protein in exercise
TRANSCRIPT
NDD 30503
LECTURE 4Protein in Exercise
DR. SHARIFAH WAJIHAH WAFA BTE SST WAFA & HH02
WEDNESDAY (27 SEPTEMBER 2017), 3:00-5:00PM
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 2
Functions of Proteins
2
Enzymes
Hormones
Structural
Immunologic
Transport and storage
pH buffering
Energy source
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 3
Structure of Proteins
• Proteins are made of individual “building block” units called
________ that are linked together
– A chain of AAs is called a _______
– Long peptides are ______
• The order of the AAs allows different proteins to have
different functions
3
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 4
What Are Amino Acids?
• Building blocks of proteins– Body uses 20 different amino acids to make proteins
• ____ of the 20 amino acids must be consumed in the diet (essential amino acids; EAA)
• Other ___amino acids are not essential (NEAA)
• Some NEAAs can become EAAs under certain conditions– Infants have different needs for growth
– Defects in amino acid metabolism• Tyrosine can become essential in individuals with
phenylketonuria (PKU), an inborn error of phenylalanine metabolism
4
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 5
Basic Structure of an
Amino Acid
• Central carbon atom (alpha carbon [Cα])
linked to
– Amino group (positive)
– Carboxylic acid group (negative)
– Hydrogen
– Distinctive side chain (R)
• Makes each AA different
5
+–
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 6
R Groups for Some Amino Acids
H-
CH3-
H3C
H3C
CH-
H3C
H3C
CH-CH2-
CH2
CH2
CH-
CH3
Glycine
Alanine
Valine
Leucine
Isoleucine
HO-CH2- Serine
Threonine
Cysteine
Methionine
Aspartic acid
CH3-CH-
OH
CH2-
SH
CH2-CH2-
S-CH3
-OOC-CH2-
Berg JM, et al. Biochemistry. 5th ed. New York, NY: WH Freeman & Co.; 2002.6
Protein Digestion and
Absorption
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 8
Protein Digestion
Gastric phase (stomach)
Hydrochloric acid (HCl) from cells in stomach unfolds protein
Pepsinogen (chief cells)HCl
Pepsin (enzyme)
Pepsin digests proteins Large peptide fragments
Small intestine phase
Cholecystokinin (hormone released in upper small intestine)
triggers pancreas to secrete digestive enzymes once digestion
products leave the stomach
Digestive enzymes are activated and continue to break down
peptides into di-/tripeptides and free amino acids, which are
taken up by intestinal cells
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 9
Amino Acid and Peptide Absorption
• Transporters can carry
– Free AAs
– Di- and tripeptides
• For example, can transport carnosine, a dipeptide
– Nonprotein AAs
• For example, can transport creatine from intestine to blood
9
Lumen
Amino acids
Oligopeptides TripeptidesDipeptides
Intestinal cell Blood
Cellular membrane
Peptidases
Transporters
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 10
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 11
Fast Versus Slow Digestion of Proteins
• Proteins are digested at different rates– Similar to glycemic index concept for carbohydrates
• Whey vs casein– _____ is rapidly digested and results in quick rise in plasma AAs
(fast protein)
– ______ forms a curd and takes longer to empty from the stomach (slow protein)
• Less dramatic, but more sustained rise in plasma AAs after consumption
• Soy protein– Digested faster than whole milk protein, which contains both
whey + casein
• Overall, more like a fast protein, but slower than whey 11
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 12
Protein Turnover
• There is a constant flux between making new muscle
protein and breaking down old muscle protein
– Known as “protein turnover”
• Goal for increasing muscle size is for muscle protein
synthesis to exceed breakdown
12
Muscle
synthesis
Muscle
protein
Muscle
breakdown
Amino
acids
Amino acidsBlood
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 13
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 14
Fast- vs. Slow-Digested Proteins in
Protein Turnover
• Milk proteins are superior to soy for
stimulating protein synthesis
– Whey (fast protein) stimulates protein synthesis
to a greater extent than casein (slow protein)
and soy (moderate-fast protein)
– Casein reduces muscle protein breakdown better
than whey protein
• Mixed protein sources provide benefits of all
14
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 15
Branched Chain Amino Acids (BCAAs)
• BCAAs are:
• Unlike other AAs, most BCAA metabolism occurs in
skeletal muscle
– Liver lacks first 2 enzymes in the pathway that break
down BCAAs
• Leucine is also unique among AAs in its ability to
stimulate synthesis of new muscle proteins 15
CH2
H3C
H3C
CH-
H3C
H3C
CH-CH2-
CH2
CH-
CH3
C COO-
NH3+
H
C COO-
NH3+
H
C COO-
NH3+
H
Leucine Isoleucine Valine
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 16
BCAAs and β-hydroxy-β-
methylbutyrate (HMB)
• What is HMB?– Derived from breakdown of leucine
– Hypothesized to inhibit muscle protein breakdown
and increase muscle synthesis, especially in
combination with resistance training
– Some evidence in humans that doses of 3 g/day may
be effective
• Additive benefits with creatine
– Some studies suggest that HMB may provide greater
benefit to untrained people who start weight
training compared with previously conditioned
athletes16
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 17
Protein Quality
• Complete protein
– Contains all the essential AAs in amounts that meet or exceed the amounts needed by humans
• Animal proteins (except gelatin)
• Soy protein
• Incomplete protein
– Too low in one or more of the essential AAs to support human growth and development
• Cannot serve as a sole source of protein in the diet
