Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 6 Protein

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chapter 6Protein

What is protein?

• Protein is a complex structure containing carbon, hydrogen, oxygen, and nitrogen, and in some cases sulfur. These elements combine to form amino acids.

Formation of peptides and protein

Amino Acids

Two types:

1) Essential (9)• Must be obtained from foods in the diet

2) Nonessential (11)• May be formed in the body

Animal vs. Plant Protein• Complete proteins

– Contain adequate amounts of all 9 essential AA– Are found in animal foods– Contains a higher concentration of protein

• Incomplete proteins– Limiting AA: A deficiency of one or more essential AA

• Legumes (methionine) Grains (Lysine)– Plant foods are incomplete proteins– Contains a smaller concentration of protein

What are some common foods that are good sources of protein?

• The Food Groups– High

• Meat and meat substitutes (legumes)• Milk

– Lower • Starch• Vegetable• Fruit• Fat

Figure 6.4

How much protein do I need?

• Humans need enough protein to provide adequate amounts of nitrogen and essential amino acids

• Recommended Dietary Allowance (RDA)– Based on age and body weight

• Acceptable Macronutrient Distribution Range (AMDR)– Based on percentage of daily energy/calorie intake

Protein RDA

Protein RDA and AMDR

• Adult RDA is 0.8 g pro/kg body Wt• Protein AMDR is 10-35% of daily energy intake

Example - Female, 135 lbs (60 kg), eating 2,000 cal/d

• RDA is 48 grams of protein (60 x 0.8)• AMDR of 10% provides 50 grams of protein

– 2,000 x 0.10 = 200 protein Calories– 200/4 Calories per gram of protein = 50 grams of protein

AMDR of 35% provides 175 grams of protein

Summary of protein functions in the human body

• Structural• Transport• Enzyme• Hormone and neurotransmitter• Immune• Acid-base balance• Fluid balance• Energy • Movement

Dietary protein needs:Strength-Type Athletes

• Additional protein is often recommended to help support or promote increases in muscle tissue

Dietary protein needs:Endurance-Type Athletes

• Need to recognize that carbohydrate is the main fuel for endurance-type athletes

• More dietary protein is recommended to – Restore protein used for energy– Promote synthesis of oxidative enzymes and

mitochondria– Help prevent sports anemia

What are some general recommendations relative to protein intake for athletes?

1. Obtain the RDA for protein– All athletes should obtain at least their RDA for

protein– About 0.95 to 0.85 g/kg for young athletes– About 0.80 g/kg for adult athletes

Recommendations for protein intake in athletes

2. Increase the protein RDA by 50 to 100 %– Will increase an adult’s protein intake to 1.2 to 1.6

grams/kg body weight, and a young athlete to about 1.7 to 1.9 grams/kg body weight

– These values are within the AMDR of 10-35% of daily energy intake


3. Obtain about 15 percent or more of daily energy intake from protein– Some athletes may need more protein than

others• Athletes in weight-control sports• Female endurance athletes with low energy intake

– Protein intake is within the AMDR

Protein intake in a wrestler

• College wrestler of 132 pounds (60 kg)• RDA is 48 grams of protein/day• Diet of 1,600 Calories to maintain body weight• A diet with 12% protein will provide the RDA

– 0.12 x 1,600 = 192 Calories; 192/4 = 48 g of protein

• A diet with 20% protein will provide about 1.7 grams of protein/kg body weight, which is near the recommendation for strength athletes– 0.20 x 1,600 = 320 Calories; 320/4 = 80 g of protein– 80/48 = 1.66 grams of protein/kg


4. Consume protein, preferably with carbohydrate, before and after workouts: The concept of Nutrient Timing.– There appears to be little difference in anabolic

responses if protein is consumed either before or after exercise

– The protein source should contain all essential amino acids

• About 0.1 gram per kg body weight is recommended• 7 grams for a 70-kg individual


– Consuming carbohydrate with the protein may also enhance the anabolic effects after exercise, possibly attributed to increase insulin secretion

– Whole foods, such as a turkey breast sandwich, appear to be as effective as amino acid solutions

– The carbohydrate: protein ratio should be about 3:1 or 4:1

• Commercial products such as Endurox• Chocolate milk


5. Be prudent regarding protein intake. – There is insufficient evidence that increased protein intake

will enhance exercise performance– Experts contend that given sufficient energy intake, lean

muscle mass may be maintained within a wide range of protein intakes

– There is a metabolic rationale for increasing protein intake if muscle hypertrophy is the goal, but the intake need not be excessive and may be within the AMDR of 10-35% of daily energy intake

Protein: Ergogenic Aspects

• Three of the top 5 most popular sport supplements– Protein– Amino acids– Creatine

What types of protein supplements are marketed to physically active individuals?

