Chapter 4 Reading- Dietary Carbohydrate PDF

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Summary

Notes on the dietary carbohydrates family and notes about monosaccharides, disaccharides, and polysaccharides. ...

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The dietary carbohydrate family includes: - Monosaccharides: single sugars - Disaccharides: pairs of monosaccharides - Polysaccharides: chains of monosaccharides - Monosaccharides and disaccharides (the sugars) are sometimes called simple car-bohydrates, and polysaccharides (starches and fibers) are sometimes called complex carbohydrates. - Hydrogen atoms: one - Oxygen atoms: two - Nitrogen atoms: three - Carbon atoms: four Carbohydrates: compounds composed carbon, oxygen, and hydrogen arranged as monosaccharides or multiples of monosaccharides. Most, but not all, carbohydrates have a ratio of one carbon molecule to one water molecule. The two carbons each have four bonds represented by lines; the oxygen has two; and each hydrogen has one bond connecting it to other atoms. Sugars: simple carbohydrates composed of monosaccharides, disaccharides, or both Monosaccharides: - Glucose - Fructose - Galactose Monosaccharides: carbohydrates of the general formula CnH2nOn that typically form a single ring. The monosaccharides important in nutrition are hexoses, sugars with six atoms of carbon and the formula C6H12O6. Glucose: a monosaccharide; sometimes known as blood sugar in the body or dextrose in foods - Glucose serves as an essential energy source for all the body’s activities Fructose: a monosaccharide; sometimes known as fruit sugar or levulose. Fructose is found abundantly in fruits, honey, and saps - Has the same chemical formula as glucose but structure differs - Occurs naturally in fruits and honey - Soft drinks, cereals, and desserts are sweetened with high-fructose corn syrup Galactose: a monosaccharide; part of the disaccharide lactose - Occurs naturally in foods as a single sugar only in very small amounts - Same numbers and kinds of atoms as glucose and fructose, different arrangement Disaccharides: pairs of monosaccharides linked together - The three disaccharides most important in nutrition all contain glucose Condensation: a chemical reaction in which water is released as two molecules combine to form one larger product - To make a disaccharide, condensation links two monosaccharides together

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A hydroxyl (OH) group from one monosaccharide and a hydrogen atom (H) from the other combine to create a molecule of water (H2O). The two originally separate monosaccharides link together with a single oxygen (O) Hydrolysis: a chemical reaction in which one molecule is split into two molecules, with hydrogen (H) added to one and a hydroxyl group (OH) to the other (from water, H2O). - To break a disaccharide in two, hydrolysis occurs - A molecule of water (H2O) splits to provide the H and OH needed to complete the resulting monosaccharides. Hydrolysis reactions com-monly occur during digestion. Maltose: a disaccharide composed of two glucose units; sometimes known as malt sugar - Maltose is produced whenever starch breaks down—as happens in human beings during carbohydrate digestion. It also occurs during the fermentation process that yields alcohol. Maltose is only a minor constituent of a few foods, most notably barley. - Results from hydrolysis of starch and in fermentation (glucose and glucose) - Glucose + glucose = maltose Sucrose: a disaccharide composed of glucose and fructose; commonly known as table sugar, beet sugar, or cane sugar. Sucrose also occurs in many fruits and some vegetables and grains. - Sweetest of the disaccharides because it has fructose (sweetest of the monosaccharides) - From sugar cane or sugar beets - white or brown (glucose and fructose) - Glucose + fructose = sucrose Lactose: a disaccharide composed of glucose and galactose; commonly known as milk sugar. - Known as milk sugar, lactose contributes half of the energy (kcalories) provided by fat-free milk. - Milk sugar (glucose and galactose) - Glucose + galactose - Principle carbohydrate of milk (milk sugar) - Contributes 30 to 50% of calories in milk depending on fat content - Lactate helps hydrolyzes lactose Lactose, sucrose, and maltose needs glucose Polysaccharides: compounds composed of many monosaccharides linked together. An intermediate string of 3 to 10 monosaccharides is an oligosaccharide. Glycogen is a storage form of energy in the body; starch is the storage form of energy in plants; and fibers provide structure in stems, trunks, roots, leaves, and skins of plants. Both glycogen and starch are built of glucose units; fibers are composed of a variety of monosaccharides and other carbohydrate derivatives.

