Fat soluble vitamins

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Fat soluble vitamins

• A,D,E, and K

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Overview

• Require bile for absorption
• Enter lymph then blood along with large products
  of fat digestion
• Excesses stored in liver and adipose tissue
  retrieved as needed
• Do not have to be eaten daily
• Because of storage, average daily intakes are
  recommended
• Not readily excreted
• Risk of toxicity greater than with water soluble
  vitamin

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2 Sources and 3 forms of vitamin A
In food retinyl esters
Beta-carotene from animal
foods from plants In the body retinol
retinal
retinoic acid (supports
(participates (regulates
reproduction)
in vision) growth)
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Vitamin A and vision

• Retinal helps maintain cornea
• Is part of pigment of retina that responds to
  light
• Some retinal converts irreversibly to retinoic
  acid which is inactive in the eye, and is lost
• Retinal must be replenished

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Vitamin A and protein synthesis and cell
differentiation

• Needed for differentiation of tissues that cover
  the surface of the body and line interior spaces
  (epithelial tissues) and associated mucus glands
  (goblet cells)
• Role in differentiation may explain cancer
  preventing properties of Vitamin A

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Vitamin A and reproduction and growth

• In men
• Retinol participates in sperm development
• In women
• Supports normal fetal development
• In children
• Necessary for growth

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Vitamin A and bone remodeling

• Remodeling complex phenomena involved in bone
  growth
• Small bone converts into larger bone as parts of
  small bone are dismantled and replaced
• Vitamin A participates in dismantling by aiding
  enzymes that degrade bone

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Remodeling in the adult

• Phenomena continues as bone maintenance

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Antioxidant properties of beta carotene

• The small amount of beta carotene that does not
  convert into vitamin A acts as an antioxidant and
  protects the body against a variety of diseases

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Vitamin A deficiencies

• Do not appear until stores have been depleted
• Rare in U.S.
• More common in undeveloped countries

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Vitamin A deficiency and Infectious disease
susceptibility

• Measles, pneumonia and diarrhea
• Potentially fatal
• Severity correlates with degree of deficiency
• Large problem in developing countries

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Night blindness

• One of the first signs of Vitamin A deficiency
• Due to lack of retinal in retina, which is
  located in the back of the eye

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Blindness (xeropthalmia)

• Total blindness due to lack of vitamin A in
  cornea, which is located in the front of the eye

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Epithelial cells

• Epithelial cells of skin become hard because of
  extra keratin deposits
• Goblet cells in GI tract do not secrete enough
  mucus
• Other epithelial cell weaken and become
  susceptible to infection

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Toxicity of Vitamin A

• Children are most vulnerable to high levels
• Beta carotene excess from food do not contribute
  to toxicity
• Conversion to Vitamin A is inefficient
• Excesses are stored in skin
• Give skin a yellowish hue
• Beta carotene excesses from supplements can
  contribute to toxicity
• Acts as prooxidant
• Promotes cell division and destruction of vitamin
  A
• Effects are most evident in people who drink
  alcohol and smoke cigarretes

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Toxicity and bone defects

• Excessive intake may weaken bones
• Recent research suggest most people do not need
  supplement, and even levels in common
  multivitamins may be excessive

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Toxicity and birth defects

• High intakes before 7th week are most damaging
• Can cause abnormal fetal development and birth
  defects (teratogenic effect)

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Vitamin A and acne

• All forms of naturally occurring vitamin A are
  ineffective in treating acne
• Accutane, prescription oral medication, is made
  from vitamin A and used to treat cystic acne
• Patients must use birth control
• Highly toxic to fetus
• Retin-A, prescription topical medication, also
  made from vitamin A
• Effective against acne, wrinkles and other skin
  conditions
• Smoothes, softens, lightens skin
• Causes redness and peeling of skin

