Digest and absorbtion

• Food


  Products derived from plants or animals that can be taken into the body to yield energy and nutrients for the maintenance of life and the growth and repair of tissues
• Diet


  The food and beverages a person eats and drinks
• Nutrients


  Chemical substances obtained from food and used in the body to provide energy, structural materials, and regulating agents to support growth, maintenance, and repair of the body tissues
• Nutrition


  The science of foods and the nutrients and other substances they contain, and of their actions within the body (including ingestion, digestion, absorption, transport, metabolism and excretion)
• Hunger & Appetite


  • Influences food choices
• Influences on Food Choices


  • Personal preferences of the sensory properties of food
  • Taste
  • Habits
  • Social interaction
  • Availability, convenience, economy
  • Positive and negative associations
  • Emotional comfort
  • Values
  • Body weight
• A person select foods for a variety of reasons. Whatever those reasons may be, food choices INFLUENCE health.
• Nutrients in Foods and in the Body

  • Composition of foods includes the six nutrient classes of water, carbohydrates, lipids, proteins, vitamins and minerals
  • Foods can also contain non-nutrients and other compounds, such as fibers, phytochemicals, pigments, additives, alcohols and others
  • Composition of the human body is made of chemicals similar to food
  • Essential nutrients are those the body cannot make or cannot make in sufficient quantities to meet needs. These are also called indispensable nutrients
• General functions of nutrients

  Source of energy
• Classification of Nutrients


  • Based on the yield of energy: energy-yielding nutrients (carbohydrate, fat, protein), non energy-yielding nutrients (vitamins, minerals, water)
  • Based on chemical composition: inorganic nutrients (minerals & water), organic nutrients (carbohydrate, fat, protein, vitamins)
• Carbohydrates


  • Sugars, starch & fibers
  • Function: source of energy
  • Food sources: cereal and grains, tubers, fruit, vegetables
• Fats


  • Triglycerides, phospholipids and sterols
  • Food sources: fats and oils, meat, eggs, dairy products
• Proteins


  • Made of amino acids
  • Food sources: meat & eggs, dairy products, legumes
• Vitamins


  • Fat-soluble: A, D, E, K

  Water-soluble: B vitamins, vitamin C

  Food sources: vegetables, fruit, dairy products
• Transport of Nutrients

  1. Circulation of nutrients

  2. Blood Vessels

  3. Lymphatic System
• Blood Vessels

  • Arteries and veins infiltrate villi
  • Arteries pick up nutrients
  • Veins take away wastes
• Lymphatic System

  • Vessels infiltrate villi
  • Lymphatic fluid has substances to bind fat and carry it to blood stream

  
• The circulatory system

  1. Nutrient molecules cross the villi in intestine

  2. Water-soluble nutrients and small fats are released into the bloodstream and routed to the liver before being transported to the cells

  3. Fat-soluble nutrients enter the lymphatic system, bypass the liver at first and eventually enter the vascular system near the heart

  
• Vascular system (blood circulatory)

  • Consists of arteries, capillaries & veins
  • Hepatic portal veins directs blood from the GI tract to the liver
  • Hepatic vein takes blood from the liver to the heart
  • The route: heart -> arteries -> capillaries (in intestine) -> hepatic portal vein -> capillaries (in liver) -> hepatic vein -> heart

  
• Lymphatic system

  1. Consists of one-way vessels to transport fluid

  2. Lymph: clear, yellowish fluid without red blood cells/platelets; moves through the body by muscle contractions

  3. Thoracic duct: the main lymphatic vessel that collects lymph and drains into the left subclavian vein

  4. Subclavian vein: the vein that provides a way from the lymphatic system to the vascular system

  5. Lacteals: lymphatic vessels of the intestine that absorb nutrients and pass them to the lymphatic system

  6. Lymph draining from GI tract is milky white (lacte = milk) because of fat digestion products - chyle ("juice")

  
• Beyond absorption

  1. Cells use nutrients directly for energy, body structures, or the regulation of body processes, or convert them into other usable substances

  2. Glucose delivered to cells can be used "as is" for energy formation or converted to glycogen and stored for later use

  3. Fatty acids, an end product of fat digestion, can be incorporated into cell membranes or used in the synthesis of certain hormones

  4. Vitamins and minerals freed from food by digestion can be used by cells to control enzyme activity or can be stored for later use

  5. The body has a limited storage capacity for some vitamins and minerals

  6. Excessive amounts of certain vitamins and minerals such as vitamin C, thiamin, and sodium are largely excreted in urine