LECTURE 3-4 - PROT-LIPDS

Proteins

Types of Proteins

  • Definition: Proteins are essential macromolecules made of amino acids that perform a variety of functions in the body.

  • Types of Proteins:

    • Animal Sources: Meat, Fish, Eggs, Milk, Cheese

    • Plant Sources: Legumes, Nuts, Seeds

Functions and Roles in Nutrition

  • Chemical Reactions: Proteins act as enzymes, facilitating biochemical reactions.

  • Transport: Proteins assist in moving substances across cell membranes.

  • Structural: Proteins provide structural support in cells and tissues (e.g., muscle fibers).

  • Hormonal Functions: Hormones such as insulin and glucagon are types of proteins.

  • Immune Response: Proteins function as antibodies that help defend the body from pathogens.

  • Fluid Balance: Proteins maintain osmotic balance in fluids (e.g., albumin).

  • Acid-Base Balance: Proteins can buffer pH changes in blood.

  • Energy Source: Proteins can serve as an energy source when carbohydrates are low.

Health Implications of Protein Intake

  • Excess Protein: Overeating protein may have limited negative health impacts but is generally a lesser issue than underconsumption in some populations.

  • Insufficient Protein: Insufficient intake can lead to negative health conditions:

    • Kwashiorkor: Caused by low protein intake, characterized by edema, enlarged fatty liver, and skin conditions.

    • Marasmus: Result of severe energy and protein deficiency, leading to wasting.

    • Marasmic Kwashiorkor: Combination of both conditions, presenting symptoms from each.

Recommended Protein Intake

  • Guidelines: 10-35% of total energy intake should come from proteins.

  • Protein Quality: High-quality proteins contain all essential amino acids; examples include meat and dairy.

Amino Acids

Classification

  • Essential Amino Acids: 9 amino acids that must be obtained through diet.

  • Nonessential Amino Acids: 11 amino acids that the body can synthesize.

  • Conditionally Essential Amino Acids: Nonessential amino acids that can become essential under specific physiological conditions.

List of Amino Acids

  • Essential Amino Acids: Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine

  • Nonessential Amino Acids: Arginine, Histidine, Alanine, Asparagine, Aspartate, Cysteine, Glutamate, Glutamine, Glycine, Proline, Serine, Tyrosine

Complementary Proteins

  • Definition: Combinations of two or more incomplete protein sources that together provide all essential amino acids.

  • Examples:

    • Legumes: Low in methionine but high in lysine

    • Grains: High in methionine but low in lysine

    • Common Combinations: Rice and beans

Protein Deficiency Symptoms

  • Symptoms associated with protein deficiency include:

    • Growth failure

    • Loss of muscle mass

    • Decreased immunity

    • Weak heart and respiratory systems

    • Severe cases can lead to death

Kwashiorkor and Marasmus

  • Kwashiorkor:

    • Symptoms include edema, enlarged liver, light-colored hair, and skin lesions.

    • Often noted in children after maternal breastfeeding ends.

  • Marasmus:

    • Symptoms include extreme thinness, weakness, and low metabolism due to inadequate intake of both protein and calories.

Summary of Features of Kwashiorkor and Marasmus

Kwashiorkor

  • Growth Failure: Present

  • Wasting: Present

  • Edema: Present

  • Hair Changes: Common

  • Mental Changes: Very common

Marasmus

  • Growth Failure: Present

  • Wasting: Marked

  • Edema: Absent

  • Hair Changes: Less common

  • Mental Changes: Uncommon