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Chapter 3

Carbohydrates

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Photosynthesis

Plants can make their own carbohydrates from the carbon dioxide in the air and water taken from the soil.

Photosynthesis converts energy from sunlight into energy stored in carbohydrates, which the plants uses to grow and be healthy.

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Categories of Carbohydrate

Simple carbohydrates Natural sugars Added (Refined)

sugars

Complex carbohydrates (polysaccharides) Starch Fiber

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Functions of Carbohydrate

Functions as primary source of body’s energy Central nervous system and red blood cells

rely almost exclusively on glucose. Glucose is stored in liver and muscles as

glycogen. Spares protein from being burned for energy Helps body use fat efficiently Part of various materials in body, such as

connective tissue, some hormones & enzymes, and genetic material

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Monosaccharides and Disaccharides

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Relative Sweetness of Sugars and Artificial SweetenersSweetener Rating

Sugars

Lactose 20

Glucose 70 – 80

Sucrose 100

High-fructose corn syrup 120 – 160

Fructose 140

Artificial Sweeteners

Aspartame (Nutrasweet, Equal) 160–220

Acesulfame-K (Sunette) 200

Saccharin (Sweet ’N Low) 200 – 700

Sucralose (Splenda) 600

Neotame 7,000–13,000

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Added Sugars

Added sugars: Sugars added to a

food for sweetening or other purposes, do not include natural sugars

Examples: Granulated white sugar, high fructose corn syrup

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Sugars on the Nutrition Facts Label

The number of grams of “Sugars” includes both natural and added sugars.

To find out if a food contains added sugar, look at the ingredient list.

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Examples of Added Sugars

White sugar (sucrose) High-fructose corn syrup or corn syrup Invert sugar Brown sugar Molasses Honey Powdered sugar Raw sugar Demerara sugar

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Added Sugars and Health

Dental caries (sugar & starch)

Obesity Diabetes Heart Disease Hypoglycemia Hyperactivity in Children

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Glycemic Response

How quickly and how high your blood sugar rises after eating.

Eating mainly foods with a low glycemic response is important for people with diabetes and seems to decrease the risk of heart disease, type 2 diabetes, and colon cancer, as well as enhancing weight management.

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Glycemic IndexGlucose

Corn flakes

Waffles, French-fried potatoes, jelly beans Bagel, white breadWhite sugar, cantaloupeRaisins, tortilla chips, cola soda, ice cream, pizzaRye breadOrange juiceFresh orange, peas, carrotsFresh peach, old-fashioned oatmeal, apple juiceWhite rice, spaghetti, apple, pear, tomato soupSkim milk, low-fat yogurtKidney beansGrapefruit

SoybeansPeanuts

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Lactose Intolerance

An intolerance to milk and most milk products due to a deficiency of the enzyme lactase.

Symptoms often include flatulence and diarrhea within 30 minutes to 2 hours.

Especially prevalent among Asian Americans, Native Americans, African Americans, Latinos, and other groups.

Treatment requires a diet limited in lactose. Most people can drink small amounts of milk

especially if taken with food.

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Complex Carbohydrate: Starch

Made of a long chain of glucoses linked together.

The glucose chains may be straight (amylose) or branched (amylopectin).

Found only in plant foods: grains, legumes, vegetables, some fruits.

Most starchy foods are cooked to make them flavorful and able to be digested.

Gelatinization – When starches are heated, they absorb water and swell in size.

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Structures of Starch and Glycogen

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Fibers

Polysaccharides found in plant foods that the body can’t digest or absorb.

Some fiber is digested by bacteria in the large intestine.

Two types: soluble or viscous fiber

insoluble or nonviscous fiber

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Food Sources of Fiber

Soluble fiber1. Fruits

2. Legumes

3. Oats, barley, and rye

4. Also seeds and vegetables

Insoluble fiber1. Wheat bran, brown

rice, whole grains

2. Vegetables (cabbage, carrots)

3. Fruits

4. Legumes

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Health Effects of Fiber

Soluble, viscous fiber Lowers risk of heart

disease & stroke by: Binding bile

Lowers risk of diabetes and controls diabetes by: Slowing glucose

absorption Also holds moisture in

stools, softening them

Insoluble, nonviscous fiber Alleviates constipation

and lowers risk of hemorrhoids and diverticulosis by: Increasing fecal

weight and speeding fecal passage through the colon

May help with weight management

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If you decide to eat more fiber…..

Do so slowly and Drinks lots of fluids

to give time for your intestine to adapt.

