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4) Nutrition Through Life > 5) Fat, Carbohydrate, Water, Mineral, Electrolyte, and Vitamin Requirements in Adulthood (Part II) > Flashcards

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

1
Q

What are the major functions of vitamin A?

A

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

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2
Q

What factor determines the requirement for vitamin A?

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
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3
Q

Where may preformed vitamin A be acquired?

A

Certain animal-derived foods

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4
Q

Where are provitamin A carotenoids found?

A
  • Darkly coloured fruits and vegetables
  • Oily fruits
  • Red palm oil
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5
Q

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?

A
  • B-carotene: 12 ug
  • a-carotene: 24 ug
  • B-cryptoxanthin: 24 ug
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6
Q

What are the two major functions of vitamin D?

A

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

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7
Q

How is vitamin D implicated in cancer and tumour cells?

A

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

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8
Q

What is vitamin D2?

A

Ergocalciferol

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9
Q

What are sources of vitamin D2?

A

Yeast and plant sterols

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10
Q

What is vitamin D3?

A

Cholecalciferol

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11
Q

What are sources of vitamin D3?

A

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

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12
Q

How does the requirement for vitamin D vary with age?

A

The requirement increases after reaching 70 years of age

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13
Q

What is the major function of vitamin E?

A

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

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14
Q

What factor determines the requirement for vitamin E?

A
  • 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
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15
Q

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

A
  • α-tocopherol (trimethyl)
  • β-tocopherol or γ-tocopherol (dimethyl)
  • δ-tocopherol (monomethyl)
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16
Q

Are the forms of vitamin E interconvertible?

A

No, they are not interconvertible

17
Q

What is the characteristic structure of tocopherols?

A

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

18
Q

What is the difference between tocopherols and tocotrienols?

A
  • The side chain of tocopherols are saturated

- The side chain of tocotrienols are unsaturated

19
Q

Where are the synthetic forms of vitamin E contained?

A

Fortified foods or supplements

20
Q

What characterizes the stereochemistry of synthetic vitamin E?

A

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

21
Q

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

A
  • 3 asymmetric carbon atoms

- 8 possible stereoisomers, which are not treated equally by the human body

22
Q

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

A
  • RRR-a-tocopherol

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

23
Q

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

A
  • 2R-stereoisomeric forms

- In which carbon at position 2 is an R carbon

24
Q

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

A
  • RRR-
  • RSR-
  • RRS-
  • RRS-a-tocopherol
25
Q

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

A

Rac-a-tocopherol contains half of the activity

26
Q

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?

A
  • RRR-a-tocopherol: 15 mg/day
  • 2R-stereoisomeric forms: 15 mg/day
  • Rac-a-tocopherol: 30 mg/day
27
Q

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

A

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

28
Q

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

A

RRR-a-tocopherol

29
Q

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

A

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

30
Q

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

A

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

31
Q

The EARs, RDAs, and AIs apply to which stereoisomeric forms of vitamin E?

A

2R-stereoisomeric forms

32
Q

Why is there an increased risk of overestimating vitamin E intake?

A

Because most nutrient databases and nutrition labels offer no distinction between different tocopherols in food

33
Q

What is the major function of vitamin K?

A

Functions as a coenzyme during the synthesis of the biologically active form of a number of proteins involved in blood coagulation and bone metabolism

34
Q

Which DRI is used for the recommendation of vitamin K?

A

Adequate Intake (AI)

35
Q

What is the major form of vitamin K in the diet?

A

Phylloquinone

36
Q

What are menaquinones?

A

Produced by bacteria in the lower bowel

37
Q

How does the AI for vitamin K differ between men and women?

A

The AI is higher for men than it is for women

4) Nutrition Through Life (19 decks)

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