NTR 301 Exam 2
Longitudinal muscles- creates "waves" of movement by shortening and lengthening the tract to propel the bolus forward Circular muscles- open and close the tract behind the bolus to prevent the bolus from moving backward
Compare and contrast the roles that longitudinal and circular muscles play in the movement of food material along and out of the GI tract
Macronutrient absorption is ALWAYS greater than 90%, regardless of how much is consumed because they are a source of calories (feast/famine); and foods high in miacronutrients tend to be high in micronutrients and fiber Micronutrient absorption- small intestine only absorbs natural levels of vitamins and minerals (aka micronutrients obtained from supplements will not be digested)
Compare the efficiency of macronutrient and micronutrient absorption and explain why the difference exists
Hyperglycemia is an elevated fasting blood glucose level. Type 1 diabetes (5-10% of all cases): pancreas stops producing insulin as an autoimmune response, most commonly develops at childhood. Symptoms include excessive urination, thirst, and weight loss. Some genetic predisposition. Dietary recommendations include high complex carbohydrates, especially foods with a low glycemic index (foods high in soluble fiber), and low fat Type 2 diabetes (90-95% of all cases): Body's cells responds less well to the presence of insulin, strongly associated with abdominal obesity and strong genetic predisposition. Symptoms develop gradually, often few outward symptoms. Dietary recommendations are weight loss (10-15% of starting weight) and a diet of moderate to high complex carbohydrates (low glycemic index), and moderate to low fat
Define the term hyperglycemia and match the characteristics (cause and symptoms) and dietary recommendations associated with each of the two types of diabetes
Digestion-the chemical and mechanical breakup of complex food molecules (macronutrients) into smaller molecules that can be absorbed Absorption-the process of bringing smaller molecules inside the body
Define the terms digestion and absorption
Scan ingredient list for the word "whole" in front of grain identified first on list Only whole grain products if specifically state "100% whole grain" Dark or brown bread does not indicate whole grain content When evaluating a food for fiber content, remember: Lots of grain does not mean lots of fiber (e.g. enriched wheat flour does not contain lots of fiber)
Describe how someone can be sure that a product is truly whole grain and other issues to be aware of when evaluating a food for its fiber content
Fiber contains glucose, fructose, and other monosaccharides varying from chains of 10-1,000s
Describe the basic structure of fiber and how it differs from starches
Starches are polysaccharides made up of 1,000s of glucose Starchers have different thickening and gel-forming characteristics, based on the number of glucose molecules in the chain and the degree of branching in the molecule (stickier rice = more highly branched) Found in tuberous vegetables, cereal grains, rice, legumes, nuts, and seeds
Describe the basic structure of starches, how they differ from one another and how that affects their characteristics, and list examples of their dietary sources
Heartburn: consuming chemicals, such as alcohol, caffeine, peppermint, citrus fruits, tomatoes, and nicotine; pressure-related: lying down after eating, rapid eating, consuming high-fat meals, and carbonated drinks can all cause the esophageal sphincter to relax or open leading to acid flowing back into esophagus Ulcers: Large meals increase pressure in stomach and therefore increase acid output, eating irritating foods can also cause discomfort. Ulcers are caused when the mucosal barrier is disrupted.
Describe the diet-related factors related to heartburn and ulcers and explain why they have the effects that they do
Glucose, fructose, and galactose cannot be digested further and are therefore absorbed as the same form. Lactose is digested by the amylase lactase and absorbed as glucose and galactose. Sucrose is digested by the amylase sucrase and is absorbed as glucose and fructose. Starches are broken down by amylases and absorbed as glucose. **Both fructose and galactose can be converted to glucose and fats once they have been absorbed and brought to the liver.
