Ch 26 Nutrition and Digestion PDF

BIOL 1111: Ch 26 Nutrition and Digestion Outline Part 1: Nutrition Chemical energy powers the body Essential Nutrients What’s a healthy diet? Part 2: The Human Digestive System Obtaining and Processing Food The Human Digestive System Part 1: Nutrition and Exercise ...

BIOL 1111: Ch 26 Nutrition and Digestion Outline Part 1: Nutrition Chemical energy powers the body Essential Nutrients What’s a healthy diet? Part 2: The Human Digestive System Obtaining and Processing Food The Human Digestive System Part 1: Nutrition and Exercise What three needs must a healthful diet satisfy? An animal’s diet must provide: 1. Fuel for its activities. 2. Raw materials for making the body’s own molecules. 3. Essential nutrients that the body cannot make. A nutritious diet provides all the nutrients our body needs in appropriate amounts. Energy for the body’s activities Animals require energy for our cells to do work Includes: Basal metabolic rate – the energy a resting animal requires to stay alive each day (~75%: heating, cooling, digestion, etc) Energy needed to perform “extra” activity (~25%: standing, thinking, sleeping, sports) These energy needs are expressed in terms of Calories*  Note: The energy content is measured in kilocalories; 1 kcal = 1000 cal; Dietary calories are actually kcal and are written as Calories Energy is expressed in Calories Calorie: a unit that describes the potential energy content of foods Tells us how much cellular work can be powered by the energy released from the breakdown of that food A person’s daily caloric needs vary greatly by age, sex, height, and physical activity levels What would happen in each of these situations?? Chemical energy powers the body Once nutrients are inside cells, they can be oxidized by cellular respiration to generate energy in the form of ATP Where does this reaction take place? What is the purpose of the multiple arrows? (  ) What would produce more ATP: 1 g carbohydrate or 1 g fat? Essential nutrients must be supplied by the diet Undernourished: deficiency in calories. Malnourished: deficiency in one or more essential nutrients. Essential nutrients: materials that must be supplied through diet because the animal cannot make them. There are 4 classes of essential nutrients: 1. Essential fatty acids e.g., linoleic acid 2. Essential amino acids There are 8 essential amino acids 3. Minerals 4. Vitamins Macronutrients Macronutrients are the nutrients that our body requires in large amounts These provide the vast majority of the energy we require There are 3 macronutrients 1. Carbohydrates 2. Proteins 3. Lipids Carbohydrates – Review… List the 3 elements carbohydrates are composed of: List the 3 sizes of carbohydrates and give a specific example of each: Monosaccharides Single sugar units E.g. Glucose, Fructose, Galactose Glucose is most easily used by the body. It is a simple carbohydrate. It circulates in the blood. It is the main source of energy for the muscles, central nervous system, and is the ONLY source of energy for the brain. Fibre Fibre consists of carbohydrates that cannot be digested. There are two main ways of categorizing fiber types: 1. From the foods the fiber comes from. e.g. Cereal fiber comes from grains. 2. If the fiber is soluble fiber or insoluble fiber. Benefits of Fibre Normalizes bowel movements and maintains bowel health Fibre decreases risk of constipation, diverticular disease, and colon cancer(?) Lowers cholesterol levels, blood pressure and inflammation Fibre decreases risk of heart disease Helps control blood sugar levels by slowing the absorption of sugar Fibre decreases risk of Type II Diabetes Aids in achieving a healthy weight (foods high in fibre are more filling, less energy dense) Glycemic Index Glycemic index measures how fast and how far blood sugar levels will rise after eating carbohydrates High GI foods are digested quickly and converted to blood sugar immediately, causing blood sugar levels to spike  Low GI foods are digested more slowly, causing a slower rise in blood sugar  Especially important for people with diabetes Proteins: Review List the 4 elements proteins are composed of: Proteins are relatively large molecules made up of amino acids joined together by peptide bonds. Functions of proteins: Form hormones, enzymes, and antibodies. Help the body regulate fluids and electrolytes. Buffer pH. Transport nutrients. Amino Acids There are 20 standard amino acids used by cells in making proteins Our bodies can synthesize 12 amino acids from other starting materials There are 8 amino acids that our bodies cannot make so we must get these amino acids from our diets They are easily obtained from animal protein They can also be obtained from the proper combination of plant foods (important for vegetarians!!) Why do we need amino acids?  