Chapter 10: The Water-Soluble Vitamins

1. Chapter 10: The Water-Soluble Vitamins

2. Overview of Water-Soluble Vitamins • Dissolve in water • Easily destroyed or washed out during food storage and preparation. • Are easily absorbed and excreted • Not stored in the body tissues and must be replaced each day. • Seldom reach toxic levels

3. Overview of Water-Soluble Vitamins • Many B-complex vitamins needed for energy metabolism and form an integral part of coenzymes • Help the body metabolize CHO, lipids and amino acids • Thiamin pyrophosphate – TPP (thiamin) • Flavin Adenine Dinucleotide (FAD), Flavin Mononucleotide (FMN)(riboflavin) • Nicotinamide Adenine Dinucleotide (NAD), Nicotinamide adenine dinucleotide phosphate (NADP)(niacin) • Coenzyme A (pantothenic acid) • Pyridoxal phosphate (PLP) (Vitamin B-6) • Tetrahydrofolic acid (folate) • Cofactor (biotin)

4. Enrichment Act of 1941 and 1998 • Many nutrients lost through milling process of grains • Grain/cereal products are enriched with • Thiamin, riboflavin, niacin, folate, iron • Enriched grains still deficient in B-6, magnesium and zinc • Whole grains contain original nutrients

5. Distinction between water-soluble and fat-soluble vitamins

6. Thiamin • Functions as a coenzyme: Thiamin pyrophosphate (TPP) • In metabolism of CHO; & amino acids • Decarboxylation of alpha keto acids (page 227) • Enzyme is Transketolase: coverts glucose to a 5-carbon sugar

7. Food Sources of Thiamin • Wide variety of food • White bread, pork, hot dogs, luncheon meat, cold cereal • Enriched grains/ whole grains

8. RDA For Thiamin • 1.1 mg/day for women • 1.2 mg/day for men • Most exceed RDA in diet • Surplus is rapidly lost in urine; non toxic

9. Deficiency of Thiamin • Beriberi • first observed in the Far East where polished rice replaced rice where bran remained intact. • characterized by • loss of sensation in the hands and feet, muscular weakness, advancing paralysis,and abnormal heart action. • Peripheral neuropathy • Dry beriberi • Weakness, nerve degeneration, irritability, poor arm/leg coordination, loss of nerve transmission • Wet beriberi • Edema, enlarge heart, heart failure

10. Wenicke-Koisakoff Syndrome • Mainly in alcoholics • Alcohol diminishes thiamin absorption • Alcohol increases thiamin excretion • Poor quality diet • Involuntary eye movement; double vision • Ataxia: staggering, poor muscle coordination • Mental confusion, “drunken stupor”

11. Riboflavin • Coenzymes: • Flavin mononucleotide (FMN) • Flavin adenine dinucleotide (FAD) • Oxidation-reduction reactions • Electron transport chain • Citric Acid Cycle • Catabolism of fatty acids: beta oxidation • FMN shuttles hydrogen ions and electrons to into the electron transport chain

12. Food Sources of Riboflavin • Milk/products • Enriched grains • Liver • Oyster • Brewer’s yeast • Sensitive to uv radiation (sunlight) • Stored in paper, opaque plastic containers

13. RDA for Riboflavin • 1.1 mg/day for women • 1.3 mg/day for men • Average intake is above RDA • Toxicity not documented

14. Deficiency of Riboflavin • Ariboflavinosis • Glossitis, cheilosis, seborrheic dermatitis, stomatitis, eye disorder, throat disorder, nervous system disorder

15. Niacin • Nicotinic acid (niacin) & nicotinamide (niacinamide) • Coenzyme • Nicotinamide adenine dinucleotide (NAD) • Nicotinamide adenine dinucleotide phosphate (NADP) • Oxidation-reduction reaction

16. Mushroom Enriched grains Beef, chicken, turkey, fish, eggs,milk Amino acid tryptophan can be converted to niacin Heat stable; little cooking loss 60mg tryptophan can be converted into 1 mg niacin Estimate by dividing the total gram of protein by 6 Food Sources of Niacin

17. Deficiency of Niacin • Pellagra • 3 Ds: Dermatitis, dementia, diarrhea • appeared in Europe in early 1700s when corn became staple food • corn lacks niacin and tryptophan

18. Niacin as a Medicine • 75-100 x RDA can lower LDL and increase HDL • Slow/ reverse progression of atherosclerosis with diet and exercise • Toxicity effects • Flushing of skin, itching, nausea, liver damage

19. Content Review • How are water-soluble vitamins different from fat-soluble vitamins? • Many of the B vitamins all function as a coenzyme, what is a coenzyme? • What disease is associated with a deficiency of niacin? • What disease is associated with a deficiency of thiamin? • What is the Enrichment Act? What nutrients are involved?

20. Pantothenic Acid • Part of Coenzyme-A • Essential for metabolism of CHO, fat, protein Glucose Fatty acids Acetyl-CoA Amino Acids Alcohol

21. Food Sources of Pantothenic Acid • Meat • Milk • Mushroom • Liver • Peanut • Adequate Intake = 5 mg/day • Average intake meets AI

22. Biotin • Free and bound form • Biocytin (protein bound form) • Freed by Biotinidase in small intestine • Infant with genetic defect : low levels of biotinidase • Metabolism of CHO, fat, protein (C skeleton) • DNA synthesis

23. Functions of Biotin • Required to convert pyruvate to oxaloacetate (TCA cycle) and thus ATP production. • Required for fatty acid synthesis • Breaks down leucine • Sources • Widely distributed in foods and is produced by intestinal bacteria • Liver, egg yolk , whole grains, cauliflower are good food sources • Avidin in raw egg whites bind biotin

