Niacin revision questions - week 10

Question 1

Food source

Answer 1

meat, poultry, fish, enriched grains

Question 2

Absorption

Answer 2

• bioavailability low in grains, especially corn: tightly bound to protein - less than 30% can be absorbed
• some antibiotics inhibit niacin absorption
• some absrobed in stomach but mainly in SI (active transport and passive diffusion depending on conc. available)

Question 3

Transport and activation

Answer 3

converted to coenzyme form in all tissues; NAD+ and NADP-

Question 4

Storage

Answer 4

limited storage in liver

Question 5

Excretion

Answer 5

in liver

Question 6

Coenzyme form

Answer 6

nicotinamide adenine dinucleotide (NAD)

nicotinamide adenine dinucleotide phosphate (NADP)

Question 7

Main Function

Answer 7

coenzyme to numerous oxidation-reduction reactions in energy metabolism and the synthesis and breakdown of FAs

Question 8

RDI

Answer 8

men - 16mg

women - 14mg

Question 9

UL

Answer 9

35mg - supplements and fortified foods only

based on observed flushing after intake due to peripheral vasodilation

Question 10

only water-soluble vitamin to

Answer 10

be made in the body
- can be endogenously synthesised from tryptophan
60mg tryptophan = 1mg niacin

Question 11

Toxicity

Answer 11

Flushing of skin

Question 12

Deficiency

Answer 12

• pellagra (rough skin)

- dermatitis, diarrhea, dementai, death