3.1 carbohydrate

FST 307 BASIC NUTRITION

CHAPTER 3MACRONUTRIENTS

CHAPTER OUTCOMES

At the end of this chapter, students should be able to:-

a) Explain briefly about classification, function, digestion of carbohydrate

b) Describe recommeded intake and related diseases for carbohydrate

Carbohydrates are primary fuel source for certaincells such as nervous system, red blood cells andbrain cells.

1 gram of carbohydrates yields about 4kcal of energy

We obtain about 50% - 60% of our energy intake fromcarbohydrates (maybe higher % in the developingworld)

COMPOSITION Composed of carbon, hydrogen, oxygen in the ratio

1:2:1 respectively: (CH2O)

Plants use CO2, H2O and energy (from the sun) toproduce the CH2O we eat.

The process is called photosynthesis

MONOSACCHARIDE

Also known as simple carbohydrates / simple sugars

Consist of 3 monosaccharide (single sugar) such as:

a) Glucose

b) Fructose

c) Galactose

1. GLUCOSE

Major monosaccharides in body

Also known as dextrose and blood sugar

Essential energy source for all body activities

Glucose in the body exist in ring form

2. FRUCTOSE

Major monosaccharides in diet

Also known as levulose

Sweetest among the sugars

Same chemical formula with glucose but differentstructure

Arrangement of the atoms stimulates the taste buds

Abundant in fruit, honey, corn syrup

Used in the production of soft drinks, confectionaries,frozen foods

3. GALACTOSE

Not found free in nature

Always combines with glucose to form lactose

Available in milk and dairy products

DISACCHARIDE Double sugars formed by chemical bonding of two

monosaccharide

2 types of bonding:a) alpha glycosidic bond: can be digested by human

intestinal enzymesb) beta glycosidic bond: cannot be digested by human

intestinal enzymes

3 types of disaccharidesa) Maltose = glucose + glucoseb) Sucrose = glucose + fructosec) Lactose = glucose + galactose

CONDENSATION

HYDROLYSIS

1. MALTOSE Mixture of: Glucose + Glucose

Link by alpha glycosidic bond

Situation where starch breakdown into maltose:

a) CH2O digestion

b) Fermentation process -> alcohol

Source: Grains

2. SUCROSE Mixture of: Glucose + Fructose

Link by alpha glycosidic bond

Also known as table sugar

Sucrose refine from juice of sugarcane or sugar beet

Sources: from plant only – honey, maple syrup,sugarcane

3. LACTOSE Mixture of: Glucose + Galactose

Link by Beta glycosidic bond

Also known as milk sugar

Source: milk, milk products

POLYSACCHARIDE Also known as complex carbohydrate

Mainly consist of:

a) Starch

b) Glycogen

c) Fibers (indigestible polysaccharide)

1. STARCH

Storage form of energy in plants

Long, branch (amylopectin) andunbranch (amylose) chain of glucosemolecules

All starchy food derives from plant

Source: rice, corn, barley, oats, legumesand tubers

2. GLYCOGEN Storage form of energy in animal body– temporary storage in muscle andliver

Glucose molecules in glycogenstructure linked in highly branchedchains that permits rapid hydrolysis

More branches – more sites forenzyme reaction quickly brokendown when needed

Limited sources in food becauseanimal muscles rapidly hydrolyze afterslaughter

3. FIBERS(INDIGESTABLE POLYSACCHARIDES)

Provide structure in stem, trunks, roots, leaves and skin of plants

Polysaccharide cannot be broken down by digestive enzyme

a) Lignin – woody parts in carrot, seeds in strawberry

b) Cellulose – primary constituents of plant cell wall

c) Hemicelluloses – main constituents of cereal fibers

d) Pectin – commonly found in vegetables and fruits, forms gelin water, control texture and consistency, thicken jelly

e) Gums – used as additives

f) Mucilage – used as stabilisers

1. Yielding energy

2. Sparing protein from use as an energysource

3. Preventing ketosis (pronounce : kitousis)

4. Imparting flavor and sweetness to foods

5. Maintaining health of large intestine

HOW BODY MAINTAIN BLOOD GLUCOSE LEVEL

Storing glucose as glycogen

a) Muscle glycogen – fuel muscle activity

b) Liver glycogen – to maintain blood glucose

c) Glycogen can be quickly release for energy as needed

d) Glycogen will last from a few hours to one day depending on activity level

Using glucose for energy

a) primary fuel for brain, RBC, nervous system, fetus and placenta

b) Need to metabolize fat completely

c) Glucose in blood used by body cell (undergo metabolic reaction) - produce energy

