Vitamin B3 (Niacin): Sources, Requirements, Absorption, Deficiency and Functions
Posted on : 25-11-2017 Posted by : Admin

Vitamin B3 Introduction

In 1937, Conrad Elvehjem identified nicotinic acid in fresh meat and yeast. This discovery led to a cure for pellagra, a disease related to vitamin B3 deficiency. The disease pellagra is characterized by dermatitis (skin inflammation), diarrhea, dementia (confusion) and death.

Niacin and its derivative nicotinamide are dietary precursors of nicotinamide adenine dinucleotide (NAD), which can be phosphorylated (NADP) and reduced (NADH and NADPH). NAD functions in oxidation-reduction (redox) reactions and non-redox reactions. Niacin is pyridine-3-carboxylic acid. It occurs in tissues as nicotinamid

Sources of Niacin

The meat group especially organ meats and poultry, is the chief source of preformed niacin. Dark green leafy vegetables, whole grain, enriched breads and cereals are fair sources. Other sources of Vitamin B3 include Avocado, Spinach, Tomatoes, mushrooms and carrots.

Requirements of Niacin

The recommended niacin allowance is 6.6 mg/1000 k cal. This can be supplied by exogenous niacin in the diet and by the tryptophan, an essential amino acid that is the precursor of niacin.

Absorption and storage of Niacin

Nicotinic acid and nicotinamide are absorbed from the intestine through the portal vein into the general circulation. Excess nicotinic acid is not stored in the body.

Deficiency of Niacin

Pellagra is the major deficiency disease resulting from the lack of niacin. The symptoms of the disease pellagra are

• Dermatitis of the skin exposed to the sun,
• Soreness of the mouth,
• Swelling of the tongue,
• Diarrhea

Mental changes including depression, confusion, disorientation and hallucinations are typical of the advancing stages of the disease, which ends to death if not treated. The disease is sometimes referred to as the “4 Ds” - dermatitis, diarrhea, dementia and death.

Functions of Niacin

The following are the functions of Niacin

• Niacin is required for the stepwise breakdown of glucose to yield energy.
• Niacin is essential for the healthy skin, normal functions of the gastrointestinal tract and maintenance of the nervous system.