NUTR 251 Lesson Notes
NUTR 251 Lesson Notes NUTR 251
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This 73 page Bundle was uploaded by Julie Notetaker on Sunday May 22, 2016. The Bundle belongs to NUTR 251 at Pennsylvania State University taught by in Fall 2015. Since its upload, it has received 11 views. For similar materials see Introductory Principles of Nutrition in Nutritional Science at Pennsylvania State University.
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Date Created: 05/22/16
OVERVIEW 19 and 20 century people in US suffered from nutrient disease o Rickets: vitamin D o Pellagra: niacin Essential nutrients: vitamins, minerals, fat, carbohydrates, proteins Adequacy: eat enough of the essential nutrients, fiber, and energy Balance: neither consume nor under consume nutrients Calorie control: balance energy intake from foods with energy expenditure. You can maintain a weight that is healthy for you Nutrient density: choose foods that are good nutrient sources relative to the energy they contain Moderation: avoid excessive consumption of food high in solid fats and added sugars Variety: those who narrow their intake to only a few foods are missing other components of foods Food Guides: my pyramid and myplate Goals to myplate o Balancing calories: avoid oversized portions o Foods to increase: make half your plate fruits and vegetables, half grains, switch to low fat milk o Foods to reduce: compare sodium foods like soup, bread, and frozen meals and choose the foods with lower numbers…drink water instead of sugar drinks Outcomes if success o Increased intake of nutrient dense foods containing vitamins, minerals, and dietary fiber o Increased intake of fruits, vegetables, and whole grains, which would displace high fat and high added sugar foods o Calorie intake balanced with energy needs, which could help to prevent weight gain Dietary Guidelines for Americans Focus on consuming nutrient dense foods and beverages Adults should do at least 150 minutes a week of moderate intensity or 75 minutes a week of vigorous intensity aerobic physical activity Reduce sodium intake to less than 2300 milligrams o Reduce to 1500 mg if over age of 51 or black or have hypertension, diabetes, or chronic kidney disease Consume less than 300 mg per day of cholesterol Consume less than 10% of calories from saturated fatty acids by replacing them with monounsaturated and polyunsaturated fatty acids Reduce intake of calories from solid fats and added sugars Limit consumption of foods with refined grains Limit alcohol up to one drink per day for women and two drinks for men Eat a variety of vegetables, dark green, red orange, Consume at least half of all grains as whole grains Increase intake of fat free or low fat milk products like yogurt, cheese, fortified soy beverages Choose variety of protein foods: seafood, lean meat and poultry, eggs, beans and peas, soy products, unsalted nuts and seeds Increase amount of variety of seafood Use oils to replace solid fats where possible Choose foods with more potassium, dietary fiber, calcium, and vitamin D Nutrient Standards: Dietary reference intakes (DRI) Estimated Average Requirement (EAR): middle amount for which people require to remain healthy and not display deficiency symptoms Recommended Dietary allowance (RDA): amount determined to be what almost all people need to prevent deficiency Adequate Intake (AI): scientist best estimate of the RDA based on current information Tolerable Upper intake level (UL): maximum amount of the nutrient that is safe and above this amount could have negative health effects Acceptable Macronutrient Distribution Ranges (AMDR): for fats, proteins, and carbohydrates Estimated Energy Requirement (EER): is set at the 50 th percentile to prevent over consumption of kcalories and weight gain Food Labels Since 1907 all food labels are required to list name of food, net amount of food in terms of weight, measure or count, name and address of manufacture, and ingredient list Daily values based on 2000 daily calories Nutrient Claims: descriptive terms that follow defined guidelines “low in fat” Health claims: statements about health benefits must be accurate and balanced “may reduce risk of heart disease” Structure function claims: similar to health claims but can be done without FDA approval “promotes digestive health” DIGESTIVE SYSTEM Functions Ingestion: food enters into the system through the mouth Peristalsis: food is passed through a series of organs by muscle contractions Digestion: food is broken down by two kinds of processes o Mechanical digestion occurs through chewing and mixing of food o Chemical digestion occurs when food is mixed with gastric acid (HCI) and digestive enzymes Breaks chemical bonds. Large molecules from dietary carbs, proteins, and fats are broken down to four basic components: monosaccharide’s (such as glucose), amino acids, fatty acids, and glycerol Absorption: Once the food has been broken down it is absorbed directly into bloodstream or lymphatic system Defecation: materials that cannot be digested are not absorbed are disposed of by fecal elimination Anatomical Features Lumen: long tube where digestion and absorption take place Upper GI tract: mouth, pharynx, esophagus Lower GI tract: stomach, small intestine, large intestine Accessory organs: used to aid digestion and absorption of food in GI tract o Teeth, tongue, salivary glands, liver, gallbladder, pancreas Mouth Chewing (mastication) grinds food and begins to mechanically digest it While chewing food is mixed with salivary amylase which begins chemical breakdown of carbohydrates Food is swallowed and becomes bolus Mouth produces 1-1.5L of saliva a day o Contains salt, water, enzymes (such as amylase) o Salivary amylase starts the breakdown of starch in foods like bread and potatoes Sphincters and Valves Work to regulate the chyme Epiglottis: controls passage of food, drink, and air into either the esophagus or trachea Upper esophageal sphincter: allows passage of food particle from the mouth to the esophagus Lower esophageal sphincter (cardiac sphincter): allows passage of food particles from the esophagus to the stomach. Prevents food particles and stomach juices from backing up from the stomach to the esophagus Pyloric sphincter: allows passage of food particles and digestive juices to flow from the stomach to the small intestines. Prevents food particles and intestinal juices from backing up from the small intestine into the stomach Ileoceacal valve: allows passage of GI tract substances from the small intestine to the large intestine When food is swallowed the bolus passes into the throat or pharynx and then into the esophagus. While food goes into the esophagus air gets passed to the trachea. The epiglottis helps direct the food and air