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Glycogen: an animal polysaccharide composed of glucose; a storage form of glucose manufactured and stored in the liver and muscles. Glycogen is not a significant food source of carbohydrate and is not counted as a dietary carbohydrate in foods. - Food is not a significant source of glycogen - Stores glucose for future use - Glycogen is made of many glucose molecules linked together in highly branched chains Starches: plant polysaccharides composed of many glucose molecules. - All starchy food come from plants - Grains are the richest food source of starch Dietary fibers: n plant foods, the nonstarch polysaccharides that are not digested by human digestive enzymes, although some are digested by GI tract bacteria. - Found in all plant-derived foods (vegetable, fruits, whole grains, and legumes) - Most dietary fibers are polysaccharides - Often described as non-starch polysaccharides Soluble fibers: nonstarch polysaccharides that dissolve in water to form a gel. An example is pectin from fruit, which is used to thicken jellies. - Benefits heart disease, diabetes, caners, and weight management Insoluble fibers: nonstarch polysaccharides that do not dissolve in water. Examples include the tough, fibrous structures found in the strings of celery and the skins of corn kernels. - Benefits GI health Viscous fibers: fibers that have gel-forming properties. Fermentable fibers: fibers that can be digested by bacteria in the GI tract.

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Amylase: an enzyme that hydrolyzes amylose (a form of starch). Amylase is a carbohydrase, an enzyme that breaks down carbohydrates. - Works in the mouth, hydrolyzing starch to shorter polysaccharides and to the disaccharide maltose Carbohydrate digestion ceases in the stomach. The activity of salivary amylase diminishes as the stomach’s acid and protein-digesting enzymes inactivate the enzyme. The stomach’s digestive juices contain no enzymes to break down carbohydrates. Fibers are not digested, but because they linger in the stomach, they delay gastric emptying, thereby providing a feeling of fullness and satiety. Carbohydrate digestion begins again in the small intestine. Satiety: the feeling of fullness and satisfaction that occurs after a meal and inhibits eating until the next meal. Satiety determines how much time passes between meals. The small intestine performs most of the work of carbohydrate digestion - A major carbohydrate-digesting enzyme, pancreatic amylase, enters the in-testine via the pancreatic duct and continues breaking down the polysaccharides to shorter glucose chains and maltose. The final step takes place on the outer membranes of the intestinal cells

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Maltase: an enzyme that hydrolyzes maltose. - Breaks maltose into 2 glucose molecules Sucrase: an enzyme that hydrolyzes sucrose. - Breaks sucrose into one glucose and one fructose molecule Lactase: an enzyme that hydrolyzes lactose. - Breaks lactose into one glucose and one galactose molecule Resistant starches: starches that escapes digestion and absorption in the small intestine of healthy people - Common in whole or partially milled grains, legumes, and just-ripened bananas - Cooked potatoes, pasta, and rice that have been chilled also contain resistant starch. - Similar to insoluble fibers, resistant starch may prevent chronic diseases such as diabetes, colon cancer, and obesity FODMAP: a collective term used to describe fermentable, oligosaccharides, disaccharides, monosaccharides, and polyols (sugar alcohols) that are commonly found in such foods as wheat, onions, some fruits and vegetables, sorbitol, and some dairy. - Attract fluid - increase bloating - As ferment - cause gas and changes in bowel habits such as diarrhea or constipation - Low FODMAP restricts: wheat, onions, sugar alcohols, milk, and legumes - FODMAPS are different types of sugar and fiber that ferment and cause GI symptoms in some people Lactose intolerance: a condition that results from the inability to digest the milk sugar lactose; characterized by bloating, gas, abdominal discomfort, and diarrhea. Lactose intolerance differs from milk allergy, which is caused by an immune reaction to the protein in milk. - Lactase activity is highest immediately after birth - Lactase activity usually declines during childhood and adolescence to 5 to 10% of the activity at birth - Only a small percentage (30%) will retain enough lactase to digest and absorb lactose efficiently throughout life - Declines with age - Lactase may be damage by disease - May be damaged by medicines - May be caused by prolonged diarrhea - May cause malnutrition - May lead to permanent or temporary malabsorption - Rare case- infants may be born with lactase deficiency - Highest prevalence- native North Americans and Southeast Asians - Lowest prevalence- Scandinavians and other northern Europeans Lactase deficiency: a lack of the enzyme required to digest the disaccharide lactose into its component monosaccharides (glucose and galactose)

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Fortunately, many people with lactose intolerance can consume foods containing up to 6 grams of lactose (½ cup milk) without symptoms

