Digestion Pdf


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Some information on the digestion system and how it works.

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Digestion Pdf

  2. 2. Digestive System  Digestion  Absorption  Digestive Organs  Enzymes & Hormones  Common Digestive Disorders
  3. 3. Digestive System  Digestion: breaking food into components small enough to be absorbed by the body.  Digestion occurs before entry of nutrients into circulation.  Absorption: movement of nutrients, including water and electrolytes across intestinal wall and into blood and lymph.  Digestive System: including the mouth, pharynx, esophagus, stomach, pancreas, gallbladder, liver, small/large intestines.
  4. 4. Whole Body System  Digestive system does not act alone.  Endocrine system: stimulates hormones.  Nervous system: send signals that control passage of food, control hunger, etc.  Cardiovascular system: transports nutrients to cells.  Urinary and Integumentary system: eliminate waste.
  5. 5. Gastrointestinal (GI) Tract  Long hollow tube about 30 feet in length that runs from the mouth to the anus.  Transit time = 24 to 72 Hours  Transit time affected by composition of diet, physical activity, emotions, medications and illnesses.
  6. 6. Secretions  Mucus – moistens, lubricates, protects  Enzymes - protein molecules secreted by the pancreas that aid in digestion.  Hormones – chemical messengers that are secreted into the blood by one organ to regulate bodily function elsewhere.
  7. 7. Immune System  70% of the immune system is located in or around the digestive tract  Underneath the mucosal lining of the stomach is lymphatic tissue  Constantly assessing good vs. bad  Secretory IgA antibodies are present in gut mucosa
  8. 8. Digestion Begins in the Mouth  Just the smell of food starts saliva flowing  Chewing increases the surface area of food and allows for the mixing of saliva.  Saliva: 99.5% water and amylase – Moistens food and carries dissolved food molecules to taste buds  Salivary amylase: breaks starches into sugars.
  9. 9. Pharynx  Shared by the digestive tract and the respiratory tract  Funnel shaped opening the connects the nasal passages and mouth to respiratory passages and esophagus  Common passageway for air and food and is responsible for swallowing.
  10. 10. Esophagus/Peristalsis  Tube extending from mouth to stomach  Peristalsis: wave like flow to move food toward stomach  Esophageal sphincter protects food once in the stomach from moving back to the esophagus  Reflux is caused by weakening of the sphincter
  11. 11. The Stomach  Temporary storage place for food  While in the stomach food mixes with HCL  Only some water, alcohol, and a few drugs like Tylenol are digested here  Food exits through P.S.
  12. 12. Gastric Juices  The stomach contains gastric glands  HCL kills most bacteria  HCL stops action of salivary amylase  HCL starts the digestion of protein by activation of the enzyme pepsin  HCL drops the pH of the stomach from 3.5 – 4 to 1- 2 (only acidic environment in the body)
  13. 13. Ulcers  Stomach lining protected by mucus  Ulcers form when acid/pepsin penetrate mucus  Typically caused by poor diet and bacterial infection (Heliobacter pylori or H Pylori)
  14. 14. Gastric Triggers  Churning and acid production is regulated by signals from hormones and nerves  These signals come from the brain, stomach and small intestine  The thought and sight of food causes the brain to tell the stomach to release gastric juices  Food local nerve signals brain to release gastin (hormone that triggers HCL release/stomach motility)
  15. 15. Gastric Triggers  Food small intestines hormonal and nervous signals decrease stomach motility/secretions  A hormone CCK signals the release of leptin – a hormone that tells the brain to signal fullness  Once empty another hormone – ghrelin is produced that tells the brain to send a signal of hunger
  16. 16. Stomach Emptying  Stomach empties in 2-6 hours  Determined by the size and composition of the meal  To move into the small intestines food passes through the pyloric sphincter  Food composition affects transit time  Emotions affect transit time