• Variety of products, but the protein source is usually natural protein from milk, eggs, or soy– Special high protein foods or diets– Commercial liquid meals such as Nutrament– Sports drinks and shakes; sports bars

• Whey and colostrum– Whey protein isolates from cheese-making process– Colostrum is first milk form cows (Theory: IGF-1)

• Other protein sources• Protein/carbohydrate solutions

Do high-protein diets or protein supplements increase muscle mass and strength in

resistance-trained individuals?

• High-protein diets– Research data are equivocal, but suggest additional

protein may increase lean body mass but has no effect on measures of strength

– Consuming protein after strenuous resistance exercise may enhance muscle repair

Do high-protein diets or protein supplements increase muscle mass and strength in

resistance-trained individuals?

• Whey – Research findings are mixed, but in general show positive

effects of whey protein supplementation, about 1.2-1.5 grams per kg body weight daily, on lean body mass and muscular strength. In one study, soy protein was also effective.

• Colostrum– Several studies suggest colostrum supplementation may

increase lean body mass, but effects on strength are mixed

• Additional research is recommended to evaluate the ergogenic potential of whey and colostrum

Do high-protein diets or protein supplements improve aerobic endurance performance in

endurance-trained individuals?

• High-protein diets or meals– The Zone Diet (40:30:30), a high-protein diet, has been

advocated for endurance athletes– Studies do not support an ergogenic effect of high-protein

diets on aerobic endurance– Several studies suggest that a Zone Diet eating plan over

the course of a week may actually impair aerobic endurance performance, particularly if protein replaces carbohydrate in the diet

High-protein diets and aerobic endurance:Protein/Carbohydrate Preparations

• Effects on aerobic endurance performance– Early studies have shown increased endurance with

protein/carbohydrate versus carbohydrate alone; however, the protein/carbohydrate solutions contained more energy

– More recent studies balanced the energy content of both solutions and report no difference between the two

High-protein diets and aerobic endurance:Protein/Carbohydrate Preparations

• Effects on recovery from exercise– Recent studies find that when energy content is balanced,

protein/carbohydrate solutions provide no advantage over carbohydrate alone on subsequent exercise performance

– Some data suggest protein/carbohydrate solutions may prevent muscle soreness, while other research does not

Arginine, Lysine, and Ornithine

• Theory– Infusion of these amino acids may increase human growth

hormone (HGH); may increase IGF-1

• Main research findings:– Arginine may decrease HGH response to exercise– Early, poorly controlled research found ergogenic effects– More recent well controlled studies report

• No significant increases in HGH• No favorable changes in body composition• No increases in strength

Tryptophan

• Theory– Needed to form serotonin, a neurotransmitter in the

brain, which has been theorized to decrease pain perception and delay fatigue during exercise

• Main research findings:– Findings from studies are somewhat equivocal, but in

general suggest that tryptophan supplementation is not an effective ergogenic aid for either strength or aerobic endurance exercise

Branched Chain Amino Acids (BCAA)

• Leucine, isoleucine, and valine are three major amino acids in muscle tissue

• Theoretical ergogenic mechanisms:– Use as a fuel during exercise and spare muscle glycogen– Decrease the rate of muscle tissue degradation – Prevent adverse changes in brain neurotransmitter

function

BCAA and the Central Fatigue Hypothesis

• Main research findings:– Some human research suggests increases in serotonin may

be associated with fatigue, but other neurotransmitters, like dopamine, are also involved

– BCAA supplementation may be used for energy and may help maintain serum BCAA levels


• Main research findings:– Mental performance: Results of field studies are equivocal,

but several have found enhanced mental alertness in prolonged sport events, such as tennis and soccer

– Perceived exertion: Results of laboratory studies involving intense endurance exercise are equivocal.


• Main research findings:– Physical performance with acute supplementation

• Study with 193 marathon runners suggested improved performance in slower runners (3:05-3:30) but not faster runners (<3:05) when consuming 7-12 grams during running

• Suggested slower runners may have depleted muscle glycogen earlier and thus benefited more from supplementation

• Criticism of the study– Unorthodox statistical procedure

BCAA supplementation

• Additional research findings:– BCAA supplementation not necessary if carbohydrate

is available• Carbohydrate is the best fuel for endurance athletes• Carbohydrate helps attenuate decreases in fTRP:BCAA

– BCAA supplementation may be an effective protocol for athletes in weight-control sports who are on a diet

– Research is needed to help clarify the role of BCAA supplements, or protein in general, on muscle tissue recovery following strenuous exercise

Glutamine Supplementation and Endurance Performance

• Theory– May promote muscle growth

• Stimulate HGH• Increase cell volume

– May stimulate glycogen synthesis• Glutamine is gluconeogenic

– Major fuel for key cells in the immune system• Prevent infections associated with overtraining