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After a meal, blood glucose rises, and liver cells link excess glucose molecules by condensation reactions into long, branching chains of glycogen When blood glucose falls, the liver cells break down glycogen by hydrolysis reactions into single molecules of glucose and release them into the bloodstream. Thus, glucose becomes available to supply energy to the brain and other tissues regardless of whether the person has eaten recently. Glucose fuels the work of most of the body’s cells and is the preferred energy source for brain cells, other nerve cells, and developing red blood cells. Inside a cell, a series of reactions can break glucose into smaller com-pounds that yield energy when broken down completely to carbon dioxide and water Fat cannot make glucose to any significant extent - The amino acids of protein can be used to make glucose to some extent, but amino acids and proteins have jobs of their own that no other nutrient can perform. Gluconeogenesis: the making of glucose from a noncarbohydrate source such as amino acids or glycerol. Protein-sparing action: the action of carbohydrate (and fat) in providing energy that allows protein to be used for other purposes. Ketone bodies: acidic compounds produced by the liver during the breakdown of fat when carbohydrate is not available. Ketosis: an undesirably high concentration of ketone bodies in the blood and urine. Acid-base balance: the equilibrium in the body between acid and base concentrations Insulin: a hormone secreted by special cells in the pancreas in response to (among other things) elevated blood glucose concentration. Insulin controls the transport of glucose from the bloodstream into the muscle and fat cells. Glucagon: a hormone secreted by special cells in the pancreas in response to low blood glucose concentration. Glucagon elicits release of glucose from liver glycogen stores. Epinephrine: a hormone of the adrenal gland that modulates the stress response; formerly called adrenaline. When administered by injection, epinephrine counteracts anaphylactic shock by opening the airways and maintaining heartbeat and blood pressure. Diabetes: metabolic disorder characterized by elevated blood glucose resulting from insufficient insulin, ineffective insulin, or both; the complete medical term is diabetes mellitus. When blood glucose levels are higher than normal, but below the diagnosis of diabetes, the condition is called pre diabetes. Type 1 diabetes: the less common type of diabetes in which the pancreas produces little or no insulin. Type 1 diabetes usually results from autoimmune destruction of pancreatic beta cells.

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Type 2 diabetes: the more common type of diabetes in which the cells fail to respond to insulin. Type 2 diabetes usually accompanies obesity and results from insulin resistance coupled with insufficient insulin secretion. Hypoglycemia: an abnormally low blood glucose concentration. Glycemic response: the extent to which a food raises the blood glucose concentration and elicits an insulin response. Glycemic index: a method of classifying foods according to their potential for raising blood glucose.

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Dental caries: decay of teeth If a person eats three pieces of candy at one time, the teeth will be exposed to approximately 30 minutes of acid destruction. But, if the person eats three pieces at half-hour intervals, the time of exposure increases to 90 minutes. Beverages such as soft drinks, orange juice, and sports drinks not only contain sugar but also have a low pH. Dental plaque: a gummy mass of bacteria that grows on teeth and can lead to dental caries and gum disease Artificial sweeteners: sugar substitutes that provide negligible, if any, energy; sometimes called non-nutritive sweeteners. Nonnutritive sweeteners: sweeteners that yield no energy (or insignificant energy in the case of aspartame). Acceptable Daily Intake (ADI): the estimated amount of a sweetener that individuals can safely consume each day over the course of a lifetime without adverse effect. Generally Recognized as Safe (GRAS): food additives that have long been in use and are believed to be safe. First established by the FDA in 1958, the GRAS list is subject to revision as new facts become known. Sugar alcohols: sugarlike compounds that can be derived from fruits or commercially produced from dextrose; also called polyols. Examples include erythritol, isomalt, lactitol, maltitol, mannitol, sorbitol, and xylitol. Nutritive sweeteners: sweeteners that yield energy, including both sugars and sugar alcohols

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Whole grains, vegetables, legumes, and fruits provide not only starch, fibers, and natural sugars, but also valuable vitamins and minerals. High-fiber foods—especially whole grains—play a key role in managing and preventing type 2 diabetes.When soluble fibers trap nutrients and delay their transit through the GI tract, glucose absorption is slowed, which helps prevent glucose surge and rebound. Dietary fibers also enhance the health of the large intestine. The healthier the intestinal walls, the better they can block absorption of unwanted constituents. Taken with ample fluids, insoluble fibers such as cellulose (as in ce-real brans, fruits, and vegetables) increase stool weight, ease passage, and reduce transit time.