  17. 17. Transit Time  Large meal moves slower than small one  Solid meal moves slower than a liquid one  Mixed meal takes 4 hours  Higher fat slows transit  Protein alone moves faster than with fat  Carbohydrates move the quickest  Sadness/fear slow movement  Aggression/anger speed movement
  18. 18. Small Intestines  Narrow tube – 20 feet in length - Duodenum: 1st 12 inches - Jejunum: Next 8 feet - Illeum: Last 11 feet  The small intestine is the main site for digestion and absorption of water, vitamins, minerals, CHO, fat, and protein  Accessory organs (pancreas/gallbladder) aid in digestion
  19. 19. The Pancreas: Exocrine Tissue  Secretes pancreatic juices  Bicarbonate: brings pH up  Enzymes: Amylase, Trypsin/Chymotrypsin and Lipase
  20. 20. Digestive Enzymes  Protein molecules that aid in the breakdown of food for absorption  Food needs to be broken down into smallest molecules before they can be absorbed  Lipase breaks fats into fatty acids and glycerol  Amylase splits carbohydrates into simple sugars  Protease breaks proteins into single amino acids
  21. 21. The Pancreas: Endocrine Tissue  Produces 2 very important hormones: Insulin and Glucagon  Insulin: released when blood sugar rises allowing muscles and other tissues to take in glucose for fuel  Glucagon: released when blood sugar is low, causing liver to break down glycogen and release to the blood
  22. 22. The Gallbladder  Stores and secretes bile  Bile: produced by the liver, necessary for digestion and absorption  Secreted in the SI, mixes with fat, and breaks it into smaller globules, allowing lipases to access it
  23. 23. Diffusion  Movement of substances from one area of higher concentration to an area of lower concentration (Water)  Simple diffusion: no energy required  Facilitated diffusion: helped by carrier protein, no energy required  Active Transport: Needs both carrier protein and energy
  24. 24. Lining of the SI  Large surface area for absorption (the size of a tennis court)  Intestinal walls arranged in circular/spiral folds, Villi, Microvilli (brush border)  The villi contain one cell layer that needs to be crossed to reach the bloodstream / lymphatic system
  25. 25. Getting Nutrients to the Cells  Once absorbed nutrients have to be sent to the rest of the body  AA and sugars enter the bloodstream at the intestine and travel to the liver  Fat travels via the lymphatic system before entering the blood
  26. 26. Blood Flow  When at rest: ¼ blood goes to the GI, 1/5 to your skeletal muscles, and the rest goes to the heart, kidneys, brain, skin and other organs  Changes when you eat and exercise  When you are exercising – 85% goes to the skeletal muscles to deliver oxygen  When you eat a large meal more blood flows to help digest it
  27. 27. The Liver: Gatekeeper  Amino acids, sugars, water-soluble vitamins cross the mucosal cells and end up moving to the hepatic portal vein which goes to the liver  In the liver they are processed, some stored, or sent to general circulation  The liver modifies products of protein breakdown to make them safe to get to the kidneys
  28. 28. Lymphatic System  System of vessels, organs, and tissues that drains excess fluid from the spaces between cells, transports fat-soluble substances from the digestive tract, and contributes to immune function  Functions in the absorption and transport of fat- soluble substances (cholesterol, long chain fatty acids, fat-soluble vitamins)  These substances do not go to the liver first before the bloodstream
  29. 29. Large Intestines  Anything that has not been absorbed by the SI moves into the LI  LI is – 5 feet long and includes colon and rectum  Slow movement: fecal matter may stay in LI up to 24 hours which favors growth of bacteria
  30. 30. Intestinal Microflora  Permanent residents of the LI (300 – 500 different species)  Bacteria in gut – 10 x greater than cells in the body  Breakdown unabsorbed portion of food (fiber)  Producing nutrients for bacteria to flourish  These micronutrients synthesize some of the B vitamins and Vit K, which are absorbed  This breakdown produces flatulence