Glutamine Supplementation and Endurance Performance

• Main research findings– Recent studies and reviews indicate that

glutamine supplementation will increase plasma glutamine levels but will not

• Increase muscle mass or strength• Provide any advantage over adequate carbohydrate on

muscle glycogen levels• Prevent the effects of overtraining• Decrease the frequency of respiratory infections

Aspartates

• Theory– Potassium and magnesium aspartates hypothesized to

• Spare muscle glycogen• Reduce accumulation of ammonia• Improve psychological motivation

• Main research findings– Studies are equivocal, finding

• Either increased or decreased ammonia levels• Laboratory cycling tests to exhaustion

– Additional research recommended: Dosage may be a factor

Glycine

• Theory– Glycine is used in the formation of creatine

• Main research findings– Contemporary research reveals no ergogenic effect of

glycine supplementation– Glycine is part of a multicomponent supplement

containing arginine and alpha-ketoisocaproic acid that has been found to enhance sprint power in one study. Additional research is needed for confirmation.

Glucosamine and Chondroitin

• Dietary supplements– Glucosamine derived from shellfish; chondroitin from cattle cartilage

• Theory– Glucosamine helps form the structural basis of cartilage

(proteoglycans), and chondroitin helps provide resiliency– May help prevent joint pain associated with exercise training


• Research findings– Limited research with highly trained individuals; most are

with older, arthritic individuals – A substantial number of studies and reviews indicate

supplementation reduced joint pain and improved mobility

– Large NIH study (GAIT) found no overall reduction in knee pain in osteoarthritic individuals, but the supplement did provide relief to a subset of individuals with moderate to severe knee pain


• Research findings– Beneficial effects were minimal in two studies with

younger, physically active males– Glucosamine sulfate appears to be the most effective

form; chondroitin is not effective


• Precautions and recommendations for use– Considered safe, but may cause bloating and diarrhea– Consult with your physician as there may be

complications, such as with blood glucose control in diabetics

– Reasonable dose would be 1,500 mg of glucosamine and 1,200 mg of chondroitin for 2-4 months. If pain symptoms have not improved, they probably are not going to.

Creatine

• Creatine is found naturally in animal foods, especially meat

• Creatine may also be synthesized by the liver and kidney

Food g/KgMilk 0.1Tuna 4.0Salmon 4.5Beef 4.5Pork 5.0

Creatine

• Discovered 1927• Synthesized in 1990s as

a dietary supplement• Research as an

ergogenic aid progressed rapidly

Creatine Supplementation

• Theory– May increase muscle levels of PCr– May increase performance in very high intensity

exercise– May enhance performance in prolonged

endurance events which incorporate short sprints– May enhance interval training

Loading phaseFast protocol: 20-30 grams/day for 5-7 daysSlow protocol: 3 grams/day for 30 days

Maintenance phase2-5 grams/day

Recommended Protocol

Creatine Supplementation (20g/day for 5 days) with and without Carbohydrate (360g)

Adapted from Green, A., et al. ACTA Physiol Scand, 1996.

Creatine Supplementation

• In general, research findings also indicate that creatine supplementation may enhance performance in very high-intensity exercise tasks, such as the 100-meter sprint in track and sprint cycling

Creatine Supplementation• Of seven recent well-controlled studies using a standard

creatine-loading protocol and evaluating the effect on single or repetitive sprint-run or sprint-cycle performance ranging from 5 to 100 meters, creatine supplementation improved performance in five of the trials, but had no effect in the other two.

• For example, one study reported significant improvements in male sprinters in 100-meter sprint velocity and time to complete six intermittent 60-meter sprints.

• A meta-analysis of 57 studies revealed an effect size of 0.24 favoring creatine over the placebo treatment

Creatine Supplementation:Effect on body mass

• In general, research indicates increases in body mass, mainly as muscle tissue, in both males and females, including both trained and untrained

• Studies report increases in myosin and myonuclei concentration

Creatine supplementation: Safety

• Kidney and liver function– Consuming recommended dose does not appear to

increase health risks– Those with liver or kidney disease may be at risk

• Gastrointestinal distress– Large doses may cause nausea, vomiting and diarrhea

• Dehydration, muscle cramps and tears– Appears to cause few problems with exercise in the heat– Possibility of anterior compartment syndrome

• Overdoses and contaminants– Creatine appears to be safe at 5 grams per day– Some products may contain contaminants, like ephedrine

Creatine supplementation:Medical applications

• Increased strength in some conditions– Muscular dystrophy– Patients with heart disease– Injury to the spinal cord

• Facilitate rehabilitation from musculoskeletal injury• Reduce the loss of muscle mass (sarcopenia) with

aging

Beta-Hydroxy-Beta-Methylbutyrate(HMB)

• Theory– Beta-hydroxy-beta-methylbutyrate (HMB), a by-product of

leucine metabolism, is theorized to inhibit the breakdown of muscle tissue during strenuous exercise


