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Flashcards in Niacin (B3) Deck (13)
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1

Tryptophan

60 mg tryptophan = 1 mg niacin

Niacin equivalent (NE)

Creates NAD+ in liver

2

Excretion

NMN (n methyl nicotinamide)
Liver catalyzes the hydrolysis of nicotinamide with glycohydrolase.

3

NAD

Oxidation rxns

4

NADPH

Reduction rxns

5

Deficiency: pellagra

3 D's: dermatitis, diarrhea, dementia, (death)

Can be caused by deficiency in B6, riboflavin, and iron.

Caused by poor tryptophan diet.
Bound niacin not available (corn). Lime treatment.
Malabsorption, alcoholism, cancer drugs, TB.

6

RDA

16 NE men
14 NE women

1 NE = 1 mg niacin/ 60 mg tryptophan

7

Assessment

Urinary excretion of niacin metabolite NMN
>1 mg/d desirable

Plasma not good indicator b/c concentrations of niacin are low in healthy individuals who are assessed.

8

Functions:
Electron transport (NAD)
Biosynthesis pathways (NADPH)

NAD: glycolysis, oxidative decarboxylation pyruvate, oxidation of acetyl CoA, beta oxidation

NADPH: fatty acid synthesis, regenerates glutathione and vitamin C, folic acid metabolism

9

Niacin and Vitamin C

Reduces glutathione
Glutathione recycles vitamin C
Vitamin c regenerates/ reduces vitamin E

10

UL 35 mg

Vasodilation due to increased histamine

11

Megadosing

6 g nicotinic acid NOT nicotinamide to treat hypercholsterolemia

Low LDL
High HDL

12

Sources

Meats especially chicken and tuna.
Fortified cereal.
Milk products.

100% absorption up to 3-4 g dose

13

Pregnancy

Trp dioxygenase enzyme activity increases.
Prevents fetus for being rejected.

Drives immunological tolerance of fetus.