DeBruyne_7e_PPT_ch05

Chapter 5: Protein

Overview

• Textbook: Nutrition for Health and Health Care, Seventh Edition by Linda Debruyne and Kathryn Pinna

• Focus: Understanding protein and its role in nutrition.

Learning Objectives

• Chemical Structure of Proteins:

  • Understand the distinctions between nonessential and essential amino acids.

• Protein Digestion and Absorption:

  • Summarize the process of how proteins are digested and absorbed in the body.

• Protein Turnover and Nitrogen Balance:

  • Explain the concept of protein turnover and describe various forms of nitrogen balance.

• Roles of Body Proteins:

  • Identify specific functions that different proteins carry out in the body.

Chemist’s View of Proteins

• Element Composition:

  • Proteins consist of carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) atoms.

• Amino Acid Structure:

  • Common backbone structure shared by all amino acids: amino group, acid group, and a distinctive side group (R) that varies.

  • Side groups influence amino acid properties, including size, shape, and charge.

Structure of Proteins

• Amino Acid Bonds:

  • Amino acids join to form chains through peptide bonds:

    • Dipeptides: 2 amino acids

    • Tripeptides: 3 amino acids

    • Polypeptides: longer chains

  • Complex shapes result from folding and twisting of polypeptide chains, tailored to specific functions.

Types of Amino Acids

• Nonessential Amino Acids:

  • Can be synthesized by the body.

• Essential Amino Acids:

  • Must be obtained through diet as they cannot be produced by the body, with certain amino acids being conditionally essential under specific circumstances.

Protein Turnover and Nitrogen Balance

• Protein Turnover:

  • Continuous process of synthesizing and degrading proteins.

  • Amino acids are circulated in the bloodstream for reconstructing proteins and energy production, with a significant portion (25%) utilized for energy.

• Nitrogen Balance:

  • Positive Nitrogen Balance: More nitrogen intake than excretion (common in growing individuals).

  • Negative Nitrogen Balance: More nitrogen is being lost (common in starvation or severe conditions).

Roles of Body Proteins

• Structural Components:

  • Provide the framework for muscles, bones, blood, and other tissues.

• Enzymatic Functions:

  • Facilitate chemical reactions without being consumed in the process.

• Transport Proteins:

  • Assist in moving substances such as hemoglobin (transports oxygen) and lipoproteins (transports lipids).

• Regulatory Functions:

  • Maintain fluid and electrolyte balance across membranes, regulating body pH and immune responses through antibodies.

• Hormonal Functions:

  • Certain hormones (like insulin) are proteins influencing body functions.

Functions Summary

• Structural support, catalyst for biochemical processes, transport functions, fluid balance, acid-base homeostasis, immune defense, hormonal regulations, and energy supply.

Protein and Health

• Protein Deficiency:

  • Results in symptoms like impaired brain function, weakened immunity, and stunted growth.

• Malnutrition Types:

  • Protein-energy malnutrition (PEM): Occurs due to inadequate dietary protein.

  • Acute vs. Chronic Malnutrition:

    • Severe Acute Malnutrition (SAM): Rapid weight loss and immediate health risks.

    • Chronic malnutrition can lead to long-term growth stunting.

• Health Risks of Excess Protein:

  • Potential for heart disease and kidney strain, especially with high consumption of red meat and dairy.

Supplement Considerations

• Protein Supplements: Generally unnecessary for healthy individuals; focus on whole food sources for nutrition.

• Amino Acid Supplements: Varying safety and efficacy; whole proteins are better absorbed by the body.

Protein Recommendations

• Daily Intake: Recommended 0.8 grams of protein per kilogram of body weight for adults.

• Emphasize consumption of high-quality proteins for optimal health benefits.

Protein Quality in Foods

• High-Quality Proteins:

  • Animal-derived proteins generally contain all essential amino acids.

  • Combinations of plant proteins can provide complete amino acid profiles through complementary sources.

• Vegetarian Diet Considerations:

  • Should focus on a variety of plant-based foods to ensure adequate nutrient intake.

  • Whole grains, legumes, seeds, nuts, and vegetables are vital components.

Conclusion

• Proteins are crucial macronutrients with diverse roles in maintaining health, supporting bodily functions, and preventing malnutrition.