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Vitamins: An Overview

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Title: Vitamins: An Overview


1
Vitamins An Overview
2
Vitamins
  • Essential organic substances (contain carbon)
  • Not synthesized
  • Inadequate synthesis
  • Yield no energy, but facilitate energy-yielding
    chemical reactions
  • If absent from a diet, it will produce deficiency
    signs and symptoms

3
Body Needs Vitamins for Normal
  • Function
  • Growth
  • Maintenance
  • Reproduction

4
Two Forms of Vitamins
  • Precursor/Provitamin
  • Dietary form inactive
  • Activated in body
  • Active form
  • Dietary form active
  • Not changed in body

5
Vitamins Often Serve as Coenzymes
6
Vitamin Classification
  • Fat-soluble vitamins
  • Dissolve in substances such as ether and benzene
    but not readily in water
  • Include vitamins A, D, E, and K
  • Water-soluble vitamins
  • Vitamins that dissolve in water
  • Include B vitamins and vitamin C

7
Vitamin Classification
  • Category determines
  • Food sources
  • How handled in body
  • Best preservation methods

8
Vitamin History
  • First discovered fat soluble substance essential
    for health in 1912-1914 (vitamin A)
  • B complex 1915-1916 (water soluble nutrient)
  • Vitamin C isolated 1912
  • Vitamin D, Vitamin E 1922
  • Last vitamin (B12) discovered in 1948
  • Likely all vitamins have been discovered, since
    people can be maintained on IV solutions
    fortified with known vitamins

9
Vitamin Facts
  • Megadose (10x needs) proved useful in treating
    certain conditions
  • Plant and animal foods provide vitamins
  • Synthesized vitamins work equally well in the
    body

10
Fat-Soluble Vitamins
  • Dissolve in organic solvents
  • Not readily excreted can cause toxicity
  • Absorbed along with fat
  • Deficiency with fat malabsorption
  • Fat blockers (Orlistat/Xenical)
  • Mineral oil

11
Fat Soluble Vitamins
  • Requires protein carrier
  • Transported like fat in chylomicrons, VLDL, LDL
  • Stored in body (except Vitamin K)
  • Fat tissue/liver
  • Can cause toxicity
  • Vitamin D and A most likely to be toxic

12
Fat Soluble Vitamin Preservation
  • Not easily destroyed
  • Fat addition in cooking vegetables
  • Fat soluble vitamins leach out
  • Lost if liquid discarded
  • Add fat after vegetables drained, just before
    serving
  • Baking soda
  • Used to preserve color of green vegetables
  • Destroys Vitamin D

13
Water Soluble Vitamins
  • Found in grains, fruits, vegetables, meat
  • Low risk of toxicity
  • Not stored in large amounts
  • Excess excreted inurine
  • Need daily intakes
  • Easily destroyed
  • Heat increases enzyme activity
  • Light destroys riboflavin
  • Oxygen breaks down

14
Water Soluble Vitamins - Preservation
  • Cooking
  • Heat destroys vitamins
  • Water leaches out vitamins
  • Baking soda destroys thiamin
  • Conserve vitamins
  • Store foods covered in refrigerator
  • Consume soon after purchase (freshest possible)
  • Minimal cooking/minimal liquid
  • Freezing preserves vitamin content

15
Vitamin A
  • Deficiency is most common cause of non-accidental
    blindness worldwide
  • Up to 500,000 children in developing nations
    especially Asia, become blind each year because
    of Vitamin A deficiency

16
Functions of Vitamin A
  • Prevents night blindness
  • Prevents xerophthalmia (dry eye)
  • Maintains cell health (epithelial cells)
  • Growth, development, reproduction
  • Cardiovascular disease prevention
  • Cancer prevention

17
Night Blindness
  • Vitamin A is needed for dark vision
  • Rhodopsin in retina
  • Light destroys
  • Constantly reformed
  • Allows for a chemical process to signal the brain
    that light is striking the eye
  • Allows eyes to adjust to dark vision

18
Xeropthalmia
  • In Vitamin A deficiency, the cells that line the
    cornea lose their ability to produce mucus
  • When dirt particles scratch the dry surface of
    the eye, becomes infected
  • Leads to blindness
  • Worldwide public health efforts are fortifying
    sugar, margarine, MSG, giving large doses of
    Vitamin A 2x year