Describe the process of digesting and absorbing dietary carbohydrates and predict in what form each type of dietary carbohydrate will enter the body following digestion and absorption
Serves as a type of "seeking" and "avoidance" behavior: Sweet -> carbs (energy) Salty -> sodium Savory (Umani) -> protein (glutamate) Bitter -> avoid toxins Sour -> to avoid spoiled foods (microorganisms)
Describe the role that taste plays in the digestive process and in health more generally
Cephalic (brain) phase stimulates secretion of saliva and gastric juices to prepare body for D&A Cooking softens tough connective (meat) and fibrous (plants) tissue, increasing the variety of foods we can consume and we'll be more likely to get all essential nutrients because of it
Describe the roles that the cephalic phase and cooking play in digestion
Pancreas- synthesizes and secretes digestive enzymes, bicarbonate Gall Bladder- stores bile that was synthesized in the liver
Describe the roles that the pancreas and gall bladder play in the digestive process
Glycogen is a highly branched polysaccharide of glucose molecules, used as an alternative energy source
Describe the structure of glycogen and how it is used by the body
Increase fiber intake slowly, drain and rinse canned beans before using, rinse dry beans several times Use BEANO to digest gas-causing indigestible carbs in beans and other vegetables
Describe ways to reduce discomfort (gas) associated with high-fiber vegetable and legume consumption
Excess insulin production in response to carbohydrate intake, causing blood glucose to drop too low. Prevented by eating smaller, more frequent meals, each with protein and fat
Describe what can cause hypoglycemia and how to prevent it
Circulatory: all water-soluble compounds enter capillaries Lymphatic: all fat-soluble compounds enter lacteals
Distinguish between the roles that the circulatory and lymphatic systems play in the absorptive process
We have the: cutting incisors of rodents, the pointed canines of carnivores, and the grinding molars of herbivores
Explain how our teeth reflect our being omnivores
Plants use cellulose, a type of fiber (100% glucose) to provide structure and support in its cell walls Seeds are starchy because the starch provides energy during germination
Explain how plants might use simple sugars and complex carbohydrates (why fruits are sweet and seeds are starchy)
Total carbohydrates per serving is in grams of total fiber (g) and total sugars (g) (added and natural) Percent Daily Value a) 300g for carbohydratesb) 25g for Dietary Fiber
Explain the carbohydrate-related components on a food label
Lactose intolerance is caused by low levels or no lactase production->decreased or no digestion of lactose->undigested lactose in the large intestine Symptoms: bloating, diarrhea, gas People at risk: non-caucasians are likely to experience it because they contain the least amount (or no) levels of dairy in traditional food. Symptoms are likely to appear after weaning. Lactase would be found in the poop. The elderly of any ethnic group are at risk because lactase production tends to decrease with age
Explain the cause of lactose intolerance, its symptoms, identify who is likely to experience it and why, and ways to handle it
Prebiotics- "food" for the bacteria that they live on(e.g. fiber) Probiotics- bacteria-containing foods and supplements
Explain the difference between a probioitic and a prebiotic
Indigestion describes common GI tract ailments; like heartburn and gas Indigestibility (Non-digestion) describes the inability to digest Supplement assume people need to take enzyme supplements; however we have more than enough dietary enzymes and, in a typical person, digestion is extremely efficient (>90% of protein, carbs, and fats are digested) Fad diets are wrong making the assumption that undigested food turns into extra weight (is actually excreted)
Explain the difference between indigestion and indigestibility and how that relates to claims associated with fad diets and supplement products
In sugar, glucose and fructose are bonded together while they are separate in honey . They are the same thing in the body. Nectar is sucrose, bees use enzymes to break down the sucrose into its monosaccharides. Honey is already digested, while sucrose still needs to be cleaved by our enzymes.
