Chapter 4 carbohydrates

Carbohydrates Classification– Soluble – Insoluble... Dietary Fiber• Soluble fibers • Insoluble fibers... Dietary Fiber• Soluble fibers: – dissolve in water – form gels viscous – can be

Carbohydrates

Carbohydrates

Carbohydrates Classification

– Soluble – Insoluble

Chemist’s view of CHO

• Carbohydrates are made of carbon, hydrogen and oxygen atoms

• These atoms form chemical bonds

Atoms and Bonds

• Glucose

• Fructose

• Galactose

Glucose

Hexagon

Glucose

• Pairs of Monosaccharides

• One is always GLUCOSE

• Maltose

• Sucrose

• Lactose

Simple Carbohydrates

How the Disaccharides are

formed ?

Condensation

Hydrolysis

Complex Carbohydrates

Complex Carbohydrates

• Few (oligosaccharides) or many

(polysaccharides) glucose units

bound/linked together in straight or branched chains.

Complex Carbohydrates

• Starch - amylose & amylopectin

• storage form in plants

• Energy yielding - 4 kcal/g

• Glycogen - storage form in animals

but is not a dietary source of CHO

• Dietary fibers Non-energy yielding

Glycogen and Starch

Starch - Amylopectin

Starch - Amylose

Dietary Fiber

• Structural parts of plants not

subject to digestion by human

digestive enzymes

• Some are digested by GI bacteria

Dietary Fiber

• Soluble fibers

• Insoluble fibers

Dietary Fiber

• Soluble fibers:

– dissolve in water

– form gels (viscous)

– can be digested by intestinal bacteria

(fermentable)

– Found in fruits and vegetables (oat, barley,

legumes, citrus fruits)

– Protect against Heart Disease and Diabetes.

Water Soluble Fiber

• Functions:

– Delay GI transit

– Delay Glucose Absorption

– Lower Blood Cholesterol

Dietary Fiber

• Insoluble fibers:

– Do not dissolve in water.

– Do not form gels (nonviscous).

– Not digested by intestinal bacteria

– Found in whole grains and vegetables.

Non-Water Soluble Fiber

• Functions:

– Accelerate GI transit

– Promotes bowel movement

– Alleviate constipation

– Slow starch hydrolysis

– Delay glucose absorption

Fiber Sources

• Found in plant foods.

• Functional fibers are health-benefiting

fibers that are added to foods or

supplements.

Starch and Cellulose

Carbohydrates in Foods

Glucose in the Body

• Primary role: ENERGY

• Attach to proteins and fats, change

their shape and function.

• Glucose main fuel for the brain and

the Nervous System and red blood cells.

• Blood glucose levels: 70-100 mg/dL.

Beta cells

Alpha cells

If we are out of the normal

– weakness, tachicardia, sweating,

anxiety, hunger, trembling.

Glycemic Index

• Classifies foods according to their

potential for raising blood glucose

Health Effects of Simple

Dental Caries

• Simple sugars and starches start

digestion (breakdown) in the mouth

• CHO sticks to teeth or stays in

mouth and produce acids that

damage the teeth

• Baby bottle tooth decay syndrome

Recommended Intakes

of Sugar

• Dietary Guidelines

–limit intake of foods and beverages that are

high in added sugars.

Health Effects of Starch and Fibers

• May be some protection from heart

disease and stroke

– Soluble fibers bind with bile and thereby

lower blood cholesterol levels.

– Fiber may also displace fat in the diet.

• Reduce the risk of type 2 diabetes by

decreasing glucose absorption

Health Effects of Starch and Fibers

• Enhance the health of the GI tract which

can then block the absorption of unwanted particles

Health Effects of Starch and Fibers

• Promote weight control

– complex carbohydrates provide less fat

and added sugar.

• Harmful effects of excessive fiber intake

– Displaces energy and nutrient-dense

foods

– Abdominal discomfort and distention

– May interfere with nutrient absorption

Recommended Intakes of

Starch and Fibers

• RDA for CHO:

• encourage a variety of whole grains,

vegetables, fruits and legumes daily.

• World Health Organization

• no more than 40 g per day.

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