Ecology pt 1

• Ecology


  The branch of biology concerned with the total complex of interrelationships among living organisms, encompassing the relations of organisms to each other, to the environment and to the entire energy balance within a given ecosystem
• Ecology


  The study of organisms and how they interact with the environment around them
• Term "Nutrition Ecology" coined by a group of nutritionists from the University of Giessen, in Germany


  1986
• Nutrition Ecology

  • Inter-disciplinary science, which examines all components of the food chain and evaluates their effects from four main points of view: human health, the environment, society and the economy
• Food chain


  1. Production

  2. Harvesting

  3. Conservation

  4. Storage

  5. Transport

  6. Processing

  7. Packaging

  8. Sales

  9. Distribution

  10. Preparation

  11. Consumption

  12. Disposal of waste
• Nutrition Ecology


  • Looks at food chain and external factors that affect what food is available, accessible, affordable to people
  • Also looks at internal/physiologic factors and social and behavioral factors that affect the food choices people make and that determine what foods are acceptable for their consumption
• Food


  Atoms & Molecules
• Body


  Structures & Processes
• Determinants of Food behaviour

  • Internal Environment
  • External Environment
• Nutrition


  Nutritional Health
• Nutrients


  Organic (carbohydrates, fat, protein, vitamins) and inorganic (water and minerals)
• Nutrition


  Transformation of atoms + molecules of food into the kinds of atoms and molecules that make up the body (cells)
• You are what you eat
• Nutrients from food


  • Supply energy for activity of the body
  • Provide structural materials of every cell
  • Provide regulatory substances essential for all body processes
• Energy is supplied by carbohydrates, proteins and fats
• Vitamins & minerals are not a source of energy, but required in many steps to release energy
• Amino acids and mineral elements are required for the growth and maintenance of body tissue
• Approximately 96% of body weight is protein, fat, water and small amount in the form of glycogen
• Remaining 4% of body weight is mineral elements (3/4 = calcium + phosphorous)
• Water accounts for 50-70% of body weight
• Normal body fat: Females 20-25%, Males 15-18%
• Nervous, chemical and physical factors

  • Control secretion of gastric juices
  • Control motor activity of the tract
  • Control speed and completeness of digestion
• The only activities under voluntary control are mastication and defecation
• Hormones


  • Secreted and released directly into circulation by glands
  • Stimulate organs to perform specific actions
  • Regulate many body processes
• Nutrition affects the hormonal system

  Fasting, feeding, exercise... - alter hormonal balance
• Hormones affect nutrition


  • Regulate hunger and appetite
  • Regulate digestion (e.g. secretion of digestive enzymes according to specific foods that have been eaten)
• Nervous system


  • Brain and spinal cord are the central controllers
  • Receives and integrates sensory information from all over body and tells systems and organs what to do
  • Role in hunger regulation
• Nutrients' components are only considered to be inside the body once they have been absorbed
• Some nutrients and non-nutrients are absorbed whereas others are undigestible and therefore unabsorbable; for example fiber
• Digestion process


  • Mechanical
  • Chemical
• Mechanical aspects of digestion

  1. Ingestion of food

  2. Mastication

  3. Saliva secretion

  4. Swallowing

  5. Peristalsis

  6. Stomach contractions

  7. Chyme formation
• Different nutrients move through the stomach at different rates: fluids fastest, then carbohydrates, then protein, then fat
• Mixtures of fat and protein leave the stomach even more slowly than when alone
• Proteins and fat stimulate secretion of hormones that inhibit gastric motility, slowing emptying of food into the intestine and therefore allowing more time for the digestion and absorption of these
• Fatty foods and protein tend to maintain satiety for a longer period of time
• Mechanical aspects of digestion

  1. Peristalsis moves chyme into the intestine

  2. Chyme slowly moves through the small intestine

  3. Digestion and absorption occur

  4. Chyme moves through the colon

  5. Water and some minerals are absorbed

  6. Undigested material is excreted as faeces
• Chemical aspects of digestion

  1. Salivary amylase digests starch in the mouth

  2. Protein digestion begins in the stomach

  3. Gastric juice secretion

  4. Enzymes in the small intestine digest protein and carbohydrates
• Absorption


  • Nutrients' components cross the intestinal border into the body
  • Cells are selective in what they absorb
  • The villi and microvilli in intestinal cells provide a large absorptive surface
  • Fat and fat-soluble vitamins are absorbed into the lymphatic system
  • Water soluble nutrients are absorbed directly into the bloodstream
• Undernutrition/starvation


  Gut atrophy occurs, preventing maximum absorption of nutrients
• Lack of fiber


  Colon muscles become weak due to lack of "exercise"