19
Macular Degeneration
  • Leading cause of legal blindness among North
    American adults over 65
  • Changes in the macular area of the eye
  • Age, smoking, and genetics are risk factors
  • Macula contains carotenoids lutein and
    zeaxanthin
  • High intakes of carotenoids associated with lower
    risk (but may be fruit and vegetable intake)
  • Also may reduce risk of cataracts
  • Multivitamins are adding lutein

20
Cell Health
  • Vitamin A maintains health of cells that line
    internal and external surfaces (epithelial
    cells)
  • Barriers to bacterial infections
  • Epithelial cells produce mucus
  • Without vitamin A, these cells do not produce
    mucus
  • Increases infections and decreases immune system

21
Growth
  • Vitamin A binds to DNA
  • Assists in protein synthesis
  • Affects growth, reproductive system, and bone
    growth

22
Cancer and Cardiovascular Disease
  • Role in cell development and immune-system
  • Role as an antioxidant
  • Lower risk of breast cancer with vitamin A
    supplements
  • Megadoses are not recommended
  • Mixed results in cancer/vitamin A studies
  • Foods rich in vitamin A and other phytochemicals
    are advised

23
Prostate Cancer and Carotenoids
  • One of the most common cancers among North
    American men
  • Lycopene (tomatoes, watermelon, other fruits)
    seems to protect against it, possibly due to
    antioxidant activity

24
Vitamin A and Your Skin
  • Topical treatment and oral drug
  • Accutane (oral) and Retin-A (topical)
  • Can induce toxicity symptoms
  • Contraindicated in pregnant women
  • Use only under supervision of a physician

25
Sources of Vitamin A
  • Preformed
  • Liver, fish oils, fortified milk, eggs
  • Contributes to half of vitamin A intake in North
    America
  • Provitamin
  • Dark leafy green, yellow-orange
    vegetables/fruits carrots, spinach and other
    greens, winter squash, sweet potatoes, broccoli,
    mangoes, cantaloupe, peaches and apricots
  • Contributes to half of all the vitamin A intake

26
Vitamin A from the Food Guide Pyramid
27
Deficiency of Vitamin A
  • Night blindness
  • Decrease mucus production leading to bacterial
    invasion in the eye
  • Irreversible blindness

28
Deficiency of Vitamin A
  • Follicular hyperkeratosis
  • Keratin protects the inner layers of skin and
    maintains moisture
  • Kertinized cells replaces the normal epithelial
    cells in the underlying skin layers
  • Hair follicles become plugged
  • Bumpy, rough, and dry skin

29
Measuring Vitamin A
  • International unit (IU)-crude method of
    measurement
  • Retinol activity equivalent (RAE) -current, more
    precise method of measurement
  • 1 ug of retinol 1 RAE 3.3 IU 12 ug
    beta-carotene 24 ug of other provitamin A

30
RDA for Vitamin A for Adults
  • 900 mcg REA for men
  • 700 mcg REA for women
  • Average intake meets RDA
  • Daily value used on food and supplement labels is
    1000 mcg
  • Much stored in the liver
  • Vitamin A supplements are unnecessary
  • No separate RDA for carotenoids

31
Who is at Risk For Deficiency
  • Breast fed infants
  • Preschooler with poor vegetable intake
  • Urban poor
  • Elderly
  • Alcoholics and people with liver disease
  • Individual with fat malabsorption
  • HIV, AIDS

32
Toxicity of Vitamin A
  • Large intake of vitamin A over a long period
    supplements, liver, fish oil
  • Bone/muscle pain, loss of appetite, skin
    disorders, headache, dry skin, hair loss,
    increased liver size, vomiting
  • Possible permanent damage
  • Discontinue supplement

33
Toxicity of Vitamin A
  • May produce fetal malformations and spontaneous
    abortions in pregnant women
  • May occur with as little as 3 x RDA of preformed
    vitamin A
  • Pregnant women and women who may become pregnant
    should limit to 100 DV
  • Upper Level for Vitamin A
  • 3000 ug for adults
  • Fatal dose -12 g of vitamin A can be fatal