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Research studies suggest that a high-fiber diet protects against cancer of the colon and rectum. - High-fiber and whole-grain foods may help a person to maintain a healthy body weight.Foods rich in fiber tend to be low in solid fats and added sugars and therefore prevent weight gain and promote weight loss by delivering less energy per bite.In addition, as fibers absorb water from the diges-tive juices, they swell, creating feelings of fullness and delaying hunger - The DRI recommends that carbohydrates contribute between 45 and 65 percent of daily energy intake. - Intakes within this range can support healthy body weight and do not contribute to obesity—when added sugar intake is moderate and total energy intake is appropriate. Similarly, added sugars increase energy intake, but need not contribute to obesity—when added sugar intake is moderate and total energy intake is appropriate. When choosing carbohydrates, emphasize a variety of naturally occurring carbohydrates—such as whole grains, legumes, vegetables, and fruits—and limit foods and beverages with added sugars. Powerpoint - The brain uses glucose as its primary energy source - Muscles store simple sugars in the form of glycogen - Glycogen and glucose provide the muscles and tissues with about half the energy they need. Sugars, starches, and fiber are in the carbohydrate family. Grains, legumes, fruit, vegetables, and milk are carbohydrates that deliver nutrients and fiber - Complex carbohydrates → polysaccharide - Sucrose → disaccharide - Galactose → monosaccharide - Lactose → disaccharide - Fructose → monosaccharide - Maltose → disaccharide - Glucose → monosaccharide - Mono: one - Di: two - Saccharide: sugar Monosaccharides - Same numbers and kinds of atoms - Differing sweetness - Glucose: blood sugar - Essential energy source - Part of every disaccharide - Fructose - Sweetest of the sugars - Galactose

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Only in a few foods

Disaccharides - Three pairs of monosaccharides - Maltose: two glucose units - Sucrose: glucose and fructose - Lactose: galactose and glucose - Condensation - Links two monosaccharides together, releases water - A chemical reaction in which two reactants combine to yield a larger product - A hydroxyl (OH) group from one monosaccharide and a hydrogen atom (H) from the other combine to create a molecule of water - The two originally separate monosaccharides link together with a single oxygen - Hydrolysis - Breaks a disaccharide in two, uses water Polysaccharides - Glycogen and starch are examples of polysaccharides - Glycogen is the storage form of energy in animals - Starch is the storage form of energy in plants - If starch is highly branched it is called amylopectin - If starch is unbranched, it is called amylose Dietary Fibers - Structural parts of plants - Differ from starches - Bonds - Not digested - Soluble fibers-- benefits - Insoluble fibers-- benefits - Functional fibers Carbohydrate Digestion - The ultimate goal of carbohydrate digestion is the absorption of glucose - Carbohydrate digestion starts in the mouth. The salivary enzyme amylase works to begin starch digestion - The activity of the above enzyme diminishes in the stomach due to stomach acid - If fiber is present in the stomach delays gastric emptying - The delay in gastric emptying increases one’s feeling of fullness and satiety Intestinal Role in Digestion - Majority of carbohydrate digestion → small intestine - Majority of carbohydrate absorption → small intestine

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Fiber attracts water → large intestine FODMAP digestion produces gas and other symptoms → large intestine Maltase, sucrase, lactase, pancreatic amylase are present → small intestine Fermentation and short-chain fatty acids → large intestine - Fiber attracts water which softens the stool. Benefits of resistant starch as they resist digestion. Limited research suggests low- FODMAP diets improve irritable bowel syndrome.

Carbohydrate Absorption - Active transport - Glucose - Galactose - Facilitate diffusion - Glucose and galactose - Carbohydrate-rich meal - Fructose-specific transporter - Liver - Conversion of fructose and galactose Lactose Intolerance - Lactose activity - Highest immediately after birth - Declines with age - Symptoms of intolerance - Causes of intolerance beyond age - Prevalence - Trait has a genetic component Dietary Changes with Lactose Intolerance - Manage dairy intake rather than restrict intake - GI bacteria - Fermented milk products - Benefits to lactose digestion - Individualized diets - Presence of lactose in non-dairy products - Potential nutrient deficiencies - Potassium, vitamin D, and calcium - Elimination of milk products is not necessary - Most people can tolerate ½ c. servings - Acidophilus milk may be ...