• Most plant proteins are incomplete proteins (except soy)
17
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 18
Protein Quality (cont’d)
• Complementary proteins
– Combinations of incomplete proteins that,
when added together, result in a complete
protein
• Legumes: methionine, lysine
• Grains: methionine, lysine
• Example: rice and beans
18
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 19
Protein Quality (cont’d)
– Usually, combining a complete protein with an incomplete protein is considered complementary• Exception is milk and legumes
– Although milk has a greater amount of sulfur-containing AAs (eg, methionine and cysteine) per gram compared with legumes,
• Not enough sulfur-containing AAs are present for an ideal AA profile when the 2 foods are consumed together
– Combining complementary proteins at each meal for vegetarians is not necessary• What matters is total intake of complementary
proteins spread over the course of the day
19
Determining Protein
Recommendations
for Athletes
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 21
Protein Requirements
• Current RDA for protein is 0.8 g/kg body weight per day
• The RDA for protein is set to prevent deficiency (ie, maintain protein balance) in healthy adults
• Does not consider potential benefits that might be obtained from amounts beyond RDA• For example, the optimal protein intake for muscle
function and athletic performance
21
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 22
Protein Intake
Recommendations
• American College of Sports Medicine (ACSM)
/ American Dietetic Association (ADA)
–Endurance athletes, 1.2 to 1.4 g/kg per day• Accounts for greater use of protein as fuel for energy
–Strength athletes, 1.2 to 1.7 g/kg per day• To support muscle growth, particularly during early training phase when
gains are greatest and protein utilization is less efficient
• Clinical studies suggest there is no apparent
benefit at intakes above 2.0 g/kg per day
22
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 23
Vegetarian Diets
• Most vegetarian athletes meet the RDA
for protein of 0.8 g/kg per day
• Protein quality of non-animal / non-dairy
sources is lower
• ACSM/ADA recommends 1.3 to 1.8 g/kg
per day for vegetarian athletes
23
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 24
How Much Protein Are Athletes
Eating?• Many athletes may already meet or exceed
protein recommendations• Definition of “high protein” can be the absolute
amount of protein, % of total energy (calories), or protein ingested per kg of body weight
• Strength athletes in particular may believe that much higher protein intakes are needed for muscle building• Intakes at 4- to 6-g/kg range are not uncommon
• Unlikely to provide benefit beyond 2.0 g/kg
• It is possible that this much protein intake could adversely affect the nutrient quality of the overall diet
24
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 25
How Much Protein Are Athletes
Eating?
25
• Protein intake below 2 g/kg per day is safe
in healthy individuals
• Protein intake above 2 g/kg per day is not
recommended due to lack of proven benefit
and potential for adverse health effects
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 26
Potential Downside to “High-
Protein” Diets
• Hydration status
• Nitrogen that is obtained from consuming protein must be excreted in the urine as urea
• Increased urinary output due to high protein load may increase chances of dehydration
26
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 27
Potential Downside to “High-
Protein” Diets
• Diets very high in protein may lack appropriate amounts of carbohydrate, fiber, and some vitamins/minerals
• Could impair exercise performance
• Could increase long-term risk of diseases such as colon cancer
• Possibly due to lack of fiber or increased intake of red meat
27
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 28
Potential Downside to “High-
Protein” Diets
• Excessively fatty protein sources could increase risk of cardiovascular disease
Choose mostly lean protein sources
For example, salmon is more desirable than a ribeye steak
28
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 29
Potential Downside to “High-
Protein” Diets
• Kidney disease
• No good evidence of damage in individuals with healthy kidneys
• Protein-rich diets are high in phosphorus, which can be harmful to individuals with kidney disease – Primarily a concern with elderly or sick
individuals, as opposed to healthy athletes
29
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 30
Potential Downside to “High-
Protein” Diets (cont’d)
• Bone health
• Higher protein diets may increase calcium loss in urine
–However, gut absorption of calcium is likely improved, so there may be no net difference
• Elevated protein diets appear to have either no or a slightly beneficial effect on skeletal health
30
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 31
Summary of Protein
Recommendations• Daily Recommended Intake is 0.8 g/kg per day
(2002)–No recommendation for increase in athletes
• American College of Sports Medicine– Strength athletes: 1.2 to 1.7 g/kg per day
– Endurance: 1.2 to 1.4 g/kg per day
• Vegetarians may have higher dietary supplementation protein needs than omnivores
31
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 32
Summary of Protein
Recommendations• Protein intakes up to 2.0 g/kg per day are
generally safe in healthy adults and may be beneficial• Many athletes may already unconsciously eat this
amount of protein
• Few convincing data show that > 2 g/kg per day is helpful• May actually increase risk of adverse events
32
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 33
What About Amino Acid
Supplements?
