1. Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Chapter 81 Vitamins

2. 2 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Vitamins  Organic compounds  Required in minute amounts for growth and maintenance of health  Do not serve as a source of energy  Essential for energy transformation and regulation of metabolic processes  Several vitamins are inactive in native form; must be converted to active compounds in the body

3. 3 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Intake of Vitamins  Recommended dietary allowances (RDAs) for vitamins are set by the Food and Nutrition Board of the National Academy of Sciences  RDAs represent the average daily dietary intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals in a particular life-stage or gender group

4. 4 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Intake of Vitamins  The tolerable upper intake limit (UL) for a vitamin is the highest average daily intake that can be consumed by nearly everyone without significant risk for adverse effects  The UL is an index of safety—not a recommendation to exceed the RDA  Estimated average requirement (EAR) is the level of intake that will meet nutrition requirements for 50% of the healthy individuals in any life-stage or gender group

5. 5 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Vitamins  Classification of vitamins  Fat-soluble Vitamins A, D, E, K Vitamins A, D, E, K  Water-soluble Vitamin C Vitamin C Vitamin B complex—thiamin, riboflavin, niacin, pyridoxine, pantothenic acid, biotin, folic acid, cyanocobalamin Vitamin B complex—thiamin, riboflavin, niacin, pyridoxine, pantothenic acid, biotin, folic acid, cyanocobalamin

6. 6 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Vitamin A (Retinol)  Multiple functions in the eyes  Toxicity  Birth defects, liver injury, bone-related disorders  Deficiency causes  Night blindness  Xerophthalmia  Keratomalacia  Blindness  Therapeutic uses

7. 7 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Vitamins D and E  Vitamin D  Regulates calcium and phosphorus  Deficiency causes rickets or osteomalacia  Vitamin E  Antioxidant properties  Dietary sources—fresh greens, seeds, oils  Toxicity may increase risk for bleeding

8. 8 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Vitamin K  Action required for synthesis of prothrombin and other clotting factors  Deficiency produces bleeding  Adverse effects  Hypersensitivity reaction  Hyperbilirubinemia in parenteral administration to newborns  Therapeutic use  Warfarin overdose

9. 9 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Water-Soluble Vitamins  Vitamin C  Members of the vitamin B complex

10. 10 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Vitamin C  Action required for production of collagen and other compounds that bind cells together  Part of the biochemical reaction for the synthesis of adrenal steroids  Sources  Citrus fruits/juices, tomatoes, potatoes, strawberries, melons, spinach, broccoli  Has antioxidant properties  Facilitates iron absorption  Deficiency can lead to scurvy

11. 11 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Vitamin B Complex  Niacin (nicotinic acid)  Riboflavin (vitamin B 2 )  Thiamin (vitamin B 1 )  Pyridoxine (vitamin B 6 )  Cyanocobalamin (vitamin B 12 )  Folic acid

12. 12 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Niacin (Nicotinic Acid)  Deficiency  Pellagra: dermatitis characterized by scaling and cracking of the skin in areas exposed to the sun  GI disturbances  CNS Irritability, insomnia, memory loss, anxiety, and dementia Irritability, insomnia, memory loss, anxiety, and dementia

13. 13 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Niacin (Nicotinic Acid)  Adverse effects  Small doses devoid of adverse effects  Large doses Vasodilation with flushing, dizziness, nausea Vasodilation with flushing, dizziness, nausea  Therapeutic uses  In capacity as a vitamin, used only as treatment for niacin deficiency  If given in large doses, can decrease cholesterol

14. 14 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Riboflavin (Vitamin B 2 )  Actions  Involved in numerous enzymatic reactions  First, must be changed to flavin adenine dinucleotide (FAD) or flavin mononucleotide (FMN)  Adverse effects  None for humans, no UL  Therapeutic uses  Riboflavin deficiency  Migraine headaches (see Chapter 30)

15. 15 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Thiamin (Vitamin B 1 )  Actions  Coenzyme for carbohydrate metabolism  Requirements increased slightly during pregnancy and breast-feeding  Deficiency  Beriberi  Wernicke-Korsakoff syndrome

16. 16 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Thiamin (Vitamin B 1 )  Wet beriberi  Fluid accumulation in the legs  Cardiovascular complications (palpitations, ECG abnormalities, high-output heart failure)  May progress to circulatory collapse and death  With treatment: recovery dramatic with replacement therapy  Dry beriberi  Neurologic and motor deficits, no edema or cardiovascular symptoms  Recovery slow

17. 17 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Thiamin (Vitamin B 1 )  Wernicke-Korsakoff syndrome (caused by alcoholism)  Alcoholism: most common cause of thiamin deficiency in United States  Serious CNS disorder (neurologic and psychologic) Nystagmus, diplopia, ataxia, inability to remember the recent past Nystagmus, diplopia, ataxia, inability to remember the recent past

18. 18 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Pyridoxine (Vitamin B 6 )  Coenzyme in the metabolism of amino acids and proteins  Must first be converted to its active form: pyridoxal phosphate  Sources  Fortified breakfast cereals, meat, fish, poultry, white potatoes, other starchy vegetables, and noncitrus fruits

19. 19 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Pyridoxine (Vitamin B 6 )  Deficiency  May result from poor diet, isoniazid use, inborn errors of metabolism  Symptoms  Seborrheic dermatitis, microcytic anemia, peripheral neuritis, convulsions, depression, confusion  Dietary deficiency of B 6 is rare in United States, except in alcoholics

20. 20 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Vitamin B Complex  Cyanocobalamin (vitamin B 12 ) and folic acid  Both essential factors in the synthesis of DNA  Deficiency of either manifests as megaloblastic anemia (see Chapter 55)  Cyanocobalamin deficiency produces neurologic damage as well

21. 21 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Folic Acid  Food folate vs. synthetic folate  Synthetic form is more stable  FDA ordered synthetic folate to be added to all enriched grain products  Deficiency of folic acid during pregnancy can impair CNS development  Can result in neural tube defects, anencephaly, spina bifida  Important for any patient who may become pregnant to take additional folic acid