The body requires amino acids to produce new body proteins and to replace damaged proteins Lipids: Review… List the 3 elements lipids are composed of: Functions: 1. Stored energy (adipose tissue). 2. Organ protection. 3. Derivatives of vitamins and hormones. 4. Temperature regulator. 5. Insulation such as myelin that covers nerve cells. 6. Lipid membrane around cells. 7. Emulsifiers to keep fats dispersed in body fluids. Types of Lipids 1. Triglycerides Composed of three fatty acids and one glycerol molecule. 2. Saturated fatty acid Fatty acid with carbon chains fully saturated with hydrogen. 3. Monounsaturated fatty acid Fatty acid that has a carbon chain with one unsaturated double bond. 4. Polyunsaturated fatty acid Fatty acid that has two or more double bonds on the carbon chain. Essential fatty acids Essential fatty acids are required for good health but the body cannot make them (therefore, we need to ingest them!) Only 2 fatty acids are known to be essential for humans Alpha-linolenic acid (an omega-3 fatty acid) Used to make phospholipids of cell membranes and are converted into other important molecules (i.e. anti-inflammatory molecules) Found in seeds (especially flax and chia), nuts, and vegetable oils Linoleic acid (an omega-6 fatty acid) Used to make phospholipids of cell membranes and are converted into other important molecules (i.e. pro-inflammatory molecules) Found in vegetable/plant and nut oils These two fatty acids cannot be synthesized by humans because humans lack the specific enzymes required for their production. Some other important fatty acids There are some fatty acids that the body can make from other starting molecules BUT the conversion process is limited, resulting in lower levels than if we consume them directly It is more efficient for us to include them in our diet! Eicosapentaenoic acid (EPA) (an omega-3 fatty acid) Important anti-oxidant and anti-inflammatory effects Obtained by eating oily fish or fish oil e.g. Cod liver, herring, mackerel, salmon, menhaden and sardine, and various types of edible seaweed and phytoplankton Docosahexaenoic acid (DHA) (an omega-3 fatty acid) Important structural component of the human brain, retina, skin, sperm, and testicles Found in fish oil and breast milk What’s an “omega-3” or “omega-6” polyunsaturated fatty acid?? The last position is labelled omega, the last letter of the Greek alphabet α-linolenic acid Omega-3 Linoleic acid Omega-6 Polyunsaturated fatty acids (PUFAs) have two or more double bonds There are two types of PUFAs in dietary oils: omega-3 and omega-6 They are distinguished by the position of the first double bond. Omega-3 fatty acids have their first double bond at the third carbon atom from the methyl end of the carbon chain while omega-6 fatty acids have their first double bond at the sixth carbon atom from the methyl end The balance of omega 3 to 6 fatty acids in our diet is important for health Both omega-3 and omega-6 fatty acids are required for the body to function However, omega-3 and omega-6 fatty acids have opposite effects when it comes to the inflammatory response and cardiovascular health Omega-3 fatty acids promote good cardiovascular health and are anti-inflammatory Omega-6 fatty acids increase risk of cardiovascular problems and are pro-inflammatory We need more omega-3 and less omega-6 in our diets!! Sources of Omega-3 vs. Omega-6 FAs Omega-3 FAs (Eat more!) Omega-6 FAs (Eat less!) Flaxseed oil Sunflower oil Salmon oil Corn oil Sardine oil Soybean oil Codliver oil Safflower oil Shrimp Sesame oil Our Western Diet has many Olive oil Avocado oil sources of Omega-6 fatty acids Fatty cold water fish Margarine Salmon, herring, anchovy Canola oil Almond oil Major and minor dietary elements Dietary elements aka minerals Inorganic elements that are essential for body processes Humans need seven major dietary elements: Calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium Require more than 200 mg/day Other dietary nutrients, such as vitamins and trace