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Chapter ThreeThe Carbohydrates: Sugars, Starch & Fiber
NUT SCI 242 Spring 05 © Karen Lacey, MS ,RD, CD
I. Carbohydrate Basics
Compounds composed of carbon, hydrogen, and oxygen atoms.
The primary role: energy source – 4 cal/gram
Ideal fuel for the bodyTwo types:
– Simple– Complex
II. Simple Carbohydrates
Structure: – A single sugar (Monosaccharide)– A pair of two sugars linked together
(Disaccharide)6 carbons in ring form All are chemically similar to glucose and
can be converted into glucose
A. Monosaccharides
1. Glucose “blood sugar”
used for energy Found in fruits,
vegetables, honey
2. Fructose Sugar of fruits,
honey, maple & corn syrup
Cont’d
3. GalactosePart of milk
sugar
B. Disaccharides (double sugars)
Two sugar units linked together
1. SucroseGlucose +
FructoseTable Sugar
Cont’d
1. Lactose Glucose + Galactose Milk sugar
2. Maltose Glucose + Glucose Product of starch
breakdown
After eating sugar, intestinal enzymes split the double sugars into single sugars.
C. Sugar & Health Guidelines recommend limiting
sugar in the form of sweets to less than 10% of calories.
Sugar is an “empty calorie” food. Evidence on sugar
– Causes dental decay & gum disease
– Low nutrient content– Promotes and maintains
obesity
D. Keeping Sweetness in the Diet
Read food labels for clues on sugar content
Use less added sugar Limit soda, surgary
cereals, candy Choose fresh fruits or
those canned in water or juice
III. Complex Carbohydrates
Long chains of sugars (glucoses) arranged as starch or fiber
Also called polysaccharidesTwo types
– Starch– Fiber
A. Starch A plant
polysaccharide composed of hundreds of glucose molecules, digestible by human beings
The storage form of glucose in plants
Found in grains, vegetables, legumes
B. Adding Whole Foods to the Diet
A whole food is one that is altered as little as possible from the plant or animal tissue from which it was taken.
Whole foods have a nutritional advantage over their empty-calorie processed forms.
Parts of a Wheat Kernel
Germ: the nutrient-rich and fat-dense inner part of a whole grain
Endosperm: the bulk of the edible part of a grain; contains starch & protein
Bran: the fibrous protective covering of a whole grain & the chief source of fiber
Husk: the outer, inedible covering of a grain
C. The Bread Box Terms:
– Refined: the process by which the coarse parts of food products are removed
– Enriched: the process by which the B vitamins thiamin, riboflavin, niacin, folic acid & the mineral iron are added to refined grains & grain products at levels specified by law
Cont’d
– Fortified Foods: foods to which nutrients have been addedCommonly eaten foods are fortified
with nutrients such as iodine, vitamin D or calcium to help prevent a nutrient deficiency or to reduce the risk of chronic disease
– Whole grains: a grain that is not refined
D. Fiber
The indigestible residues of food, composed mostly of polysaccharides
Yields few calories, if any Helps support plant structure Two types:
– Insoluble– Soluble
Cont’d
Insoluble fiber– Does not dissolve in water– Cellulose, hemicellulose & lignin
Soluble fiber– Either dissolves or swells in water– Pectin, gums, mucilages & some
hemicelluloses
E. Health Effects of Fiber Fiber in the diet is associated with several
diseases– Digestive tract: Maintain health & function– Cardiac: Helps control blood cholesterol– Diabetes: Moderates blood glucose levels– Cancer: Hinders action of cancer-causing
agents– Obesity: May help prevent obesity
Different forms of fiber have different health effects
Cont’d TOO MUCH FIBER?
– No RDA; recommended is 20-35 grams per day
– Too much fiber can:Cause dehydrationCarry minerals out of the bodyCause nutrient and energy deficiencies
from eating too much bulk in the malnourished, elderly and children
F. Adding Fiber to Your Diet
Foods that are high in fiber include:– Plant foods
(especially those with skins & seeds)
– Whole grains– Fruits– Vegetables
IV. How the Body Handles Carbohydrates
A. Maintaining blood glucose levels
B. Hypoglycemia
C. Hyperglycemia (Diabetes)
V. Alternatives to Sugar
Minimal or no calories Many times sweeter than sugar Current products:
– Saccharin– Aspartame– Sucralose– Acesulfame
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