Exam 2 Flashcards
How were vitamins first discovered
While searching for cures for common diseases
What vitamin micronutrients are measured in micrograms
RDA’s measured in mcg: vit. A, B12, D, K, folate and biotin
What are the functions of vitamins
Membrane stabilizer, hormones, coenzymes, H+and e- donor/acceptors (antioxidants)
What are identifiers of vitamin clinical deficiency
Pellagra, burning feet syndrome, keshan’s disease
What is subclinical deficiency (insufficiency) associated with
Increased risk of chronic diseases such as HTN, CA, and atherosclerosis
Which vitamin metabolism is associated with being absorbed as part of micelles
Fat soluble vitamins
Which vitamin metabolism is associated with being transported in the portal vein
Water soluble
Which vitamin metabolism absorption is enhanced with fat intake
Fat soluble
How are fat soluble vitamins transported
In lipoproteins in lymphatic system
Why are water soluble vitamins less likely to be toxic
Most are not stored in appreciable quantities
Why is fat soluble vitamins more likely to be toxic
Its stored in liver/adipose
What do water soluble vitamins rely on to meet requirements
Daily intake
What are fat soluble vitamins
ADEK
Which vitamin A retinoid is associated with reproduction and growth
Retinol
Which vitamin A retinoid is associated with vision
Retinal
Which vitamin A retinoid is associated with cell differentiation
Retinoic acid
Which type of vitamin A is preformed plant or animal
Animal
Where is preformed (active) vitamin A found
Animal products
What is a retinol ester
Retinol with fatty acid attachment
What is one type of retinal ester and also a storage form of Vitamin A
Reinyl Palmitate (vit A palmitate)
What are proformed vitamin A
Plant products (orange, yellow, red colors)
What are precursors to vitamin A
Carotenoids (antioxidants)
Which type of vitamin A is used only when we don’t get enough preformed in the diet
Proformed
How many carotenoids are known and how many can be converted to retinol
> 600 known carotenoids; <10% can be converted to retinol
What are the structures of carotenoids
B-carotene and lycopene
Where is vitamin a highly concentrated
In the rods of the retina
What is important for vision in dim light
Rhodopsin
How do you get rhodopsin
Retinol converts to retinal and added with opsin
What will a decrease in vitamin a produce in regards to rhodopsin
Decrease in rhodopsin = night blindness
A decrease in vitamin A does what to keratin producing cells
Keratin producing cells replace mucus secreting cells in respiratory, GI, and urinary tracts
What causes hyperkeratinization
Vitamin a deficiency
What do keratinocytes along with vitamin A (retinoic acid) become
Mature epidermal cells
What are 2 carotinoid funx
Antioxidant and cell growth/differentiation
What do carotenoid antioxidants do
Quench reactive oxygen species
What carotenoid antioxidants are concentrated in the macula and what is their funx
Lutein and xeaxanthin that prevent UV induced eye damage
What do carotenoids have to do with cell growth/differentiation
Specific carotenoids may inhibit growth and proliferation of several cancer lines
Supplemental carotenoids can cause what
Increased risk of several cancers due to cell growth and differentiation
What do carotenoids consist of
Carotenes (no oxygen) and xanthophylls (contain oxygen; ex lutein)
What is vitamin A RDA measured as
Retinol activity equivalents (RAE)
What is the RAE for men
900
What is the RAE for women
700
What stores 70% of the body’s vitamin A
The liver
What can toxicity of vit A affect
Can cause liver damage
What is the primary cause of vitamin a deficiency
Inadequate intake
What is the secondary cause of vit a deficiency
Fatty malabsorption
What is the leading cause of preventable blindness in children
Vit a deficiency
What are two common vit a deficiency symptoms besides vision problems
Depressed immune system, skin problems
What does vit a deficiency cause in the immune system
Depressed system, more infx with higher mortality rates
What type of skin problems come from vit a deficiency
Follicular hyperkeratosis caused by plugs of keratin
What causes hypervitaminosis A
Due to preformed only (not carotenoids)
What happens when someone takes in excessive vitamin A during pregnancy
It becomes teratogenic
