Rishi Desai, MD, MPH

Niacin (Vitamin B3) deficiency

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Chapter 53 Water Soluble Vitamins Deﬁciency  NIACIN (VITAMIN B3) DEFICIENCY osms.it/niacin-(vitamin-b3)-deficiency PATHOLOGY & CAUSES ▪ Insufﬁcient niacin (nicotinic acid, nicotinamide) for body’s metabolic needs ▫ Niacin obtained in diet ▫ Liver converts tryptophan to niacin (60g tryptophan = 1mg niacin) ▪ Active forms ▫ Nicotinamide adenine dinucleotide (NAD+), nicotinamide adenine dinucleotide phosphate (NADP+) ▪ Moderate/↑ doses of niacin supplement → ↓ total/low-density lipoprotein (LDL) cholesterol Sources of niacin ▪ Present in plant, animal products (e.g. dairy products, meat, grain (↓ corn), legumes, seeds) ▪ Dietary supplement; enriched grain, cereal, milk  Metabolic defects ▪ E.g. carcinoid syndrome → impaired tryptophan metabolism Accelerated niacin depletion ▪ Prolonged isoniazid use → ↓ pyridoxal phosphate (active form of vitamin B6) → ↑ tryptophan synthesis Tryptophan-to-niacin conversion nhibited by medication ▪ E.g. phenobarbital, chloramphenicol, pyrazinamide  COMPLICATIONS ▪ Pellagra  RDAs ▪ Children 9–13: 12mg ▪ 19+ male: 16mg; 19+ female: 14mg ▪ Pregnancy: 18mg ▪ Lactation: 14mg  RISK FACTORS Insufﬁcient niacin/tryptophan intake ▪ Alcohol abuse ▪ Self-imposed dietary restrictions ▪ Chronic systemic disease; mental illness; advanced age ▪ Food insecurity ▪ Corn-based diet (unless corn treated with alkali, e.g. tortillas) Malabsorption ▪ E.g. bariatric surgery, malabsorptive disease states ▪ Hartnup disorder: defective tryptophan absorption  Figure 53.1 A desqauamating rash on the skin of an individual who presented with diarrhea and confusion. The diagnosis was conﬁrmed as pellagra.  OSMOSIS.ORG 303   

Glycolysis

Citric acid cycle

Electron transport chain and oxidative phosphorylation

Gluconeogenesis

Glycogen metabolism

Pentose phosphate pathway

Physiological changes during exercise

Amino acid metabolism

Nitrogen and urea cycle

Fatty acid synthesis

Fatty acid oxidation

Ketone body metabolism

Cholesterol metabolism

Biochemistry and metabolism

Essential fructosuria

Hereditary fructose intolerance

Galactosemia

Pyruvate dehydrogenase deficiency

Glucose-6-phosphate dehydrogenase (G6PD) deficiency

Lactose intolerance

Glycogen storage disease type I

Glycogen storage disease type II (NORD)

Glycogen storage disease type III

Glycogen storage disease type IV

Glycogen storage disease type V

Leukodystrophy

Metachromatic leukodystrophy (NORD)

Krabbe disease

Gaucher disease (NORD)

Niemann-Pick disease types A and B (NORD)

Niemann-Pick disease type C

Fabry disease (NORD)

Tay-Sachs disease (NORD)

Mucopolysaccharide storage disease type 1 (Hurler syndrome) (NORD)

Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)

Cystinosis

Hartnup disease

Alkaptonuria

Ornithine transcarbamylase deficiency

Phenylketonuria (NORD)

Cystinuria (NORD)

Homocystinuria

Maple syrup urine disease

Abetalipoproteinemia

Familial hypercholesterolemia

Hypertriglyceridemia

Hyperlipidemia

Disorders of carbohydrate metabolism: Pathology review

Disorders of fatty acid metabolism: Pathology review

Dyslipidemias: Pathology review

Glycogen storage disorders: Pathology review

Lysosomal storage disorders: Pathology review

Disorders of amino acid metabolism: Pathology review

Metabolic disorders

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Proteins

Carbohydrates, fat and protein

Vitamin K deficiency

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Excess Vitamin A

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Folate (Vitamin B9) deficiency

Vitamin B12 deficiency

Vitamin C deficiency

Wernicke-Korsakoff syndrome

Beriberi

Iodine deficiency

Zinc deficiency

Marasmus

Kwashiorkor

Fat-soluble vitamin deficiency and toxicity: Pathology review

Zinc deficiency and protein-energy malnutrition: Pathology review

Water-soluble vitamin deficiency and toxicity: B1-B7: Pathology review

Nutritional disorders

Nutrition

Niacin (Vitamin B3) deficiency

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