jimtrue.com : school : HS1322 : CH03: Carbohydrates

Posted by Jim True on October 28, 2009 6:31 AM. Last Updated October 28, 2009 6:31 AM

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CH03: Carbohydrates

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

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 burn fat efficiently
• Part of various materials in body, such as connective tissue, some hormones & enzymes, and genetic material
• Fiber
• Promotes normal functioning of intestinal tract
• Lowers blood cholesterol
• You need at least 100-150 grams of carbohydrate daily to spare protein and fat from being burned for fuel and to provide glucose to the central nervous system and red blood cells

Categories of Carbohydrate

• Simple Carbohydrates: (monosaccharides) natural sugars and added (refined) sugars
• Complex Carbohydrates: (polysaccharides), starch and fiber
• Monosaccharides & Disaccharides (figure 3.1), 3 mono: Glucose, Fructose and Galactose
• Disaccharides: 2 units of the former: Sucrose (glucose & fructose), Maltose (glucose & glucose), Lactose (glucose & galactose)
• Sources of glucose: grapes, honey, small or trace amounts in most plant foods
• Sources of fructose: fruits and honey
• Sources of galactose: does not occur alone, has to be with glucose in lactose, milk sugars
• Sources of sucrose: table sugar (99% pure sugar, lots of calories, no nutrients), sugar cane, granulated sugar

Added Sugars

• Sugars added to a food for sweetening or other purposes, do not include natural sugars
• Ex: white sugar, brown sugar, high fructose corn syrup
• Functions of added sugars: prevent spoilage in jams/jellies, provide food for yeast (breads), retain moisture
• Figure 3.3 and 3.5

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
• 4 grams sugar = 1 teaspoon (16 kcalories)

Added sugars and Health

• Dental caries (sugar & starch): dried fruits, bread, cereal, cookies, crackers, potato chips. Do not cause cavities: cheese, peanuts, sugar-free gum, meats and fish
• Obesity
• Diabetes
• Heart Disease
• Hypoglycemia
• Hyperactivity in Children

Lactose Intolerance

• An intolerance to milk and most milk products due to a deficiency of the enzyme lactase
• Symptoms often include flatulence & diarrhea within 30 minutes to 2 hours
• Especially prevalent among asian/native/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
• Don't eat the following: milk, ice cream, cream, ice milk, cheese

Complex Carbohydrate: Starch

• Made of long chains 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

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
• Examples: whole grains, fruits, vegetables, nuts and seeds

Food Sources of Fiber

• Soluble Fiber: beans and peas, some cereal grains (barley, oats), many fruits (apples, pears, grapes, citrus), many vegetables (carrots)
• Insoluble Fiber: Wheat bran, brown rice, whole grains, many vegetables (cabbage, carrots), many fruits, beans and peas, seeds

Health effects of Fiber

• Soluble, Viscous Fiber
• Traps carbohydrates to slow digestion and absorption of glucose
• Binds to cholesterol in the GI tract
• Reduces risk of diabetes and heath disease
• Insoluble/nonviscous fiber
• Increase fecal weight so that feces travels quickly through the colon
• Provides feeling of fullness
• Helps prevent and treat constipation, diverticulosis, and hemorrhoids
• Helpful in weight management

Health Effects of Fiber (cont)

• Reduces risk of type 2 diabetes and helps control diabetes
• A diet high in fruits, vegetables, beans and grains that contain soluble fiber can lower blood cholesterol levels and therefore lower the risk of heart disease
• More research needs to be done on whether fiber helps prevent colon cancer

If you decide to eat more fiber...

• Do so slowly and...
• Drink lots of fluids, to give time for your intestine to adapt

Nutrition Science Focus: Regulation of Blood Glucose

1. High blood glucose (after eating a meal)
2. Pancreas releases insulin (beta cells), take up glucose from blood stream/cells
3. Transport to liver to make glycogen (glycogenesis)
4. Adipose cells make fat (lipgenesis)
5. Low Blood Glucose (inbetween meals)
6. Pancreas releases Glucagon (alpha cells)
7. Breaks down Glycogen to Glucose (glycogenolysis)
8. Achieve Normal Blood Glucose Levels

Dietary Reference Intakes

• RDA for Carbohydrate: 1 year old + 130 grams daily (minimal amount you really need 2x)
• AMDR (acceptable macromolecule distribution range) - 1 year old + 45-65% of kcalories
• AI for total fiber: 14g/1000kcal
• Men 19-50 yo: 38g
• Men over 50yo: 30g
• Women 19-50: 25g
• Women over 50: 21g
• DRIs: added sugars < 25% of total kcalories

Whole Grains

• A Kernel of Wheat, figure 3.12, refined grains, only have endosperm (white flour); whole grains have bran, endosperm and germ
• Examples: Whole wheat, whole rye, oatmeal, whole oats, whole hulled barley, popcorn, brown rice
• Offers more: nutrients, phytochemicals (substances in plants that may reduce cancer and heart disease when you eat more often), more fiber
• Dietary Guidelines for Americans recommends 3+ servings of whole grains each day

Culinary Science

• Gelatinization: when heated starches absorb water and swell in size
• Starchy thickeners: flour, cornstarch, arrowroot, potato starch, rice flour

Artificial Sweeteners

• Approved: saccharin, aspartame, acesulfame-K, sucralose, neotame
• Possibilities: alitame, cyclamate
• Reduced-KCal Sweeteners: tagatose

Sugar Replaces or Polyols

• A group of carbohydrates that are sweet and occur naturally in plants
• Ex: Sorbitol, xylitol found in sugar-free gums and candy
• Benefits:
• Don't provide as many kcals as sugar: only 2/kcal per 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

Digestion, Absorption & Metabolism of Carbohydrates

1. Starch digestion begins in your mouth with enzyme called amylase (in saliva called salivary amylase)
2. Before absorption, carbohydrates must be broken down to monosaccharides
3. Enzymes in your small intestines such as Lactase, Maltase, Pancreatic Amylase, Sucrase, ensure that everything is broken down to monosaccharides for absorbtion

Disclaimer: These are MY notes taken from classroom lectures while I'm in the classroom. While I'm perfectly happy to share my notes with my classmates and I know I take very good notes, you should still make every effort to attend the class and TAKE YOUR OWN NOTES. I will not transcribe everything the instructor says in the classroom, and I will NEVER post pre-exam reviews. My notes will not replace the value of actually attending class and taking your own class notes.I also cannot attest to their accuracy, other than they are what was provided in the lecture; you should not reference my notes as "expert opionion" by any means, and if you notice an error or omission, please do me the favor of e-mailing me with the correction and I will re-post my notes. End of Disclaimer.