into the appropriate next passageway o When breathing the epiglottis is open and air passes around it into the trachea. When food is swallowed the epiglottis folds over and covers the entrance of the trachea Esophagus Once passed the epiglottis food moves down the esophagus towards the stomach Runs through the chest cavity and into the abdominopelvic cavity where most digestive organs are housed o Diaphragm serves as barrier between chest cavity and abdominopelvic cavity Esophageal hiatus: opening that the esophagus passes through to the diaphragm Food enters stomach through lower esophageal sphincter Heartburn (acid reflux) Occurs when lower esophageal sphincter stays open or leaks Hydrochloric acid inside stomach backwashes into and irritates esophagus Acid damages the esophagus lining and causes a burning feeling that gets mistaken for heart pain If you get heartburn you should not lay down or sleep right after a meal Structure of digestive tract Inside to out: Lumen, submucosa, circular layer, longitudinal layer, serosa Lumen is surrounded by two layers of smooth muscle: circular layer and longitudinal layer o Circular layer contracts and pinches off the tube o Muscle running lengthwise contracts and pushes material forward in one direction Lumen is pinched off so materials can only go in one direction so you can swallow food upside down or in zero gravity Stomach Bolus enters through lower esophageal sphincter and is mixed into the stomach juices producing a liquid called chyme Gastric pits: deep foldings of the epithelial layer o Gastric gland: located at bottom of each pit, where variety of exocrine cells that secrete gastric juices are found Gastric juices are a mixture of water, enzymes, hydrochloric acid Hydrochloric acid: prevents bacterial growth and kills most bacteria consumed with food Mucus: protects the stomach cells from gastric juices to prevent the burning of the stomach lining Pyloric sphincter: controls the flow of chyme from the stomach into the small intestine Peptic Ulcers Occurs when protective mucous lining of stomach becomes degraded and thinned. Acidic contents of the stomach core can come into physical contact with the epithelial lining of the stomach Damage and bleeding occur. Severe ulcer can lead to internal bleeding or perforation of the stomach which pours acid on all the internal organs Ulcers take a long time to form and a long time to heal Causes of ulcers: o Infection by the bacteria H. pylori…80% caused by bacteria o Routine use of anti-inflammatory drugs such as ibuprofen and aspirin o Disorders that cause excessive gastric secretion If bacterial should be treated with antibiotic, medicines that suppress acid production can increase inflammation Small intestine Stomach releases chyme into the duodenum a teaspoon at a time through the pyloric sphincter Small intestine has reduced mucous layer so it is not as well protected from acid o Bicarbonate: neutralizes acidic chyme Digestive juices include bicarbonate, digestive enzymes, and bile salts o Juices enter the lumen via the common bile duct o Bile salts are made in the liver and are necessary to emulsify the large fat particles to small fat particles o Digestive enzymes are made and secreted into the lumen from the pancreas and glands located in lining of small intestine o Other juices flow into small intestine from pancreas and liver Villi: Cells are found in big folds so that more cells can be packed into a linear food of the intestine Absorption of Nutrients Microvilli: hair like projections off the villi. Where the absorption takes place. They increase the surface area of each cell to increase the amount of transport that of nutrients into the body Once food is broken down into basic units, the units are absorbed into either the vascular or lymphatic system After 3-4 hours most nutrients are absorbed via the small intestine Water soluble nutrients: monosaccharide’s, amino acids, water soluble vitamins, minerals, and small fatty acids are absorbed directly into the bloodstream 90% water is secreted from body fluids back into the small intestine to keep chyme juicy and flowing o 2 liters comes from diet, 8 liters is endogenous (coming from within) Fat soluble nutrients: fat soluble vitamins, fatty acids, cholesterol enter small intestinal cell where they are packaged into chylomicrons (deliver dietary lipids to body cells) Lymph fluid eventually pours into the vascular system via the Thoracic duct (near the heart) where there can be rapid mixing so the liver is not clogged with lipids Pancreas Endocrine cells: secrete hormones 1% Exocrine cells: secrete digestive enzymes, bicarbonate, and pancreatic juice 99% o Pancreatic juice Sodium bicarbonate HCO3 : buffers acidity of chyme leaving the stomach Pancreatic amylase and carbohydrases: break down carbs Proteases: break down proteins to amino acids Lipases: break down large fat molecules to fatty acids and glycerol Liver Makes bile salts from cholesterol o Bile salt emulsify fats or take large masses of fat and break them down into smaller particles of fat Increases surface area of the fat particles so that lipases can break lipid molecules down to fatty acids Stored in gall bladder until needed. Liver secretes continuous supply and excess is stored until a high fat meal is consumed Bile contains waste products that require disposal o Cholesterol and bilirubin o Excess bile can lead to malfunction of gall bladder and formation of gallstones o Gallstones: occur when bile becomes saturated with waste products that crystalize in the gall bladder Can get stuck and cause blockages of bile duct resulting in severe pain and sometime surgical removal Even if gall bladder is removed, the liver can adequately supply bile for normal ingestion Large Intestine (colon) Leftover materials that were not needed are concentrated by removing water and salts to form feces Salts are removed from the large intestine which makes the area outside the colon hypertonic o Causes the water inside the colon to leave and enter the bloodstream 10% of water absorbed along large intestine Gastrointestinal microbiota: Trillions of bacteria and microbes found in colon (over 400 species in the gut) o Microbiome: microbata, genes, and their environment o Specific bacteria produce beneficial products like biotin and vitamin K which can be absorbed in large intestine o Can partially digest or ferment various dietary fibers producing absorbable byproducts such as short chain fatty acids Dietary fiber provides indigestible food and fecal bulk ensuring that undigested materials keep moving at regular intervals as prolonged retention of feces irritates the colon and may lead to cancerous conditions Neutral pH and slower peristalsis of lower small intestine and large intestine provide environment