Simple sugars, complex carbohydrates, and fiber. The Carbohydrates Simple sugars, complex carbohydrates, and fiber.

Carbohydrates Body’s preferred source of energy Cells of body use the carb. Glucose Most food sources of carbohydrates are plant sources Why? One animal source of carbs

Classifying Carbohydrates Simple Sugars Monosaccharides Disaccharides Complex Carbohydrates Starch Glycogen Cellulose (a form of fiber)

Carbohydrate Intake Recommended intake of carbohydrate 45-65 % daily kcal should come from carbohydrates RDA ~130 g carbohydrate/day Maximum 25% daily kcal from added sugars ~500 kcal/day Controversial with nutritionists WHO recommends a maximum of 10% daily kcal from simple sugars

Fiber Intake General recommendations: 25g (women) - 38 g (men) fiber/day Amount recommended drops after age 50 to: 21 g (women) - 30 g (men) fiber/day Maximum intake recommended: ~40 g/day Why is too much not a good thing?

Evaluating Your Intake Intake Goals:* 45-65 % daily kcal from carbohydrate Select primarily from complex carbohydrates Make half of the complex carbohydrates whole grains Limit added sugars 25-38 g fiber/day or 21 – 30 g fiber/day of over 50. max 40 g/day *Computer programs may suggest different values

Carbohydrates All nutritionally important sugars are hexose sugars All hexose sugars have the same chemical formula

Simple Carboydrates Monosaccharides – C6H12O6 Glucose Fructose Galactose Glucose, fructose and galactose all have the same chemical composition, but they very different properties! Why?

Glucose

Glucose Also called  dextrose Sugar to which all others are converted after absorption Occurs in the liver Cell’s preferred source of energy Under most conditions the brain requires glucose as an energy source Natural food sources of glucose are limited. Honey contains glucose

Fructose Also called fruit sugar Sweetest of all the carbohydrates Sources Fruits Honey Added - High fructose corn-syrup is often used to sweeten foods Too much fructose can draw water into GI tract and cause GI distress

Galactose Not very sweet Not found naturally in many foods Found in “lactaid” milk

Disaccharides Disaccharides are made by joining two monosaccharides by a chemical bond

Disaccharides There are three disaccharides: Sucrose Maltose Lactose Glucose is a component of each disaccharide.

Disaccharides 3 disaccharides Sucrose = glucose--fructose Maltose = glucose--glucose Lactose = glucose--galactose Chemical bond

Disaccharides Maltose = glucose-____________ Not in many foods Made when starch breaks down Find some in barley Made during fermentation – alcohol synthesis

Disaccharides Maltose digestion occurs in the SI Absorption Digestion breaks the bond between the glucose molecules. Requires the presence of the SI enzyme maltase. maltose  _________ + ___________ Absorption

Disaccharide Digestion maltase

Disaccharides Sucrose = glucose-____________ Food sources Table sugar Made from sugar beets and sugar cane Fairly sweet Food sources

Disaccharides Sucrose digestion occurs in SI Absorption Enzyme needed = sucrase Sucrose  _________ + __________ Absorption

Disaccharides Lactose = glucose- ___________ Also called milk sugar Food Sources Milk Ice cream, sherbet Smaller amounts in cheese and yogurt

Disaccharides Lactose digestion in SI Absorption Enzyme required is lactase Lactose  glucose + ___________ Absorption

Lactose Intolerance Who in class is lactose intolerant? Populations at greatest risk: Asian - ~ 80% African descent - ~ 75% Hispanic -~ 50% Native Americans - ~ 80%

Lactose Intolerance Some refer to this as lactose maldigestion Biological cause of lactose intolerance SI does not make enough (or any) lactase As a result the lactose is not digested Undigested lactose cannot be absorbed Amount of lactase made decreases in many people as they age

Symptoms of Lactose Intolerance Undigested lactose: Draws water into GI tract Results in bloating, diarrhea, cramps Metabolized by bacteria in the colon Bacteria thrive and make gases and acids These add to the GI distress

Managing Lactose Intolerance Limit intake of milk products Includes: milk, ice cream, cottage cheese, sherbet, yogurt with added milk solids To limit the amount of lactose in GI tract at any time Ingest milk products with other foods Spread intake over the day

Managing Lactose Intolerance Many can eat: Hard cheeses Cheese making process removes much of lactose Lactose levels decrease as cheeses age Yogurt and kefir – fermented milk products Fermentation process breaks down much of the lactose Lactase treated milks – Lactaid milk

Monosaccharide- Summary Monosaccharrides are single sugars All isomers of C6H12O6 Glucose serves as the essential energy source, and is commonly known as blood sugar or dextrose. Fructose is the sweetest, occurs naturally in honey and fruits, and is added to many foods in the form of high-fructose corn syrup. Galactose rarely occurs naturally as a single sugar.

Disaccharide - Summary Disaccharides are pairs of monosaccharides, one of which is always glucose Condensation reactions link monosaccharides together. Hydrolysis reactions split molecules and commonly occur during digestion. Maltose consists of two glucose units. It is produced during the germination of seeds and fermentation. Sucrose is fructose and glucose combined. It is made from sugarcane and sugar beets, and tastes sweet. Lactose is galactose and glucose combined. It is found in milk and milk products. © 2008 Thomson - Wadsworth

Polysaccharides All polymers of glucose We will consider: Glycogen Starch Cellulose

Polysaccharides Polysaccharides differ in: Function and sources # glucose Type of bonding between glucose Incidence of branching or coiling

Polysaccharides Glycogen Function: animal storage form of glucose Found, made, and used in: Liver ……. Muscle cells …. Stores …..

