Ch. 17

Nutrition Overview

  • Definition: Nutrition is the process of taking in food and utilizing it through digestion, absorption, transport, and metabolism.
  • Nutrients: Chemicals taken into the body that provide energy and serve as building blocks for new molecules.

MyPlate

  • Introduction: Developed by the USDA in June 2011 to guide Americans on healthy eating.
  • Visual Representation: Comprises a plate and a glass, showcasing the food groups:
    • Fruits
    • Vegetables
    • Grains
    • Proteins
    • Dairy
  • Strategy: Emphasizes half of the plate being fruits and vegetables.

Nutritional Classes

  • Major Classes: 6 classes of nutrients:
    1. Carbohydrates
    2. Lipids
    3. Proteins
    4. Vitamins
    5. Minerals
    6. Water
  • Balanced Diet: Contains adequate nutrients in correct proportions.
  • Essential Nutrients: Must be ingested as they cannot be synthesized by the body (e.g., certain amino acids, fatty acids, vitamins).

Energy Measurement

  • Caloric Units:
    • Calorie (cal): Energy to raise 1 gram of water by 1extoC1^{ ext{o}}C.
    • Kilocalorie (kcal): Equal to 1000 calories.

Carbohydrates

  • Composition: C, H, O with a 2:1 hydrogen to oxygen ratio.
  • Types:
    • Monosaccharides: Single sugar (e.g., glucose, fructose).
    • Disaccharides: Two sugars (e.g., sucrose, lactose).
    • Polysaccharides: Many sugars (e.g., starch, glycogen).
  • Dietary Function:
    • Provides short-term energy.
    • Excess glucose stored as glycogen or converted to lipids.
  • Diet Recommendation: Should consist of 45-65% complex carbohydrates of total kilocalories.

Lipids

  • Definition: Primarily insoluble in water, includes triglycerides, steroids, phospholipids, and fat-soluble vitamins.
  • Types:
    • Saturated Fats: Solid at room temperature, typically from animal sources.
    • Unsaturated Fats: Liquid at room temperature, considered healthier (e.g., oils).
  • Diet Impact: Excessive lipid intake linked to weight gain, heart disease, and increased cancer risk.

Cholesterol

  • Types:
    • LDL (Low-Density Lipoprotein): "Bad" cholesterol that deposits cholesterol into cells.
    • HDL (High-Density Lipoprotein): "Good" cholesterol that carries cholesterol back to the liver.

Proteins

  • Structure: Chains of amino acids, composed of 20 different amino acids (9 essential).
  • Complete vs. Incomplete: Complete proteins provide all essential amino acids (usually animal sources), while incomplete do not.
  • Daily Requirement: A daily supply is necessary as amino acids are not stored, recommended at 1-2 servings from dairy, nuts/beans, and sparingly from red meat.

Vitamins

  • Types:
    • Fat-Soluble: A, D, E, and K.
    • Water-Soluble: B-complex and C.
  • Functions: Essential for metabolism; act as coenzymes.
  • Deficiencies: Can lead to various health issues (e.g., Vitamin C deficiency leads to scurvy).

Minerals

  • Definition: Inorganic nutrients crucial for metabolic functions.
  • Examples: Calcium, iron, potassium, etc.

Metabolism

  • Definition: Totality of chemical reactions in the body, encompassing catabolism and anabolism.
    • Catabolism: Breaking down larger molecules for energy (e.g., ATPoADP+PATP o ADP + P).
    • Anabolism: Building larger molecules from smaller ones (e.g., ADP+PoATPADP + P o ATP).
  • ATP: Primary energy carrier produced mainly in mitochondria.

Metabolic States

  • Absorptive State: Period following food intake; nutrients are absorbed and utilized for energy storage.
  • Postabsorptive State: Period following nutrient absorption; focuses on using stored energy.

Body Temperature Regulation

  • Normal Range: Average is 98.6extoF98.6^{ ext{o}}F.
  • Mechanisms: Involves sweat glands, blood vessel dilation/constriction, and hypothalamus control centers.
  • Heat Loss Mechanisms:
    • Radiation: Transfer of heat without contact (e.g., from the sun).
    • Conduction: Transfer via direct contact.
    • Convection: Heat transfer via air or water.
    • Evaporation: Water converting from liquid to gas.