unit 5- vitamins Flashcards
vitamins
- organic compounds that are vital to life and indispensable to body fxn
- only needed in minute amounts, and are non-caloric, essential nutrients
2 classes of vitamins
1) fat soluble
2) water soluble
-the solubility of a vitamin confers on its many characteristics and determines how it is absorbed, transported, stored and excreted
fat soluble vitamines
ADEK
- dissolve in lipid and require bile for absorption
- absorbed into lymph and travel through blood with protein carriers
- they are not readily excreted, tend to build up and therefore higher risk for toxicity
can fat soluble vitamins collect up?
-can be stored in liver or with other lipids in fatty tissues, and can build up to toxic amounts
(therefore caution fat soluble supplements)
3 active forms of vitamin A in body
And what are food sources of Vit A
1) retinol
2) retinal
3) retanoic acid
-preformed vit A is only found in foods of animal origin (liver and fish oil, as well as milk (lost when skim), cheese, and fortified cereal
retinol
-stored in liver, and the body’s cells convert retinol to the two other active forms
b-carotene
- found in plant foods (i.e. orange veggies such as carrots, sweet potatoes and apricots; and dark green veggies like spinach and broccoli; and other colour veggies such as iceberg lettuce, beets, and sweet corn)
- can be converted to vitamin A
vitamin A functions
-gene expression, vision, cell differentiation, reproduction and growth, and immunity
Vitamin A toxicity
- chronic intake of even small excesses can weaken bones and contribute to hip fractures
- pregnant women must use caution as it can cause malformations to fetus
- children are the most sensitive to toxicity
Vit D
- cholecalciferol
- UV light from sun can convert cholesterol in human skin into Vit D precursor, which is absorbed into blood
- liver and kidneys then finish converting precursor to active Vit D
D functions
- hormone
- plays role in regulating blood calcium and phosphorus levels, thus maintaining bone integrity
D deficiency
- low levels may be linked to high bp, some types of cancer, T1D, heart disease, RA, IBD, and even MS
- the well established problems are calcium balance and bones=> rickets in children and osteomalacia in adults
what does the risk of vit D deficiency increase with?
age
-due to lower intake, housebound, decreased ability to activate vit D, and need increases after 50
Vit D toxicity
-most potentially toxic of all vitamins (but no risk just form sun)
factors that affect conversion to active Vit D from sun?
-skin tone, sunscreen use, pollution, clothing, geography, and time of year
Food sources of Vit D
- fortified milk and margarine, eggs, butter, fortified soy beverages (some rice and almond beverages), as well as some fatty fish
- more foods are starting to be fortified
is breast milk high or low in Vit D
-low (therefore supplementation of breasted infants is recommended)
Vit E
-tocopherol (god standard= alpha version)
function of Vit E
- antioxidant (main defender against oxidative damage)
- especially important in RBC and lungs (high exposure to oxygen)
- may protect LDL from oxidation and reduce inflame (thus protecting against heart disease)
Vit E deficiency: rare or common
rare (usually only occurs in premature infants)
why is Vit E deficiency rare?
3 reasons:
1) found in many foods
2) body stores enough in fatty tissue to last a long time
3) cells recycle their working supply of vitamin E, using the same molecules over again
Vit E toxicity
rre
-no adverse affects reported from naturally occurring Vit E
when is Vit E toxicity more likely to occur?
frm supplements and fortified foods
Food sources of Vit E
MANY:
-vegetable oils, f+v, fortified cereals/grains, meats+alts, and milk products
what destroys Vit e?
heat processing and oxidation
Vit K functions
- help synthesize proteins that help clot the blood
- also needed for synthesis of key bone proteins
Vit K Deficiency
-few have
why are infants given a dose of Vit K at birth
- they are born with sterile intestinal tract, and vit K producing bacteria take weeks to establish
- give to prevent hemorrhage
Vit K toxicity
-rare (no upper limit set)
Vit K sources
- intestinal bacteria
- dark, leafy greens, and members of cabbage family
which 2 fat soluble vitamins can be derived from non-food source?
Vid D and K
water soluble vits
- C and B
- dissolve in water, so they are absorbed into blood stream where they travel freely
- most not stored; are excreted in urine
- less risk of toxicity; needed in frequent doses
The B Vitamins
- act as coenzymes, and some are also involved in energy metabolism
- play important roles in body, and typically deficiencies occur together, as many food sources contain a combo of the Bs
In north america, which product is fortified by vit B
-refined grain products
Thiamin function
- plays critical role in energy metabolism of all cells
- occupies site on nerve cell membranes therefore, nerve processes and muscles depend heavily on thiamin
thiamin food sourses
-small amounts occur in many nutritious foods, such as legumes, enriched/whole grain cereals, sunflower seeds and pork
thaimin deficiency
= beriberi
-characterized by loss of sensation in the hands and feet, muscular weakness, advancing paralysis and abnormal heart action
