Principles of Nutrition Year 2 Unit I

Nutrition Overview

• Nutrients are essential food components needed for normal body functions.
• Two main categories of nutrients:
  • Macronutrients: Fats, proteins, carbohydrates
  • Micronutrients: Minerals and vitamins

Functions of Nutrients

• Provide energy for bodily functions.
• Supply essential molecules that:
  • Cannot be synthesized by the body or
  • Are insufficiently synthesized for growth and maintenance.

Essential Nutrients

• Proteins/Amino Acids
• Fatty Acids
• Carbohydrates
• Vitamins: Include both water-soluble and fat-soluble types.
• Minerals: Important minerals include calcium, phosphorus, sodium, potassium, and iron.

Dietary Reference Intakes (DRI)

• DRI serves as guidelines for nutrient intake to prevent deficiencies and ensure optimal health.
• DRI values vary by age and gender.
• Key components of DRI:
  • Estimated Average Requirement (EAR)
  • Recommended Dietary Allowance (RDA)
  • Adequate Intake (AI)
  • Tolerable Upper Intake Level (UL)

DRI Definitions

• EAR: Average daily intake level for 50% of healthy individuals within a specific stage and gender.
• RDA: Nutrient amount needed for 97-98% of individuals, calculated using EAR + 2 standard deviations (2SD).
• AI: Used as a guideline when RDA is not available, based on healthy individuals' nutrient intake.
• UL: Maximum daily intake unlikely to cause adverse health effects for most individuals.

Energy Requirements

• Estimated Energy Requirement (EER) is the average intake required for energy balance in healthy adults.
• Recommended energy intake varies by activity level:
  • Sedentary adults: 30 kcal/kg/day
  • Moderately active adults: 35 kcal/kg/day
  • Active adults: 40 kcal/kg/day

Energy Content of Foods

• Energy content measured by calories (kcal), reflecting the total combustion of food.
• Energy values:
  • Fats: >2x energy content of proteins or carbohydrates
  • Ethanol: Intermediate energy content between fat and carbohydrates.

Energy Use in the Body

• Energy from macronutrients supports three primary processes:
  • Basal Metabolic Rate (BMR): Energy for basic functions like respiration and circulation.
  • Physical Activity: Varies significantly based on exercise intensity and duration.
  • Thermic Effect of Food: Increased energy expenditure (up to 30%) during digestion and absorption.

Dietary Fats

• Triacylglycerols (TAG) make up about 90% of dietary lipids.
• Types of fats:
  • Saturated fats: No double bonds; raise LDL cholesterol and heart disease risk (found in meats and dairy).
  • Monounsaturated fats (MUFA): One double bond; lower total cholesterol and LDL cholesterol (found in fish and vegetable oils).
  • Polyunsaturated fats (PUFA): More than one double bond; effects vary based on fatty acid type (omega-3 and omega-6).
  • Trans fats: Behave like saturated fats, increase LDL cholesterol, raise cardiovascular disease risk.

Dietary Carbohydrates

• Types of carbohydrates:
  • Monosaccharides: Examples include glucose, fructose, and galactose.
  • Disaccharides: Common types include sucrose, lactose, and maltose.
  • Polysaccharides: Complex sugars such as starch from plants.
  • Dietary fiber: Non-digestible carbohydrates that enhance bowel health and reduce cancer risk.

Dietary Proteins

• Provide essential amino acids necessary for protein synthesis.
• Sources of proteins:
  • Animal proteins: Complete amino acid profiles.
  • Plant proteins: Generally lower biological value, may lack some essential amino acids.
• Nitrogen Balance: Reflects the balance between nitrogen consumed and excreted.
  • Positive nitrogen balance occurs when intake exceeds excretion, often seen in growth phases (children, pregnancy) and during recovery from illness.