MIdterm 2 Section 5 Flashcards
teratogenic definition
toxic side effects
vitamin A deficiencies and toxicity side effects
deficiency can lead to blindness, susceptibility to measles
toxicity can cause birth defects
retinal deficiency: night blindness
retinoic acid deficiency: bitot’s spots, xerophthalmia, keratomalacia
vitamin A forms and functions
food sources: retinoids (animal) and carotenoids (plant)
converted in the body: retinol (from retinoids) –> retinal –> retinoic acid
supplement sources: retinyl ester
retinol - supports reproduction
retinal - participates in vision
retinoic acid - regulates growth
what role does vitamin A play in sight?
within the retinal cells (rods and cones) in the back of the eye
retinal sits in a cis configuration as part of rhodopsin, adjacent to the opsin protein
when a photon hits rhodopsin (low intensity light), retinal changes to trans configuration, sending an electrical impulse to the brain
bitot’s spots
lesions that appear in the white of the eye due to retinoic acid deficiency
xerophthalmia
dry eyes
keratomalacia
Changes structure of surface of eye, causes drying and clouding
Causes irreversible blindness
Due to retinoic acid deficiency
Cataracts
Lens becomes less flexible with age (difficulty seeing up close)
Cataracts - lens gets cloudy, surgery vibrate lens to break up lens and take it out, and then replace the lens
Vitamin A role in mucous membrane health
Necessary in mucous membrane of GI and lungs
Maintains differentiated goblet cells and columnar cells
Allows pathogens into the body more easily
GI and respiratory illness risk increases
Retinoic acid functions
1) cell differentiation: controls gene expression
- goblet/epithelial cells and embryonic growth (deficiency/toxicity)
- membrane integrity, taste, digestion, absorption, malformations in toxicity
2) Immunity: direct and indirect (epithelium)
3) Growth: cell division and bone remodeling
RDA and UL for vitamin A
in RE retinol equivalents
500mg RE RDA
15000mg RE UL
Good food sources of vitamin A or beta carotene
dark green and deep orange veggies
sweet potatoes, beef liver, dairy is fortified, carrots, broccoli
vitamin K forms and function
phylloquinone - plant form
menadione - vitamin form
functions:
- carboxylation of glutamic acid residues in proteins to enable Ca binding (ex. osteocalcin)
- blood clotting cascade
vitamin K deficiency occurs with
fat malabsorption, newborns, antibiotic use
contraindicated with anti-clotting drugs
vitamin K in the blood clotting cascade
vitamin K helps to form a prothrombin precursor
calcium and thromboplastin activate prothrombin to thrombin active enzyme
fibrinogen and thrombin form a mesh to trap RBC and clot
when taking Warfarin (coumadin)
sudden changes in vitamin K can affect medication from working (anti-clotting)
maintain dietary intake of vitamin K from liver, brassica veg and eggs
Zinc functions
metalloenzyme cofactor: DNA/protein synthesis, release of vitamin A stores, taste perception, free radical protection, heme synthesis, immune function, wound healing, growth/development, pancreatic enzymes for digestion
good food sources of zinc
oysters, dairy, beef, crab, sunflower butter
why is zinc deficiency difficult to diagnose?
because the body will pull from stores to supply blood zinc values, so blood tests are not effective
easily misdiagnosed as PEU protein energy malnutrition
RDA and UL for zinc
don’t supplement
women 8mg/day
men 11mg/day
UL 40mg/day
Zinc enteropancreatic pathway
Zn2+ once absorbed in SI, Zn is bound to albumin and transferrin
and carried to the liver
bound to albumin Zn continues to pancreas to make digestive enzymes and other metalloenzymes, to be secreted into SI
recycled and cycled backed to intestinal cells
Zinc stored as metallothionein in intestinal cells and liver
Some losses in feces, shed intestinal cells, urine, skin, blood and semen
Zinc absorption efficiency
33%, increases when deficient
Divalent metal transporter in jejunum same as Ca, Fe, Cu and Pb
absorption enhance and inhibited by same factors as Ca
Zinc toxicity symptoms
nausea, vomiting, diarrhea
copper deficiency
increased intestinal metallothionein which binds copper and is shed in mucosal cells in feces
can contribute to iron deficiency (DMT competition)
Thyroid hormones and functions
T3 - triiodothyronine
T4 - thyroxine
Both made from tyrosine amino acid
Functions: metabolic rate of cells, body temp, RBC synthesis, growth, reproduction, brain development
Goiter is caused by
signaling thyroid to make more hormone but cannot due to iodine deficiency
how much iodized salt to meet RDA?
2g (average intake is 8g)
Normal thyroid pathway
Healthy: hypothalamus senses decreased T3/T4
signals pituitary to secrete TSH
TSH signals increased T3/T4 synthesis
levels increase
Deficient: same until TSH signals increased T3/T4 synthesis
no iodine available leads to continued signaling with no effect
leads to goiter
Mineral interactions
Increased iron occupies transferrin binding sites and decreases Zn transport and absorption
Increased Zn/metallothionein causes Cu to be bound more tightly, and not released from mucosal cells
Decreased protein intake decreases albumin availability, decreased Zn released from mucosal cells (growth failure, immune deficiency)
Vitamin C functions
Ascorbic acid - antioxidant/reducing agent
collagen synthesis
bone/teeth development
scar tissue, wound healing
hormone synthesis
Vitamin C RDA and UL
10mg to prevent scurvy
75-90 RDA
2000 UL - mega doses produce Fe Fenton reaction
Good sources of vitamin C
broccoli, orange, tomato, strawberries, red bell pepper, kiwi brussel sprouts
Vitamin E functions and deficiency symptoms
Functions: antioxidant, protects PUFAs in membrane lipids, protects lungs, protects lipids in foods
Deficiency symptoms: RBC/WBCs break, cataracts, arthritis, cancer, fibrocystic breast disease, CVD (LDL oxidation)
Types of vitamin E
Alpha-tocopherol is supplement form
Many isomers (8) of vitamin E tocopherols , Not sure all have the same effect
Antioxidants to know
Food sources: vitamin C fruits and veg, vitamin E veggie oils, nuts, fruits and veg, B-carotene dark green or orange veg
Metalloenzymes: Se, Mn, Zn, Fe
Glutathione - tripeptide major intracellular antioxidant
Phytochemicals - polyphenols, resveritrol, lutein, zeaxanthin, carotenoids
lutein and zeaxanthins
protect against cataracts and macular degeneration
health effects of higher dose vitamin E, beta-carotene and vitamin A
increase risk of mortality
Definition of functional foods
foods that contain physiologically active compounds that provide health beyond their nutrient contributions
ex. flax, dark chocolate, tomatoes, blueberries, salmon, soybeans