34
Toxicity of Carotenoids
  • Dont produce toxic effects because
  • Rate of conversion to Vitamin A is slow and
    regulated
  • Efficiency of absorption decreases as oral intake
    increases

35
Carotenoids
  • High amounts of carotenoids in the bloodstream
  • Excessive consumption of carrots/squash/beta-carot
    ene supplements
  • Skin turns a yellow-orange color

36
Vitamin D
  • Prohormone
  • Derived from cholesterol
  • 90 of needs is synthesized from sun exposure
  • Insufficient sun exposure makes this a vitamin

37
Sun Exposure to Prevent Vitamin D Deficiency
  • 15 minutes 2-3 times a week
  • Between 8 a.m. and 4 p.m.
  • Hands, face, arms
  • Light skin
  • No sunscreen greater than SPF8

38
Activation of Vitamin D
  • To become the active hormone, Vitamin D must be
  • Acted on by the liver to produce
    25-hydroxyvitamin D
  • Acted on by the kidney to produce 1,25
    dihydroxyvitamin D (active hormone form)

39
Functions of Vitamin D
  • Regulates blood calcium
  • Regulates calcium and phosphorus absorption from
    the intestine
  • Reduces kidney excretion of calcium
  • Regulates calcium deposition in bones
  • Serum calcium involved in nerve transmission and
    muscle contraction

40
Functions of Vitamin D
  • Influences cell differentiation
  • Linked to reduction of breast, colon, and
    prostate cancer
  • Controls the growth of the parathyroid gland,
    aids in immune function, contributes to skin cell
    development

41
Role in Bone Formation
  • Vitamin D causes Ca Phos to deposit in the
    bones
  • Strengthen bones

42
Food Sources of Vitamin D
  • Fatty fish (salmon, herring)
  • Fortified milk and yogurt
  • 10 mcg per quart in US and Canada
  • Some fortified cereal

43
The Adequate Intake (AI) for Vitamin D
  • 5 ug/d (200 IU/day) for adults under age 51
  • 10-15 ug/day (400 - 600 IU/day) for older
    Americans
  • Light skinned individuals can produce enough
    vitamin D to meet the AI from casual sun
    exposure
  • Infants are born with enough vitamin D to last 9
    months of age.

44
Vitamin D Toxicity
  • Upper level is 50 mcg/day
  • Vitamin D can be very toxic especially in
    children
  • Regular intake of 5-10x the AI can be toxic
  • Results from excess supplementation (not from sun
    exposure or milk consumption)

45
Vitamin D Toxicity
  • Signs/symptoms overabsorption of calcium
    (hypercalcemia)
  • Signs of high blood calcium weakness, loss of
    appetite, diarrhea, vomiting, mental confusion,
    increased urine output
  • Calcium deposits in kidneys, heart, and blood
    vessels
  • Mental retardation in infants

46
Vitamin D Deficiency
  • At risk
  • Dark skinned
  • Lack of sun exposure
  • Northern climates in wintertime
  • Breastfed babies

47
Vitamin D Deficiency Rickets
  • Is the result of vitamin D deficiency in children

  • Poor mineralization of bones because of low
    calcium content
  • Fortification of milk has greatly reduced rickets
    in children
  • Most rickets is associated with fat
    malabsorption, as in cystic fibrosis

48
Vitamin D Deficiency Osteomalacia (soft bone)
  • Is rickets in the adult
  • Low calcium content in bones due to lack of
    vitamin D

49
Vitamin E
  • Group of fat-soluble compounds, tocopherols and
    tocotrienols
  • Alpha-tocopherol is the most potent
  • Fat-soluble antioxidant
  • Resides mostly in cell membranes

50
Redox Agent
  • Vitamin E is able to donate electron to oxidizing
    agent
  • Protects the cell from attack by free radicals
  • Protects PUFAs within the cell membrane and
    plasma lipoproteins
  • Prevents cell death
  • Prevents the alteration of cells DNA and risk
    for cancer development

51
Vitamin E, An Antioxidant
52
The More The Better?
  • Vitamin E is only one of many antioxidants
  • It is likely that the combination of antioxidants
    is more effective
  • Best to diversify antioxidant intake with a
    balanced and varied diet
  • Megadose of one antioxidant may interfere with
    the action of another