elements, are needed by the human body in very small quantities Called micronutrients Generally need less than 100 mg/day. Include elements such as iron, cobalt, chromium, copper, iodine, manganese, selenium, zinc, and molybdenum Nine of the essential minerals in the body account for less than 0.01% of your body weight. Functions of Dietary Elements Ions are found in blood plasma and cell cytoplasm (e.g., sodium, potassium, and chloride). Minerals represent much of the chemical composition of bones (e.g., calcium and phosphorus). Ions contribute to nerve and muscle activity (e.g., sodium, potassium, calcium). Mineral Requirements A healthful diet includes 13 vitamins Vitamins: are organic compounds that are essential for our body to function properly but required in very small amounts. Most vitamins are obtained from what you eat, because the body is unable to manufacture most of the essential vitamins needed to survive. Most vitamins function as, or as part of, coenzymes and have catalytic functions that are used in metabolic reactions. Severe problems can result if the diet is deficient or if these vitamins are consumed in excess. Vitamins are either fat soluble or water soluble. What properties would you expect vitamins in each of these classes to possess? Water Soluble Vitamins * * Folic Acid decreases risk of birth defects and cancer  Folic acid is required in the first four weeks of pregnancy for proper development of the brain, skull, and spinal cord.  Prevents spina bifida and neural tube defects  The current recommended intake for folic acid is 400 mg/day People who get more than the recommended amount of folic acid have lower the risk of developing colon or breast cancer. Sources of folic acid: Dark green vegetables like broccoli and spinach Dried legumes such as chickpeas, beans and lentils In Canada, folic acid is added to all white flour, enriched pasta and cornmeal products Fat Soluble Vitamins Include vitamins A, D, E, and K You need to have fat in your diet to absorb these vitamins Dietary fat  bile secretion  absorption of vitamins Fat soluble vitamins are stored in “fatty organs” including liver, spleen, and adipose tissue Excessive amounts of fat soluble vitamins can accumulate and result in toxicity Toxicity rarely results from excessive dietary intake, but rather from improper use of vitamin supplements. Why do water soluble vitamins not build up to toxic levels?? Fat Soluble Vitamins Vitamin D and Cancer Risk Low vitamin D levels and inadequate calcium intake are important risk factors for various types of cancer Strongest evidence links vitamin D to decreased risk of colorectal cancer How can you get vitamin D? Skin cells exposed to sunshine can make vitamin D. Dietary sources include a few foods that naturally contain vitamin D, such as fatty fish, fish liver oil, and eggs. However, most dietary vitamin D comes from foods fortified with vitamin D, such as milk, juices, and breakfast cereals. Vitamin D can also be obtained through dietary supplements but too much can cause toxic effects What do you think these toxic effects are?? Too much calcium  deposition in tissues and excessive levels in blood Are diet supplements necessary? What are the advantages? What are the disadvantages? Who might benefit from supplements? Water Water is the main component of your body! Makes up 60% of your body weight! What purposes does water serve? Carries nutrients to your cells Required for cell metabolism Provides a moist environment for ear, nose, and throat tissues Allows kidneys to expel toxins/wastes Prevents kidney stones and constipation Improves digestion Can help decrease food intake How much water should you drink? Depends on: Your size and weight Your activity level Where you live The “current” rule of thumb: 0.5-1 oz. per pound of body mass If you weigh 150 lbs = 2.2-4.4 L water/day How can you tell if you’re dehydrated? Urine color/odor Reading Food Labels Food labels provide important nutritional information about packaged foods Ingredients are listed from greatest to least amounts Nutrition facts include: Serving size, Calories per serving, Amounts of selected nutrients per serving and as a percentage of daily value (based on a 2000 cal/day diet) Recommendations for daily minimums of selected nutrients. Determined by a national scientific panel Where do scientists get our information about nutrition from? Many insights into human nutrition have come from epidemiology, the study of human health and diseases within populations. The essential need for vitamin C was revealed by the high incidence of scurvy in sailors on long sea voyages. Early epidemiologic research showed that incidence and death rates for certain cancers were lower among individuals living in southern latitudes, where levels of sunlight exposure are relatively higher than among those living at northern latitudes.  