Explain the differences between honey and sugar (sucrose) and the implications for choosing honey instead of sugar
Regulation issued by the FDA in 1943 requiring refined cereal gran products to be fortified with certain nutrients (iron, thiamin, riboflavin, niacin, and later folate) Good solution to deficiency diseases because almost everyone ate cereal grains Refining removes the bran and germ of the grain, which removes much of the fiber, vitamins, minerals, and phytonutrients as well
Explain the genesis of the federal enrichment program and the ways in which enriched flour is the same and different from whole wheat flour
It used to be assumed that complex carbohydrates (starches) would take longer to be digested, and therefore for their monosaccharide units to be absorbed, than simple sugars because they are bigger molecules. It was discovered that many other factors affect the rate of glucose appearance in the bloodstream Factors than can influence the rate of carbohydrate digestion and absorption include: Length of cooking time(more the starch grains swell, the more quickly it is digested), starch strucuture (more branched = quicker digestion), relative amounts of fructose or galactose v. glucose (fructose and galactose must first be converted to glucose), amount of soluble fiber, fat, and protein in food (all delay stomach emptying, slows D&A)
Explain the history of the development of the glycemic index and list and explain the factors that can influence the rate of carbohydrate digestion and absorption
Primary function is to provide energy in the form of glucose DRIs recommend that 45-65% of the total calories in our diets come from carbohydrates (to power the brain and CNS, as well as because foods naturally rich in carbs tend to be great sources of micronutrients and fiber) DRIs recommend that added sugars amount to less than 25% of total calories because most foods high in added sugars are nutrient poor
Explain the primary function of digestible carbohydrate in the body, list the DRI for total carbohydrate consumption and for added sugars, and explain the rationale for each
Created as a way to compare different foods' effects on blood glucose levels Determined by feeding test subjects the amount of that food (at one time) that provides 50g of carbs, then drawing their blood over a 2 hour period and blood glucose levels are plotted against time and compared to a standard (50g of pure glucose) Significant relative to weight loss, in theory, the more quickly blood glucose levels rise after eating the more likely they are to fall quickly and go lower, producing a more rapid return to hunger and lack of energy Limitations: we don't always eat a food by itself, we don't eat the amount of food used in the glycemic index test, the lists vary widely, and temperature of the food can affect the GI Best way to use it is to be aware of foods with a naturally low GI (<55), especially legumes, and include them more frequently in your diet than foods with higher GIs (>70)
Explain the purpose of the glycemic index, how it is determined for an individual food, and describe its potential significance, limitations, and appropriate use
Liver- screens for unwanted compounds the small intestine has let in (e.g. toxins) and converts absorbed/desirable compounds into other forms (e.g. fructose->glucose) Kidney- filter the blood by excreting absorbed, water-soluble compounds and water-soluble waste products of metabolism, control nutrient levels by increasing/decreasing excretion
Explain the roles that the liver and kidney play in processing and/or eliminating absorbed compounds
Highly specialized type of circular muscle found in-between each organ in the GI tract that acts as a valve to control the movement of the food material from organ to organ (e.g. between esophagus and stomach-prevent backflow; between stomach and small intestine, small intestine and large intestine- limit the rate of flow into the next organ)
Explain the structure, function, and location of sphincters
Peristalsis is the muscular movement that propels food (bolus) along the GI tract
Explain what peristalsis is
Type 2 diabetes often goes unnoticed because there are few outward symptoms, over years of gradual weight gain. Rates are rising in the US because of rising obesity rates. Some potential effects include blindness, amputations (decreased awareness of injury), cardiovascular and kidney disease
Explain why type 2 diabetes often goes unnoticed, why rates are rising in the US and describe the potential effects of the disease
Make the assumption that neutralization of chyme occurs in the stomach, and also wrong by claiming that fat is formed when energy (calories) are not available to break down fat
Identify and explain the inaccuracies related to digestion and absorption found in popular fad diet plans that focus on the principle of "food combining"
Were popular because they "worked" over the short term; causing rapid weight loss, palatable "forbidden" fatty foods were allowed, high fat and protein foods produced satiety, limited choices, appealed to men, gave excuse to avoid vegetables, and reduced consumption of high-calorie junk food. Water loss in urine, induced by ketosis lead to short-term weight loss but not effective because difference is weight-loss disappears after one year
Identify reasons why carbohydrate restricted diets became so popular, explain why they work over the short term and whether there is evidence for their effectiveness over the long term
Bran (outer covering): rich source of niacin, thiamin, riboflavin, magnesium, phosphorus, iron and zinc, contains most of the plants' fiber Germ (plant to-be): concentrated source of niacin, thiamin, riboflavin, vitamin E, magnesium, phosphorus, and healthful unsaturated fats Endosperm: contains majority of the plant's protein and carbohydrate
Identify the 3 parts of a grain kernel, and their primary nutrient constituents
Short-term energy storage: conversion to glycogen (functions as an energy source for muscle during fight/flight response while in the liver it provides energy for the brain and CNS overnight) Long-term energy storage: conversion to fat (excess glycogen in liver converted to fat)
Identify the two potential fates for glucose that isn't used immediately for energy
Manufacturers could add inulin (chicory root extract), oligofructose, polydextrose, modified wheat starch, soy fiber, and sugarcane fiber Degree to which these purified fibers will have similar effects remains largely unknown The health benefits specific to soluble fiber require it to be viscous (gooey). Most of the purified soluble fibers (e.g. inulin) are not
Identify ways by which manufacturers can add purified fiber to foods and discuss what is, or is not known, about their healthfulness as compared to whole food fiber sources
Part of GI tract: esophagus, stomach, small intestine, large intestine Related to GI tract: liver, gallbladder, and pancreas
Identify which organs are part of the GI tract itself and which are related to its function
***Need background information***
In general, you should be able to trace a meal through the GI tract-indicating what is happening to which parts of it along the way. In so doing, you should be able to compare and contrast the roles that each part of the tract and its associated organs play.