  31. 31. The Colon  Colon absorbs small amounts of water and electrolytes  Material not absorbed is excreted  Feces – undigested matter, dead cells, water, bacteria  Amount of water in feces depends on fiber and water
  32. 32. The Rectum  End of the colon  Feces stored prior to excretion  Connected to the anus  Defection regulated by a sphincter that is under voluntary control
  33. 33. Common Digestive Problems  Reflux  IBS  IBD ( Crohn’s or Ulcerative Colitis)  Lactose Intolerance  Constipation/Diarrhea  Celiac Sprue  Gallstones
  34. 34. Reflux (GERD)  Acid from stomach re-enters esophagus  Often related to obesity  Dietary components include: - Lowers LES:chocolate, caffeine, coffee, tea, peppermint, spearmint, alcohol -Increased HCL: large portions, fatty foods, spices, tomato products, citrus  Avoid eating close to bedtime  Eating too fast and high stress play a role  Some medications cause such as Fosamax
  35. 35. Constipation  Usually caused by lack of fiber and/or fluids  Lack of exercise plays a role  Can be caused by medications such as iron supplements, calcium supplements  Increase fiber in the diet with fruits, vegetables, whole grains, legumes, flaxseeds  Magnesium  Add exercise  Probiotics
  36. 36. IBS (Irritable Bowel Syndrome)  Can cause constipation or diarrhea, bloating, gas and abdominal pain  Can be triggered by stress, food intolerance, high far, lactose intolerance, hormone imbalances, or environmental sensitivities  Low fat, high fiber, dairy free diets work best  Exercise and stress reduction helps a great deal  Some people are sensitive to fructose or mannitol
  37. 37. IBD (Inflammatory Bowel Disease)  Crohn’s Disease/Ulcerative Colitis  Inflammation of digestive tract  Can cause pain, bloody diarrhea, cramping, fever, weight loss and FTT in children  Usually sensitive to dairy and grains  On low fiber diet when in active flare-up  Probiotics and digestive enzymes work well  Specific Carbohydrate Diet (Elaine Gotschall)
  38. 38. Diarrhea  Can be caused by bacteria, virus, food intolerances (lactose intolerance), medications  Avoid high fiber foods  Add banana and white rice  Remove intolerant food  Add probiotics  Fermented foods
  39. 39. Gallstones  Most common disorder of the gallbladder  Often related to diet  Low fat, low meat, high fiver diet recommended  Limit coffee, increase water (coffee triggers CCK which stimulates the gallbladder)  Maintain healthy weight  Exercise reduces the risk
  40. 40. Celiac Disease  Gluten Intolerance: genetic/inheritable disease  Gluten: protein found in wheat, barley, rye and ?Oats  Autoimmune response that damages SI decreasing the ability to absorp nutrients and can lead to many deficiencies if left untreated  Only treatment is to avoid gluten
  41. 41. Macronutrients  Carbohydrates  Fiber  Lactose Intolerance  Proteins  Vegan Dishes  Fats  Toxins
  42. 42. Carbohydrates  Makes up the largest group of food  Found only in plant foods with the exception of lactose  All fruits, vegetables, grains, legumes, nuts and seeds  Should make up 50-60% of daily calories  Provide 4 calories/gram
  43. 43. Whole vs. Refined  Whole Grain: foods that have not been significantly altered from how they occur in nature  Refined (processed): foods that have undergone processing to remove the coarse part of their original form
  44. 44. Refining  Milling process separates the layers  White flour – milling only the endosperm  White flour is enriched (thiamin, riboflavin, niacin, and iron)  Refined sugars are added to many foods  Once sugar is removed from its plant source it no long contains fiber, vitamins or minerals Empty Calories
  45. 45. What are carbs?  Chemically they all contain carbon, hydrogen, and oxygen molecules  Classifications include:  SimpleCarbohydrates  Complex carbohydrates: starches and fibers
  46. 46. Simple Carbohydrates  Monosaccharide (mono – one) simple sugar molecule  Disaccharide (Di – two) two sugar molecules linked together  Glucose, fructose, galactose  Each contain 6 contain, 12 hydrogen, and 6 oxygen but differ in arrangement