Polysaccharides Structure of glycogen ~ million glucose joined by alpha glycosidic bonds Highly branched Branch every 5-6 glucose Why branching is important Food sources: none We make glycogen from extra glucose

Starch – Complex Carbohdrate Function: plant storage form of glucose All food sources of starch are plant sources Goal is for the majority of the carbohydrates in your diet to be from starch Starch rich foods include:

Starch Structure of starch ~ 100,000 glucose joined by alpha glycosidic bonds Two Forms Branched form - amylopectin branches every ~20 glucose Coiled form - amylose

Starch Starch digestion and absorption Mouth Stomach SI

Polysaccharides Cellulose Function: structural component of all plant cells Structure Many glucose bonded by beta glycosidic bonds We do not have the enzymes needed to digest beta bonds in cellulose Long, unbranched chains that coil around each other to form fibers Very strong

Polysaccharides Cellulose One of the polysaccharide fibers We do not have the enzymes needed to digest the bonds in fibers.

Fiber Structural components of plants we cannot digest Classes of fibers: Cellulose and hemicellulose Pectins Gums and mucilages Lignins

Another way to classify fibers Soluble fibers – viscous, fermentable by bacteria Gums, mucilages, pectins, some hemicellulose Food sources Fruits Oat bran, Legumes Insoluble fibers – nonviscous, not digested by intestinal bacteria Cellulose and lignins Wheat bran, corn, rye, most vegetables…

Functional Fibers Soluble fibers help lower cholesterol levels How? Soluble fibers bind/trap bile in the SI As a result the bile is excreted and not recycled Bile is made from cholesterol Therefore, the liver uses cholesterol to make more bile This lowers cholesterol levels

Benefits of fiber in diet Promotes bowel health Reduces risk of diverticulitis/osis and appendicitis Softens stools (keeps you regular) ?? Decreased risk colon cancer Soluble fiber reduces cholesterol levels

Diverticular Disease

Benefits of fiber in the diet Slows gastric emptying time Aids in weight control – feel full longer Aids in management of diabetes Fiber slows the absorption of glucose and reduces spikes in blood glucose levels Adds in weight control Fiber adds bulk w.o. kcal

Fiber Adding fiber to the diet Food sources: approximate fiber level Add slowly Increase water intake Food sources: approximate fiber level Whole grain breads and cereals: 1-2g/serving Higher level in many cereals Vegetables: 2-3 g/serving Legumes: 5-8 g/serving Fruits with skins: 2 g/serving Dried fruit: 2-3 g/serving

© 2008 Thomson - Wadsworth

Too much fiber in the diet Harmful effects of excessive fiber intake Displaces energy and nutrient-dense foods from the diet Bulk without nutrients Abdominal discomfort, bloating, and gas from fermentable fibers May interfere with nutrient absorption

Sugar and Health Many high sugar foods are a source of empty calories All carbohydrates increase risk of dental caries (cavities) Longer the sugar/starch is on the teeth the greater the risk

Sugar Myths Sugar and: Obesity Heart disease Hyperactivity Extra/empty calories from sugar are converted to fat and can contribute to obesity Heart disease High sugar diets have been shown to alter blood lipid levels Hyperactivity Criminal behavior

Carbohydrate Digestion in the GI Tract Copyright 2005 Wadsworth Group, a division of Thomson Learning

Alternatives to Sugar © 2008 Thomson - Wadsworth

Artificial Sweeteners Also called nonnutritive sweeteners Saccharin Used primarily in soft drinks and as a tabletop sweetener Rapidly excreted in the urine Does not accumulate in the body Has been removed from list of cancer-causing substances © 2008 Thomson - Wadsworth

Artificial Sweeteners Aspartame General purpose sweetener Warning about phenylalanine for those with PKU Controversial finding that aspartame may have caused cancer in rats Excessive intake should be avoided by those with epilepsy © 2008 Thomson - Wadsworth

Artificial Sweeteners Acesulfame-K (acesulfame potassium) Research confirms safety Sucralose Made from sugar Passes through digestive tract Neotame Most recent on the market Very sweet Phenylalanine not an issue © 2008 Thomson - Wadsworth

Artificial Sweeteners Tagatose Used for foods and beverages Provides less kcalories than sugar High doses can cause flatulence and loose stools. Alitame and Cyclamate Pending FDA approval Approved in other countries © 2008 Thomson - Wadsworth

Stevia – An Herbal Alternative Lacks research Classified as a dietary supplement Not required to have testing and FDA approval © 2008 Thomson - Wadsworth

Sugar Replacers Also called nutritive sweeteners, sugar alcohols, and polyols Maltitol, mannitol, sorbitol, xylitol, isomalt, and lactitol Absorbed more slowly and metabolized differently in the body Low glycemic response Side effects include GI discomfort © 2008 Thomson - Wadsworth

© 2008 Thomson - Wadsworth