The types, sources, function and metabolism of them…

What they mean to me!

One of the six Essential Nutrients Your body’s main source of energy

↓ Carbs form the bulk of your diet,

contributing between 55 and 60 percent of your daily calories

Carbs are made from 3 common chemical elements: carbon, hydrogen and oxygen

These elements are combined in many different ways which determines the type of sugar it will be…

These are carbs composed of single sugar units (monomers)

They are the smallest of the carb molecules

They are: (1)GLUCOSE (2) FRUCTOSE (3)GALACTOSE

Same formula, but different structures

C6H12O6

A disaccharide is composed of two monosaccharides. It is formed when two sugars are joined together and a molecule of water is removed.

Disaccharides: (monosaccharides)

1.Maltose = glucose + glucose2.Sucrose = glucose +

fructose3.Lactose = glucose +

galactose

Cells link monomers by a process called dehydration

synthesis (removing a molecule of water)

This process joins two sugar monomers to make a double

sugar

Remove H

Remove OH

H2O Forms

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SUCROSE!! (Table Sugar) •Primary sugar in foods coming from sugar cane or sugar beet

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Fructose!!! •Natural sources of fructose include fruits, vegetables and honey..the SWEETEST of the sugars!

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Lactose!!!•Lactose Intolerant? Inability to break down lactose, because of a lack of the required enzyme lactase in the digestive system•Lactase enzyme decreases with age!

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Maltose!!! •It is found in germinating seeds such as barley as they break down their starch stores to use for food….important part of the “brewing” process.

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Glucose – (Blood Sugar)..Very important biological molecule in your body!

They are made up of many monosaccharides joined together by glycosidic linkages

Very large, often branched, molecules

They tend to be insoluble in water, and have no sweet taste

The 3 main types are Starches and Fibers and Glycogen

Starches = storage form of energy in plants (corn, potatoes etc)

Fibers = these make up the tough, fibrous cell walls of plants. They are found only in plant foods

Glycogen - = secondary long term storage form of energy in animals (muscle/liver)

Starch

Glycogen

Cellulose

Glucose Monomer

Because of their ‘simple structure’ MONO SACCHARIDES AND DISACCHARIDES are considered to be part of the Simple carbohydrates (1 or 2 sugar units)

3-10 sugar units are called Oligosaccharides

Oligosaccharides and POLYSACCAHRIDES (greater than 10 sugar units) are considered to be the complex carbohydrates.

Soluble = can dissolve in water and develop a gel-like consistency

- These fibers are the ones that help lower blood cholesterol levels.

Ex: legumes (peas, beans), oats, rye, barley, plum, broccoli, carrots, sweet potatoes

Insoluble = do not dissolve in water- These are associated with reducing

cancer risks. Ex: Whole grain, wheat, nuts, seeds, potato skins,

flax, bananas, green beans, cauliflower, celery, skins of tomato

• Adding fiber to the diet– Add slowly – Increase water intake

• Food sources: approximate fiber level– Whole grain breads and cereals:

1-2g/serving• Higher level in many cereals

– Vegetables: 2-3 g/serving– Legumes: 5-8 g/serving– Fruits with skins: 2 g/serving– Dried fruit: 2-3 g/serving

© 2008 Thomson - Wadsworth

• Slows gastric emptying time– Aids in weight control – feel full longer– Aids in management of diabetes

• Fiber slows the absorption of glucose and reduces spikes in blood glucose levels

• Adds in weight control– Fiber adds bulk w.o. kcal

Harmful effects of excessive fiber intake Abdominal discomfort, bloating, and gas from

fermentable fibers May interfere with nutrient absorption

There are 4 main Functions:1. Produce Energy = 4 cal of energy/gram2. Spare Proteins = save proteins for

maintaining cellular structure 3. Break down fats = fats cannot be

totally broken down without carbs. Incomplete breakdown → Ketone body formation which is basically an acidic build up (Ketosis).

4. Provide Bulk in the Diet = helps promote normal digestion and elimination of body wastes. Fiber softens stools and also slows the rate at which the stomach empties

The liver transforms them into GLUCOSE which is the universal form of carbs

maltase cleaves maltose into two molecules of glucose

lactase cleaves lactose into a glucose and a galactose

sucrase cleaves sucrose into a glucose and a fructose

Nutrient absorption takes place in the SI Glucose and galactose leave the cells

lining the SI by active transport (pushed through the cell membranes using ATP) – big spike in blood sugars

Fructose leaves by facilitated diffusion, which slows its entry and produces a smaller rise in blood sugar. (no ATP needed to push it through)

Intake Goals:*45-65 % daily kcal from carbs

Select primarily from complex carbohydrates Make half of the complex carbohydrates

whole grainsWHO recommends a maximum of 10% daily

kcal from simple sugarsLimit added sugars

25-38 g fiber/day or 21 – 30 g fiber/day of over 50. max 40 g/day

1. Natural sugars = sugars that occur naturally in foods (ex. Honey)

2. Refined sugars = sugars that have had additives added to it like the sugar found in soft drinks (ex. Table sugar/high fructose corn syrup)

3. No-calorie sweeteners = currently used in foods include saccharin, aspartame and acesulfame-K. Saccharin is about 300 times sweeter than table sugar (sucrose). It's used in several brands of table-top sweeteners (sugar twin/sweet n’low) *Splenda, in canned foods and in low-calorie soft drinks….limited studies/research!

Lacks research Classified as a dietary supplement Not required to have testing and FDA

approval

© 2008 Thomson - Wadsworth

Also called nutritive sweeteners, sugar alcohols, and polyols

Maltitol, mannitol, sorbitol, xylitol, isomalt, and lactitol

Absorbed more slowly and metabolized differently in the body

Low glycemic response Side effects include GI discomfort

© 2008 Thomson - Wadsworth

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