for bacterial proliferation o A lot of the bacteria is killed by acid in stomach and activity of bile salts but some can sneak through and multiply o Probiotics: beneficial bacteria Yogurts, soft cheeses, miso Prebiotics: foods which support the growth of probiotics Fiber rice foods contain fiber molecules and short carb type molecules that act as prebiotics in gut Typical flatulence after bean dishes reflect content of these prebiotics to nourish gas producing bacteria Many kinds of fiber and short saccharides are resistant to digestive enzymes in small intestine but bacteria can thrive on them in large intestine Lactobacillus from yogurt: prevents diarrhea, constipation, lactose intolerance, few chronic diseases May be linked with prevention of inflammatory bowel disease, enhancement of immune function, and weight control Heat and food processing kills much of bacteria in foods o Small amount of bacteria in small intestine while majority is in large intestine, if an imbalance is created then the bacteria back up into the small intestine, over populate, and result in inflammation, diarrhea, nausea, bloating, and other GI diseases o Pathogenic bacteria: such as E.coli, listeria, salmonella Regulations of the GI tract Regulation of digestion and absorption is coordinated by two systems: nervous and hormonal o Sight, smell, and thought of food can trigger responses Extrinsic nerves: come to the digestive organs from the unconscious part of the brain or from the spinal chord. Cause GI muscles to squeeze with more force and increase the push of food an juice through the digestive tract Intrinsic nerves: made up of dense network embedded in walls of esophagus, stomach, small intestine, and colon. o Triggered when wall of hollow organs are stretched by food o Release many different substances that speed up or delay the movement of food and the production of juices by the digestive organs Hormones in regulation of digestion are stimulated by action and causes the GI tract to respond causing the initial stimulus to diminish o Gastrin: stimulates stomach to secrete more hydrochloric acid when food arrives in stomach; lowering the PH o Secretin: stimulates pancreas to secrete bicarbonate rich pancreatic juice into the duodenum causing cells in wall of duodenum to release the hormone secretin back into the blood Juice neutralizes acidic chyme mixture so it becomes close to pH of blood 7.35 Higher pH leads to reduction in release of secretin Only small amounts of acidic rich chyme are released at the same time to release of secretin is adjusted frequently until all chyme for one meal is released from the stomach into the small intestines and neutralized Neutral pH allows digestive enzymes to be active o Cholecystokinin (CCK): when foods rich in fat reaches small intestines, it causes small intestinal cells to release CCK into blood stream Stimulates gallbladder to contract and secrete bile into small intestines Stimulates pancreas to release bicarbonate and digestive enzymes into small intestine Slows motility of GI tract to provide more time for digestion Carbohydrates Carbohydrate rich foods are our main source of energy and our only source of fiber Body functions optimally when adequate carbohydrates are available to easily maintain blood glucose. The cells in the brain and rest of nervous system depend primarily on glucose for energy. If glucose is too high or too low symptoms such as feeling dizzy, fatigued, or death may occur o Diabetes results when body cannot properly control homeostatic mechanisms that regulate blood glucose resulting in a series of physiological malfunctioning Carbohydrate foods are rich in vitamins, minerals, fiber, and phytochemicals Healthy carb foods include grains, vegetables, fruits, legumes, and dairy foods Carbohydrates should provide 45-65% of total energy needs All carbohydrates that are digestible provide 4kcal/gram With exception of lactose found in milk, we obtain carbs from foods of plant origin o Through photosynthesis plants containing chlorophyll transform carbon dioxide and water into glucose and oxygen with energy input from the sun o 6CO +62 OC 2 O +66 12 6 2 Essential roles include: o Burning of fat: incomplete burning of fatty acids results in carbon fragments converted into ketones. Ketones provide emergency fuel for brain under starving conditions but prolonged ketosis can cause acid/base imbalance o Required energy for the brain, other nerve cells, and red blood cells o Glucose can be stored as glycogen in liver and muscle to maintain blood glucose between meals or during prolonged activity Some amino acids can be converted to glucose under emergency conditions Protein sparing action: minimizes the conversion of amino acids to glucose so amino acids can do other important jobs o Sugars and carbohydrate fragments are structurally important to some proteins and membranes of the cell and are involved in cell signaling processes Fatty acids can never be turned into glucose If you eat more carbohydrates than your body needs, glucose is converted and stored as fat Carbs can be divided into sugars and complex carbohydrates Sugars Monosaccharaides contain one single sugar unit and disaccharides contain two sugar units All monosaccharide’s have same chemical formula: C H O bu6 12ra6,ement of carbons, hydrogen’s, and hydroxyl groups vary in orientation, making them distinct molecules o Sucrose: Fructose + Glucose o Maltose: Glucose + Glucose o Galactose: Glucose + Galactose Naturally occurring sugars found in apples, carrots, and milk Added-sugar found in candy, honey, corn syrup Complex Carbohydrates Polysaccharides: composed of many glucose units in straight or branched chains Starches (polysaccharides): storage form of glucose in plants to be used as energy for the plant or animal which eats it o Especially rich in tubers (potatoes) or seed (wheat, corn, beans, rice) o Low in most fruits (except bananas) and many vegetables like lettuce and celery o Amylose (alpha 1-4 linkages between glucose) o Amylopectin (alpha 1-4 and alpha 1-6 causing branching) Glycogen: stores glucose in humans and other animals and is found in limited quantities in the liver and muscles o Average adult stores 340g of glycogen, equivalent to 1360 kcal available for energy o No dietary source for glycogen o When animal is slaughtered glycogen stored in its muscles is converted into lactic acid, a product of anaerobic glucose metabolism o Structure similar to amylopectin Fiber: nonstarch polysaccharides o Found only in foods of plant origin and are generally associated with structural components of the plant o Cellulose: a component of plant cell walls, is a long chain of glucose units (linkages called beta 1-4) o Resistance to digestion and absorption in small intestine, cellulose has