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Vitamin A recommendations

• Measured in retinol activity equivalents (RAE)
• 1 microgram of retinol1RAE
• 12 micrograms of dietary beta carotene1RAE
• Men
• 900 micrograms of RAE/day
• Women
• 700 micrograms of RAE/day

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Upper level

• 3000 micrograms/day

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Significant sources

• Retinol
• Fortified milk and dairy products and margarine
• Eggs
• Liver
• Beta carotene
• Spinach and other dark leafy green
• Broccoli
• Deep orange fruits and vegetables

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Vitamin D the sunshine vitamin

• Also known as calciferol or calcitriol
• Not an essential nutrient
• Body can synthesize it with exposure to UV in
  sunlight to form its precursor D3
• D3 is made from cholesterol
• Precursors are also found in some foods
• D3 is first modified by the liver, then by the
  kidneys into the active form

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Roles in the body

• Acts as a hormone, not a vitamin
• Chemical messenger

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Vitamin D and bones

• Works in concert with vitamins A,C, and K other
  hormones, collagen, calcium, phosphorus,
  magnesium and fluoride in bone making and
  maintenance
• Helps maintain adequate levels of blood calcium
  and phosphorus needed for bone formation
• Enhances absorption from GI tract
• Enhances reabsorption of calcium and phosphorus
  from kidneys, so they are not lost in urine
• Enhances their mobilization from bone into blood

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Other functions

• Affects many other cells
• Immune system
• Brain and other parts of nervous system
• Pancreas
• Skin
• Muscles
• Cartilage
• Reproductive organs
• Role in protection against some diseases
• TB
• Gum inflammation
• Multiple sclerosis
• Some cancers

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Vitamin D deficiency

• Rickets
• Inadequate mineralization of bones in children
  usually caused by vit.D deficiency
• Bowed legs or knock knees, outward bowed chest,
  knobs on ribs

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• Osteomalacia
• Usually in adult women
• Bones are soft, flexible, brittle, deformed
• Bent spine and bowed legs

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• Osteoporosis
• Reduced bone density leading to fractures

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Vitamin D and the elderly

• Deficiencies more likely to develop in elderly
• Skin, liver and kidneys are not as efficient
• Older adults often do not drink milk, which is
  supplemented with vitamin D
• Often elderly do not get adequate exposure to
  sunlight

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Vitamin D RDA

• Adults
• 5 micrograms/day (19-50)
• 10 micrograms/day (51-70)
• 15 micrograms/day (over 70)

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Upper level

• Adults
• 50 micrograms/day

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Toxicity

• Hypervitaminosis D
• Toxicity symptoms
• Elevated blood calcium
• Calcifications of soft tissues

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Significant sources of vitamin D

• Exposure to sunlight
• Fortified foods, including milk
• Veal
• Beef
• Egg yolks
• Liver
• Fatty fish

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Vitamin E

• Other names
• Alpha tocopherol
• RDA
• 15 mg/day
• Upper level
• 1000 mg/day
• Chief functions
• Antioxidant stabilizes cell membranes,
  regulation of oxidation reactions, protection of
  polyunsaturated fatty acids and vitamin A

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• Significant sources
• Polyunsaturated plant oils
• Leafy green vegetables
• Wheat germ
• Whole grains
• Liver
• Eggs yolks
• Nuts and seeds
• Fatty meats

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• Deficiency symptoms
• Red blood cell breakage
• Nerve damage
• Toxicity symptoms
• Augments effects of anticlotting medications
  (enhances bleeding)

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Vitamin K

• Other names
• Phylloquinone, menaquinone, menadione,
  naphthoquinone
• RDA
• Men 120 micrograms/day
• Women 90 micrograms/day
• Upper level
• None established
• Chief functions
• Synthesis of blood clotting proteins and bone
  proteins

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• Significant sources
• Bacterial synthesis in digestive tract
• Liver
• Green leafy vegetables
• Cabbage type vegetables
• Milk
• Deficiency symptoms
• Hemorrhage
• Toxicity symptoms
• None known

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The End