• Main research findings with strength-trained athletes– Overall, research findings are equivocal regarding the

ergogenic effect of HMB supplementation on muscle mass and strength in untrained individual

– The available data indicate that HMB supplementation does not appear to affect muscle strength, body composition, or anaerobic exercise performance in resistance-trained individuals

– Research does not support any protective effects against muscle tissue damage during resistance training


• Main research findings with endurance athletes– One study with distance runners reported HMB

supplementation (3 g/day for 6 months) decreased markers of muscle damage following a 20K run

– One recent study found HMB could increase VO2max during 5 weeks of interval training in active college students

– No studies have shown improvement in endurance exercise performance following HMB supplementation

Beta-alanine and Carnosine

• Theory– Beta-alanine may increase intramuscular stores of

carnosine, which can serve as an antioxidant or as a buffer of hydrogen ions, reducing acidity, and increasing the lactate threshold

– Beta-alanine may also form another peptide, anserine, which may function as an antioxidant in muscles

Beta-alanine and Carnosine

• Main research findings– Anserine supplementation increases muscle

carnosine– Research findings are equivocal relative to

ergogenic effects on anaerobic-type exercise performance

• Improved performance cycling @ 110% VO2max• No effect on 400-meter run time

– No ergogenic effect on aerobic-endurance• No effect on maximal aerobic power

Tyrosine

• Theory– Tyrosine is a precursor for the catecholamine hormones

and neurotransmitters epinephrine, norepinephrine, and dopamine; augmentation may have an ergogenic effect

• Main research findings– Research is very limited– No effect on aerobic endurance, anaerobic power, or

muscular strength

Taurine

• Theory– Taurine is synthesized from amino acids, but is not

classified as an amino acid– Theorized to help prevent muscle tissue damage during

exercise; may function as an antioxidant

• Main research findings– One study has shown ↑ stroke volume during exercise– One study reported ↑ VO2max and exercise time to

exhaustion associated with antioxidant effects– These preliminary findings need further research

Inosine• Theory

– Inosine is a nucleoside, not an amino acid– Theorized to improve ATP production and also to improve

oxygen delivery to muscles during exercise

• Main research findings– Well-controlled studies indicate inosine supplementation

• Does not increase VO2max or related physiological variables

• Does not improve 3-mile treadmill run time• Has no effect on cycling tests of the three energy

systems• May impair anaerobic energy production

Does a deficiency of dietary proteinpose any health risks?

• Protein-Calorie malnutrition is a worldwide problem– Political and economic problems– Impaired immune functions

• The elderly may be prone to protein undernutrition– May impair immune functions; increase infections– May hamper optimal bone development

• Young athletes in weight-control sports– Loss of muscle mass and hemoglobin

Does excessive protein intake pose any health risks?

• Excess amounts of specific proteins may cause allergic reactions in some individuals

• AMDR range is 10-35% of energy intake• No UL has been established for protein intake

– High protein intake poses no health risks to most persons– NAS indicates the source of protein may be related to

various health risks

Excessive protein intake and health risks• Cardiovascular disease and cancer

– Dietary protein itself does not appear to cause CHD or cancer

• High meat diets may be rich in saturated fats• AICR indicates there is convincing evidence that red and processed

meats contribute to colorectal cancer

– High protein diets may actually help promote weight loss, a preventive measure against CHD

– Soy protein in natural, whole foods may have beneficial health effects

Excessive protein and health risks• Liver and kidney function

– The liver processes ammonia and the kidneys excrete urea and ketones, which are formed on high protein diets

– In general, high-protein diets do not have adverse effects on individuals with normal liver and kidney functions

– Individuals prone to liver or kidney disease should use caution with protein intake

• Chronic kidney or liver disease• Diabetics• Individuals prone to kidney stones

Excessive protein and health risks• Bone and joint health

– Excessive protein intake may increase urine acidity, which may increase calcium excretion

– Calcium loss is predicted to be 1 mg of calcium for an average increase of 1 gram of dietary protein

– A diet low in calcium and high in protein may promote bone loss

– The key is to obtain adequate calcium and protein because both are needed in adequate amounts for bone formation

Excessive protein and health risks• Heat illnesses

– The excretion of urea and ketone bodies in urine could lead to excessive fluid losses and dehydration

– A high-protein diet could increase resting energy expenditure

– Both of these effects could compromise temperature regulation during exercise in the heat, which will be discussed in chapter 9

Does the consumption of individual amino acids pose any health risks?

• No UL has been established for specific AA, but the NAS notes caution is warranted in using any single AA in amounts greater than normally found in food

• Free AA are manufactured to serve as drugs or dietary supplements

• Excessive amounts may cause health problems– Interfere with absorption of other AA– Cause gastrointestinal distress

• Sound advice is to obtain your AA through foods

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 6 Protein