greatest resistance o Insoluble fiber: more abundant in US diet than soluble fiber. Comprised of cellulose, hemicellulose, and lignin. Example is wheat bran Chemically lignin is not a polysaccharide but shares characteristics of insoluble fibers and is indigestible Promotes GI health by adding bulk to stools. Preventing constipation, diverticulosis, hemorrhoids, and appendicitis, colon cancer o Soluble fiber: can be suspended in solution. It absorbs water and cholesterol, delays glucose absorption, and slows GI transit. Found in fruit, oats, barley, soy, and legumes Pectin (used to thicken jam and jelly), gums, and mucilage are examples Reduces risk of heart disease because soluble fiber hangs onto cholesterol dragging it out of the body via fecal elimination Fermentation products in colon, which are absorbed, can travel to the liver and are capable of suppressing cholesterol synthesis. Lowering blood cholesterol Healthy choice for those with diabetes o Dietary fiber is not digested by human enzymes but can be digested by bacteria in the colon, producing short-chain fatty acids that can be metabolized for energy (1-2.5 kcal/g fiber) Energy provided is relatively small Calories from dietary fiber are not added in on Calories estimated on food labels or nutrient data bases o Diets with healthful amounts of fiber are often low in energy and increase satiety (helps you feel full longer), useful for weight management o Americans encouraged to increase fiber intake to 25-35 g/day. DRI recommends Americans consume 14g/1000 kcal. Dietary fiber does have AI that represents 2-3 times current intake o Foods that are high in fiber (above 40g/day) can displace energy and nutrients from other foods GI discomfort: bloating and gas Cation-exchange capacity (ability to bind minerals) and can decrease absorption of important trace materials such as iron and zinc Half of grains should be whole grains DIGESTION AND ABSORPTION Starch o Mouth and salivary glands: salivary amylase starts digestion o Stomach: stomach acid stops the activity of salivary amylase, interrupting starch digestion o Pancreas: pancreatic carbohydrases including amylase digest large polysaccharides into smaller units o Small intestine: further digesting of disaccharides by maltase, sucrase, and lactase occur at microvilli of small intestine o Monosaccharaides are absorbed into the blood stream and transported to the liver via the portal vein o Galactose and fructose are converted to glucose in the liver Fiber o Mouth: chewing tears fiber in food and mixes it with saliva before swallowing occurs o Stomach: fiber is not digested, so gastric emptying is delayed o Small intestine: fiber is not digested, so absorption of other nutrients is slowed o Large intestine: fiber is partially digested by bacterial enzymes and is either generated into fatty acids, gas and water, or carried out of the body with feces Fatty acids can be used as fuel for cells of the large intestine or absorbed into blood stream and find way to liver Lactose intolerance: Inadequate lactase activity in small intestine Lactase is produced by intestinal cells and reside on microvilli Undigested lactose remains in GI tract and is fermented by bacteria in large intestine resulting in bloating, discomfort, and diarrhea o Diarrhea is caused by increased endogenous water in the gut diluting the overload of the solute, lactose (simple case of osmosis) Lactase can decline as you age, especially in Southeast Asians, Native north Americans, African Americans, and Mediterranean peoples Rare in infants and children Sometimes results from damage to villi resulting from illness, medications, or malnutrition, often temporary Avoidance of high lactose foods, use of lactose supplements, or fermented foods helps reduce symptoms GLUCOSE HOMEOSTASIS Pancreas produces insulin and glucagon to regulate glucose homeostasis Fasting blood glucose for healthy individuals is 70-99mg/dL After a meal glucose is circulated in blood stream, when blood sugar rises, insulin is released, stimulating cells to take glucose where it can be used as energy, stored as glycogen, or converted to fat and stored, lowering blood sugar When blood sugar falls glucagen is released from the pancreas to stimulate the release of glucose stored as glycogen in the liver and muscles. Causes the liver cells to break down the glycogen and release it into the blood. In times of stress epinephrine (adrenaline) is released which acts to release glucose from stored glycogen for quick energy DIABETES MELLITUS: a group of diseases characterized by hyperglycemia from inadequate or ineffective insulin Hyperglycemia: high blood sugar 9.3% of US population is diagnosed with type 2 diabetes Individuals with impaired glucose tolerance have a slightly elevated fasting blood glucose, while an individual with diabetes has significant elevation o Impaired glucose tolerance is risk factor for diabetes and heart disease Gestational diabetes occurs in approximately 4% of all pregnancies, usually during second or third trimester o Usually resolves after delivery but is a risk facto for type 2 diabetes later in life Type 1 diabetes: o 5-10% of all cases o Lean bodies, usually under the age of 30, average 12 years old o Pancreas cannot make insulin o Requires insulin injections or insulin pump o Must balance food intake with insulin and energy expenditure, adequate nutrients for growth in children o Risk factors include: Genetic susceptibility, autoimmune destruction, viral infection, toxic chemicals o Severe symptoms: hyperglycemia, excessive thirst, frequent urination, significant weight loss despite increased appetite, electrolyte imbalances, diabetic acidosis (from excess ketone production), diabetic coma Type 2 diabetes o 90-95% of all cases o 55% of persons with type 2 are obese o Usually over age of 30, but with increasing obesity it is seen in children and young adults o Insulin insensitivity or insulin deficiency relative to need o Oral medications to increase amount or efficiency of insulin produced. Insulin injections only if needed o Must promote weight loss or maintenance, spread nutrient intake throughout the day. Regular physical activity improves insulin sensitivity o Risk factors: physical inactivity, age, obesity, family history o Moderate symptoms: hyperglycemia, excessive thirst, frequent urination, increased appetite, weight gain Long term complications of diabetes o Diseases of large and small blood vessels (macrovascular and microvascular) o Macrovascular: Arteriosclerosis: thickening of artery walls Myocardial infarction (MI/heart attack) Stroke o Microvascular: Poor circulation in the extremities Permanent damage to minute blood vessels of the kidney and eyes Diabetes is leading cause of kidney disease and blindness Neuropathy: damage