Vitamin C and Biotin Flashcards Preview

Nutrition > Vitamin C and Biotin > Flashcards

Flashcards in Vitamin C and Biotin Deck (20):
1

Vitamin C/ascorbic acid RDA

F - 75 mg/day
pregnancy - 100 mg/day
lactation - 120 mg/day
M - 90 mg/day
400-500 mg/day saturates body's vit c pool

**smokers require 35 mg more**

2

Vitamin C/ascorbic acid absorption

easily absorbed in SI
transport proteins = down-regulated with excess
must slowly incr to achieve max dose
70-90% absorbed (30-180 mg/day)

3

Vitamin C/ascorbic acid metabolism

diffusion from enterocyte to portal vein
free form in blood, no transport protein required
recycled/reduced by GSH
tissue concentrations = higher than plasma (80x higher in WBCs)
highest concentration =
- adrenals
- pituitary
- eyes
- brain

4

Vitamin C/ascorbic acid functions

collagen synthesis
neurotransmitter synthesis: DA, 5HTP, NE
antioxidant
carnitine synthesis
enhances non-heme iron absorption
stabilizes WBCs/antihistamine effect

5

Vitamin C/ascorbic acid: collagen synthesis

maintains skin, tendons, cartilage, bone, dentin, capillaries
cross-links proteins with hydroxyproline

6

Vitamin C/ascorbic acid: antioxidant activity

reducing agent - donates e- to minimize free radicals
recycles oxidized vitamin E
protects DNA and PUFAs

7

Vitamin C/ascorbic acid: enhanced iron absorption

reduces ferric to ferrous iron (more easily absorbed)
max benefits = 75 mg

8

Vitamin C/ascorbic acid excess

> 2 g/day
nausea
diarrhea
incr risk of kidney stones (causes precipitation of oxalates)

9

Vitamin C/ascorbic acid deficiency

scurvy
fatigue
delayed wound healing

10

Scurvy

Hemorrhagic signs: easy bruising, petechiae
Hyperkeratosis of hair follicles
Hypochondriasis: cognitive impairment
Hematological abnormalities: iron malabsorption and impaired copper/iron metabolism

give 100-300 mg/day until resolved

11

Vitamin C assessment

reduced intake
malnourished/malabsorption/cachexia
incr alcohol use
tobacco use
elderly

12

Vitamin C/ascorbic acid food sources

bell peppers
citrus
berries
brassicas
tomatoes
potatoes

13

Vitamin C/ascorbic acid availability

destroyed by heat, oxygen, light

14

Vitamin C/ascorbic acid supplements

natural = identical to synthetic
mineral ascorbates (ca ascorbate) may be gentler on stomach

15

Biotin

produced by gut bacteria
absorption rate unknown, happens in proximal and mid-transverse colon
RDA = 30 mcg/day

16

Biotin absorption

bound to biocytin (lysine residue) in food
requires biotinidase (from pancreas) to break amide bond
almost 100% absorbed in proximal SI (inhibited by alcohol)

17

Biotin functions

Enzyme cofactor - esp carboxylase enzymes
- FA synthesis/oxidation
- Gluconeogensis: catabolism of BCAA, threonine, and methionine
Gene expression
- histone modification: causes uncoiling to allow activation
- DNA repair, gene replication, regulation, **cell cycle regulation**

18

Biotin metabolism

can be recycled, so deficiency = rare
incr demand during pregnancy/lactation, tobacco use, anticonvulsant meds

19

Biotin deficiency

= rare
hair loss
brittle nails
seborrheic dermatitis
paresthesia

20

Biotin food sources

liver
eggs, cooked
avocado
salmon
almonds
legumes
pork