The need for folic acid to prevent neural tube defects in newborns was revealed by studies of pregnant women of low socioeconomic status. Since 1998, folic acid has been added to foods such as bread and cereals sold in the United States. Unbelievably Amazing Foods! Unbelievably Amazing Foods! Unbelievably Amazing Foods!  What do you think about Discussion: these foods? What’s true? What’s the purpose of this marketing? 41 Obesity is an important health problem Overnourishment is the consumption of more food energy than is needed for normal metabolism. Obesity is the excessive accumulation of fat that has a negative impact on health Obesity is a major global health problem. Obesity now surpasses smoking in its contribution to disease and the shortening of healthy life spans. In the United States, the percentage of obese people has doubled to more than 30% in the past two decades, and another 35% are overweight (total of 65%!) Weight problems often begin at an early age Obesity leads to Type 2 diabetes, Cancer of the colon and breasts, and Research on mice has shown that a defect in the gene for leptin may cause obesity Weight control is a complex issue controlled by dozens of genes Leptin is a hormone produced by adipose (fat) cells that suppresses appetite. As adipose cells increase in size  leptin levels increase  tells the brain to suppress appetite Loss of body fat  _____________  ________________ What is this an example of?  In some people, a defective leptin gene leads to obesity  Synthetic leptin may help  Only a few humans have this A mouse with a defect in a gene for leptin, an appetite-suppressing hormone deficiency… (left); a normal mouse (right) What causes obesity in people? A combination of: Lack of exercise Diet Amount of food Quality of food(?) Hormones Obesity Activity Genetic factors Endocrine abnormalities Too little thyroid hormone Too much cortisol Genes Too little growth hormone Medications Evolution and Obsesity Humans tendency to be obese may partly stem from an evolutionary advantage of fat hoarding Would have been an advantage when we were hunter/gatherers Natural selection would have favoured those with a physiological need to gorge on fatty foods and store energy for times of famine These individuals would have had a better chance of surviving and passing on their genes than their thinner friends. What’s the best diet?? Weight loss is big business The U.S. market for weight loss products and services has gone from about $60 million a year in 1999 to more than $48 billion a year today. Some popular diets… 5:2 diet (5 days normal: 2 days fasting) Dukan diet (low-carb, high protein) Paleo diet (hunter-gatherer diet, no agriculture, no processed foods) Atkins diet (no carbs, lots of protein, fat is OK) Red meat, butter, cream, cheese and mayonnaise… Alkaline diet (modern diets cause our body to produce too much acid; this excess acid is turned into fat, leading to weight gain) Lots of fruit and veggies, cut down on meat, sugar, and alcohol Some popular diets… Weight Watchers diet(calorie-controlled diet; get a “points” (calorie) allowance to spend how you like) South Beach diet (low glycemic index) Slim-Fast diet (low-calorie meal replacement) Zone diet (40% carbs, 30% fats, 30% protein in all meals/snacks) Raw Food diet (uncooked, unprocessed, organic food) Nutritional benefits but difficult to get some essential nutrients Claims that cooking kills food… Juice cleanse (drink juiced fruits and vegetables in place of some meals) Claims to detoxify your body… Range from few days to much longer… It’s not sexy but it works! Scientific studies of weight loss diets indicate that the best way to lose weight and keep it off is to increase exercise and eat a balanced diet with adequate amounts of all essential nutrients. A healthy diet may reduce the risk of cardiovascular disease and cancer.  