Carbohydrates and Fibre - Week 4 Part 1

Energy provided by carbohydrates

1g of carbohydrate provides an average of 16 kJ of energy.

Main role of carbohydrates

To provide energy in the body, primarily as glucose which fuels cells, especially the brain and nervous system.

Alternative brain fuels during low carbohydrate intake

Lactate and ketones can be used by the brain when glucose availability is limited.

Three responses to insufficient carbohydrate intake

Mobilization of glycogen stores, gluconeogenesis from amino acids, and ketosis producing ketone bodies from fats.

Chemical elements of carbohydrates

Carbon, hydrogen, and oxygen, often abbreviated as CHO.

Three monosaccharides

Glucose, fructose, and galactose.

Three disaccharides and their components

Maltose is glucose and glucose; lactose is glucose and galactose; sucrose is glucose and fructose.

Cause of lactose intolerance

Insufficient production of the lactase enzyme by intestinal cells, leading to bacterial fermentation of undigested lactose.

Storage form of glucose in the human body

Glycogen, stored mainly in the liver and muscles.

Two main forms of digestible plant starches

Amylose which is an unbranched chain and amylopectin which is a highly branched chain.

Soluble vs Insoluble dietary fibre

Soluble fibre dissolves in water and is easily fermented by colon bacteria; insoluble fibre does not dissolve and promotes bowel regularity.

Glycaemic Index (GI)

A measure of the blood glucose response of a given food compared to a standard food.

Carbohydrate digestion in the mouth

Salivary amylase begins hydrolysing starch into shorter polysaccharides and maltose.

Carbohydrate digestion in the small intestine

Pancreatic amylase and brush-border enzymes break down carbohydrates into absorbable monosaccharides.

Fate of excess carbohydrates

Stored as glycogen, used to reduce fat oxidation, or converted into fat via de novo lipogenesis.

Acceptable Macronutrient Distribution Range for carbohydrates

45% to 65% of total energy intake.

WHO recommendation for free sugars

Reduce intake of free sugars to less than 10% of total energy intake.

Definition of free sugars

Added sugars plus sugars naturally present in honey, syrups, fruit juices, and fruit juice concentrates.

Fibre intake targets

Suggested Dietary Targets are 38g/day for men and 28g/day for women to reduce chronic disease risk.