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Chapter 6 Digestion and Absorption; Alcohol What Happens to the Food We Eat? The food we eat undergoes three processes: 1) Digestion 2) Absorption 3) Elimination These processes occur primarily in the gastrointestinal tract. What Happens to the Food We Eat? Gastrointestinal (GI) tract: series of organs arranged as a long tube The GI tract includes: organs such as the stomach, liver, and intestines Table 6.1 sphincters muscles that control the passage of material from one organ to the next Gastrointestinal Tract Digestion Digestion the process of breaking large food molecules down into smaller molecules Digestion includes breaking food down: Mechanically Includes peristalsis chemically Digestion Overview – Smell/Taste Digestion Overview - Mouth Digestion begins in the mouth Mechanical Chewing Chemical Saliva: lubricates and contains enzymes Start to digest CHOs Food becomes a bolus Bolus enters esophagus Peristalsis No digestion Enzymes Enzyme A protein that induces a chemical change in another substance Enzymes speed up the rate of chemical reactions. Typically end in “ase” (amylase) Digestion is dependent on many different enzymes. Digestion Overview - Stomach The lower esophageal sphincter separates the esophagus from the stomach. Digestion in the stomach includes: extensive mechanical digestion, mixing food with gastric juice to produce chyme chemical digestion of proteins and fats Holds food for 2 to 6 hours Gastric Juice What It Is What It Does Mucus Keeps stomach from digesting itself HCl Denatures PRO; activates pepsin Intrinsic Factor Protects vitamin B12 until it can be absorbed Proenzyme converted to pepsin (an Pepsinogen Hormones enzyme) for PRO digestion Regulate digestive process and enzyme release Gastric lipase Enzyme that begins digestion of fat Anatomy of Stomach Digestion Overview - Small Intestine Duodenum Neutralizes stomach acid (bicarb) Pancreatic enzymes take over Gallbladder releases bile Jejunum Majority of digestion and absorption Ileum Vitamin B12 absorption and immune functions Small Intestine Anatomy Folds Villi & Microvilli Secrete digestive enzymes and absorb nutrients Small Intestine Anatomy Small Intestine Summary Accessory Organs Liver: largest digestive organ produces bile emulsifies fats Receives products of digestion Gallbladder Stores and releases bile Pancreas produces many hormones and digestive enzymes produces bicarbonate Digestion Overview – Large Intestine Very little digestion* Absorption of water and sodium Formation of waste for elimination Remains 12-24 hours *Filled with bacteria! Bacterial Flora About 100 trillion bacteria in large intestines They help metabolize remaining nutrients Break down some fibers to create short-chain fatty acids Fuel supply for colonic cells They produce vitamin K and B vitamins Why newborns get a vitamin K shot Is this why pre/probiotics are important? Pre/Probiotics Probiotics: Live microbial products (lactobacillus and Bifidobacterium) that health of the gut Restore microbial balance Prebiotics: Food for the probiotics and good gut bacteria Indigestible CHO sources (inulin) Synbiotics Combo of pre and probiotics (supplements) Pre/Probiotics Possible health benefits include: Decreased diarrhea and constipation Decreased growth of H. Pylori Enhanced immunity Increased nutrient absorption Reduced risk of colon cancer Fewer allergies in kids Improved blood lipids Lower blood pressure © 2013 Pearson Education, Inc. Pre/Probiotics Where To Find Prebiotics: Where To Find Probiotics: Asparagus Fermented Foods: Bananas Yogurt Oatmeal Kefir Jerusalem artichokes Buttermilk Legumes Tempeh Onions Miso Leeks Sauerkraut Cabbage Some pickles Follow The Path Now that we have learned the basics, let’s look at what happens when we eat a turkey sandwich on whole wheat bread with lettuce, tomato, cheese, and avocado Digestion - Mouth Digestion begins in the mouth. Chewing is the mechanical digestion that breaks all food into smaller pieces. Some chemical digestion takes place. Saliva lubricates and contains amylase – an enzyme produced by the salivary glands. Salivary amylase begins the