Simple carbohydrates: monosaccharides (glucose, fructose, galactose); disaccharides (lactose, sucrose) Complex carbohydrates: polysaccharides (starches, fiber)
List the 2 basic classifications of carbohydrates and their members
Proteases- breaks up proteins; synthesized in stomach, pancreas, small intestine; acts in the stomach and small intestine Amylases- breaks up carbs; synthesized in mouth, pancreas, small intestine; acts in the mouth and small intestine Lipases- breaks up lipids; synthesized in the pancreas and small intestine; acts in the small intestine Hydrochloric acid (HCl)- denatures protein; synthesized in the stomach; acts in the stomach Bicarbonate- neutralization of acidic chyme from the stomach; synthesized in the pancreas; acts in the small intestine Bile- emulsification of lipids; synthesized in liver, stored in the gallbladder; acts in the small intestine
List the 6 chemicals or types of chemicals involved in digestion and identify their functions, sites of synthesis, and sites of action
Fecal matter contains undigested food (mostly fiber), sloughed off intestinal cells, and mostly dead bacteria Excretion requires sufficient bulk pressing against the walls of the colon to stimulate peristalsis, as well as sufficient water for lubrication and softening
List the components of fecal matter and explain what the excretion of waste from the GI tract requires
1. Effect of macronutrients on stomach emptying first time after a meal: Presence of fat, protein, or soluble fiber in a meal will delay stomach emptying (Have some fat/protein in every meal instead of high carb/low fat meals to reduce total calorie intake 2. Effect of large vs. small meals: Bigger meal = quicker emptying (Eat smaller meals to lower calories) 3. Effect of liquids vs. solids: Liquids leave stomach sooner (Don't drink your calories!) 4. Order of macronutrient release from stomach once it begins to empty: Carbs first, then proteins and fat (Have protein and fat in every meal to reduce total calories) 5. Fast v. slow eating: Takes ~20 min. for brain to catch up to stomach (Eat more slowly!)