  47. 47. Simple Sugars  Glucose: most important fuel for the body – blood sugar - Rarely found alone in nature – usually found as part of a disaccharide  Fructose: found in fruit, vegetables, honey, tastes sweeter than glucose  Galactose: rarely found alone in nature, usually part of lactose
  48. 48. Disaccharides  Maltose (glucose and glucose) - Forms when starch is broken down, provides sweet taste when bread is chewed  Sucrose: table sugar (glucose and fructose) - Sugar cane, sugar beets, honey, maple syrup - Only sweetener that can be labeled as sugar  Lactose: milk sugar (glucose and galactose) - Only sugar found naturally in animal foods
  49. 49. Glycogen and Starch  Glycogen: storage form of glucose in animals  Starch: storage form of CHO in plant - When we eat starch we are eating stored energy - Potatoes – starchy root - Legumes/grain – starchy seed  Starches are thickeners when heated
  50. 50. Fiber  Cannot be digested by human enzymes  Soluble fiber: absorbs water and increases weight of feces - Can be absorbed by bacteria in LI and cause gas - Oats, fruit, beans, seaweed, pectin  Insoluble fiber: does not absorb water, increase bulk of stool and speeds transit time - Wheat, rye, vegetables
  51. 51. Benefits of Fiber  Promotes healthy gut function by stimulating peristalsis – muscles of the colon work harder and get stronger  High fiber diets increase transit time  High fiber can cause constipation without enough water  Soluble fibers and oligosaccharides promotes healthy gut flora  Reduces cholesterol
  52. 52. Low Fiber Diets  Constipation  Diverticulosis  Hemmorrhoids  Some evidence of increased colon cancer risk  Obesity  Diabetes
  53. 53. Carbohydrates = Energy  Glucose: main energy source for the body  In the body glucose is broken down into carbon dioxide, water and ATP  Glucose not needed is stored: glycogen  Glucose can be made from protein  Energy can be made from fat: ketone productions (low CHO diets)
  54. 54. Glycemic Response  How quickly blood sugar rises after food is consumed  Affected by the amounts and type of CHO, protein and far in the meal  Affected by how quickly food leaves the stomach  Refined CHO leaves the stomach quickly  Whole foods (fiber) leave slowly  Fat and protein leave the stomach slowly
  55. 55. Carbohydrate Digestion  Begins in mouth pancreatic enzymes absorbed by brush border  Sugars broken down in mono/disaccharides before absorption transported to the liver  Glucose stored in the liver and sent to the organs via blood  Substances not completed digested LI and are utilized by bacteria
  56. 56. Insulin’s Role  Allows cells to take in glucose  Promotes storage of glycogen by the liver  Leads to uptake of glucose for energy and synthesis of glycogen in muscle  Promotes protein synthesis in muscle  Promotes conversion of glucose to fat in fat cells
  57. 57. Lactose Intolerance  Newborns almost always produce lactase (enzyme to digest milk)  As we age lactase is produces less and less  Lactose not digested in the SI therefore moves to LI for bacteria to attack  The undigested lactose, acids and gas draws water to the LI causing diarrhea  -100% Asians/ African, - 30-50% other Americans
  58. 58. Lipids (Fats)  Group of molecules most of which do not dissolve in water  Fats give food texture, flavor, aroma and calories  Lowering the fat in the diet doesn’t necessarily make it healthier  Fat should make up -30% of daily calories  9 calories/gram
  59. 59. Fats in the Body  Provide structure, regulation and energy  Stored as adipose tissue under skin and around organ  Insulates the body and protects the body from shock  Important structural part of cells  Lubricates body surfaces  Used to make hormones
  60. 60. Triglycerides  Major form of lipid in food and the body - Contains 3 fatty acids and a glycerol backbone - Each fatty acid is a chain of carbon atoms with an acid group on the end  The fatty acids can be either saturated or unsaturated
  61. 61. Saturated Fatty Acids  All carbon atoms in the fatty chain are saturated with hydrogen (no double bonds)  Found mostly in animal foods (meat/dairy)  Solid at room temperature with the exception of tropical oils  High intakes leads to high cholesterol, heart disease, etc.
