Niacin Deficiency Causes

Niacin Deficiency Causes

• Dietary deficiency of Tryptophan leads to Pellagra, commonly seen in people whose staple diet is maize (South and Central America) or sorghum (Central and Western India)
• Maize contains bound Niacin, making it unavailable, while sorghum's high Leucine content inhibits the QPRT enzyme, preventing Niacin conversion to NAD+
• Deficient synthesis of Niacin occurs in Pyridoxal deficiency, as Kynureninase, an essential enzyme, is dependent on Pyridoxal phosphate
• Isoniazid (INH), an anti-tuberculous drug, inhibits Pyridoxal phosphate formation, blocking Tryptophan to NAD+ conversion
• Hartnup disease, a congenital disorder, impairs Tryptophan absorption and leads to excessive urinary excretion, resulting in Niacin deficiency
• Carcinoid syndrome involves a tumor that utilizes most available Tryptophan for Serotonin synthesis, making it unavailable for Niacin production

Dietary Sources of Niacin

• Richest natural sources of Niacin include dried yeast, rice polishing, liver, peanut, whole cereals, legumes, meat, and fish
• About half of daily Niacin requirement is met through Tryptophan conversion to Niacin, with 60 mg of Tryptophan yielding 1 mg of Niacin

Recommended Daily Allowance (RDA)

• Normal daily requirement of Niacin is 20 mg/day
• During lactation, an additional 5 mg/day is required

Therapeutic Use of Niacin

• Nicotinic acid inhibits free fatty acid flux from adipose tissue, reducing serum cholesterol levels

Toxicity of Niacin

• Oral or parenteral administration of Nicotinic acid causes transient vasodilatation of cutaneous vessels, accompanied by itching, burning, and tingling sensations
• Excessive intake (over 50 mg/day) may lead to liver damage

Functions of Thiamine and Pyridoxine

• Thiamine pyrophosphate is involved in carbohydrate metabolism
• Pyridoxal phosphate is involved in protein metabolism

Learn about the causes of niacin deficiency, including dietary deficiency of tryptophan, pellagra, and the effects of leucine on niacin conversion.