Chapter 9: Vitamin B3 (Niacin) Flashcards
other names:
nicotinamide acid
nicotinamide or niacinamide
pellagra-preventive factor
niacin b3
niacin - chemistry
occurs in 2 forms
both of which can be utilized by man
niacin or nicotinic acid and niacinamide
niacin - chemistry
converted in the body to the cofactor _____ that can exist in its phosphorylated form (NADP)
nicotinamide adenine dinucleotide (NAD)
niacin - chemistry
NADP cycles between its oxidized form NAD+ and the reduced form NADH + H+
-
niacin - chemistry
a white, crystalline substance that is stable in the heat, light, alkali, acid and oxidation
niacin
niacin - chemistry
forms occurring in foods are NAD, NADH, NADP, and NADPH that functions as coenzymes
niacin
niacin - chemistry
1 mg niacin = _____ tryptophan
60 mg
niacin - absorption, transport, utilization
absorbed in the stomach but is more readily absorbed in the _____
small intestine
niacin - absorption, transport, utilization
at low concentrations, the vitamin is absorbed by carrier-mediated _____
facilitated diffusion
niacin - absorption, transport, utilization
at high concentrations, absorption is by _____
diffusion
niacin - absorption, transport, utilization
circulated in the blood and rapidly removed by the _____ and erythrocytes and converted to NAD and NADP
liver
niacin - absorption, transport, utilization
any excess niacin is excreted in the urine as _____ and _____
methyl nicotinamide and methyl-carboxamide
niacin - absorption, transport, utilization
NAD can be synthesized in the _____ from the amino acid tryptophan; only about 3% of the tryptophan is converted
liver
niacin - absorption, transport, utilization
NAD can be synthesized in the liver from the amino acid _____; only about 3% of the tryptophan is converted
tryptophan
niacin - functions
release of energy from cho, lipid, and chon
-
niacin - functions
synthesis of _____ (3) needed for dna formation
cho, protein, and pentoses
niacin - functions
acts as an ____ in the breakdown of cho, fatty acids, ketones, amino acids, and alcohol
electron acceptor
niacin - functions
involved in the biosynthetic reactions such as
-fatty acid synthesis
-cholesterol and steroid hormone synthesis
-glutamate synthesis
-synthesis of deoxyribonucleic acid (DNA)
niacin
niacin - deficiency
individuals whose staple diet relies on untreated _____ (2) and chronic alcoholics are at risk of niacin deficiency
maize or barley
niacin - deficiency
severe niacin deficiency could lead to _____
characterized by dementia, diarrhea, dermatitis, and death
early signs: muscular weakness, anorexia, indigestion, and skin eruptions
pellagra
niacin - toxicity
syptoms:
-diarrhea
-heartburn
-nausea, vomiting
-ulcer irritation
-fainting, dizziness
-painful flush and rash
-itching, burning
-excessive sweating
-abnormal liver functions
-low blood pressure (BP)
niacin toxicity
niacin - recommended intake
for adults (19 - >70 y/o) males
16 mgNE
niacin - recommended intake
for adults (19 - >70 y/o) females
14 mgNE
niacin - recommended intake
for adults (19 - >70 y/o) pregnant
14 mgnE +4
niacin - recommended intake
for adults (19 - >70 y/o) lactating
14 mgNE +3
niacin - recommended intake
recommended intake of niacin corresponding to an excretion of _____ that is above the minimal excretion at which deficiency symptom occurs
n-methyl-nicotinamide
niacin - food sources
protein-containing foods, liver, milk, eggs, meat, poultry, fish, beans, nuts and seeds, legumes, whole grain cereals, avocado, figs, dates, prunes, are common sources of vitamin b3
niacin food sources
niacin - assessment status
niacin status is assessed by measuring _____ of niacin after administering a test dose of the vitamin
urinary metabolism
niacin - assessment status
2 urinary metabolites are measured and their ratio is used to measure niacin status
pyridine and nicotinamide
niacin - niacin status
for all ages
deficient: ?
< 0.5
niacin - niacin status
for all ages
marginal: ?
0.5-1.59
niacin - niacin status
for all ages
adequate: ?
> 1.6