List the factors that can affect the rate of stomach emptying and predict how that could affect total calorie intake
Men (35g) Women (25g) Americans are not close to meeting these goals because we tend to avoid foods high in fiber, such as legumes, F&V, and whole grains
List the levels of fiber intake that are recommended by the DRIs and explain why Americans are/are not close to meeting these goals
Bacteria can prevent pathogenic growth, maintian a healthy colon through by-products, produce vitamin K, and produce gas
List the roles that bacteria play in health
Mouth: cephalic phase, preparation for rest of GI tract, starts digesting carbs Stomach: begins digestion of protein, slow release of contents into small intestine Small Intestine: emulsifies fats, mixes with longitudinal and circular muscles, uses villi to maximize absorption, diversion of blood supply Different facilitators of activity: ~30 digestive enzymes, ~10 different hormones
List the ways by which the GI tract maximizes efficiency
Glucose ("blood sugar, "dextrose"): used by any cell for energy (brain and CNS use it exclusively), excess glucose is converted to fat in the liver. Naturally occuring in F&V, honey (mono-), lactose and sucrose containing foods (di-) and all starch and some fiber containing foods (poly-) Fructose ("fruit sugar"): some used for energy, or converted to glucose or fat by the liver. Occurs in same monosaccharides as glucose, only found in sucrose and fiber containing foods Galactose: some may be converted to glucose by the liver. Occurs limited in monosaccharides, part of lactose containing foods Lactose ("milk sugar): a dissacharide of glucose and galactose, only found in mammalian milk and its products Sucrose("refined white sugar, "white sugar," "table sugar," "sugar"): dissacharide of glucose and fructose, found naturally in F&V
Match the different types of simple sugars with their monosaccharide components (where applicable), how they are used in the body, major dietary sources and the name of the simple sugar with other name(s) that it goes by, as applicable
Saliva: lubricates food Digestive Enzymes: Amylase- carbs; Lipase- lipids; Protease- proteins Bicarbonate: neutralizes acidic chyme Bile: emulsifies lipids
Match the digestive chemicals saliva, the digestive enzymes, hydrochloric acid, bicarbonate, and bile with the compounds upon which they act and/or their function
Mouth: mechanical breakdown, saliva and amylase secretion, taste detection Esophagus: pathway to stomach, no digestion or absorption Stomach: holding tank, mechanical breakup of chyme, denaturation of protein, protease further breakdown protein, some alcohol absorption Small Intestine: neutralization of acidic chyme, emulsification of lipids, release of digestive enzymes, finish digestive of macronutrients and micronutrients, absorption and reapsorption of nutrients and enzymes Large Intestine: holding tank for waste, bacterial activity, reabsorption of water and absorption of minerals and some vitamin K
Match the mouth, esophagus, stomach, small intestine, and large intestine with the digestive and/or absorptive activity(ies) that take(s) place there
Insoluble Fiber: wheat bran, whole wheat products, legumes, nuts, F&V. Examples: cellulose (100% glucose). Does not dissolve in water and only small amounts can be digested by intestinal bacteria. May prevent or reduce risk of constipation and conditions associated with it (e.g. hemmorrhoids, diverticulitis) and obesity Soluble Fiber: oat bran, oat products, legumes, F&V. Examples: gums, mucilages, pectin. Does dissolve in water (will form gels), slows rate at which stomach empties, larger amounts can be digested (fermented) by intestinal bacteria. Potential health benefits of dietary fiber - Soluble Fiber 1. May help to prevent obesity -Delays stomach emptying→increased satiety 2. Control blood glucose levels -Delays stomach emptying→ delays the rate of glucose absorption from the small intestine 3. Lower serum cholesterol -Binds to cholesterol in GI tract→ prevents absorption→ lower levels in the body 4. Lower dietary fat absorption -Binds to dietary fat in GI tract→ decrease fat absorption -NOT a significant effect because it binds to small amounts
Match the two different types of fiber with their good sources, general characteristics, and health conditions that may be prevented or ameliorated by increasing their intake, explaining the reasons behind the health benefits as well as the potential significance, as applicable
***Need background information***
Predict the consequences of a loss of functioning of a component or components of the GI tract or organs associated with it (e.g. What would happen relative to nutrient digestion or absorption if you had a disease that limited the functioning of your pancreas, liver, stomach, etc.)
Weight gain because the normally undigestible cellulose is broken down into glucose and absorbed Additionally, constipation would result because the newly digested cellulose is unable to provide bulk; as it did when it was a fiber Soluble fiber -> fatty poop
Predict the potential consequences of using a cellulase supplement and explain why, and a soluble fiber supplement that binds to dietary fat and explain why
Eating food without enzymes does NOT make our digestion more difficult b/c we make more than enough digestive enzymes on our own Lack of digestion CANNOT cause obesity
Provide a critique of the claims made by proponents of the raw food diet
Expressed as a percentage of the sweetness of sucrose: Fructose: 173% Sucrose: 100% Glucose: 74% Galactose: 33% Lactose: 16%
Rank the sweetness of fructose, glucose, lactose, and galactose
