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 $1^{ ext{o}}C$.
  • 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., $ATP o ADP + P$).
  • Anabolism: Building larger molecules from smaller ones (e.g., $ADP + P o ATP$).
• 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 $98.6^{ ext{o}}F$.
• 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.