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vitamins: fat-soluble (long version)

Terms in this set (19)

fat-soluble vitamins
A, D, E, K
require bile and dietary fat for absorption
once absorbed, they are transported with fats through the lymphatic system in chylomicrons before entering the blood
can be stored in body fat, intakes can vary without risk of deficiency- as long as there are average intakes over time
not easily excreted, increases risk of toxicity with high intakes
vitamin A
found preformed from animal products or supplements or in precursor form from plant foods
key role in night vision, cell differentiation, growth and regulation, immune system (association with measles)
preformed vit. A compounds are known as retinoids
plants contain precursors to vit. A known as carotenoids- most common is B (beta) carotene, which gives carrot orange color
vitamin A in the body
retinoids and carotenoids are transported from the intestine in chylomicrons, which then deliver them to the liver
in the lover, some carotenoids can be converted to retinol or retinal
to move from liver to tissues, retinol is bound to retinol binding protein
retinol
circulates in the blood
can be interconverted with retinal
retinal
important for vision
can be interconverted with retinol
retinoic acid
formed from retinal
used for modulating gene expression not vision
cannot be converted back to retinol or retinal
carotenoids
carotenoids that are not converted to vita min A may act as antioxidants
B-carotene the most common carotenoid won't act like vit. A until it has active retinal
vitamin A- light
perception of light
in the eye, the retinal for of vitamin A combines with the protein opsin to form the visual pigment rhodopsin
rhodopsin helps transform the energy from light into nerve impulse that is sent to the brain
the nerve impulse is then interpreted by the brain as vision
*retinal + opsin = rhodopsin
-rods are used for interpreting light as vision and cones are used for color
vitamin A- gene expression
retinoid acid form of vit. A enters the nucleus of specific target cells
in the nucleus, RA binds to specific protein receptors
the RA- receptor complex then binds to regulatory region of DNA on a vit. A responsive gene
once bound, the level of mRNA produced is altered (either increased or decreased), thus regulating the production of proteins
ONLY RETINOIC ACID THAT CAN MODULATE GENES
genes regulated are involved in growth and development, embryogenesis, and the immune system
vitamin A deficiency and toxicity
deficiency= threat to the health, sight, and lives of millions of children
can be caused by insufficient intake of vit. A, fat, protein, or zinc
-can result in blindness: go blind not because of retinal problem but because the retinoic acid is needed for particular cells of the cornea and these genes won't be working- through retinoic acid not regulating the gene to get those cells of the eye
-preventable with supplementation of vit. A
toxicity= preformed vit. A can be toxic if taken in high amounts, medications can be made from vit. A (retina A or Accutane) that can cause serious side effects
vitamin D
sunshine- can be produced by skin exposure to UV light
liver, fatty fish, fish oil, egg yolks (not many foods)
can be toxic at high levels, limitations on foods that can be fortified
important for bone health, normal functioning of the parathyroid gland and regulating of the immune system
def. goes along with increased risk of infectious diseases
vitamin D in bone health
maintain levels of Ca and phosphorus in the blood to favor bone mineralization- want these amounts to be stable in the blood and use vit. D to do that
vitamin D actions
(similar to RA) active vit. D works at gene regulation
regulates number of genes, most involved in bone health, although other genes regulated by vit. D include genes that regulate immune response, reproductive functions, and skin growth
vitamin D deficiency and toxicity
def.: dietary Ca cannot be absorbed efficiently and there can be improper bone mineralization and abnormalities in bone structure
children= rickets (soft bones) and adults= osteomalacia (need sun exposure to have active vit. D)
toxicity: high blood and urine Ca conc. depositing of Ca in blood vessels and kidneys, cardiovascular damage and possibly death
vitamin E/ tocopherol
antioxidant properties
alpha-tocopherol is the form of vit. E absorbed by the human body
nuts, peanuts, plant oils, wheat germ
absorption depends on normal fat absorption
once absorbed is incorporated into chylomicrons
def. in newborns might result in hemolytic anemia
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