to the nerves. Prevents people from recognizing and treating an injury Left untreated an infection in a leg or foot can progress to gangrene necessitating amputation of the diseased foot or leg Regular foot care and visits to podiatrist are important for individuals with diabetes Sugar Substitutes FDA approved several including saccharin, aspartame, and sucralose, stevia For people that need to restrict carb intake, like those with diabetes, artificial sweeteners offer a safe way to incorporate sweet foods Up to 95% of artificial sweeteners is fillers because they are so much sweeter than regular sugar o Saccharin: 200-700 times more sweet than sucrose No calories Low risk for tooth decay Been in food supply over 100 years Initially linked with bladder tumors in rats, but further research has indicated it is safe in amounts normally consumed o Stevia is 300 times the sweetness of sucrose and is extracted from a south American plant Glycosides isolated from the leaves of the Stevia plant No calories Heat stable Low risk for tooth decay No bitter after taste More expensive than other sugar substitutes o Aspartame: 200 times more sweet Low risk for tooth decay Very few calories Components are absorbed Heat and time cause the breakdown of the compound. This is not harmful but it looses its sweetness. Cannot be used to cook with or sweeten hot drinks o Sucralose: 600 times more sweet No calories Low risk for tooth decay Heat stable Made from sugar, so some see it as more natural Is not absorbed Sugar replacers are widely used in chewing gums and mints because they do no promote dental caries o Sugar alcohols like sorbitol and xylitol: half or as sweet as sucrose Lower in calories (2 cal/g) Lower glycemic response Low risk for tooth decay Can cause diarrhea and gastrointestinal distress if too much is consumed An Acceptable Daily Intake (ADI): the amount in food or beverages that has no appreciable health risk if consumed on a daily basis over a lifetime o Is established for each alternative sweetener o Safety factor in establishing ADI of 100. The safe level is divided by 100 to account for genetic difference o Aspartame has ADI of 50 mg/kg body weight which translates to 18 cans of diet soda a day Actually the safe level is 100 times or 1800 cans of soda per day Phenylketonuria (PKU): genetic disorder that cannot metabolize phenylalanine o Can not have aspartame o Consuming a huge amount of aspartame is needed to affect blood levels of phenylalanine The CARB DEBATE Dietary guidelines encourages us to reduce the intake of kcalories from added sugars Refer to these foods as discretionary calories Most people can accommodate some foods with lower nutrient density if they do no exclude foods with higher nutrient density Dental carries: dietary sugars and sugars from partial digestion of starch can be fermented in bacteria in the mouth producing an acid capable of dissolving tooth enamel o Increased exposure to sugar from sticky foods or repeated snacking throughout the day increases acid production o Brushing teeth, flossing, or rinsing mouth with water after meals helps reduce damage caused by bacteria DRI suggest that no more than 25% of total daily calories should be consumed by added sugar High intakes of added sugars over many years may be associated with risk for type 2 diabetes Any low calorie diet can result in weight loss and improves biomarkers such as blood lipids High fructose corn syrup is chemically similar to sucrose, both are composed by 50% glucose and 50% fructose o High means that it is higher than other corn syrups that are 100% glucose o Fructose itself is not imposing a health issue except that some individual may be consuming too many kcalories from discretionary or empty calories DRI concluded that healthy diet is composed of 45-65% kcals from carbohydrates o Without carbohydrates, the quality of diet suffers Lipids Heart disease is number one killer in US adults Types of Lipids Triglycerides: 3 fatty acids linked by glycerol Phospholipids: occur when one fatty acid from a triglyceride is removed and a phosphorus is added instead o Organize themselves in water in unique ways o Partly non-polar (long tails) and partly polar (the phosphorous end) Sterols: have a ring structure but are still fat soluble o Cholesterol is most famous sterol. Found only in animals Cell membranes are lipid bilayers composed of phospholipids and cholesterol. Water is found on either side but not in the center Triglycerides Commonly known as fats or oils Most abundant lipid in food and human body make up 95% of dietary fat Composed of a 3carbon glycerol backbone with 3 fatty acids extending from each of the carbons of glycerol Fatty acids usually part of triglyceride rather than on their own Triglycerides and fatty acids are composed of 3 atoms, Carbon, Hydrogen, and Oxygen. With more C and H than O Fat gives us 9 kcals/gram One end of fatty acid is a carboxylic acid group (COOH) and the other is a methyl group (CH3) o Carboxylic acid portion of fatty acid combines with glycerol via a condensation reaction when a triglyceride is made Fatty acids can vary by length of carbon chain, number of double bonds, and position of double bonds Chain length o Most fatty acids contain even numbers of carbon in their chains up to 24 carbons in length o Carbon lengths of 12-24 are called long chain fatty acids o 18 carbons in chain are the most abundant in our food supply o Long chains are common in meats, fish, and vegetable oils o Medium chains 6-10 carbons and short chains <6 carbons occur in small amount in foods Chemistry of fatty acids Saturated: fatty acids with only single bonds, carbon atoms are saturated with H atoms o Stearic acid: saturated fatty acid with 18 carbons Monounsaturated: fatty acids with one double bond o Oleic acid: monounsaturated fatty acid with 18 carbons Polyunsaturated: fatty acids with two or more double bonds o Linoleic acid: polyunsaturated acid with 18 carbons o Polyunsaturated fatty acids are characterized by the position of the first double bond in reference to the methyl carbon rd th Omega 3 fatty acid: When the first double bond is between the 3 and 4 carbons from the methyl carbon Omega 6 fatty acid: when the first double bond is six carbons out from the methyl carbon Butter is high in saturated fatty acids, while canola oil and olive oil are high in monounsaturated acids o Triglycerides rich in saturated fatty fats 50% or more are solid at room temperature. The regular shape of the saturated fatty acid chain tends to allow the molecules to stack and pack firmly o Triglycerides containing unsaturated fatty acids are usually liquid at room temp o Monounsaturated and polyunsaturated fatty acids have kinks in the carbon chain wherever a double bond occurs. This irregularity creates