Carbohydrates
© 2009 Cengage - Wadsworth
The Chemist’s View of Carbohydrates Carbohydrates are made of carbon, hydrogen and oxygen atoms. These atoms form chemical bonds that follow
the laws of nature. The chemical formula for carbohydrates are similar, Cn(H2O)n In other words, for every carbon, there is a molecule
of water, hence the name “carbo-hydrates” or “hydrated carbons” © 2009 Cengage - Wadsworth
Common Carbohydrates in Human Nutrition
Sucrose (table sugar)
glucose
fructose
Lactose (milk sugar)
Maltose
glucose
Glucose
Galactose
Glucose
Oligo/ Polysaccharides; Starch and Glycogen
Glucose
Fiber
Soluble (fermentable)
Insoluble
Two Monosaccharides: Glucose and Fructose
© 2009 Cengage - Wadsworth
Two Monosaccharides: Glucose & Galactose
© 2009 Cengage - Wadsworth
The Simple Carbohydrates Disaccharides Maltose consists of two glucose units. It is produced during the germination of seeds and fermentation. Sucrose is fructose and glucose combined. It is refined from sugarcane and sugar beets, tastes sweet, and is readily available. Lactose is galactose and glucose combined. It is found in milk and milk products. © 2009 Cengage - Wadsworth
The Complex Carbohydrates Few (oligo-) or many (poly-) saccharides Multiple glucose units linked together in straight or
branched chains.
Glycogen (carbohydrate storage in animals) Storage form of glucose in the body Provides a rapid release of energy when needed
Starches Storage form of glucose in plants
Found in grains, tubers, and legumes © 2009 Cengage - Wadsworth
The Complex Carbohydrates Dietary fibers provide structure in plants, are very diverse, and cannot be broken down by human enzymes. Soluble fibers are viscous and can be digested by
intestinal bacteria (fermentable). These fibers are found in fruits and vegetables. Insoluble fibers are nonviscous and are not digested by intestinal bacteria. These fibers are found in grains and vegetables.
© 2009 Cengage - Wadsworth
© 2009 Cengage - Wadsworth
The Complex Carbohydrates Fiber Sources Dietary fibers are found in plant foods.
Functional fibers are health-benefiting fibers that
are added to foods or supplements. Total fiber considers both dietary and functional fibers.
Resistant starch is starch that escapes digestion
in the small intestine and that may be fermented in the large intestine. © 2009 Cengage - Wadsworth
The Complex Carbohydrates Resistant Starch Starches physically inaccessible to digestive
enzymes: partly milled grains & seeds Starch resistant to digestion due to the nature of the starch granule: raw potato, unripe banana, some legumes and high amylose starches (e.g., high amylose corn) Starch that forms from retrograded amylose & amylopectin during food processing: e.g. potatoes, bread, cornflakes Starch produced by chemical modification
Glucose in the Body Primary role Energy
Red blood cells and cells of the nervous system
require glucose for energy
Other Roles Glycoproteins (e.g. intrinsic factor) Glycolipids
© 2006 Thomson-Wadsworth
Glucose in the Body The body stores glucose as glycogen in liver
and muscle cells. The body uses glucose for energy if glycogen stores are available.
© 2009 Cengage - Wadsworth
Glucose in the Body If glycogen stores are depleted, the body
makes glucose from protein. Gluconeogenesis is the conversion of protein
to glucose. Protein-sparing action is having adequate carbohydrate in the diet to prevent the breakdown of protein for energy.
Body fat is metabolized more efficiently
when some carbohydrate is available © 2009 Cengage - Wadsworth
Glucose in the Body In fasting, starvation or situations of
carbohydrate depletion, the body can obtain energy by mobilizing fat stores. In the absence of carbohydrate, however this
can lead to a condition known as “ketosis”.
The body can use glucose to make body fat
when carbohydrates are consumed excessively. © 2009 Cengage - Wadsworth
Glucose in the Body The Constancy of Blood Glucose The Regulating Hormones
Insulin moves glucose into the cells and helps to lower blood sugar levels. Glucagon brings glucose out of storage and raises blood sugar levels. Epinephrine acts quickly to bring glucose out of storage during times of stress.
Blood glucose can fall outside the normal range
with hypoglycemia or diabetes.
© 2009 Cengage - Wadsworth
Glucose in the Body The Constancy of Blood Glucose Maintaining Glucose Homeostasis
Low blood glucose may cause dizziness and weakness. High blood glucose may cause fatigue. Extreme fluctuations can be fatal.
