Kin110_Chapter 4 Carbohydrates.docx

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Biomedical Physio & Kines
BPK 110
Gina Whitaker

Kin110 Chapter 4 Carbohydrates: Sugars, Starches, and Fibers Carbohydrates in the Diet Based on the amount of glucose our brain needs per day Recommended carbohydrate intake AMDR = 45–65% of calories Daily Value (for 2,000 kcal) = 300 grams Minimum = 130g/day – meets energy needs Dietary Guidelines (Canada Food Guide) Make at least half your grains whole grains Variety of grains, fruits, vegetables Limit added sugar intake Carbohydrates in our Food Unrefined carbohydrates-sources eaten in their natural form or with minimal processing E.g. fruits, vegetables, whole grains Method of cooking affects the amount of carbohydrates in our food Refined carbohydrates-processed to remove coarse parts of the food E.g. flours (white breads, cookies, muffins, etc), candies, sweetened drinks -can be source of empty Calories Enrichment-a type of fortification which adds back some of the nutrients lost in processing Whole Grains Germ-the embryo or sprouting portion of a kernel grain -contains vegetable oil, vitamins, and minerals Bran-the protective outer layers of whole grains which is a concentrated source of dietary fiber Endosperm-the largest portion of a kernel grain -primarily starch and serves as a food supply for the sprouting seed Whole Grains vs. Refined Grains Products that say whole grain may contain a little or a lot of whole grain -in Canada, products with these stamps must have at least 8g of whole grain per serving Refined grains have most or all of the bran and germ removed -fiber and many vitamins and minerals lost during refining process Refined Sugars-chemically similar to natural sugars found in food but lacks the fiber, micronutrients and phytochemicals that come from natural food sources EMPTY CALORIES • Low nutrient density Types of Carbohydrates Chemical compounds made up of at least 1 sugar molecule Simple Carbohydrates Monosaccharides-single sugar molecules -must be in this form to be absorbed Disaccharides-2 sugar molecules Complex Carbohydrates Polysaccharides-3+ sugar molecules Monosaccharides Glucose-a 6-carbon monosaccharide that is the primary form of carbohydrate used to provide energy in the body -circulates in the blood Fructose-a monosaccharide found in fruits and honey that is composed of six carbon atoms arranged in a ring structure (commonly called a fruit sugar) -makes up about half the sugar in honey and in the high-fructose corn syrup used to sweeten many food and beverages Galactose-a monosaccharide found in fruits and vegetables composed of 6 carbon atoms arranged in a ring structure; when combined with glucose, it forms the disaccharide lactose -part of milk sugar Disaccharides Maltose-a disaccharide made of two glucose molecules linked together Sucrose-a disaccharide commonly known as table sugar made up of glucose linked to fructose Lactose-a disaccharide made of glucose linked to galactose that is found in milk Complex Carbohydrates Glycogen-the storage form of carbohydrates in animals made up of many glucose molecules linked together in a highly branched structure -not a source of carbohydrate we take in our diets -only in form of supplement -found in muscle and liver to be broken down quickly when the body needs glucose Starches-carbohydrates found in plants made up of many glucose molecules linked in straight or branched chains E.g. grain products, legumes, other starchy vegetables Fiber (cellulose)-an insoluble fiber that is in most prevalent structural material of plant cell walls E.g. wheat bran and broccoli How Starches and Fibers are formed in plants Carbon dioxide + water (sunlight/energy) → (glucose (C 6H1206) →starch/fiber) + oxygen Starch-storage form of energy in plants Fiber-plant structure There are no human enzymes present in the small intestine that can break down fiber Soluble Fiber-fiber that dissolves in water or absorbs water and can be broken down by intestinal microflora Insoluble Fiber-fiber that does not dissolve in water and cannot be broken down by bacteria in the large intestine Most sources of fiber contain a mix of fiber types AI = 25 g/day (women), 38 g/day (men) Soluble Fiber Pectins, gums, some hemicelluloses Bacteria in the large intestine can break this down Some absorbed here → Yields approx 3kcal/g Functions Delay gastric emptying Slow transit through GI tract Delay glucose absorption Bind to bile; help decrease cholesterol absorption Some food sources: oats, apples, beans, seaweed Heart healthy fiber Insoluble Fiber Cellulose, some hemicelluloses, lignins Cannot be broken down by bacteria in large intestine Functions Speed transit through the GI tract Delay glucose absorption Increase fecal weight and soften feces to prevent constipation Reduces risk of hemorrhoids (swelling of veins in the rectal or anal area), diverticulitis and appendicitis Some food sources: wheat bran, rye bran, broccoli, celery Promotes intestinal health Effects of ExcesFiber With all its health advantages, high fiber can cause problems, especially in those who drastically increase their intake in a short period of time Sudden increase can cause intestinal gas and bloating If you increase fiber intake, you should increase your water intake to prevent constipation Effect of Fiber on Mineral Absorption Fiber binds certain minerals in the GI tract E.g. wheat bran fiber binds Zinc, Calcium, Magnesium, Iron Can prevent absorption Some tips for increasing fiber intake Choose whole grain breads and pasta Try brown rice instead of white Choose a high fiber (and low sugar) cereal Add fruit to oatmeal, cereal or any snack Add legumes, such as lentils and pinto, navy, kidney and black beans to salads, casseroles, pasta sauce, dips Choose fruit and vegetables with their peel instead of juices Carbohydrate Digestion In the mouth, the enzyme salivary amylase starts breaking starch into shorter polysaccharides In the stomach, salivary amylase is inactivated by acid
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