• As long as the complete protein requirements are met, the individual AA requirements will be met as well No need for additional AA supplements to prevent
deficiency
• Because vegetarians eat few complete sources of protein, they should be cognizant of complementary protein sources throughout the day to prevent deficiency of particular AAs
33
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 34
What About Amino Acid
Supplements?
• BCAA are popular as a supplement among athletes – Claims mainly center on decreasing muscle soreness
and improving either performance or recovery from exercise
– Doses can range from 2 to 7 g/day to more than 20 g/day
• There are potential risks associated with AA supplements• Large doses of single AAs can prevent the
absorption of other AAs, which may lead to diarrhea
• Can indirectly cause deficiency of other AAs as a result 34
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 35
Is Protein Used for Energy
in Athletes?
• In general, the body prefers to spare its own
protein stores from use for energy production
• Skeletal muscle, in particular, will be protected in
order to allow crucial fight or flight response
• Only in conditions of starvation or extreme energy
requirements (eg, ultramarathons) will the body
break down muscle for energy
35
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 36
Is Protein Used for Energy
in Athletes?
• Dietary protein is commonly used as a fuel
source in certain situations (eg, during
endurance exercise, which can deplete
carbohydrate stores in muscle)
• 6 of the 20 amino acids can be metabolized for
energy in resting muscle (frequent during exercise)
36
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 37
Timing of Ingestion and Macronutrient
Content of Meals
• There is increasing agreement that immediate post-exercise ingestion of protein and/or carbohydrate has beneficial effects on• Muscle glycogen replenishment (particularly
carbohydrate)
• Muscle protein synthesis (particularly protein)
37
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 38
Timing of Ingestion and
Macronutrient Content of Meals
• A combination of both protein and carbohydrate work better than either carbohydrate or protein alone• Proportions of carbohydrate/protein vary based on
individual needs• Endurance athletes prioritize carbohydrate intake for
glycogen replenishment
• Bodybuilders prioritize protein intake for muscle growth
38
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 39
Putting a Meal Plan Together
• Example: 70-kg athlete requiring 4,000 kcal/day who is exercising 120 min/day, 4 to 6 times/week
• Macronutrient target recommendations
– Grams/kg body weight/day
• Carbohydrate 7-10 g/kg (490-700 g/day)
• Protein 1.5-2.0 g/kg (105-140 g/day)
• Fat Typically use percentage of energy
– Percentage of energy
• Carbohydrate 55-65% of energy (550-650 g/day)
• Protein 10-15% of energy (100-150 g/day)
• Fat 20-30% of energy (88-133 g/day)
• Target recommendations for this athlete
− Carbohydrate 600 g/day (60% of energy)
− Protein 130 g/day (13% of energy)
− Fat 120 g/day (27% of energy)39
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 40
Remember!
• For building muscle mass and for maintaining muscle mass through a positive muscle protein balance, an overall daily protein intake in the range of 1.4–2.0 g protein/kg body weight/day (g/kg/d)
• higher protein intakes (>3.0 g/kg/d) may have positive effects on body composition in resistance-trained individuals (i.e., promote loss of fat mass).
• General recommendations of 0.25 g of a high-quality protein per kg of body weight, or an absolute dose of 20–40 g to maximize MPS.
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 41
Remember!
• Acute protein doses should strive to contain 700–3000 mg of leucine and/or a higher relative leucinecontent, in addition to a balanced array of the essential amino acids (EAAs).
• Rapidly digested proteins that contain high proportions of essential amino acids (EAAs) and adequate leucine, are most effective in stimulating MPS.
• Different types and quality of protein can affect amino acid bioavailability following protein supplementation.
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 42
Remember!
• Athletes should consider focusing on whole food sources of protein that contain all of the EAAs (i.e., it is the EAAs that are required to stimulate MPS).
• Endurance athletes should focus on achieving adequate carbohydrate intake to promote optimal performance; the addition of protein may help to offset muscle damage and promote recovery.
• Pre-sleep casein protein intake (30–40 g) provides increases in overnight MPS and metabolic rate without influencing lipolysis.
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 43
Summary
• Adequate protein intake is critical for athletic
performance and good health
• For most athletes, protein intakes of 1.5 to 1.8
g/kg/day will meet protein requirements
• High-quality protein sources (eg, dairy products,
meats, fish, chicken, soy, eggs) should be included
in the diet
• Eating a combination of carbohydrate and protein
soon after exercise can help with muscle recovery
and muscle building
43
Click to edit Master title
style
• Click to edit Master text styles
– Second level
• Third level
– Fourth level
» Fifth level
10/11/2017 44
Summary
• There are potential disadvantages to excessive
protein intake above 2 g/kg/day
• No additional benefit for strength or muscle
building
• Increased water loss from the body that may lead
to dehydration
• High-protein intake may replace carbohydrates and
other vital nutrients for athletic performance and
good health
• Decreased overall diet quality
44
Gracias