a more fluid compound Essential fatty acids Linoleic acid and linolenic acid are essential in their role in membrane structure, they are precursors to other fatty acids, and to an important classification of molecules called eicosanoids Deficiency is extremely rare, reported in cases where infants were fed almost fat free diets o Skin lesions, growth retardation, multiple organ and neurological problems Linoleic acid: an omega 6 fatty acid rich in leafy vegetables, grains, nuts, seeds, and vegetable oils o AI recommendation of 17g/day for males and 12g/day for females Linolenic acid: omega 3 fatty acid rich in fats and oils from canola, soybean, walnut, flaxseed, and wheat germ o AI recommendations 1.6g/day males and 1.1g/day females o EPA and DHA are long chain omega 3 fatty acids (20 and 22 carbons in length) can be made from linolenic acid but are also found in fish, shellfish, sea algae, human breast milk Eating preformed DHA and EPA improves eicosanoid status even though we can make them Plays role in structure and function of eyes and brain Precursors to eicosanoids Eicosanoids are produced in extremely small amounts in cells and then act in those cells to regulate some physiological function o Affect regulatory processes in immunity, reproduction, and blood clotting o Prostaglandins: made from omega 3 fatty acids DHA and EPA play a role in inhibiting the clotting response during atherosclerosis leading to a heart attack or stroke o Enhancing EPA DHA status is reported to have beneficial effects that may decrease risk of heart disease by improving blood lipids, lower high blood pressure, and reduce inflammation Americans encouraged to increase intakes of Omega 3 o Increasing use of vegetable oils like canola, flaxseed, walnut, and soybean oils. o Fish (salmon, mackerel, lake trout, sardines, tuna) o Eggs from chickens fed sources of EPA and DHA All fats are a mixture of saturated, monounsaturated, and polyunsaturated fatty acids o For heart health look for those rich in polyunsaturated, monounsaturated, and linolenic acid o Palm oil and coconut oil are tropical oils high in saturated fatty acids. They tend to be liquid because they contain a large portion of medium chain fatty acids Hydrogenation: allows food manufacturers to stabilize polyunsaturated fats by adding hydrogen and removing double bonds, converting them to saturated fatty acids Polyunsaturated fatty acids make them prone to oxidation and rancidity Saturated fats are more resistant to oxidation, increasing shelf life Partial hydrogenation: produces double bonds where the position of hydrogen atoms shifts from being on the same side (cis formation) to opposite sides (trans formation) o In nature most double bonds form cis formation o Decreasing double bonds and increasing trans fatty acids serve to solidify vegetable oils creating products like margarine and shortening Trans fatty acids o Trans fatty acids can be created when fats are heated to high temperatures such as deep fat frying o Chemically and functionally trans fats are similar to saturated fat o Consuming diets rich in trans fatty acids is a risk for heart disease o Trans fatty acids naturally occur in animal foods but in small amounts. Experts recommend reducing trans fats in your diet that are industrially produced Phospholipids Synthesized in our bodies and are important components of cell membranes Resemble triglycerides except a phosphorylated alcohol replaces one fatty acid chain. This changes the molecule to being partially hydrophobic and partially hydrophilic Act as emulsifiers: helping fat soluble and water soluble compounds mix Naturally arrange themselves into lipid bilayers, the basic formation of all cell membranes Lecithin is most family phospholipid Sterols: Cholesterol Found in plants (phytosterols) and animals (cholesterol) Bodies make more endogenous cholesterol in liver than they consume in their diet o Amount the body makes and how it is transported in blood is influenced by the amount of dietary total fat, saturated fat, trans fatty acids, as well as other fatty acids o Precursor to bile acids, sex hormones, adrenal hormones (cortisol), and vitamin D o Part of the structure of membranes We obtain cholesterol from foods such as eggs, meat, fish, especially shellfish, butter o Excess dietary cholesterol contributes to elevated blood cholesterol in people with hypercholesterolemia (high blood cholesterol) o Presence of soluble fiber can inhibit absorption of cholesterol in the intestines and/or suppress endogenous synthesis of cholesterol in the liver o Only way to get cholesterol out of the body is via excretion in feces as cholesterol or as bile salts, which are made from cholesterol. Most of cholesterol and bile salts are absorbed for recycling in the liver but some is always excreted in feces Functional foods containing phytosterols have been marketed under brand names Take Control and Benecol o Phytosterols are not absorbed but the chemical similarity with cholesterol allows it to compete with cholesterol absorption sites in the intestines o If unable to be absorbed, cholesterol is excreted in the feces and blood cholesterol levels may decrease. These sterol containing foods would have to be a regular part of your daily diet to effectively lower blood cholesterol Lipid digestion Mouth and salivary glands o Fat digestion begins slowly with some hard fats melting at body temperature in the mouth o The salivary gland at the base of the tongue releases an enzyme lingual lipase, which plays an active role in infants digestion of fats Stomach o Muscle contractions move the stomach contents to the pyloric sphincter and then back into the stomach, breaking up the fat into small droplets. This action causes the fat to come into contact with the gastric lipase enzyme, however minimal fat digestion occurs Small intestine o Gallbladder releases bile, which is composed of bile acids. These acids act as emulsifiers, pulling the fat into the surrounding watery fluids where it mixes with lipase enzymes from the pancreas and small intestine o In the lower part of the intestine, some bile is absorbed and recycled in the liver Large intestine o Bile that is trapped by dietary fibers in the large intestine exits the body Absorption Triglycerides with long chain fatty acids and phospholipids must first be disassembled into smaller pieces before passing through the cell membrane Triglycerides are broken down by pancreatic lipases into 3 fatty acids and a glycerol molecule, or two fatty acids and a monoglyceride Phospholipids are digested so that only one fatty acid remains on the glycerol backbone o In the lumen of the small intestine, bile emulsifies big clumps of fat producing very small particles called micelles o Micelles are soluble in the watery environment