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Whole Grains

Examples: Whole wheat Whole rye Oatmeal Whole oats Whole hulled barley Popcorn Brown rice

Whole grains offer: More nutrients Phytochemicals More fiber

Dietary Guidelines for Americans recommends 3+ servings of whole grains each day.

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Digestion, Absorption, & Metabolism of Carbohydrates

Starch digestion begins in mouth. (enzyme-salivary amylase)

Before being absorbed, carbohydrates must be broken down into monosaccharides.

Enzymes in small intestine (sucrase, lactase, maltase, and pancreatic amylase) ensure that single sugars are absorbed.

In the liver, fructose and galactose are converted to glucose or further metabolized to make glycogen or fat.

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Dietary Reference Intakes

RDA for carbohydrate – 1 year old + 130 grams daily

(minimal amount – you really need 2x) AMDR – 1 year old + 45-65% of kcalories

AI for total fiber 14 g/1000 kcal Men 19 – 50 years old 38 g Men over 50 years old 30 g Women 19 – 50 years old 25 g Women over 50 years old 21 g

DRIs – added sugars < 25% of total kcalories

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Low-Carb Foods

To reduce carbohydrates, manufacturers: Substitute soy flour, soy protein, or wheat

gluten (all higher in protein) for refined flour Substitute artificial sweeteners and/or sugar

replacers (also called polyols) for sugars Add fiber such as wheat bran Add high-fat ingredients such as nuts to

improve flavor and/or add bulk

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5. Sugar Replacers or Polyols

A group of carbohydrates that are sweet and occur naturally in plants.

Examples: sorbitol, xylitol found in sugar-free gums and candy.

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5. Sugar Replacers or Polyols

Benefits: Don’t provide as many kcalories as sugar –

only about 2 kcal/gram. Don’t promote tooth decay. Taste sweet – though not as sweet as sugar. Add bulk and texture to foods. Cause smaller increases in blood sugar and

insulin than sugar. Side effects

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Sugar Replacers or Polyols

Sugar Replacer

Kcal/gram Uses Description*

Mannitol 1.6 Chewing gum, powdered foods, chocolate coatings

•50 to 70% as sweet as sugar.•May causes a laxative effect when 20 grams or more are consumed •Does not absorb moisture so it works well as a dusting powder for chewing gum so the gum doesn’t stick to the wrapper.

Sorbitol 2.6 Candies, chewing gum, baked goods, frozen desserts

•60% as sweet as sugar. gum, baked goods,•May cause a laxative effect when 50 frozen desserts grams or more are consumed.•Cool, pleasant taste.

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Sugar Replacers or Polyols (cont’d)

Xylitol 2.4 Chewing gum, candy

•As sweet as sugar.•Pleasant taste.

Erythritol 0.2 Beverages, chewing gum, candy, baked goods

•Newest polyol.•Very heat stable.•Much less of a laxative effect than other polyols.•Works well with other sweeteners to improve flavor and body.

Isomalt 2.0 Candies, toffee, fudge, wafers

•45 to 60% as sweet as sugar.•Used to add bulk and sweetness to foods.•Very heat stable.•Works well with other sweeteners to improve flavor.

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Sugar Replacers or Polyols (cont’d)

Lactitol 2.0 Chocolate, candies, cookies and cakes, frozen dairy desserts.

•30 to 40% as sweet as sugar.•Mild sweetness with no aftertaste.•Used to add bulk and sweetness to foods.•Works well with artificial sweeteners.

Maltitol 2.1 No-sugar added ice cream, low-carb bagels, candy, chewing gum, chocolate, baked goods.

•90% as sweet as sugar.•Used to add bulk and sweetness to foods.

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Sugar Replacers or Polyols (cont’d)

Hydrogenated Starch Hydrolysates

3.0 Candy, baked goods

•25 to 50% as sweet as sugar.•Used as bulk sweetener in low calorie foods. Performs other functions in foods as well.•Can mask unpleasant off-flavors.•Blends well with flavors. •Works well with other sweeteners.

*All sugar replacers have the following characteristics:• Occur naturally.• Don’t provide as many kcalories as sugar. The average kcalories per gram is 2, compared with 4 kcalories/gram from sugar. • Don’t promote tooth decay.• Cause smaller increases in blood glucose and insulin levels than sugar.

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Nutrition facts and ingredients for sugar-free chocolate bar

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Artificial Sweeteners

Approved Saccharin Aspartame Acesulfame-K Sucralose Neotame

Possibilities Alitame Cyclamate Stevioside

Reduced-Kcal Sweetener Tagatose

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Copyright ©2007 John Wiley & Sons, Inc.