What is the TUL for carotenoids
No TUL set, considered low toxicity
Chronic carotenoid consumption can lead to what
Yellow/orange skin
Supplements of carotenoids promote what
Oxidative damage, cell division and destruction of other forms of vitamin A
What are good sources of vit a preformed
Liver, fish, fortified dairy, eggs
What are good sources of proformed vit a
Carrots, dark green leafy veggies, sweet potatoes, tomatoes, cantaloupe
When does vit a become unstable
When exposed to heat and oxygen
What does vitamin a absorption require in order to be absorbed
Emulsification by bile salts
What is the bioavailability of preformed vitamin a
75-100%
What is the bioavailability of proformed carotenoids
3-90%(cooking increases)
What type of absorption takes place with vitamin A
Absorbed via passive diffusion
Where is vitamin a absorbed
Duodenum and jejunum as part of micelles
What is retinol bound by during vitamin A absorption
Cellular retinol binding protein (CRBP)
Retinol is reesterified to a ____ in _____ by ____
RE (retinol ester), enterocyte, lecithin and retinol acyl transferase (LRAT)
How much of RE is absorbed
80%
RE are incorporated into what and transported in what
Incorporated into chylomicrons and transported in the lymphatic system
What handles and stores vit A
Liver
What circulates in the blood bound to thyroxine T4
RBP-retinol-TTR
How much cellular vit a is stored in the liver
50-80%
What is the retinol ester (storage) for vit a
CRBP retinol by LRAT, retinol by ARAT
What is the animal form of vitamin D
Cholecalciferol (vit D3)
Where is cholecalciferol made from
Made from cholesterol
What is the plant form of vitamin D
Ergocalciferol (vitamin D2)
What is the half life of cholecalciferol
82 days
What is the half life of ergocalciferol
33 days
Is vitamin D a vitamin
Technically a prohormone, rather than a vitamin
What are problems of vitamin D insufficiency
Soft/spongy bones, rickets, osteomalacia
How does hypovitaminosis D present itself in children
Rickets = bowed legs, bilateral knee pain
What does hypovitaminosis D look like in adults
Osteomalacia = muscle weakness, bone pain
Hypovitaminosis D can present itself in osteoporosis, osteomalacia, rickets what can happen as a result
Stress fractures, low back pain
What is the best biomarker for vitamin D assessment
25- hydroxyvitamin D (calcidol)
What is vitamin d deficiency considered
<20 ng/mL
How many americans are vitamin D deficient
50% of americans
When does vitamin D toxicity happen
Arise with daily doses of 10,000 IU or more for more than 6 months
What happens when someone has vitamin D toxicity
Calcification of soft tissues. Hypercalcemia, hyperphosphatemia
Where does vitamin D regulation take place
Found in high concentration in the kidneys
Vitamin D regulation limits the amount of what
Active calcitriol
What gene mutation can lead to hypercalcemia
Gene coding from 24-hydroxylase
Whee is 24-hydroxylase found
In all cells
What conditions where vitamin D supplementation should be cautioned
Hyperparathyroidsim, granulomatous disorders (sarcoidosis, TB), some lymphomas
Where do most vitamin D sources come from
Fish, fortified dairy, egg yolk
What are poor sources of vit d
Breast milk, unfortified dairy
When is vitamin d stable
Heat, age, storage
How was vit E originally discovered
Discovered it was necessary for animal reproduction
Vit E donates H to what to protect what in membrane
Donates H to free radicals to protect PUFA in membrane
Dietary intakes of vitamin E has been shown to decrease risk of what
Heart disease, cancer, age related macular degeneration
What is the ratio of vitamin E to unsaturated FA in cell membrane
9:1000-2000
What is important for vitamin E functions
Regeneration
What is vit E main funx
Antioxidants
What does hypovitaminosis E produce
Tocopherols producing symptoms like hemolytic anemia (infants), neuropathy, retinopathy
Why does vitamin E deficiency produce neuropathy
Due to disturbance in myelin production
Is hypovitaminosis E rare
Yes
Who is most at risk for hypovitaminosis E
Patients with fat malabsorption, and premature infants
What do vitamin E supplements inhibit
Vitamin K activity
Vitamin E inhibiting vitamin K activity produces what
Increase bleeding and iimpaired bone mineralization
What is the overall best source of vitamin E
Plant oils