Protein and Exercise

Protein and Exercise

Introduction

  • Protein serves an essential role in the body:

    • Forms the structural basis of muscle tissue.

    • Acts as a major component of most enzymes present in the muscle.

    • Can be utilized as a source of energy during exercise.

Review of Chemical Structure

  • Composition of proteins:

    • Contains Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N).

    • Combines into 20 different amino acids.

  • Structural components of amino acids:

    • 3 parts:

    • Amino group (NH₂)

    • Acid group (COOH)

    • Different combinations of Carbon, Hydrogen, Oxygen, and sometimes, Sulfur.

  • Formation of peptide bonds:

    • When two amino acids link, they form a peptide bond.

Amino Acids

  • Total of 20 amino acids necessary for protein synthesis:

    • Essential Amino Acids (EAAs): 9 (must be obtained through diet).

    • Nonessential Amino Acids: 11 (can be synthesized by the body).

  • Food sources:

    • Most animal and plant foods contain amino acids.

    • The specific amounts of each amino acid vary by food source.

Types of Protein

  • Complete Proteins:

    • Contain all essential amino acids; primarily from animal products.

  • Incomplete Proteins:

    • Contain some but not all essential amino acids; primarily from plant sources.

  • Complementary Proteins:

    • Combination of plant foods that create a complete protein when consumed together (e.g., grains with legumes).

Protein Metabolism in the Human Body

  • Breakdown of proteins:

    • Proteins are broken down into polypeptides and then into individual amino acids in the stomach and small intestine.

  • Absorption of amino acids:

    • Amino acids are absorbed through the small intestine wall, entering the bloodstream, and transported to the liver via the portal vein.

  • Role of the liver:

    • Acts as a critical center for amino acid metabolism; continually synthesizes a balanced amino acid mixture to meet the body’s protein requirements.

Metabolic Fate of Proteins

  • Usage of amino acids by body cells:

    • Body cells obtain amino acids from the bloodstream to synthesize proteins specific to their needs (e.g., tissues, enzymes, hormones).

    • Storage limitation: Body cells cannot store excess amino acids.

Functions of Protein

  • Vital roles in regulating human metabolism:

    • Enzymes as catalysts in biochemical reactions.

    • Hormones regulating physiological processes.

    • Fluid balance and acid-base balance maintenance.

    • Blood clotting process regulation.

    • Immunity through the production of antibodies.

    • Serves as a carrier for nutrients in the bloodstream.

Forms of Protein in the Body

  • Notable forms of proteins include:

    • Insulin: A hormone regulating glucose levels.

    • Neurotransmitters (e.g., serotonin): Chemical messengers in the nervous system.

    • Hemoglobin: The oxygen-carrying protein in blood.

    • Oxidative enzymes in mitochondria: Involved in energy production.

Recommended Dietary Allowance (RDA) for Protein

  • Protein requirements vary throughout the life cycle:

    • Average Adult: 0.8 g/kg, updated to 1.2-1.6 g/kg according to new Dietary Guidelines for Americans (DGA).

    • Infants (0-0.5 years): 1.5 g/kg

    • Children (0.5-1 years): 1.1 g/kg

    • Children (1-3 years): 1.1 g/kg

    • Children (4-13 years): 0.95 g/kg

    • Adolescents (14-18 years): 0.85 g/kg

    • Adults (19+ years): 0.8 g/kg

Calculation of Protein Needs

  • Example calculation for protein intake based on body weight (70 kg):

    • One gram of protein = 4 calories.

  • Daily caloric intake can range from 3,500 to 4,000 calories.

  • Percent protein intake can be around 12% to 15%.

  • Calculation of grams of protein needed:

    • Grams of protein: 131-150 g or 105-120 g, depending on caloric intake.

    • Grams of protein per kg: 1.9-2.1 or 1.5-1.7 g.

Protein Restricted Diets

  • Types of vegetarian diets:

    • Vegetarian: Excludes meat, but includes other animal products.

    • Ovo-vegetarians: Includes eggs.

    • Lacto-vegetarians: Includes dairy.

    • Ovolacto-vegetarians: Includes both eggs and dairy products.

    • Semi-vegetarians: Excludes red meat but consumes fish and poultry.

    • Vegan: Excludes all animal products, deriving nutrients from plant-based foods.

  • Nutritional concerns:

    • Ensuring sufficient calories is crucial.

    • Major focus is on obtaining adequate types of protein.

    • Potential mineral deficiencies (iron, calcium, zinc) may occur, particularly in vegans.

    • Vegans may require supplementation for vitamin D if not adequately exposed to sunlight and may risk vitamin B12 deficiency.

Effects of a Vegetarian Diet on Physical Performance

  • Research findings:

    • No significant differences found in aerobic or anaerobic capacities of vegetarian and non-vegetarian individuals.

    • Important for vegetarian athletes (especially females) to ensure adequate intake of iron and calcium.

Role of Protein in Exercise

  • Contribution of protein to energy cost:

    • Accounts for less than 5% of total energy cost during activity.

    • In prolonged endurance exercise, may contribute up to 15% of the total energy cost.

    • Adequate carbohydrate (CHO) intake before and during exercise helps minimize protein utilization.

Protein Metabolism During and After Exercise

  • Protein breakdown: occurs during exercise.

  • Protein synthesis: post-exercise phase critical for recovery.