HORMONES RELEASE FROM PANCREASE Insulin

a) Produced by beta cell in pancreas

b) Functions during the rising glucose level in blood after ameal

i. Promote the storage of glucose as glycogen in liver andmuscle

ii. Stimulate protein synthesis and increase lipid synthesis

iii. Remove glucose from the blood so decreasing bloodglucose levels to the normal stage

Glucagon

a) Made in alpha cell in pancreas

b) Stimulates the breakdown of liver glycogen so glucosewere released to the bloodstream

c) It also help restore blood glucose to normal concentration

BLOOD GLUCOSE LEVEL Normal condition

Blood glucose level is about 70 – 110mg/dl (<6.1 mmol/l )

Hyperglycemia

Blood glucose level is exceeds 170mg/dl (>7 mmol/l )

Having high blood glucose

Begin to spill over into the urine

Hypoglycemia

Blood glucose level falls below 40 – 50mg/dl (<4 mmol/l )

Having low blood glucose

Symptom: nervous, hungry, headache

RECOMMENDED INTAKE OF CARBOHYDRATE

No Recommended Daily Allowance (RDA)

Recommended nutriens intake (RNI)

a) Total CHO: 55 – 70% of daily calories

b) Sugars: <10% of total energy

c) Dietary fibre: 20-30g per day

2000kcal = daily CHO intake ~ 275 to 300g

SOURCE OF CARBOHYDRATE

Sugar, honey, jam, jellies, fruits, baked potato: greatest % of kcal from CHO

Rice, bread, corn flakes, noodles: 75% of kcal/energy as CHO

Peas, broccoli, oatmeal, dry beans, legumes, fries, skim milk: moderate

Chocolate, whole milk: 30% - 40% of kcal as CHO (more fat)

Essentially no CHO: beef, chicken, fish, vegetable oil, butter, margarine.

LACTOSE INTOLERANCE

A condition that results from inability to digest the milk sugar lactose.

It can normally occur when (to normal people):-

a) Large amount of lactose is consumed more than the available lactase can handle

b) Lactose molecule remain in the intestine undigested

c) Undigested lactose becomes food for intestinal bacteria

d) Bacteria multiply and produce irritating acid and gas

e) It cause bloating, abdominal discomfort and diarrhea.

Natural causes:

a) Lactase activity commonly declines with age

b) Lactase deficiency may also develop when theintestinal villi are damaged by disease, certainmedicine, prolonged diarrhea or malnutrition.

c) Lactose malabsorption may be temporary orpermanent.

d) An infant is born with a lactase deficiency

Overcome lactose intolerance:

a) Remove all milk products from the diet – but it canlead to nutrient deficiencies (calcium, vitamin Dand riboflavin).

b) Read labels and avoid foods that include milk, milksolid, whey (milk liquid) and casein (milk protein).

c) Need to check all medications - because 20percent of prescription drugs contain lactose as afiller

d) Increase intake of milk product gradually

e) Consume fermented milk products such as yogurt

f) Consume commercially prepared milk productsthat have been treated with an enzyme that breaksdown the lactose.

DIABETES

Definition:

a) A metabolic disorder characterized by:-

i. Elevated blood glucose

ii. Altered energy metabolism

b) It is caused by:-

i. Defective insulin action

ii. Defective insulin secretion

iii. Both combination

Types of diabetesa) Type 1

i. Failure of insulin production

ii. Dependent on insulin injection because insulinnot produce by pancreas

iii. Usually happen to children and adolescent

b) Type 2

i. Not dependent on insulin injection

ii. Insufficient/inactivate insulin produced by thepancreas

iii. Usually happens to people 40 years and above,heredity and obese is the main contributor

PAUSE TO PONDER…

a) Please explain briefly about classification, function,digestion of carbohydrate

b) Try to describe recommeded intake and relateddiseases for carbohydrate

END OF CHAPTER 3.1CARBOHYDRATE