Understanding Protein and Amino Acids

Oct 8, 2024

Protein and Amino Acids: Essential Dietary Components

Overview of Protein

  • Protein is a crucial part of the human diet.
  • Found in foods like eggs, dairy, seafood, legumes, meats, nuts, and seeds.
  • Proteins are broken down into amino acids and reformed into new proteins in the body.
  • Functions include fighting infections and assisting in cell division.

Structure of Proteins

  • Proteins are chains of amino acids bound by peptide bonds.
  • Chains are twisted and folded into a final protein shape.

Amino Acids

  • Amino acids have a central carbon atom bonded to:
    • An amino or nitrogen-containing group
    • A carboxylic acid group
    • A hydrogen atom
    • A unique side chain (except proline, which has a ring structure)
  • 20 Amino Acids Used by Humans:
    • Alanine, Arginine, Asparagine, Aspartic acid, Cysteine, Glutamic acid, Glutamine, Glycine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Proline, Serine, Threonine, Tryptophan, Tyrosine, Valine.

Classification of Amino Acids

  • Non-essential Amino Acids: Can be made by the body
    • Alanine, Asparagine, Aspartic acid, Glutamic acid, Serine.
  • Conditionally Essential Amino Acids: Can be made by the body under normal conditions
    • Arginine, Cysteine, Glutamine, Glycine, Proline, Tyrosine.
  • Essential Amino Acids: Must be obtained from food
    • Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine.

Digestion and Absorption

  • Dietary protein needs to be broken down via proteolysis.
  • Begins in the stomach with hydrochloric acid and pepsin.
  • Proteins are cleaved into smaller peptides and amino acids in the duodenum.
  • Amino acids are absorbed into intestinal cells and then into the bloodstream.

Dietary Sources of Protein

  • Animal-based Proteins: Eggs, dairy, seafood, meats - provide all nine essential amino acids.
  • Plant-based Proteins: Soy provides all essential amino acids; other plant foods need combination for complete amino acid profile.
    • Examples: Rice and beans, hummus and pita, oatmeal with almond butter.

Daily Protein Requirements

  • General Guidelines:
    • WHO and US recommend 0.8g per kg of body weight per day.
  • Age-specific Recommendations:
    • Children 1-3 years: 13g
    • Ages 4-8: 19g
    • Ages 9-13: 34g
  • Gender-specific Recommendations:
    • Females 14+: 46g
    • Males 14-18: 52g
    • Males 19+: 56g
  • Special Needs:
    • Pregnant/breastfeeding women, athletes, older adults may need more.

Protein Deficiency and Risks

  • Certain conditions (malnutrition, trauma, burn injuries, etc.) may increase protein needs.
  • Usually, high protein intake is not risky except in cases like kidney disease.

Recap

  • Protein is essential to diet and bodily functions.
  • Five non-essential, six conditionally essential, and nine essential amino acids.
  • Protein requirements vary by life stage, activity level, and health.
  • A variety of foods can meet protein needs for all diets.