Niacin

By : Maryam Valavi

Introduction

o Niacin is one of the B Complex Vitamins.o It is also known as Vitamin B3.

o Made from tryptophan; essential nutrient if protein intake is inadequate.

o 60 mg tryptophan converts to 1 mg niacin. nicotinic acid nicotinamid Vitamin PP

Structure

NAD+

NADH

NADP+

NADPH

Function

o Coenzymes are active participants in oxidation-reduction reactions.

o Function in at least 200 reaction in cellular metabolic pathways , Especially ATP producing reactions.

o NAD+ Participates in catabolic reactions . Electron and hydrogen ion acceptor.o NADP+ Important in biochemical pathway for fatty-acid synthesis. Cells that synthesize a lot of fatty acids have higher

concentrations of NADP+. Liver and mammary glands.

Biosynthesis

o The liver can synthesize Niacin from the essential amino acid Tryptophan, but the synthesis is extremely slow and requires vitamin .

o Bacteria in the gut may also perform the conversion but are inefficient.

Sources

Absorption

oBoth forms are readily absorbed from the stomach and intestine by active transport and passive diffusion.

oAlmost all niacin consumed is absorbed.oAt low concentration by active

transportation.oAt high concentration by passive

diffusion.

Transportation

o Both Nicotinic acid AND Nicotinamide bind to plasma proteins for transportation.

Deficiency

Pellagra

o Early stages:AnorexiaIndigestionMuscle weaknessReddened skinRough skin

o Advanced stages:3 D’s of pellagra: dermatitis, diarrhea,

dementia

Dermatitis of Pellagra

Recommended Levels

o Pediatrics1 to 3 years (6 mg)4 to 8 years (8 mg)9 to 13 years (12 mg)

o YouthMales 14 to 18 years (16 mg)Females 14 to 18 years (14 mg)

o AdultsMales 19 and older (16 mg)Female 19 and older (14 mg)Pregnant females (18 mg)Breastfeeding females (17mg)

Medicinal Uses

o Niacin in very large doses is used to decrease blood cholesterol levels and reduce the risk of heart attack.

o Treatment of Pellagra.

Toxicityo (> 35 mg/day)

o Used to treat high cholesterol but often results in several unpeasanlt side effects including:

Flushing

Heartburn, nausea, vomiting

Liver injury, jaundice, hepatitis, liver failure

Hyperuricemia and gout

Glucose intolerance

Niacin AND Cancer

o Clearly, a deficiency of any vitamin that is involved in building new copies of your DNA is crucial in the formation of cancer.

o A further indication of the involvement of B3 came with 2010 research into beneficial bacteria and the production of sodium butyrate in the gut from certain foods. The researchers concluded that this chemical could actually kill cancer cells and recommended that people should increase their B3 levels to obtain the same effect.