 10-fold
– Muscle protein synthesis was increased 3.5
fold. There was no increase in breakdown.
– Control condition saw a net protein
breakdown.
• The effect of timing...
– If feeding is delayed by 24hours net protein balance is
negative and no muscle hypertrophy occurs.
• Order of CHO and protein in post-exercise
meal...should CHO precede protein?
– Shifting environment to the “fed” state by ingesting
CHO first may limit the oxidation of absorbed amino
acids
– Trade-off is that the stimulatory effect of amino acids
on protein synthesis is delayed with this tactic.
• CHO/PRO consumption during exercise...
– Insulin levels are very low at the end of exercise,
consuming carbohydrate would maintain them and
decrease protein oxidation.
– If athlete is using a muscle group and then moves on
to another muscle group, significant time would pass
until the post-exercise meal.
Muscle growth, fat loss
• In order to promote muscle growth we need an
anabolic environment and to be in both energy
surplus and positive nitrogen balance.
– To minimize fat gain during an anabolic state of
training, choose lean proteins (chicken/fish) vs. fatty
ones (beef/lamb)
• Fat loss requires an energy deficit, but that’s a
catabolic state.
– To minimize muscle loss during an energy deficit,
increasing protein intake >20% would be suitable to
maintain nitrogen balance.
Successfully increasing FFM is a delicate balance between energy
intake and expenditure that must be carefully planned and closely
monitored.
Protein Sources
• 9 essential amino acids that must be obtained in
the diet
• Protein Quality:
– Complete protein
• have all amino acids, including the essential ones
Ex: meat, fish and dairy products
– Incomplete protein
• Have some of the amino acids, not all
Ex: nuts, grains, legumes
(vegetarian athletes may need to supplement with synthesized
pure amino acids)
Protein Sources
•
•
•
•
•
•
Beef (3oz)
Pork (30z)
Milk (1 cup)
Egg (1)
PB (1tbsp)
Apple (1) 2g
28g
28g
8g
6g
8g
• Choose lean protein
sources. Chicken has
subcutaneous fat that
can be peeled away
but beef cuts have fat
marbled throughout
the skeletal muscle.
Whey
Whey is derived from
cow’s milk. As the
schematic on the right
shows, whole milk is 13%
“stuff”.
That stuff is ~27% protein
The protein is ~20% whey
What is whey anyway?
According to the Whey Protein Institute, whey is: a
pure, natural, high quality protein...it is a rich
source of the essential amino acids needed on a
daily basis by the body.
In its purest form, as whey protein isolate, it contains
little to no fat, lactose or cholesterol… whey
provides a number of benefits in areas including
sports nutrition, weight management, immune
support, bone health, and general wellness.
A less biased description is: cow’s milk protein
Why could whey be better
than other protein sources?
Whey protein also has a relatively high proportion of branched
chain amino acids (BCAA)
BCAA – amino acids (leucine, isoleucine, valine) are not
synthesized and therefore must come from the diet
Leucine is an initiator of protein synthesis
Whey protein is rapidly absorbed; data are mixed on whether
this affects protein synthesis
Whey protein is a dairy protein and recent research suggests
that calcium and other minerals in dairy may aid in weight loss
Athletes have expensive urine...
Food/Supplement
Approx. $/kg
G Protein/$1.00
Beef, ground
4.38
46
Chicken breasts
7.69
30
Nonfat milk
0.66
48
Eggs
1.58
76
High PRO Bars
20-25
13 (8-17) (10-34)
Whey PRO-IEW
40-50
20 (14-24) (18-48)
Soy Powders
27
31 (29-33) (38-62)
Mean Repl. Powders
21-34
17 (10-24) (12-48)