Vitamin A (Retinoids)

Question 1

Types of V-A

Answer 1

• retinol-alcohol
• retinal-aldehyde
• retinoic acid-derived from retinal
• retinyl ester- esterfication with FA

Question 2

V-A food sources

Answer 2

• preformed= retinoids=animal products

- provitamins= carotenoids=plant products

Question 3

V-A digestion

Answer 3

• released from protein/FA
• -protein=stomach and pepsin
• -FA= SI, pancreatic enzyme
• incorporated into micelles

Question 4

V-A absorption

Answer 4

• in proximal SI
• -70%-90% of retinoids
• -20%-50% of cartenoids
• storage= liver
• RBC transport in serum

Question 5

V-A functions

Answer 5

• vision at night
• mucus production in eyes
• generates pigments for the retina
• cell division
• growth-retoic acid
• -embryo, genes, bone, lungs, trachea, skin, cornea
• healthy skin (topical meds=birth defect)
• regulate immune system
• -adding T-lymphocytes and phagocytes

Question 6

V-A functions of Rods and Cones

Answer 6

• cones=bright light, color vision
• rods=dim light, black and white
• -beta-carotene-prevention of:
• -cardio disease
• -cancer prevention
• -age degeneration
• -cataracts

Question 7

V-A RDA

Answer 7

• 900 ug-male
• 700 ug-female
• RAE=1 mg of retinol= 12mg beta- carotene
• UL= 3000 ug/d (10,000 IU)= 24mg carotenoid

Question 8

V-A deficiency

Answer 8

• night blindness-impaired production of rhodpsin, reversible
• xerophthalmia- dryness of cornea, reversible
• corneal ulceration/keratomalacia/blind- sof cornea, irreversible
• hyperkaratosis-keratinized cells replace epithial cell, hair folicles plugged, bumpy/dry skin
• impaired immunity- decreased resistance to infections

Question 9

population at risk for V-A deficiency

Answer 9

• young children
• urban poor
• older adults
• alcoholism
• liver disease
• fat malabsorption

Question 10

V-A toxicity

Answer 10

none for carotenoids

• performed A=inevitable- storage cont. until toxicity develops
  1) acute-short term, symptoms disappear when intake stops: GI headache, blurred vision, poor muscle coordination
  2) chronic- long term, possibly permanent: bone/muscle pain, skin disorder, no appetite, headache, fatigue, dry skin, increased liver size, vomiting
  3) teratogenic effect-3x RDA. physical defect on fetus

Question 11

V-A nutrition assessment

Answer 11

• clinical:
• -measure of dark adaptation
• -rhodospin regeneration rate
• -CIC
• -plasma retinol conc.- change in plasma conc. before and after 5 hrs. of oral medication of RE in oils