Water Soluble Vitamins - CC2 Lecture Notes PDF

Water Soluble Vitamins Category Description Thiamine (Vitamin B1) Function Acts as a coenzyme in carbohydrate metabolism and branched-chain amino acid metabolism. Absorption & Excretion Absorbed in the small intestine...

Water Soluble Vitamins Category Description Thiamine (Vitamin B1) Function Acts as a coenzyme in carbohydrate metabolism and branched-chain amino acid metabolism. Absorption & Excretion Absorbed in the small intestine, excreted in urine. Deficiency Causes beriberi, seen in chronic alcoholism due to decreased intake and absorption. RDA 1.2 mg/day (males), 1.1 mg/day (females). Erythrocyte transketolase (ETK) activity; >25% increase after thiamine pyrophosphate (TPP) suggests Best Indicator deficiency. Riboflavin (Vitamin B2) Function Component of coenzymes FAD and FMN, involved in oxidation-reduction reactions. Absorption & Excretion Absorbed in small intestine, excess excreted in urine (no known toxicity). Sources Found in milk, liver, eggs, meat, leafy vegetables. Causes: Alcoholism, chronic diarrhea, malabsorption, drug interactions (phenothiazine, oral Deficiency contraceptives, tricyclic antidepressants). RDA 1.3 mg/day (males), 1.1 mg/day (females). Best Indicator Reduced glutathione reductase activity >40%. Pyridoxine (Vitamin B6) Function Exists as pyridoxine (plants), pyridoxal, pyridoxamine (animal products). Sources Meat, poultry, fish, potatoes, vegetables, dairy, grains. Deficiency Rare but seen in uremia, liver disease, absorption syndromes, malignancies, chronic alcoholism. RDA 1.3–1.7 mg/day (males), 1.3–1.5 mg/day (females) (varies with age). Toxicity Rare but very high doses may cause peripheral neuropathy. Best Indicator Linked to hyperhomocystinemia. Niacin (Vitamin B3) Function Derived from dietary tryptophan; exists as nicotinic acid & nicotinamide. Coenzymes Part of NAD & NADP coenzymes, essential for metabolism, glycolysis, lipid metabolism. Absorption & Excretion Absorbed in the small intestine, excess excreted in urine. Deficiency Causes pellagra: Symptoms include diarrhea, dementia, dermatitis, death; seen in alcoholism.  Therapeutic Use Large doses lower lipid levels but can cause flushing and vasodilation. RDA 16 mg/day (males), 14 mg/day (females). Folate (Vitamin B9) Function Functions as a coenzyme in one-carbon transfer reactions. Relation to Vitamin B12 Closely related to Vitamin B12 metabolism; both cause megaloblastic anemia if deficient. Sources Green leafy vegetables, fruits, organ meats, yeast. Cooking Cooking with water destroys folate. Increased Requirements Pregnancy, lactation, hemolytic anemia, iron deficiency, prematurity, dialysis. Low serum folate (early sign), Hypersegmented neutrophils, High urinary formiminoglutamic acid Deficiency Indicators (FIGLU), Low erythrocyte folate (best indicator), Elevated serum homocysteine. Drugs Affecting Folate Anticonvulsants, methotrexate, sulfasalazine, isoniazid. Toxicity No known toxicity. RDA 400 µg/day (higher in pregnancy to prevent neural tube defects). Reference Ranges Serum: 3–16 ng/mL, Erythrocyte: 130–630 ng/mL, Deficient: