5.2 Carbohydrates (nutrition)

Question 1

Why is glucose so important for the brain?

Answer 1

• It is the primary energy substrate in the brain and the body needs to meet the continuous high metabolic demand in a situation of varying plasma glucose level.
• Blood brain barrier only allows glucose to cross, not other pathogens or solutes in the blood

Question 2

How might carbohydrates have an impact on decision making?

Answer 2

• Research has linked carbohydrates to mood and decision making
• People who had a high-carbohydrate meal were more likely to implement social punishment when playing the ‘ultimatum game’ than those who ate high- protein breakfasts.
• Scientists speculate this may be caused by dopamine levels, which are higher after eating carbohydrates.

Question 3

Answer 3

Question 4

How does fibre differ from starch?

Answer 4

Bonds between glucose molecules in fibre cannot be broken by human enzymes. It passes through the body and therefore contributes little or no energy

Question 5

What is cellulose?

Answer 5

• Polysaccharide consisting of linear chains of several hundred to many thousand glucose units
• Important structural component of the cell wall of green plants
• Straight chain polymer and hydrogen bonds between each of the chains gives it structural rigidity

Question 6

Who can breakdown cellulose?

Answer 6

Ruminant animals can breakdown cellulose with the aid of cellulase producing bacteria

Question 7

Answer 7

Question 8

Starch breakdown

Answer 8

Question 9

Starch breakdown vs fibre

Answer 9

Question 10

Starch breakdown vs fibre

Answer 10

Question 11

Starch breakdown vs fibre

Answer 11

Question 12

How does the digestion of amylose compare to amylopectin?

Answer 12

• Different rate of digestion for carbohydrates
• Unbranched amylose chains more slowly digested that branched chains (amylopectin)
• In branched form, enzymes have more places to attack and can release glucose into the bloodstream more quickly
• Amylose to amylopectin ratio predict GI of food

Question 13

What are the two categories of fibre and where are they found?

Answer 13

• All plant foods, vegetables, fruit, legumes and grains, contain a mixture of fibres.
• Insoluble fibre
• Soluble fibre.
• There is usually much more insoluble fibre in plant foods than soluble fibre.

Question 14

What is resistant starch?

Answer 14

Acts in a similar way to fibre. Doesn’t get digested and ends up as food for bacteria in the large intestine

Question 15

How does soluble vs insolbule fibre affect digestion?

Answer 15

Question 16

How are glucose, galactose and fructose absorbed in digestion?

Answer 16

• Glucose and galactose traverse intestinal cells by active transport which requires energy
• Fructose absorbed by facilitated diffusion (requires specific carrier) which slows its entry to the blood stream
• Fructose and galactose are converted to glucose in the liver, extra step delays blood glucose rise

Question 17

How does lactase activity change in people?

Answer 17

• Only a small percent (~30%) retain enough lactase to digest and absorb lactose in adult life
• Lactase activity declines with age or damaged intestinal villi
• Symptoms include bloating, abdominal discomfort and diarrhoea

Question 18

How can lactose intolerance be managed?

Answer 18

• increasing consumption of milk products gradually
• mixing dairy with other foods
• spreading dairy intake throughout the day
• use of acidophilus milk, yoghurt or lactose-free products
• use of enzymes.

Question 19

What are FODMAPs?

Answer 19

• Large group of short chain carbohydrates and sugar alcohols that are found in all sorts of foods and drinks
• These sugars can be poorly absorbed in the small intestine and fermented by bacteria to produce gas

Question 20

What can a diet high in FODMAPs cause?

Answer 20

• For some people, a diet high in FODMAPs can cause a range of abdominal symptoms such as bloating, excess wind, distension, abdominal pain, constipation or diarrhoea.
• Following a low FODMAP diet can help manage these abdominal symptoms - 75% of people with IBS experience relief from their symptoms with a low FODMAP diet

Question 21

Answer 21

Question 22

What is protein sparing action?

Answer 22

Having adequate carbohydrate in the diet to prevent the breakdown of protein for energy

Question 23

What are these known as?

Answer 23

Ketone bodies

Question 24

What are ketone bodies?

Answer 24

Metabolic products that are produced during excessive breakdown of fatty acids

Question 25

What causes ketosis?

Answer 25

During prolonged starvation, very low carb diets and uncontrolled diabetes, ketones accumulate in the blood causing ketosis

Question 26

How does ketoacidosis come about?

Answer 26

Very high levels of blood ketones can disturb the body's normal acid base balance leading to ketoacidosis, a life threatening condition

Question 27

What is the pathway for maintaining blood glucose homeostasis?

Answer 27

Question 28

What happens in type 1 diabetes?

Answer 28

* The pancreas is faulty and insulin is not produced, usually childhood onset. * It was fatal in the past now controlled with insulin injections. * The cause is unknown.

Question 29

What is type 2 diabetes?

Answer 29

* Large amounts of insulin secreted but the insulin receptor on the body's cells are faulty and cells fail to respond to take up glucose as they should * Generally adult onset with fat gain, also some genetic component (insulin resistance)

Question 30

How is this curve interpreted?

Answer 30

Question 31

What factors affect the glycaemic response?

Answer 31

Question 32

Which sugars and starch have higher GI?

Answer 32

Question 33

What might be the health effects of eating a low GI diet?

Answer 33

Improvements in * BOdy weight * Blood lipids * Blood glucose control for type 2 diabetes

Question 34

Why is the usefulness of GI being debated?

Answer 34

* Relatively few foods have been tested * Responses to food vary widely between individuals * Not always indicated on nutritional labels and is not intuitively apparent. * Cooking method and how it's eaten (ie. mixed meal, standard serve vs 50g CHO portion) can effect the glycaemic response

Question 35

What is the range of values for classifying food as high low or medium GI?

Answer 35

Question 36

What are the health effects of added sugars?

Answer 36

* Excessive sugar intake can contribute to the development of nutrient deficiencies and dental caries. * Sugars ferment in the mouth, and can produce an acid that erodes tooth enamel causing tooth decay. * Not all sugars need to be avoided; only concentrated sources (e.g. soft drink, lollies, etc.)

Question 37

What are the three groups of alternative sweeteners?

Answer 37

1. Artificial sweeteners. Also known as 'non nutritive sweeteners' because they provide no energy and no carbohydrate such as aspartame, sucralose 2. Herbal products - Stevia. A herbal product that provides no energy or carbohydrates 3. Sugar alcohols. 'Nutritive sweeteners' because they still provide kilojoules. They will evoke a blood sugar response. Eg isomalt, mannitol, sorbitol

Question 38

How does a high fibre diet benefit heart disease?

Answer 38

Question 39

How does high fibre diet benefit gastrointestinal health?

Answer 39

Question 40

How does a high fibre diet lower risk of cancer?

Answer 40

Question 41

How does a high fibre diet lower risk of diabetes?

Answer 41

Question 42

How does high fibre diet improve weight management?

Answer 42

Question 43

What are the drawbacks of a high fibre diet?

Answer 43

Question 44

What is the reccomended dietary intake of carbohydrate?

Answer 44

Question 45

What is the reccomended dietary intake of fibre?

Answer 45