  62. 62. Unsaturated Fatty Acids  Contain some carbons that are not saturated with hydrogen  Tend to be liquid at room temperature  Monounaturated: olive, canola, peanut oil  Polyunsaturated: linoleic acid, corn, safflower, soybean oils
  63. 63. Omega Fatty Acids (Poly) Omega-3 fatty acids – (linolenic): flaxseed, walnuts, fatty fish - Anti-inflammatory fat - We need to increase our intake Omega-6 fatty acids )linoleic): nuts, corn, safflower, and sunflower oils - Pro-inflammatory far - We need to decrease our intake
  64. 64. Essential Fatty Acids  Omega-6: growth, skin integrity, fertility, maintaining RBC structure  Omega-3: structure and function of the cell membranes (retina, CNS)  EFA Deficiency: scaly, dry skin, liver abnormalities, poor wound healing, impaired vision & hearing, growth failure in infants
  65. 65. Cholesterol  Needed in the body but not essential: produced by the liver  Part of the cell membranes  Part of myelin (coating on nerve cells)  Needed to synthesize vitamin D in the skin  Part of bile acids and hormone  Found in animal food only
  66. 66. Lipid Digestion  Lipids need help moving through the body because they do not mix with water  Fat absorption occurs in the SI  Bile, secreted by the gallbladder, breaks down small fat droplets which can then be broken down further by enzymes
  67. 67. Lipid Absorption  Micelles: mixture of digested fatty acids, bile, and fat-soluble vitamins  Once absorbed enters the lymph and finally blood
  68. 68. Over-consumption of Fat  Obesity  Cardiovascular disease/Atherosclerosis  Elevated cholesterol/triglycerides  Cancer  Fatty liver  Diabetes  Gallbladder disease
  69. 69. Protein (Amino Acids)  Animal food, legumes, soy, nuts, bread, rice and pasta all have protein  Animal protein: provides B vitamins and minerals such as iron, zinc and calcium but has no fiber and is often high in fat and cholesterol  Plant protein: provides fiber, iron, zinc, calcium, phytochemicals, unsaturated fats, but does not provide certain B vitamins (B12)
  70. 70. Protein  Made up of amino acids:20 total in protein (9 essential)  Amino acids are strung together in chains  Needed for the building/repair of muscles, tissues, organs etc.  Should make up – 10-15% of daily calories  4 calories/gram
  71. 71. Amino Acids  Essential Nonessential Histidine - Alanine - Isoleucine - Arginine - Leucine - Asparagine - Lysine - Aspartic acid - Methionine - Cysteine - Phenylalanine - Glutamic acid - Threonine - Glutamine - Tryptophan - Glycine - Valine - Proline - Serine - Tyrosine
  72. 72. Protein Digestion  Proteins must be digested to be absorbed  Digestion begins within the acidic stomach  Broken into smaller chains before entering the SI  Amino Acids compete with each other for the transport system  Move to liver and finally blood stream once past the brush border
  73. 73. Functions of Protein  Collagen: most abundant protein in body - Holds cells together and forms framework of bones and teeth  Enzymes  Transport protein  Skin, hair, nails, muscles, organs, bones  Hormones  Regulate fluid balance  Regulates pH balance
  74. 74. Compounds Made From AA  Amino acid chains contain a nitrogen compound  Nitrogen: Non-protein compound needed to make neurotransmitters (tryptophan needed for serotonin)  DNA/RNA are also nitrogen-containing compounds  Skin pigment (melanin)  Niacin  Creatine (fuels muscle contraction)  Histamine (causes blood vessels to dilate)
  75. 75. Food Allergies  Triggered when a protein from the diet is absorbed without being completely digested  Milk, eggs, peanuts, tree nuts, wheat, soy, fish and shellfish  First time this happens, immune system is triggered  When it happens again immune system attacks causing allergic reaction
  76. 76. Excess of Protein in the Diet  Excess amino acids cannot be stored therefore they are… - Used for energy if your body does not provide enough carbohydrate and fat - Converted to fatty acids and contribute to weight gain
  77. 77. Dangers of High Protein Diets  Protein breakdown byproducts (urea) must be eliminated which increases water loss  Increases excretion of calcium in urine: kidney stones and bone loss  Long term excess of protein intake may lead to kidney and liver damage  Typical high protein diets are low in fruits, vegetables, fiber, and high in saturated fat
  78. 78. Protein Supplements  Often sold to promote immune function, healthier hair/nails, stimulate muscle growth  This will only happen if your diet is deficient in protein  Eating more protein does not build you more muscle (must lift weight)  Avoid taking separate amino acids
  79. 79. Micronutrients  Vitamins: A, C, D,E,K, thiamin (B1), riboflavin (B2), folic acid, niacin (B3), biotin, pantothenic acid, B6, B12  Minerals: Calcium, magnesium, Iron, Potassium, Sodium
  80. 80. Toxins  Air we breath, food we eat, and byproducts of metabolism  These can cause irritation and inflammation throughout our body  Liver is gatekeeper  We remove toxins in sweat, feces, urine etc.  Best way is to limit exposure (eat organic, avoid highly processed foods, alcohol, drugs, sugar substitutes)