chemical digestion of carbohydrates. Maltose & dextrins Salivary amylase Mouth Summary Digestion – Through Esophagus Digestion - Stomach Acidic HCl (from gastric juice) stops salivary amylase activity No CHO digestion HCl activates enzymes that start PRO and fat digestion Pepsinogen Pepsin Lingual and gastric lipases (fats) HCl denatures PROs Mechanical digestion through churning Still, minimal digestion takes place Absorption of alcohol Digestion - Stomach Lingual/Gastric lipase Pepsin Minimal digestion Smaller PRO units Stomach Summary Digestion – Small Intestine From the stomach, chyme is slowly released through the pyloric sphincter to the small intestine. **Most digestion and absorption occur in the small intestine. Absorption: the process by which molecules of food are taken from the GI tract into the body. Small Intestine - CHOs Pancreatic amylase dextrins maltose Intestinal cells release disaccharide-specific enzymes Enzyme Digests Into Maltase Maltose Glucose + glucose Sucrase Sucrose Glucose + fructose Lactase Lactose Glucose + galactose Monosaccharides are absorbed into capillaries Go to liver All become glucose Small Intestine - Fat Problem: Fats and watery digestive juices do not mix well Bile gallbladder _______ is released from the _______________ to help Process is called: Emulsification Bile Very important in lipid digestion Sometimes called bile salts Acts as an emulsifier What is an emulsifier? A substance that suspends lipid/fat in a watery solution Water Lipid Emulsification Lipid does not like water and sits on top Fat is emulsified in watery fluid E M U L S I F I E R Small Intestine - Fat Now that fats are emulsified Pancreatic lipase can digest triglycerides Fatty acids and glycerol Pancreatic lipase Small Intestine - Fat Now that triglycerides broken down Absorbed and reformed in chylomicrons With fat-soluble vitamins and cholesterol Get transported from lacteal to lymph Empty into blood through left subclavian vein Go to liver and cells Small Intestine - Protein Pancreas releases peptidases Proteins into peptides Small intestine releases other enzymes Peptides into amino acids Protein Peptides Amino Acids Amino acids absorbed into capillaries and go to the liver Small Intestine Summary Large Intestine Fiber and other undigested particles Colonic bacteria digest some fibers Short-chain fatty acids Make some vitamins (K & B) Absorb water and sodium Prepare waste for elimination After 12-24 hours Large Intestine Summary Vitamins & Minerals & Water Vits/Mins: Already in the smallest form Fat-soluble vitamins need to be transported in chylomicrons A, D, E, K Water-soluble nutrients go through blood B12 needs intrinsic factor Water absorbed in small and large intestines Follows sodium, glucose across intestinal wall Digestion Review Digestive System Video Disorders Related to Digestion The lining of the stomach is designed to cope with hydrochloric acid (HCl), but other regions of the GI tract are not. Heartburn is caused by HCl in the esophagus. GERD, or gastroesophageal reflux disease, is painful, persistent heartburn. GER or GERD Disorders Related to Digestion Peptic ulcers are regions of the GI tract that have been eroded by HCl and pepsin. The bacterium Helicobacter pylori contributes to the production of both gastric and duodenal ulcers. Disorders Related to Digestion Food intolerance is a group of GI symptoms associated with eating a particular food. No immune system involvement Symptoms may include gas, pain, and diarrhea. Lactose intolerance is an example. Disorders Related to Digestion Food allergies: a response of the immune system caused by a particular food component In some people, food allergies can be mild. In others, food allergies can be quite severe and require immediate medical attention. Disorders Related to Digestion Celiac disease is an immune system response to eating gluten, a protein found in wheat, rye, and barley. The immune response damages the villi in the small intestine, leading to decreased absorption of certain nutrients. Celiac disease is considered a genetic disorder. Treatment involves a gluten-free diet. Disorders Related to Digestion Diarrhea: can be caused by infection of the GI tract, chronic disease, food intolerances, stress, and bowel disorders can lead to severe dehydration is more dangerous for infants, young children, and older adults Disorders Related to Digestion Constipation: can be caused by the disruption of a person's schedule, a change in diet, or certain medications may be treated by increasing fluid and fiber consumption Disorders Related to Digestion Irritable bowel syndrome (IBS) is a disorder that interferes with normal colon function. Symptoms of IBS include: abdominal cramps and bloating either diarrhea or constipation IBS is more common in women than in men. Disorders Related to Digestion: IBDs Ulcerative Colitis Crohn’s Disease Inflammation of the large intestine Inflammation of the small and large intestines Alcohol Contained in beverages made from fermented fruits, vegetables, or grains High-energy compound: contains 7 kcal/g Not a nutrient since it is not essential and impairs body functions Alcohol Dietary Guidelines for Americans recommends that any alcohol consumption should be done in moderation. What is moderation? No more than 1 drink/day for women, 2 drinks/day for men There is no safe level for women who are pregnant or breastfeeding. “Legal” BAC limit in AZ <0.08% If >0.08% = loss of license See Table 6.4 Alcohol One drink is the amount of a beverage that supplies ½ fluid ounce of alcohol: 1 ½ oz of distilled spirits 5 oz wine 12 oz beer 1 wine cooler Metabolism of Alcohol Alcohol is not digested but is absorbed directly through the stomach and intestine. Alcohol is transported to the liver, where it is metabolized at the rate of approximately 1 drink/hour. Excess alcohol is released to the blood and excreted in urine, breath, and sweat. Does coffee/caffeine help? Levels of Consumption Level Amount Moderate Up to 1 per day women; 2 per day men Heavy 8+ drinks/week women; 15+ drinks/week men Binge 3+ drinks/time women; 5+ drinks/time men Alcohol and Liver Metabolism Liver is the ONLY organ that can metabolize alcohol Alcohol absorbs faster than nutrients Alcohol absorbs faster on empty stomach Liver metabolizes at rate of 1 drink per hour Alcohol and the Brain Decreases inhibitions, reasoning, judgment Induces relaxed feelings Impairs speech, vision, muscle movements Impairs breathing, heart rate Loss of consciousness Kills brain cells Alcohol and the Brain Alcohol and Health Benefits Moderate alcohol consumption is linked to: Improved lipid profiles Reduced risk of blood clots in arteries Stimulated appetite in the elderly Possible lower risk of cognitive impairment and other forms of dementia Stronger bones in older adults Red wine contains polyphenols Catechin and resveratrol Found in grape skins/seeds Alcohol and Health Risks Moderate alcohol consumption is linked to: Possible increase in the risk for breast cancer Possible increase in the risk for hypertension Possible increased total calorie consumption and therefore increased risk of obesity Interactions with medications Possible reduced intake/absorption of vitamins/minerals Wernicke-Korsafoff syndrome Alcohol and Health Risks Alcohol abuse: drinking too much, too often, or at inappropriate times or situations Binge drinking: the consumption of five or more drinks on one occasion. Alcohol consumption that overwhelms the liver's ability to detoxify the blood can result in alcohol poisoning. Alcohol and Health Risks Chronic alcohol abuse can lead to alcoholism, a disease characterized by: craving alcohol inability to stop drinking physical dependence tolerance Chronic alcohol abuse severely damages the liver. fatty liver hepatitis cirrhosis Fetal Alcohol Syndrome Alcohol is a teratogen – a substance known to cause birth defects. Alcohol crosses the placenta and enters the fetus. A fetus cannot metabolize alcohol, so it accumulates in the fetal bloodstream. Fetal Alcohol Syndrome Fetal alcohol syndrome (FAS) is a group of birth defects found in children whose mothers consumed alcohol during pregnancy. Children with FAS typically have emotional, behavioral, social, learning, and developmental problems throughout life. 100% Preventable!! Don’t Do It!!!
