Carbohydrates

Question 1

What are the different types of carbohydrates?

Answer 1

• monosaccharides
• disaccharides
• polysaccharides (starches & glycogen)
• polyols
• resistant starch
• non-starch polysaccharides (fibres)

Question 2

What is the WHO recommendation for added sugar intake?

Answer 2

<10% of energy (approx 50g)

Question 3

What are the monosaccharides?

Answer 3

Glucose
Fructose
Galactose

Question 4

What are the disaccharides?

Answer 4

Lactose (glucose + galactose)
Maltose (glucose + glucose)
Sucrose (glucose + fructose)

Question 5

What are food sources of oligosaccharides?

Answer 5

• legumes
• garlic and onion
• inulin from chicory root
• breast milk (& infant formula)

Question 6

What is an example of a polysaccharide?

Answer 6

Starch

Question 7

What are the 3 types of starch?

Answer 7

• resistant starch (fermentable)
• amylopectin (digestible)
• amylose (digestible)

Question 8

Why is amylopectin more soluble than amylose?

Answer 8

Amylopectin has branches, whereas amylose is unbranched

Question 9

What are sugar polyols?

Answer 9

Artificial sweeteners

Question 10

What happens if we eat excess polyols?

Answer 10

Laxative effect

Question 11

What foods are natural polyols found in?

Answer 11

• stone fruit
• mushrooms
• avocados

Question 12

What are FODMAPs?

Answer 12

Fermentable oligosaccharides (inulin), disaccharides (lactose), monosaccharides (fructose), and polyols (sorbitol)

If poorly tolerated can cause GI symptoms eg bloating, pain, constipation, diarrhoea

Question 13

What are the 3 types of dietary fibre?

Answer 13

• soluble fibre
• insoluble fibre
• resistant starch

Question 14

What are the benefits of dietary fibre?

Answer 14

• decrease gastric emptying rate
• increase transit time in small intestine
• decrease transit time in large bowel

Question 15

What is the role of insoluble fibre?

Answer 15

Absorbs water in the bowel to bulk stool

Question 16

Where is insoluble fibre found?

Answer 16

In plant cell walls e.g.

• cellulose (wheat bran)
• lignin (hard seed coats)
• hemicellulose (whole grains)

Question 17

What is the role of soluble fibre?

Answer 17

Soluble in H20 so forms a gel in SI and slows nutrient absorption, removes cholesterol from body and slows glucose release

Question 18

Where is soluble fibre found?

Answer 18

Non-cell wall components e.g.

• pectins (apples, pears, citrus)
• gums
• fructans

Question 19

Where is resistant starch found?

Answer 19

Unripe bananas
High Maize corn
cooked and chilled pasta and rice and potatoes

Question 20

Where is resistant starch fermented?

Answer 20

Large intestine

Question 21

What is the role of gut microbiota?

Answer 21

• regulation and development of gut immunity
• harvesting energy
• protecting against pathogens
• maintaining the structure and function of intestinal epithelium
• imbalance can lead to problems - dysbiosis

Question 22

What are the 2 main phylum that make up the microbiome?

Answer 22

Firmicutes ~70%

Bacteroides ~20%

Question 23

What are the short chain fatty acids produced by gut bacteria?

Answer 23

• butarate and propionate - anti-obesogenic, anti-inflammatory, protect against bowel cancer
• acetate - associated with reduced asthma, some benefit for obesity, inflammation

Question 24

What can change the gut microbiome (positive/negative)?

Answer 24

Positive - probiotics, fruit and nuts, vegetable and polyphenols, cereal fibre

Negative - sugar, high fat high protein. sweeteners, antibiotics

Question 25

What foods should we increase/decrease for a healthy gut microbiome?

Answer 25

Increase - prebiotics - probiotics - fibre and resistant starch - omega-3 - polyphenols Decrease - animal products - processed foods - omega-6

Question 26

What starts CHO digestion?

Answer 26

Salivary amylase in the mouth

Question 27

What is the mechanism of action for insulin

Answer 27

Binds to insulin receptor, activates GLUT4 transporter to signal glucose into cells to be stored as glycogen in liver and muscle

Question 28

What molecule signals the breakdown of glycogen during fasting/between meals?

Answer 28

Glucagon

Question 29

What are some conditions related to CHO metabolism?

Answer 29

- diabetes - lactose intolerance - fructose intolerance (rare enzyme converting deficiency) - fructose malabsorption - glycogen storage disease

Question 30

What is the relationship between fructose and non alcoholic fatty liver disease?

Answer 30

excess fructose in the liver goes through lipogenesis

Question 31

What is GI?

Answer 31

Glycemic index - the ranking of CHO foods based on their postprandial blood glucose response over 2 hours

Question 32

How do low GI foods promote satiety?

Answer 32

Glucose stimulates satiety hormones, so a low GI will allow glucose to be present for longer = promoting satiety

Question 33

What are the ranges for GI?

Answer 33

High >70 Medium 56-69 Low <55

Question 34

What are examples of high GI foods?

Answer 34

- brown rice - white bread - glucose - watermelon - potato

Question 35

What are examples of medium GI foods?

Answer 35

- basmati rice - sweetcorn (boiled) - sucrose - weetbix

Question 36

What are examples of low GI foods?

Answer 36

- dark chocolate - fructose - milk - legumes - apples

Question 37

What are factors that affect GI?

Answer 37

- variety of starch (eg amylopectin higher GI than amylose due to easier breakdown) - cooking - processing (eg instant oats vs traditional) - fibre - slows GER and increases intestinal transit time

Question 38

What are the different uses for GI?

Answer 38

- diabetes - controlling BGL - sports nutrition - low GI before, high GI after event - weight management - satiety

Question 39

What is GL?

Answer 39

The weighted mean of GI + g of CHO per 100g/food GL is affected by the amount of CHO in a meal

Question 40

What are the GL ranges?

Answer 40

High GL >20 Medium 11-19 Low <10 Aim for <10 per food Aim for <100 whole day (approx 33 per meal)