Niacin B3 Review

NIACIN B3

Generic term for NICOTONIC ACID AND NICOTINAMIDE (NIACIN-AMIDE)

• Nicotinamide Nucleotides:
• Nicotinamide Adenine Dinucleotide (NAD)
• Nicotinamide Adenine Dinucleotide Phosphate (NADP)

SOURCES

Primarily from fish and meats (especially beef tongue 15 mg / 3 oz)

In coffee and tea

Bacteria produce niacin

Supplement and fortification are NICOTINAMIDE

In animal food:

• NICOTINAMIDE
• Nicotinamide Nucleotides in OXIDIZED FORM:
• Nicotinamide Adenine Dinucleotide (NAD+)
• Nicotinamide Adenine Dinucleotide Phosphate (NADP+)

In Plant food: NICOTINIC ACID

When bound to complex carbohydrates, called NIACYTIN

When bound to small peptides: NIACINOGENSE

Lime water will help release bound forms of niacin.

TRYPTOPHAN can be used by liver to produce NIACIN (3% of body stores)

• Hartnup disease (genetic inability to transport tryptophan during absorption)

DIGESTION, ABSORPTION, METABOLISM, and EXCRETION

FUNCTION/MOA

Over 200 enzymes - primarily dehydrogenases - require NAD or NADP which acts as a hydrogen donor or electron acceptor

COENZYME ROLES IN NUTRIENT METABOLISM AND ENERGY PRODUCTION

• NADH - reduced form of NAD
• Transfer electrons in the ETC
• NADPH
• acts as a reducing agent in many pathways:
• fatty acids
• cholesterol
• steroid
• Oxidative reactions in which no acute changes. reduced to NADH
• Glycolysis
• Oxidative decarbosylation of pyruvate to acetyl-coA
• oxidation of acetyl coa in the TCA cycle
• B oxidation of fatty acids
• Oxidation of ethanol
• Aldehyde dehydrogenase catabolizes B6 to excretory product, requires NAD
• NADP reduced to NADPH
• Pentose phophate pathway
• Malate aspartate shuttel
• Nutrient metabolism (see above)

NONREDOX ROLES
ADP transferred to acceptor molecules, typically involving cellular processes like DNA repair, chromatin structure, intraceullular calcium signallying.

USES

• 6g/d Nicotinic Acid
• Hyperlipidemias
• Flushing
• Liver injury
• Gout
• Niacinamide does not lower cholesterol
• reduces skin inflammation
• 3g/d can cause headache, GI distress, impaired glucose tolerance, liver damage

RDA:

60mg tryptophan = 1 mg niacin

Niacin equivalents - 16 mg and 14 mg

DEFICIENCY

Pellegra

• Dernatitis, Dementia, Diarrhea, Death
• Neurological manifestations
• GI manifestations

Risks: Malabsorptive, INH, Mercaptopurine, etoh, HIV, cancer

TOXICITY

Related to vasodilatory effects

35 mg a day

ASSESSMENT

Urine excretion

Serum or RBC: NAD:NADP ratio ~ 1.0