of the intestines and have a large surface area so pancreatic lipases can do their job o The products of digestion, fatty acids and monoglycerides leave micelles to be absorbed into intestinal cells where they once again reform into triglycerides and phospholipids o Small amounts of dietary fat are small and medium fatty chains. After the digestion in the small intestine, they are passively absorbed into the blood stream Transport Short and medium chain fatty acids are absorbed by passive diffusion right into the blood Large molecules cannot enter directly into the blood stream, fats and fat soluble molecule are transported from the intestine into the lymphatic system As hydrophobic molecules, triglycerides formed inside intestinal cells cannot move freely in the lymphatic system or blood, so they are repackaged into large spherical complexes called chylomicrons o Lipoproteins: contain protein, cholesterol, and phospholipids, triglycerides Chylomicrons are largest of lipoproteins, and lowest density because of the high proportion of triglycerides they contain Travel from inside the intestinal cell through the lymphatic system and eventually enter blood stream via a duct near the heart where there is rapid mixing because of the pumping of the heart Process avoids dumping large amounts of lipids into the blood stream after a meal They function to deliver dietary lipids to most tissues in the body Very low-density lipoprotein VLDL: liver ships out VLDLs to deliver endogenous lipids to body cells. The fragments that remain after the removal of some of the lipid material are called LDL High-density lipoprotein HDL: least amount of fat and highest proportion of protein so it has the highest density. Transports cholesterol from body cells back to the liver where it can be used to make bile and other compounds Linked with higher intakes of monounsaturated fats and omega 3 fatty acids Low density lipoprotein LDL: transports lipids and cholesterol to cells in the body High incidence of heart disease Linked with higher intakes of saturated fat and trans fat Linked with higher intakes of fat above 35% of kcals Total cholesterol: sum of cholesterol found in all the different lipoproteins Desirable is <200 mg/dL Borderline is 200-239 High risk is greater than or equal to 240 mg/dL Dietary cholesterol o Concentrated in eggs, liver, and shellfish o Recommended intake 300 mg/day or less Blood cholesterol o Circulating in the blood in the various lipoproteins o Each lipoprotein has varying amounts of lipids and proteins o Chylomicrons have the least cholesterol and LDL have the most o Lipid profile associated with reduced risk for cardiovascular disease Total cholesterol <200 mg/dL HDL cholesterol >60 mg/dL LDL <100 mg/dL Triglycerides <150 mg/dL Cardiovascular disease CVD: all disease of the heart and blood vessels, usually atherosclerosis and hypertension are contributing factors Coronary heart disease: most common type of CVD. Resulting in sudden decrease of blood flow to the heart and causes heart attack or stroke (cerebrovascular accident)’ o Atherosclerosis: results from buildup of fibrous plaque inside artery walls Plaque: consists of lipids, including cholesterol, smooth muscle cells, calcium, other material forming a stiff, thickened area that can occlude arteries. Platelets often adhere to the region, increasing thickening and the possibility of total blockage Injury inducing factors Smoking Hypertension Obesity Diabetes Hypercholesterolemia Oxidized LDL High cholesterol/high saturated fatty acid diets High epinephrine: stress Risk factors o Men develop CVD 10-12 years earlier than women o Prior to age 45 women have lower LDL levels and higher HDL levels, as they approach menopause, LDL increases and HDL decreases o Physical activity can increase HDL in men and women o Smoking increases risk by 2-4 times o Obesity o High dietary fat above 35% kcal o Saturated fatty acids o Trans fatty acids o Dietary Cholesterol o Excess alcohol o Low vitamin and mineral intake Diet factors with positive effects o Polyunsaturated fatty acids o Omega 3 fatty acids o Monounsaturated fatty acids o Carbohydrate foods that contain fiber, especially soluble fibers CVD increased during first half of 20 century but decreased since peak in 60s: better medical care and changes in personal habits o Reduction in smoking and decline of consumption of dietary fats and saturated fat o Advancements in diagnosing and treating heart disease and stroke such as better control of hypertension Strategies to reduce CVD risk o Maintain healthy body weight o Total fat in moderation AMDR is 20-35% of kcal from fat 30% of kcals is a reasonable American goal o Aim for healthy fats o Minimize saturated and trans fats Less than 10% kcals of saturated fat Industrially produced trans fat as low as possible o Try a variety of complex carbohydrates rich in dietary fiber Soluble fiber has modest effect on lowering blood cholesterol Traps cholesterol in gut for excretion Produces short chain fatty acids which are absorbed and signal the liver to reduce cholesterol synthesis o Aim for modest dietary cholesterol Intake of less than 300 mg cholesterol per day o Eat like Myplate B vitamins reduce blood homocystein levels Vitamin 5 is an antioxidant fat soluble vitamin the is hypothesized to help reduce oxidation of LDL cholesterol and progression of artheroscoleolis o Eating fish adds EPA and DHA Eat fish twice a week Women who are pregnant or lactating should eat less due to mercury Fat debate o Dairy foods have a mixture of saturated fatty acids and are particularly rich in steric acid o Steric acid does not contribute to elevated LDL and contributes to more HDL o 12, 14, 16 carbon saturated fatty acids which contribute to elevation of LDL o Body fat provides compact source of stored energy and helps preserve protein, preventing muscle wasting o Subcutaneous fat helps maintain body heat and intra-abdominal fat functions as a shock absorber to protect essential organs o Women require minimal body fat of 15-20% to support reproduction o Relationship of inadequate body fat, reduced production of hormone estrogen, loss of calcium from bones is often seen in eating disorders o 20-25% of total kcals as fat o <10% total cals from saturated fat o Avoid trans fatty acids from industrial sources o <300 mg cholesterol/day Life Cycle Individuals most at risk for nutrient deficiencies tend to be those with increase nutrient needs and those with decreased appetite. Pregnant or lactating women, infants, and young children The frail, elderly or ill are at risk for nutrient deficiencies because they may have increased needs and/or decreased appetites o Elders need increased vitamin B12 and vitamin D o Risk for osteoporosis and other diseases FETAL GROWTH AND DEVELOPMENT