Role of Macronutrients

Question 1

Role of carbohydrates?

Answer 1

Important source of energy
WHO recommends 55-65% of energy should come from carbohydrates

Question 2

What are some examples of carbohydrate containing compounds?

Answer 2

Rice, wheat, maize, barley, rye, oats and millet

Question 3

What is protein-sparing action?

Answer 3

Excessive dietary restriction of carbohydrates leads to proteins being used as an energy source

Question 4

What happens if carbohydrates are excessively consumed?

Answer 4

Converted to glycogen and triacylglycerol for storage

Question 5

Sources of glucose and fructose

Answer 5

Honey, cooked food, dried fruit and some vegetables

Question 6

Source of lactose

Answer 6

Sugar in milk

Question 7

Source of maltose

Answer 7

Derived from starch and sprouts

Question 8

Source of trehalose

Answer 8

Derived from yeast and mushrooms

Question 9

Purpose of sugar alcohols

Answer 9

Used to commercially replace sucrose in sugar-free diets
E.g. sorbitol

Question 10

Characteristics of oligosaccharides (non-alpha glycans)

Answer 10

Non-digestible oligosaccharides
Cannot be broken down by amylase
They are Pre-biotics
They are Galacose or Fructose glycans

Question 11

Examples and sources of oligosaccharides

Answer 11

Examples: Raffinose, Stachyose, Verbascose and Inulin
Sources: Peas, beans and lentils

Question 12

Types of polysaccharides

Answer 12

Starch
Non-starch polysaccharides (NSP)

Question 13

Sources of starch

Answer 13

Cereals, potatoes, cassava, legumes and bananas

Question 14

Components of cereal starch

Answer 14

15-30% amylose and 70-85% amylopectin

Question 15

Purpose of non-starch polysaccharides

Answer 15

Dietary fiber

Question 16

What are the types of NSPs?

Answer 16

Cellulose (beta glucan), Hemicellulose (contains xylose and arabinose sugars) and Pectins (galacturonic acid polymers)

Question 17

What are the benefits of dietary fibers?

Answer 17

They give a feeling of satiety
Increase bulk of the feces
Improve bowel movements especially in irritable bowel syndrome
Help in regulating blood cholesterol levels
Epidemiological evidence shows that increased consumption of dietary fiber is linked to lower rates of colon cancer (protective role of fiber)

Question 18

What are prebiotics?

Answer 18

Non-viable food components that confer a health benefit on the host associated with modulation of the microbiota
Prebiotic dietary fibers act as carbon sources for primary and secondary fermentation pathways in the colon, and support digestive health in many ways
They alter the balance of bacterial flora so that there are more bifidobacteria and lactobacilli

Question 19

What are the functions of bacterial flora?

Answer 19

Maintain gut barrier to infection
Synthesize B vitamins
Breakdown carbohydrates and release metabolites that can provide energy
Good pre-biotics are fructo-oligosaccharides, inulin, galacto-oligosaccharides

Question 20

What is the glycemic index?

Answer 20

Extent to which a carbohydrate raises the blood glucose level compared with an equivalent amount of reference carbohydrate

Question 21

What are glycemic carbohydrates?

Answer 21

Provide glucose for metabolism after digestion and absorption in the small intestine

Question 22

What are non-glycemic carbohydrates?

Answer 22

Carbohydrates which pass through the small intestine undigested

Question 23

Benefit of consuming whole grain carbohydrates?

Answer 23

Rich is dietary fiber and have low glycemic index which help reduce the risk of Type 2 Diabetes and improe glycemic control in both Type 1 and 2 diabetes

Question 24

What is the minimum amount fo carbohydrates that should be consumed in a day to avoid ketosis?

Answer 24

50g/day

Question 25

Typical carbohydrate consumption in a day?

Answer 25

200-400g

Question 26

How much energy should free sugars provide?

Answer 26

Less than 10%

Question 27

How much dietary fiber should be consumed per day?

Answer 27

25g

Question 28

Dietary sources of lipids

Answer 28

Animal sources (adipose tissue, meat, milk, milk products, eggs and fish) Vegetable sources (seeds, nuts, seed oils, leaves)

Question 29

What are the roles of fats in diet?

Answer 29

Concentrated source of energy Lubricates food in the mouth helping to make chewing and swallowing easier, adds flavour to foods Dietary intake provides 30-40% of the total energy in western countries while in Asian countries its lower

Question 30

What are essential fatty acids?

Answer 30

Fatty acids which cannot be synthesized by the body and are essential in the diet

Question 31

Roles of essential fatty acids

Answer 31

Required for absorption of fat-soluble vitamins: A, D, E and K. Components of biomembranes Reduce blood cholesterol Synthesize important compounds like prostaglandins and leukotrienes

Question 32

How does reducing fat intake beneficial to health?

Answer 32

Reduces obesity and risk for cancers Replacing saturated fat with mono and polyunsaturated fat reduces risk for cardiovascular disease

Question 33

What is the purpose of hydrogenation?

Answer 33

Increase the melting point of fat and make it solid by changing the configuration of the remaining double bonds from cis to trans Partial hydrogenation improves texture and increases shelf-life and stability of foods

Question 34

What is the purpose of proteins?

Answer 34

Provides essential amino acids required for synthesis of body proteins Source of dietary nitrogen for nitrogen containing compounds (such as DNA and RNA)

Question 35

What is nitrogen balance?

Answer 35

Difference between amount of nitrogen taken into the body each day as protein and the amount of nitrogen containing compounds lost in urine (as uric acid), sweat, creatine, creatinine and feces

Question 36

What is a healthy nitrogen balance?

Answer 36

0

Question 37

What is a negative nitrogen balance and when may it occur?

Answer 37

Nitrogen output is higher than input Seen after surgery, trauma, extensive burns, excessive hemorrhage, chronic steroid therapy, poor protein intake, malignancies, prolonged starvation and chronic debilitating diseases

Question 38

What is a positive nitrogen balance and when may it occur?

Answer 38

Nitrogen intake is higher than output Seen during periods of active growth, pregnancy, convalescence and in response to growth hormone, insulin and androgens

Question 39

Why is the quality of a protein important?

Answer 39

Important for its use in biosynthetic processes

Question 40

What happens to proteins with a limiting amino acid (essential amino acid deficient in protein)?

Answer 40

Diverted to energy production instead of biosynthesis ## Footnote E.g. Gelatin lacks tryptophan

Question 41

What is a first class protein/high-quality protein?

Answer 41

Contains the highest percentage of essential amino acids ## Footnote E.g. Eggs and milk proteins