24. Biotin Needs • Adequate Intake is 30 ug/day for adults • This may overestimate the amount needed for adults • No Upper Limit for biotin

25. Biotin Deficiency • Rare • High intake of raw egg white diet • Alcoholics • Biotinidase deficiency • Anticonvulsant drug use • Signs & symptoms: skin rash, hair loss, convulsion, neurological disorders, impaired growth in children

26. Vitamin B-6 family: Pyridoxal, Pyridoxine, Pyridoxamine • Main coenzyme form: pyridoxal phosphate (PLP) • Activate enzymes needed for metabolism of CHO, fat , protein • Transamination • Synthesis of hemoglobin and oxygen binding and white blood cells • Synthesis of neurotransmitters

27. Functions of Vitamin B-6 • Participates in 100+ enzymatic reactions • Decarboxylation of amino acid (decarboxylase) • Transamination reaction (transaminase) • Structural rearrangement of amino acids (racemase) • Heme synthesis • CHO metabolism • Lipid metabolism • Neurotransmitter Synthesis • Conversion of tryptophan to niacin

28. Other Role of Vitamin B-6 Homocysteine • From the metabolism of methionine • Produces toxic effect on arterial walls (atherosclerosis) • Metabolized by vitamins B-6, B-12 and folate

29. Food Sources of Vitamin B-6 • Meat, fish, poultry • Whole grains (not enriched back) • Banana • Spinach • Avocado • Potato • Heat and alkaline sensitive

30. RDA for Vitamin B-6 • 1.3 - 1.7 mg/day for adults • Daily Value set at 2 mg • Average intake is more than the RDA

31. Deficiency of Vitamin B-6 • Microcytic hypochromic anemia • Seborrheic dermatitis • Convulsion, depression, confusion • Reduced immune response • Peripheral nerve damage

32. Factors That Affect B-6 Requirement Alcohol reduces PLP formation L-DOPA-medication used to treat Parkinson’s disease and Isoniazid-antituberculosis medication • Reduce blood concentration of PLP • Need extra vitamin B-6

33. B-6 As A Medicine? • PMS • B-6 to increase the level of serotonin • Improve depression • Not a reliable treatment • Toxicity potential • Can lead to irreversible nerve damage with > 200 mg/day • Upper level set at 100 mg/day

34. Folate (Folic acid, Folacin) • Consists of pteridine group, para-aminobenzoic acid (PABA), and glutamic acid • Coenzyme form: tetrahydorfolic acid (THFA) • Produce many identical deficiency signs and symptoms as vitamin B-12 • Vitamin B-12 is needed to recycle folate coenzyme

35. Absorption, Metabolism of Folate • Absorbed in the monoglutamate form with the help of folate conjugase • Actively absorbed during low to moderate intake • Passively absorbed during high intake • Delivered to the liver where it is changed back to the polyglutamate form • Mostly stored in the liver • Excreted in the urine and bile (enterohepatic circulation)

36. Functions of Folate • DNA synthesis • Transfer of single carbon units • Synthesis of adenine and guanine • Anticancer drug methotrexate • Homocysteine metabolism • Neurotransmitter formation • Amino acid metabolism

37. Food Sources of Folate • Liver • Fortified breakfast cereals • Grains, legumes • Foliage vegetables • Susceptible to heat, oxidation, ultraviolet light

38. RDA for Folate • 400 ug/day for adults • Daily Value is set at 400 ug • Dietary folate equivalents (DFE) • are units to express folate needs throughout life except during child bearing years • DFE = [(total synthetic folate) x 1.7] + total food folate intake

39. Deficiency of Folate • Similar signs and symptoms of vitamin B-12 deficiency • Pregnant women • Alcoholics • Interferes with the enterohepatic circulation of bile/folate

40. Megaloblastic Anemia

41. Neural Tube Defects • Spina bifida • Anencephaly • Importance of folate before and during pregnancy

42. Toxicity of Folate • Epilepsy • Skin, respiratory disorder • FDA limits nonprescription supplements to 400 ug per tablet for non-pregnant adults • OTC Prenatal supplement contains 800 ug • Upper Level for synthetic folate is 1 mg • Excess can mask vitamin B-12 deficiency

43. Vitamin B-12 • Cyanocobalamin, methlcobalamin, 5-deoxyadenosylcobalamin • Contains cobalt • Folate metabolism • Synthesized exclusively by bacteria, fungi, and algae • Maintenance of the myelin sheaths • Rearrange 3-carbon chain fatty acids so can enter the Citric Acid Cycle

44. Absorption of Vitamin B-12

45. Therapy for Ineffective Absorption • Many factors can disrupt this process • Monthly injections of vitamin B-12 • Vitamin B-12 nasal gel • Megadoses of vitamin B-12 to allow for passive diffusion

46. Synthesized by bacteria, fungi and algae (Stored primarily in the liver) Animal products Organ meat Seafood Eggs Hot dogs Milk Food Sources of Vitamin B-12

47. RDA for Vitamin B-12 • 2.4 ug/ day for adults and elderly adults • Average intake exceeds RDA • B-12 stored in the liver; little is lost • Non-toxic

48. Functions of Vitamin B-12 • Helps convert methylmalonyl CoA to succinyl CoA (citric acid cycle) • Recycles folate coenzymes • Nerve functions • Maintains myelin sheath • Megalobalstic anemia

49. Deficiency of Vitamin B-12 • Pernicious anemia • Nerve degeneration, weakness • Tingling/numbness in the extremities (parasthesia) • Paralysis and death • Looks like folate deficiency • Usually due to decreased absorption ability • Achlorhydria, especially in elderly

50. Homocysteine and the B Vitamins