Timeline of pregnancy: weeks of gestation o Conception: 0 o Preterm: <37 weeks o Term: 38-42 o Zygote: 0-2 weeks o Embryo: 2-8 weeks o Fetus: 8-40 weeks o 1 Trimester: 0-13 weeks o 2 nd Trimester: 13-26 weeks o 3 rdTrimester: 26-40 weeks o Typically a full term singleton birth is 40 weeks from the first day of the last menstrual period, a preterm birth is at least 3 weeks earlier than this The zygote (newly fertilized ovum) implants itself in the wall of the uterus within two weeks of fertilization, from this point, the zygote becomes known as the embryo and initiates the development of the placenta, umbilicus, and amniotic sac Placenta: “afterbirth”, metabolically active organ producing hormones that regulate fetal growth and maternal support tissue o Finger like projections allowing the fetus’s arteries and veins to access a pool of the mother’s blood o Nutrients, oxygen, and fetal waste products cross between the mother and fetus via this shared pool of blood o Normal development and integrity of the placenta is key for healthy growth of child Abrupto placentae: when fetus does not keep its integrity increasing risk of hemorrhaging during last trimester Placenta previa: placenta forms in lower uterus increasing risk of hemorrhaging during last trimester Embryonic stage: 2-8 weeks, is a time of rapid cell division and differentiation and a time when most of the major organ systems are developing Critical periods: early stages of embryonic development in which an organ or organ system can be irreversibly affected by an adverse event such as exposure to a toxic substance or too little or too much supply of an essential nutrient o Mostly during time of intense development, during the first 10 weeks after conception when cell differentiation and cell division is rapid Excess retinoid exposure (preformed vitamin A) o Causes severe birth defects especially if toxic exposure is during the first trimester o UL of 3000 ug/day…4x the RDA o Prenatal vitamins contain no vitamin A, but may contain carotenoids which are not teratogenic o RDA amounts of vitamin A are safe and essential for fetal growth and development Neural tube defect: o Higher intakes of folic acid (the form of folate in fortified foods and supplements) during the early stages of pregnancy have been found to reduce the occurrence of neural tube o Spina bifida: neural tube fails to close and the spinal chord is not completely protected by normal development of bones in the spine The spinal chord can be irreparably damaged leading to paralysis below the point of exposure and multiple health problems o Prior to research on folate, the only treatment was delicate surgery to tuck the spinal cord back into the vertebrae o Anencephaly: most serious tube defect, causes incomplete brain development, usually resulting in miscarriage or death soon after birth o Normally, the neural tube closes 4 weeks before gestation, thus the critical period for embryonic folate exposure is at 17-30 days Many women do not seek prenatal care early enough to be warned of this folate neural tube connection o 1998, FDA mandated that all processed grain products be fortified with folic acid to help reduce incidence of neural tube defects Has been successful at reducing the rate by about 25% (from high of 30/100000 to 20/100000 live births Fortification of foods can increase folate and folic acid intake to as high as 600 ug/day, the RDA for pregnant women Level of fortification in US is modest, since the effects of chronic intakes of higher amounts of folic acid are not known for other segments of the population o Most obstetricians recommend a multivitamin supplement for women prior to and during pregnancy to assure at least this level of intake o If a woman has given birth to a baby with neural tube defect, she is advised to consume even higher levels before and during her next pregnancy o Foods rich in folate such as green leafy vegetables, legumes, orange juice and oranges, whole grains, and fortified grains o Causes still under investigation o Risk factors Race, more common amongst whites and Hispanics than other racial groups A previous pregnancy increases risk of a second neural tube defect baby Maternal diabetes Maternal obesity Maternal anti-seizure medication Exposure to hot temperatures early in pregnancy, prolonged fever or hot tub use Birth weight is one of the best predictors of infant health o Typical 40 week gestation produces an infant weighing 6.5-8.75 lbs., this is the weight range for a healthy newborn with the lowest risks of poor health o Maternal preconception weight Women who are underweight: Smaller placenta Low birth weight infants (= or less than 2500 grams or 5.5 lbs.) Premature birth (<37 weeks gestation) Underweight women can minimize risk by gaining weight during pregnancy Women who are obese (greater than or equal to 30 BMI) Maternal medical complications o Hypertension, diabetes, postpartum infection Labor and delivery complications o Large infant, birth trauma, or cesarean section Poor development, infant death Neural tube defect Should avoid excessive weight gain but should not go on a weight loss diet because fetus requires adequate energy for growth and activity Mother needs adequate energy for increase BMR, fat storage, growth of uterus and mammary tissue, and increased blood volume Inadequate nutrition can result in fetal growth retardation, birth defects, spontaneous abortion and still birth, premature birth, and low infant birth weight o Maternal weight gain during pregnancy Only a few pounds are gained during the first trimester, while about 1 pound per week is typical during the last 2 trimesters Recommendations for weight gain over 9 months for healthiest birth weight outcomes Underweight (BMI <18.5): 28-40 pounds Healthy weight (BMI 18.5-24.9): 25-35 pounds Overweight (BMI 25-29.9): 15-25 pounds Obese (BMI >30): 11-20 pounds Health goal in US is to reduce the prevalence of low birth weight LBW infants (<5.5 pounds) from 8.2% to less than 5%, since LBW increases risk for poor health or death Pregnant teens tend to have poor diets and tend not to seek prenatal care, therefore recommendations are for the to gain on the high end of the ranges Caloric needs are hard to estimate because of individual variation and physical activity level Reasonable estimate for healthy weight women is 340 kcal/day during second trimester and 450 kcal/day for the third trimester Does not eat for two, eats for herself and a little more Elevated hunger and reduction in activity levels can result in too much weight gain, which is of minimal consequence by it is hard to lose after the baby is born o Risk factors for LBW infants Inappropriately low maternal weight gain Both younger and older mothers hav
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