Normal blood glucose levels (fasting)
70-100 mg/dl
© 2009 Cengage - Wadsworth
Maintaining Blood Glucose Homeostasis
© 2009 Cengage - Wadsworth
Glucose in the Body Diabetes Type 1 diabetes is the less common type with
no insulin produced by the body. Type 2 diabetes is the more common type where fat cells resist insulin. Prediabetes is blood glucose that is higher than normal but below the diagnosis of diabetes. Hypoglycemia is low blood glucose and can
often be controlled by dietary changes. © 2009 Cengage - Wadsworth
Health Effects and Recommended Intakes of Sugars Dental caries Caused by bacteria residing in dental plaque
Bacteria ferment the sugars from food and
the breakdown of starches in the mouth, producing an acid that erodes tooth enamel
Factors involved Length of time sugars are in contact with the teeth. Stickiness of the sugar-containing food © 2009 Cengage - Wadsworth
Health Effects and Recommended Intakes of Sugars Excessive sugar intake can contribute to the
development of body fat by adding to excess kcalorie intake. Sugar may be able to alter blood lipid levels and contribute to heart disease in some. E.g. a high intake of simple carbohydrates is
associated with elevations of blood triglycerides © 2009 Cengage - Wadsworth
Health Effects and Recommended Intakes of Sugars Excessive intakes of sugar may displace nutrients and contribute to obesity. “Natural” does not always mean nutritious. (e.g., honey) Foods with added sugars are part of discretionary
kcalories Foods with added sugars have sugars listed as a first
ingredient.
Naturally occurring sugars from fruits, vegetables and milk are acceptable sources. © 2009 Cengage - Wadsworth
Health Effects and Recommended Intakes of Sugars There is no scientific evidence that sugar causes misbehavior in children and criminal behavior in adults. Sugar consumption per se does not cause diabetes.
© 2009 Cengage - Wadsworth
Health Effects and Recommended Intakes of Sugars Recommended Intakes of Sugars The USDA Food Guide states that added sugars
can be included in the diet as part of discretionary kcalories. Dietary Guidelines for Americans 2010:
Limit SoFAS (Solid Fats and Added Sugars)
DRI suggest added sugars should contribute no
more than 25% of a day’s total energy intake.
© 2009 Cengage - Wadsworth
Look for these ingredients as added sugars on food labels Brown sugar
Invert sugar
Corn sweetener
Lactose
Corn syrup
Maltose
Dextrose
Malt syrup
Fructose
Molasses
Fruit juice concentrate
Raw sugar
Glucose
Sucrose
High-fructose corn syrup
Sugar
Honey
Syrup © 2009 Cengage - Wadsworth
Health Effects and Recommended Intakes of Starch and Fibers Health Effects of Starch and Fibers May be some protection from heart disease and
stroke
Soluble fibers bind with and increase excretion of bile. Since bile is made from cholesterol, the body must use its cholesterol stores to make new bile acids. As a result, blood cholesterol levels are decreased. Fiber may also displace fat in the diet.
© 2009 Cengage - Wadsworth
Health Effects and Recommended Intakes of Starch and Fibers Reduce the risk of type 2 diabetes by decreasing
glucose absorption Enhance the health of the GI tract which can then
block the absorption of unwanted particles May protect against colon cancer by removing potential cancer-causing agents from the body
© 2009 Cengage - Wadsworth
Dietary Fiber Soluble Fiber
Insoluble Fiber
Oatmeal
Whole wheat bread
Oat bran
Barley
Nuts & seeds
Brown rice
Most fruit (e.g.,
Couscous
strawberries, blueberries, pear, apples) Dry beans & peas
Bulgur or whole grain
© 2009 Cengage - Wadsworth
cereals Wheat bran Seeds Most vegetables Fruits
Health Effects and Recommended Intakes of Starch and Fibers Promote weight control Complex carbohydrates provide less fat and added sugar. High fiber increases viscosity of GI contents & results in slower transit time (greater time in contact with satiety receptors)
© 2009 Cengage - Wadsworth
Health Effects and Recommended Intakes of Starch and Fibers Recommended Intakes of Starch and Fibers RDA for carbohydrate is 130 g per day AMDR for carbohydrate is 45-65% of total kcalories Dietary Guidelines for Americans 2010 encourage a variety of whole grains, vegetables, fruits and legumes daily.
© 2009 Cengage - Wadsworth
Health Effects and Recommended Intakes of Starch and Fibers Recommended Intakes of Fiber FDA: 25 grams for a 2,000-kcalorie diet. DRI: 14 g per 1000 kcalorie intake (28 grams for a
2,000 kcalorie diet) American Dietetic Association: 20-35 g per day. World Health Organization suggests no more than 40 g per day.
© 2009 Cengage - Wadsworth
Health Effects and Recommended Intakes of Starch and Fibers Harmful effects of excessive fiber intake
Displaces energy and nutrient-dense foods Abdominal discomfort and distention May interfere with nutrient absorption
© 2009 Cengage - Wadsworth
© 2009 Cengage - Wadsworth
Comparison of Bread Labels
© 2009 Cengage - Wadsworth
Voluntary Whole Grain Stamps from the Whole Grain Council
Whole grain stamp – for products offering ½ serving
or more of whole grain 100% whole grain stamp – for products where ALL of the grain is whole grain http://www.wholegrainscouncil.org