  • Recovery period:

    • Muscle protein synthesis (MPS) is elevated for up to 24 hours following exercise.

Factors Influencing Muscle Protein Synthesis (MPS)

  • Friends (positive factors):

    • Frequent consumption of amino acids.

    • Adequate caloric intake.

    • Post-workout fueling strategies.

    • Proper carbohydrate intake.

  • Enemies (negative factors):

    • Low-calorie diets.

    • Frequent alcohol consumption.

    • Infrequent doses of protein.

    • Improper training techniques.

    • Lack of adequate sleep.

Training Effects on Protein Needs

  • Different types of training stimulate protein metabolism:

    • Aerobic exercise promotes the synthesis of metabolic enzymes.

    • Resistance training enhances muscle protein synthesis.

  • Recovery nutrition: ensures proper recovery post-exercise; sleep is essential.

  • Endurance training: enhances the potential for increased branched-chain amino acids (BCAA) capacity, thereby allowing muscles to derive energy from protein more effectively.

  • Training can reduce the production or accumulation of ammonia, leading to decreased fatigue.

Protein Needs for Athletes

  • Recommended dietary allowance for athletes:

    • General RDA: 0.8 g/kg/day

    • For a 175 lbs athlete, approximately 64 grams/day.

    • Athletic requirement: 1.2-2.2 g/kg/day, generally aiming for 1.6-2.2 g/kg to maximize anabolism.

    • Translation for a 175 lbs athlete: 95-175 grams/day.

    • Important to consider meal frequency: aim for 0.4 g/kg/meal for a minimum of 4 meals per day.

  • Special conditions:

    • Injury may increase the need to nearly 2.5 g/kg.

    • Aging can heighten protein requirements to preserve lean body mass.

    • Timing: of protein intake is crucial for maximizing benefits.

Worksheet: Calculate Your Athlete's Needs

  • Protein Intake Goal: 1.2 – 2.2 grams per kg of body weight per day.

  • Example calculation:

    • Weight in lbs: # / 2.2 = kg

    • kg x 1.2 – 2.2 g/kg = grams protein per day

  • Guidelines for post-workout: Aim for around 30 grams of protein.

  • Portion sizes include:

    • 4 ounces of protein resembles the size of a smartphone.

    • 1 ounce of animal-based protein contains approximately 7 grams of protein.

    • 3 ounces of grilled chicken breast = 21 grams.

    • 1 cup of milk = 8 grams.

    • 2 tablespoons of peanut butter = 7 grams.

    • ½ cup cooked beans = 7 grams.

    • ¼ cup almonds = 7 grams.

    • ¼ cup cottage cheese = 7 grams.

    • 1 ounce of hard cheese = 7 grams.

    • 1 cup of plain Greek yogurt = 15 grams.

    • 1 large egg = 7 grams.

    • 1 cup of chocolate milk = 8 grams.

Timing of Protein Intake

  • Pre-Workout:

    • Provide amino acids for upcoming activity; adjust intake as activity approaches and consider digestion times.

  • Post-Workout:

    • Focus on recovery; optimal intake includes protein, carbs, fluids, electrolytes, and antioxidants.

    • Aim for 20-30 grams (may exceed in larger meals), with excess not significantly enhancing muscle protein synthesis (MPS) but may increase amino acid oxidation.

    • Timing guidelines: consume within 2 hours post-exercise for optimal absorption.

    • Consider the quality of protein source, as plant-based sources might need larger quantities to meet EAA requirements.

Timing of All Meals

  • Every meal contributes to overall intake.

  • Bedtime Protein:

    • Potential benefits of pre-sleep protein intake include increased strength, lean muscle gain, decreased muscle soreness, and improved recovery.

    • Recommended intake: 30-40 g of high-quality protein before bed; products may vary in effectiveness based on type (casein or whey + casein combo is common).

    • More studies needed for comparisons of dairy vs. plant-based protein options.

References

  • Trommelen, Jorn et al. (2018). Presleep dietary protein-derived amino acids are incorporated into myofibrillar protein during postexercise overnight recovery. Am J Physiol Endocrinol Metab. 314(5):E457-E467.

Protein Sources and Quality

  • Protein Quality: Must contain essential amino acids.

  • Complete vs. Incomplete Proteins:

    • Complete proteins include all essential amino acids; incomplete proteins do not.

  • Protein Rich Foods: Primary sources include meats, eggs, fish, legumes, dairy, and nuts.

  • Additional nutritional benefits from protein-rich foods:

    • Yogurt provides probiotics and calcium.

    • Eggs are rich in vitamins A/D, lipids, and minerals.

    • Specific amounts of leucine in protein sources:

    • 3 oz cooked salmon/tuna/chicken breast = 2-2.5 g of leucine.

    • 1 egg = 1.2 g of leucine.

Protein Supplements

  • Types of Supplementation:

    • Isolated sources that may enter the bloodstream faster.

    • The role of carbohydrates in recovery (important for glycogen synthesis).

    • Awareness of additives such as artificial sweeteners and sugar alcohols; always read labels.

    • Common types of protein supplements: dairy-based (whey + casein) and plant-based (options include pumpkin seed, pea, soy, and blends like rice + pea).

  • Cited research:

    • Burd, Nicholas et al. (2019). Protein-containing food is more than the sum of its constituent amino acids for post-exercise muscle anabolic potential. Sports Science Exchange. Vol. 29, No. 194, 1-5.