53
Vitamin E and Cardiovascular Disease
  • Epidemiological studies suggest higher intakes of
    Vitamin E are associated with lower risk of CHD
  • Clinical trial results have been mixed
  • American Heart Association states it is premature
    to recommend vitamin E supplements to the general
    population
  • FDA has denied permission for supplement mfrs to
    claim that Vitamin E prevents heart disease and
    cancer

54
Other Functions of Vitamin E
  • Protects the double bonds in saturated fat
  • Helps vitamin A absorption
  • Role in iron metabolism
  • Inhibits LDL oxidation
  • Maintenance of nervous tissue and immune
    function

55
Food Sources of Vitamin E
  • Plant oils salad dressings, mayonnaise
  • Fortified cereals, oatmeal
  • Wheat germ
  • Asparagus, tomatoes, green leafy vegetables

56
Food Sources of Vitamin E
  • Peanuts
  • Margarine
  • Nuts and seeds (sunflower seeds)
  • Actual amount is dependent on harvesting,
    processing, storage and cooking

57
Food Sources of Vitamin E
58
Vitamin E Easily Damaged
  • Oxygen
  • Metals
  • Light
  • High heat
  • Deep fat frying

59
RDA for Vitamin E
  • 15 mg/day alpha-tocopherol for women and men
  • (22 IU of natural source or 33 IU of synthetic
    form)
  • Average intake meets RDA
  • 1 mg d-?-tocopherol 0.45 IU (synthetic source)
  • 1 mg d-?-tocopherol 0.67 IU (natural sources)

60
Deficiency of Vitamin E
  • Hemolytic anemia
  • Hemolysis occurs in preterm infants because they
    did not receive enough vitamin E from their
    mothers
  • Preemie formulas and supplements compensate for
    increased needs

61
Deficiency of Vitamin E Whos At Risk?
  • Smokers are especially at risk (smoking destroys
    vitamin E in the lungs)
  • However even megadoses may not prevent damage
  • Adults on very low fat diets
  • Fat malabsorption

62
Toxicity of Vitamin E
  • Supplements up to 800 IU probably harmless
  • Upper Level is 1,000 mg/day of any form of
    supplementary alpha-tocopherol
  • Upper Level is 1500 IU (natural sources) or 1100
    IU (synthetic forms)
  • Inhibits vitamin K metabolism especially in
    conjunction with anticoagulants
  • Possible hemorrhage

63
Vitamin K (Koagulation)
  • Family of compounds found in plants, plant oils,
    fish oils, and meats
  • Synthesized by the bacteria in the colon and are
    absorbed (10 of needs)

64
Role of Vitamin K
  • Role in the coagulation process
  • Contributes to the synthesis of several
    blood-clotting factors
  • Helps form proteins present in bone, muscle, and
    kidneys
  • Imparts calcium-binding potential
  • Poor intake linked to increase in hip fractures

65
Vitamin K in Newborns
  • Newborns intestinal tract lacks bacteria to
    allow blood to clot effectively
  • Vitamin K is routinely given by injection shortly
    after birth to bridge the gap
  • May also occur in adults with chronic
    malabsorption

66
Drugs and Vitamin K
  • Anticoagulant
  • Lessens vitamin K reactivation
  • Lessens blood clotting process
  • Monitor vitamin K intake
  • Antibiotics
  • Destroy intestinal bacteria
  • Inhibit vitamin K synthesis and absorption
  • Potential for excessive bleeding

67
Food Sources of Vitamin K
  • Liver
  • Green leafy vegetables
  • Broccoli
  • Peas
  • Green beans
  • Soybeans/canola oil
  • Resistant to cooking losses
  • Limited vitamin K stored in the body

68
Adequate Intake for Vitamin K
  • 90 ug/day for women
  • 120 ug/day for men
  • Amount met by most
  • Excess vitamins A and E interferes with vitamin
    K
  • Newborns are injected with vitamin K (breast milk
    is a poor source)
  • Toxicity unlikely readily excreted

69
Next Water Soluble Vitamins
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