Role and importance of proteins, fats and carbohydrates in human nutrition. Dietary fibers.
1. Proteins
Functions:
- Structural: Build and repair tissues (muscles, skin, hair, nails, organs)
- Enzymatic: Act as enzymes for biochemical reactions
- Hormonal: Some proteins function as hormones (insulin, glucagon)
- Transport: Hemoglobin transports oxygen; other proteins transport nutrients
- Immune: Antibodies fight infections
- Energy: 4 kcal/g if carbs and fats are insufficient
Essential Amino Acids:
- Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine
Sources:
- Animal: Meat, fish, eggs, milk, dairy
- Plant: Legumes, nuts, seeds, soy products
Recommended Intake:
- Adults: 0.8–1.0 g/kg body weight/day (higher in athletes, pregnancy, or illness)
Health Significance:
- Adequate intake: Supports growth, tissue repair, immune function
- Deficiency: Muscle wasting, edema, growth retardation, immune dysfunction
- Excess: Kidney strain, potential calcium loss
Protein Quality: How well a protein provides all essential amino acids (EAAs) and is digestible.
High-Quality (Complete):
- All EAAs present, well absorbed
- Examples: Eggs, milk, meat, fish, soy, quinoa
Low-Quality (Incomplete):
- Lacking one or more EAAs
- Examples: Wheat, rice, corn, most legumes
BV (Biological Value) and PDCAAS are tools used to measure protein quality:
- BV measures how efficiently the body retains absorbed protein for growth and maintenance.
- PDCAAS evaluates protein quality by combining amino acid composition and digestibility.