Week 4 - Carbohydrates

FST1911

How are carbohydrates classified?

• Monosaccharides

• Disaccharides

• Polysaccharides

Define glycemic index

Measure of how quickly and fast glucose levels rise after eating specific foods

Define and give me 3 examples of foods with low GI response

—> Slowly absorbed by body, no spike

• Barley

• Legumes

• Broccoli

Low GI < 55

Define and give me 3 examples of foods that have a high glycemic index

—> Glucose spikes and falls below usual blood levels

• Boiled potatoes

• Bread

• Rice

High GI >70

Glycemic Index ranks food on a scale of _____?

1 to 100

100 = pure glucose

What are simple carbs

• monosaccharides

• disaccharides

Name me the monosaccharides and the formula (GFG)

—> Same chemical formula but diff chemical structures (C6H12O6)

• Glucose

• Galactose

• Fructose

What is fructose associated with?

Sweet flavour associated with sugars

• NOT soft drinks unless sweetened with corn syrup

Glucose

Primary energy source

• building blocks for polysaccharides

Galactose

Naturally occurring sugar

• exists in very small amounts

Define dissaccharides (SML)

—> 2 monosaccharides paired together, formed by condensation and broken by hydrolysis

• Maltose

• Sucrose

• Lactose

Maltose composition

• glucose + glucose

• aka malt sugar

• formed during the breakdown of starch

Composition of sucrose

• Fructose + glucose

• aka table sugar / cane sugar

• cause of natural sweetness in fruits, veg, and grains

Composition of lactose

• glucose + galactose

• milk sugar

Lactose intolerance

• body does not produce enough lactase (small intestine) to break down lactose

• lactase production declines with age

Complex carbs

—> composed of polysaccharides, come in the form of glycogen, starch and fibres

Glycogen

molecular arrangement of glucose that allows it to be stored in the body for future use

• stored in liver and muscle cells

• does not occur in plants and rarely in meat

Starch

—> glycogen equivalent for all plants

• richest source = grains

• resistant starch

Resistant starch

• Dietary fibre (escape digestion and absorption in small intestine)

• support healthy colon

• pasta, partially milled grains, legumes. just ripened bananas, cooked potatoes

Fibres

structural part of plant not digested

• provides up to 2kcal/g depending on the type of fibre

• Soluble and insoluble

• RNI = 20 to 30g

Soluble fibres

• non starch polysaccharides that form gel when dissolved in water

• assists with weight management and prevention of heart disease

E.g Pectin from fruit to thicken jellies

Insoluble fibres

• Do not dissolve in H2o

• Promote GI health

E.g stringy part of celery, skin of corn kernels

How can soluble and insoluble fibres be further characterized

—> viscosity and fermentability

• viscous fibres have gel forming properties

• fermentable fibres can be digested by bacteria in GI tract

Digestion and absorbtion

• must be in the form of monosaccharides to be digested

• enzymes: salivary amylase and pancreatic amylases

stomach digestive juice does not contain enzymes to breakdown carbs

• fibre slows down gastric emptying

• fibre binds to cholesterol and carry them out of the body

Heart disease

—> regulating number of bodily functions

• altered level of blood lipids in the body

• lower blood pressure

• reduced inflammation

• lower blood cholesterol

Cancer

—> reduce risk of colon and rectal cancer

• Fibres assist in the removal of cancer-causing agents

• soluble fibres trigger the formation of resistant starch and fibre

Activate cancer-killing enzymes and less inflammation

Diabetes

Fibre slows glucose absorbtion and prevent sudden surge and drops

Weight management

fibre helps you feel full longer

DRI - Dietary Reco Intake for fibre

14g per 1000kcal diet

• 20-30g each day for all ages (RNI)

Fibre intake for pregnant / lactating women

12% higher than average

Fibre intake for adults over 51 years of age are

20% lower

Alternative sweetners

1. Artificial sweeteners - non nutritive, regulated

2. High intensity sweeteners - Stevia & Monk fruit

3. Sugar alcohols

• commerically produced from other carbs sucrose, glucose and starch

• Texture and sweetness

• dont brown in heat

• Do not contribute to dental cavities