MIdterm 2 Section 5 Flashcards by Samantha Sterman

teratogenic definition

toxic side effects

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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

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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

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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

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bitot’s spots

lesions that appear in the white of the eye due to retinoic acid deficiency

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xerophthalmia

dry eyes

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keratomalacia

Changes structure of surface of eye, causes drying and clouding
Causes irreversible blindness
Due to retinoic acid deficiency

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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

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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

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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

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RDA and UL for vitamin A

in RE retinol equivalents
500mg RE RDA
15000mg RE UL

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Good food sources of vitamin A or beta carotene

dark green and deep orange veggies
sweet potatoes, beef liver, dairy is fortified, carrots, broccoli

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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

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vitamin K deficiency occurs with

fat malabsorption, newborns, antibiotic use
contraindicated with anti-clotting drugs

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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

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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