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Human Nutrition > Lecture 6: Vitamins > Flashcards

Lecture 6: Vitamins Flashcards

1
Q

What are vitamins?

A

Tasteless, organic compounds

Required in small amount

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2
Q

What are the functions of vitamins?

A
  • Regulate metabolism
  • Help convert energy in fat, carbohydrate, and protein into ATP
  • Promote growth and reproduction
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3
Q

History of vitamins

A
  • Mostly undiscovered until about a century ago
  • Scientists discovered that thiamin cured beriberi and vitamin D cured rickets
  • Scientists focus on disease prevention with vitamin research
  • Each new vitamin is temporarily names when discovered
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4
Q

What is the criteria for designating vitamins?

A
  • Cannot be synthesized in ample amounts in the body
  • Chronic deficiency is likely to cause physical symptoms.
  • Symptoms will usually disappear once the vitamin level in the body is restored.
    ~Deficiency can cause permanent damage.
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5
Q

How are vitamins classified?

A

Based on solubility

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6
Q

How many water-soluble vitamins are there?

A

Nine: Entire B vitamin complex + vitamin C

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7
Q

How many fat-soluble vitamins are there?

A

Four:
~Vitamin A
~Vitamin D
~Vitamin E
~Vitamin K

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8
Q

What does vitamin solubility influence?

A
  • Digestion
  • Absorption
  • Transportation
  • Storage
  • Excretion
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9
Q

Vitamin Structure

A

All contain: Carbon, hydrogen and oxygen
Some contain: nitrogen and sulfur

The chemical structure of each vitamin is unique.

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10
Q

How are vitamins absorbed?

A

They are absorbed intact

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11
Q

Functions of vitamins

A

They perform essential functions and some vitamins perform multiple.

  • Antioxidants
  • Blood clotting and red blood cell synthesis
  • Bone health
  • Energy Production
  • Growth and reproduction
  • Immune function
  • Protein metabolism and synthesis
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12
Q

What are provitamins?

A

Substances found in foods that are not directly usable by the body

  • Can be converted into active form once absorbed
    ~beta-carotene –> vitamin A
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13
Q

What is the difference between preformed vitamins and provitamins?

A

Preformed vitamins are found in food in their active form and not need to be converted

Provitamins are found in food and need to be converted to active form

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14
Q

How can vitamin toxicity (hypervitaminosis) occur?

A
  • Rarely occurs
  • Results from ingesting excess vitamins leading to tissue saturation
  • Can damage cells
  • Results from high doses of supplements; cannot occur from foods
  • More likely to occur with fat-soluble vitamins

The DRI includes an UL for most vitamins to prevent excess

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15
Q

Where does vitamin absorption take place?

A

All absorption takes place in small intestine

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16
Q

How do fat-soluble and water-soluble vitamins differ?

A

They differ in:
~Absorption
~Bioavailability

17
Q

What does bioavailability depend on?

A

Based on:
- Amount of food
- Preparation
- Efficiency of digestion and absorption of food
- Individual nutritional status
- Natural or synthetic

18
Q

Which vitamins are more bioavailable?

A

Water-soluble are more bioavailable than fat-soluble

Animal food vitamins are more bioavailable than plant food vitamins

19
Q

Absorption of Fat-soluble vitamins

A
  • Attached to proteins in foods and released in stomach
  • Absorbed in duodenum
  • Packaged in chylomicrons –> travel through lymph system
    –> into bloodstream
20
Q

Storage of Fat-soluble vitamins

A
  • The liver is the main storage site for vitamin A; to a lesser
    extent for vitamins K and E.
  • Vitamin D is mainly stored in the fat and muscle tissue.
  • Can build up in the body to the point of toxicity
21
Q

Absorption of Water-soluble vitamins

A
  • Absorbed with water and enter directly into the bloodstream
  • Most absorbed in the duodenum and jejunum
22
Q

Excretion of Water-soluble vitamins

A
  • Excess intake excreted through the
    urine
  • Important to consume adequate
    amounts daily
  • Dietary excesses can be harmful
23
Q