7 words to sum it up: "Eat food, not too much, mostly plants." A healthy diet may decrease your risk of cancer A Healthy Diet Grains Choose whole grain and enriched products more often Vegetables and Fruit Choose dark green and orange vegetables and orange fruit more often Milk products Choose lower-fat milk products more often Meat and Alternatives Choose leaner meats, poultry, and fish, as well as dried peas, beans, and lentils more often Diet is not the only factor… Physical activity is critical for health! Benefits: Prevention of a number of diseases. Reduced anxiety and stress. Improved confidence and self- esteem. Improved fitness. Maintenance of a healthy weight. Stronger muscles and bones. Continued independent living in later life. Preventing Disease Scientific research strongly supports the role of physical activity in disease prevention and in the treatment of chronic disabling conditions: Cardiovascular Disease Cancer Diabetes Osteoporosis Arthritis Obesity Health risks of inactivity include: Premature death, heart disease, obesity, high blood pressure, Type II diabetes, osteoporosis, stroke, depression, colon cancer Exercise There are 3 types of activities you need to do to keep your body healthy: Endurance activities: help your heart, lungs and circulatory system stay healthy and give you more energy. Flexibility activities: help you to move easily, keeping your muscles relaxed and your joints mobile. Strength activities: help your muscles and bones stay strong, improve your posture and help to prevent diseases like osteoporosis. Part 2: Human Digestive System Why do we eat? All animals must eat to provide Energy and building blocks to assemble new molecules. Animals also need essential Vitamins and minerals. Animals ingest their food in a variety of ways Absorptive feeders Lack mouth or digestive tract; absorb nutrients through body surface (e.g. tapeworms) Ingestive feeders (most animals) Ingest (eat) living or dead organisms through a mouth Ingestive feeders have highly varied diets. Can be: Herbivores are plant-eaters. Carnivores are meat-eaters. Omnivores eat both plants and other animals. Methods of feeding are also highly varied… Overview: Food Processing Occurs in 4 Stages 1. Ingestion is the act of eating. 2. Digestion is the breaking down of food into molecules small enough for the body to absorb. 3. Absorption is the take-up of the products of digestion, usually by the cells lining the digestive tract. 4. Elimination is the removal of undigested materials out of the digestive tract. Recall: Chemical Digestion In chemical digestion, polymers in food are broken down to monomers What type of reactions are these? In most animals, the digestive compartment is an Alimentary Canal Alimentary Canal: a tube running between 2 openings (mouth to anus) This tube is divided into specialized regions that process food sequentially. The main specialized regions shown below in their proper order along the alimentary canal: 1. Pharynx 2. Esophagus 3. Crop = pouch that softens and stores food pre-digestion 4. Stomach 5. Gizzards = for grinding up food 6. Intestine 7. Anus Movement of food is one-way! The human digestive system consists of an alimentary canal and accessory glands Main parts of the human alimentary canal are: mouth, oral cavity, tongue, pharynx, esophagus, stomach, intestines, rectum and anus.  The digestive glands secrete digestive enzymes to break down food.  Salivary glands, gall bladder, pancreas and liver. Functions of the Digestive System The digestive system has 4 main functions: 1. Motility Movement of materials through the GI tract by ingestion  chewing  pushing into pharynx by tongue (swallowing)  peristalsis (rhythmic smooth muscle contractions) 2. Secretion Includes exocrine (digestive enzymes, bicarbonate, HCl) and endocrine (hormones that regulate digestion) secretions 3. Digestion 2 phases: Mechanical digestion and chemical digestion 4. Absorption Passage of digested food molecules into blood or lymph Digestion begins in the oral cavity The teeth break up food There are 4 types of teeth: Incisors for biting. Canines for tearing Premolars and Molars for grinding and crushing. Salivary glands produce saliva: Moistens and lubricates food for passage. Buffers neutralize acids. Antimicrobial agents kill microbes. Salivary amylase begins the hydrolysis of starch. The tongue pushes the chewed food (bolus) into the pharynx. Swallowing The food and breathing passages both open into the pharynx The swallowing reflex moves food from the pharynx into the esophagus. The epiglottis is a flap of tissue that covers the opening to the trachea (i.e., windpipe) during swallowing to prevent entry of food. Esophageal sphincter regulates the opening of the esophagus. Normally closed but opens during swallowing reflex. The esophagus squeezes food along to the stomach Peristalsis in the esophagus moves food boluses into the stomach. Cardiac sphincter (lower esophageal sphincter) regulates passage of food through the esophagus and into the stomach. The stomach stores food and breaks it down with acid and enzymes The stomach can stretch and store up to 2L of food and drink Sits just under the diaphragm Functions  Storage, mechanical & chemical digestion Secretes gastric juices, made up of 1. Mucus 2. Enzyme that breaks down protein = Pepsin 3. Strong acid (pH 2) Kills ingested bacteria Breaks apart cells in food Denatures proteins Muscles in the stomach mix the contents every 20 seconds The stomach churns the food with gastric juice to form a mixture called acid chyme. The stomach is closed at either ends by cardiac sphincter and pyloric sphincter. The pyloric sphincter opens to allow the passage of chyme into the small intestine. What is heartburn?  Occasional backflow of chyme into esophagus through the cardiac sphincter. Bacterial infections can cause ulcers Gastric ulcers are open sores in the stomach lining. Evidence suggests that a spiral-shaped prokaryote causes gastric ulcers. Helicobacter pylori growth erodes protective mucus and damages the stomach lining. The Small Intestine The small intestine is the major organ of chemical digestion and nutrient absorption Two glands empty into the small intestine and aid in digestion: 1. Pancreas  Produces digestive enzymes and an alkaline solution (bicarbonate) to neutralize acid chime 2. Liver  Produces bile, which is then stored in the gallbladder  Bile emulsifies fat droplets for attack by pancreatic enzymes. Chemical Digestion in the SI Name the 4 classes of macromolecules Enzymes from the walls of the small intestine complete the digestion of many nutrients Three Regions of the Small Intestine Duodenum: Shortest segment of small intestine (~ 25 cm). Begins at the pyloric sphincter and merges with jejunum. Function: Mixing of contents and secretions from pancreas and liver  Jejunum:  ~ 1 m long.  Function: Chemical digestion and absorption.  Ileum:  ~ 2 m long.  Joins to the large intestine at the ileocecal sphincter.  Function: Absorption The lining of the small intestine has a large surface area The lining of the small intestine has a large surface area Small intestine has a large surface area for absorption. Folds of the intestinal lining, villi, and microvilli all contribute to the large surface area The absorptive surface area of the small intestine is about 250 m2 – the size of a tennis court! The small intestine is specialized for absorption Nutrients pass into epithelial cells of villi What type of transport processes are involved? Fatty acids and glycerol are recombined into fats and transported into lymph  Other absorbed nutrients such as amino acids and sugars pass into the blood, which then flows directly to the liver The Liver Processes Nutrient-Rich Blood from the Intestines Blood travels from the intestines to the liver via the hepatic portal vein. The liver can store nutrients (i.e. glycogen), detoxify toxic substances, and convert nutrients to other substances the body can use. The large intestine reclaims water Undigested material passes to the large intestine or colon (1.5 m long, and 5 cm diameter). Water is absorbed Some bacteria in large intestine are essential for vitamin production: Vitamin K Folic acid B vitamins  Feces are produced and compacted  Consist mainly of undigested material (fibre or cellulose), bile salts, and bacteria. The rectum is a muscular organ at the end of the large intestine The rectum stores feces until they can be eliminated. There are two sphincters: One sphincter opens from the large intestine to the rectum. Involuntary Other sphincter opens into the anus. Voluntary.  What do you think causes diarrhea? Think about it… Absorption? Speed of passage? What do you think causes constipation? Absorption? Speed of passage? 79 Up Next…Nutrition and Exercise  Group Discussion:  Do you read the food labels on the food you eat?  What does the food label tell you?  What information do you pay most attention to? 80