5) Fat, Carbohydrate, Water, Mineral, Electrolyte, and Vitamin Requirements in Adulthood (Part II) Flashcards Preview

Nutrition through life Val > 5) Fat, Carbohydrate, Water, Mineral, Electrolyte, and Vitamin Requirements in Adulthood (Part II) > Flashcards

Flashcards in 5) Fat, Carbohydrate, Water, Mineral, Electrolyte, and Vitamin Requirements in Adulthood (Part II) Deck (37)
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1

What are the major functions of vitamin A?

Required for proper vision, gene expression, reproduction, embryonic development, growth, and immune function

2

What factor determines the requirement for vitamin A?

- Based on the amount of dietary vitamin A required to maintain a given body-pool size in well-nourished subjects
- To assure that vitamin A reserves cover increased needs during periods of stress and low-vitamin A intake

3

Where may preformed vitamin A be acquired?

Certain animal-derived foods

4

Where are provitamin A carotenoids found?

- Darkly coloured fruits and vegetables
- Oily fruits
- Red palm oil

5

1 ug of RAE (or 1 ug of retinol) is equal to which quantities of dietary provitamin A carotenoids, in terms of B-carotene, a-carotene, and B-cryptoxanthin?

- B-carotene: 12 ug
- a-carotene: 24 ug
- B-cryptoxanthin: 24 ug

6

What are the two major functions of vitamin D?

1) Enhances absorption efficiency of calcium and phosphorus within the small intestine
2) Produces potent anti-proliferative and pro-differentiation effects in a variety of tissues

7

How is vitamin D implicated in cancer and tumour cells?

Vitamin D may prevent the dysregulation from occurring through its anti-proliferative effects, halting the progression of tumour cells

8

What is vitamin D2?

Ergocalciferol

9

What are sources of vitamin D2?

Yeast and plant sterols

10

What is vitamin D3?

Cholecalciferol

11

What are sources of vitamin D3?

Derived from 7-dehydrocholesterol when it is synthesized in the skin

12

How does the requirement for vitamin D vary with age?

The requirement increases after reaching 70 years of age

13

What is the major function of vitamin E?

Functions as a non-specific chain-breaking antioxidant preventing the propagation of lipid peroxidation

14

What factor determines the requirement for vitamin E?

- The correlation between hydrogen peroxide-induced erythrocyte lysis and blood a-tocopherol
- Analysis of the level of a-tocopherol that protects against hemolysis caused by hydrogen peroxide

15

What are the four naturally-occurring tocopherol structures that have vitamin E antioxidant activity? How many methyl groups do they possess?

- α-tocopherol (trimethyl)
- β-tocopherol or γ-tocopherol (dimethyl)
- δ-tocopherol (monomethyl)

16

Are the forms of vitamin E interconvertible?

No, they are not interconvertible

17

What is the characteristic structure of tocopherols?

Substituted hydroxylated ring system (chromanol ring) with a long, saturated (phytyl) side chain

18

What is the difference between tocopherols and tocotrienols?

- The side chain of tocopherols are saturated
- The side chain of tocotrienols are unsaturated

19

Where are the synthetic forms of vitamin E contained?

Fortified foods or supplements

20

What characterizes the stereochemistry of synthetic vitamin E?

A synthetic mixture (all racemic) form, producing equal amounts of the possible stereoisomers

21

How many stereoisomers are there for tocopherol? How do they differ?

- 3 asymmetric carbon atoms
- 8 possible stereoisomers, which are not treated equally by the human body

22

What is the stereochemistry of a vitamin E supplement that is derived from a "natural source of vitamin E"? How?

- RRR-a-tocopherol
- Derived by methylation of γ-tocopherol isolated from vegetable oil

23

The DRI definition of vitamin E is related to which stereoisomeric forms?

- 2R-stereoisomeric forms
- In which carbon at position 2 is an R carbon

24

What are the four types of 2R-stereoisomeric forms?

- RRR-
- RSR-
- RRS-
- RRS-a-tocopherol

25

How does the activity of rac-a-tocopherol supplements differ from the activity of RRR-a-tocopherol from food and 2R forms of tocopherol?

Rac-a-tocopherol contains half of the activity

26

The RDA for vitamin E is 15 mg/day. How may it be acquired from RRR-a-tocopherol, 2R-stereoisomeric forms, or all rac-a-tocopherol?

- RRR-a-tocopherol: 15 mg/day
- 2R-stereoisomeric forms: 15 mg/day
- Rac-a-tocopherol: 30 mg/day

27

The concentration of the various forms of vitamin E in plasma are dependent on what?

Their affinity with hepatic a-tocopherol transfer protein (a-TTP)

28

a-TTP affinity is highest in which form of vitamin E?

RRR-a-tocopherol

29

How does a poor affinity for SRR-a-tocopherol and natural γ-tocopherol affect lipid metabolism?

They are poorly packaged into lipoproteins for delivery to peripheral tissue given their poor affinity

30

Which forms of vitamin E are not used to estimate the requirement?

2S-stereoisomeric forms, other tocopherols (B-, γ-, and δ-), and tocotrienols fail to bind with a-TTP, and are not used in the estimation of requirement