Best sources of vitamins

A

Whole foods:
~ Fruits, vegetables, and whole grains
~Rich in vitamins, phytochemicals, antioxidants, and fiber

24
Q

Fortification of food with vitamins

A

Fortified foods: Voluntary addition of nutrients by manufacturers to:
~Enhance the nutrient quality of food
~Prevent or correct dietary deficiencies
~Ensure adequate intake for some individuals
~Examples: vitamin D in milk, vitamin D and
calcium in juice, iodine in salt
- Enrichment is a form of fortification.
~Example: folic acid in refined flour
- Fortification can contribute to health risks.
~Lead to vitamin excess
~Displace nutrient-rich foods

25
Q

What affects vitamin activity?

A

Exposure to:
~UV light
~water
~pH changes
~heat
~air
- time since harvest
- storage conditions
- cooking methods

26
Q

Primary Functions of Fat-Soluble Vitamins

A
  • Antioxidant: Vitamins A (carotenoids) and E
  • Vision: Vitamin A
  • Gene expression: Vitamins A and D
  • Calcium balance: Vitamin D
  • Bone health: Vitamins D and K
  • Immune function: Vitamins A and D
27
Q

Primary Functions of Water-Soluble Vitamins

A
  • Antioxidant: Vitamin C
  • Nerve function: Thiamin
  • Protein synthesis: Niacin
  • Formation of red blood cells: Folate and vitamin B12
  • Several B vitamins function as coenzymes and have critical roles in metabolism
28
Q

What are antioxidants?

A

Group of compounds that neutralize free radicals, helping
to counteract the oxidation that takes place in cells
- Includes:
~Vitamin E
~Vitamin C
~Selenium
~Flavonoids
~Carotenoids

  • Antioxidant-rich foods also contain other protective compounds.
  • Antioxidant-rich foods and may reduce the risk of some cancers.
  • Antioxidants and phytochemicals from the diet have more health benefits than those from supplements.
29
Q

What are free radicals?

A

By-products of the body’s metabolic reactions

They are molecules with an unpaired electron, which makes them unstable

30
Q

What is oxidative stress?

A

Occurs when free radicals accumulate faster than the body
can metabolize them.

31
Q

What are the effects of oxidative stress?

A
  • Damages DNA and body proteins, and alters cell structure
  • Excess free radicals and not enough antioxidants may contribute to chronic diseases
    ~Heart disease
    ~Cancer
    ~Aging
    ~Cataracts
    ~Age-related macular degeneration
    ~Diabetes
    ~Parkinson’s Disease
    ~Alzheimer’s Disease
32
Q

Are vitamin supplements necessary?

A

NO

  • No evidence supports the use of supplements and preventing chronic diseases or cognitive decline.
  • Not a substitute for healthy eating
  • Can cause adverse side effects
33
Q

Vitamin supplement regulation

A

Are not regulated like drugs and do not require FDA approval to be put on the market
~Supplements can’t be removed unless they have been shown to be unsafe or cause harm.

34
Q

How to choose a vitamin supplement?

A

Choose supplements with independent verification
~Example: United States Pharmacopeial Convention seal (USP)

35
Q

Who can vitamin supplements be helpful for?

A
  • Pregnant and lactating women
  • Older individuals who need vitamin B12
  • Individuals who lack dietary vitamin D or sun exposure
  • Individuals on low-kilocalorie diets
  • Strict vegetarians
  • Individuals with food allergies or lactose intolerance
  • Individuals who abuse alcohol
  • Individuals who are food insecure
  • Breast-fed infants
36
Q

Which compounds can reduce cancer risk?

A
  • Phytonutrients (lycopene)
  • Antioxidants (carotenoids, selenium, vitamin C, vitamin E)
  • Retinoids (vitamin A)
  • Vitamin D
  • Folate
  • Omega-3 fatty acids
  • Fiber

Human Nutrition (6 decks)

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