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The Water-Soluble Vitamins: B Vitamins and Vitamin C

The Water-Soluble Vitamins: B Vitamins and Vitamin C. Chapter 10. The Vitamins – An Overview. Support nutritional health Vitamins differ from macronutrients Structure Individual units Function No energy yielded Food contents Similarities to macronutrient. The Vitamins – An Overview.

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The Water-Soluble Vitamins: B Vitamins and Vitamin C

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  1. The Water-Soluble Vitamins: B Vitamins and Vitamin C Chapter 10

  2. The Vitamins – An Overview • Support nutritional health • Vitamins differ from macronutrients • Structure • Individual units • Function • No energy yielded • Food contents • Similarities to macronutrient

  3. The Vitamins – An Overview • Bioavailability • Quantity provided by food • Amount absorbed and used by body • Factors influencing bioavailability • Efficiency of digestion • Nutrition status • Method of food preparation • Source of nutrient • Other foods consumed at same time

  4. The Vitamins – An Overview • Precursors • Provitamins • Converted to active form in body • Organic nature • Can be destroyed during storage and in cooking

  5. The Vitamins – An Overview • Solubility • Affects absorption, transport, and excretion • Water-soluble • Move directly into blood • Most travel freely • Fat-soluble • Enter lymph and then blood • Require transport proteins • Consumption frequency of vitamins

  6. The Vitamins – An Overview • Toxicity • More is not necessarily better • Excessive intakes • Levels higher than UL

  7. The Vitamins – An Overview

  8. The B Vitamins – As Individuals • Vitamins do not provide the body with fuel for energy • Coenzymes • Assist enzymes with release of energy • Without coenzyme, an enzyme cannot function

  9. The B Vitamins – As Individuals

  10. The B Vitamins – Thiamin • Part of coenzyme thiamin pyrophosphate (TPP) • Energy metabolism • Conversion of pyruvate to acetyl CoA • TCA cycle • Nerve activity and muscle activity • Recommendations

  11. The B Vitamins – Thiamin • Deficiency • Malnourished and alcoholics • Beriberi • Dry – nervous system • Wet – cardiovascular system • Toxicity • No adverse effects • No UL

  12. The B Vitamins – Thiamin

  13. The B Vitamins – Thiamin • Food sources • Prolonged cooking destroys thiamin • Leaches into water when boiling or blanching foods • Cooking methods that conserve thiamin

  14. The B Vitamins – Thiamin

  15. The B Vitamins – Riboflavin • Serves as coenzyme in energy metabolism • Flavin mononucleotide (FMN) • Flavin adenine dinucleotide (FAD) • Recommendations • Deficiency • Inflammation of membranes • Toxicity • No UL

  16. The B Vitamins – Riboflavin

  17. The B Vitamins – Riboflavin • Food sources • Milk and milk products • Other sources • Destruction of riboflavin • Ultraviolet light • Irradiation • Not destroyed by cooking

  18. The B Vitamins – Riboflavin

  19. The B Vitamins – Niacin • Two chemical structures • Nicotinic acid • Nicotinamide • Major form of niacin in blood • Two coenzyme forms – metabolic reactions • Nicotinamide adenine dinucleotide (NAD) • Carries hydrogens and their electrons • NADP (the phosphate form)

  20. The B Vitamins – Niacin • Recommendations • Body manufacturers from tryptophan • Only occurs after protein synthesis needs have been met • RDA is stated in niacin equivalents • Deficiency • Pellagra • Symptoms

  21. The B Vitamins – Niacin

  22. The B Vitamins – Niacin • Toxicity • Naturally occurring • No harm • Supplements or drugs • “Niacin flush” • Potential health benefits of large doses of nicotinic acid • Food sources • Less vulnerable to food preparation losses

  23. The B Vitamins – Niacin

  24. The B Vitamins – Biotin • Coenzyme that carries activated carbon dioxide • Critical in TCA cycle • Delivers carbon to pyruvate to form oxaloacetate • Participates in gluconeogenesis and fatty acid synthesis • Participates in breakdown of fatty acids and amino acids

  25. The B Vitamins – Niacin • Recommendations • Adequate intake (AI) • Deficiencies • Rare • Symptoms • Toxicity • No UL • Food sources

  26. The B Vitamins – Pantothenic Acid • Part of chemical structure of coenzyme A • Roles in body • Recommendations • AI • Deficiency • Rare • Toxicity • Food sources

  27. The B Vitamins – B6 • Three forms • Pyridoxal, pyridoxine, and pyridoxamine • Conversion to coenzyme PLP • Amino acid metabolism • Urea metabolism • Conversion of tryptophan to niacin or serotonin • Synthesis of heme, nucleic acids, & lecithin • Stored exclusively in muscle tissue

  28. The B Vitamins – B6 • Recommendations • Large doses • Deficiency • Symptoms • Alcohol & isoniazid • Toxicity • Irreversible nerve degeneration • Food sources

  29. The B Vitamins – B6

  30. The B Vitamins – Folate • Known as folacin or folic acid • Primary coenzyme form – THF (tetrahydrofolate) • Transfers single-carbon compounds during metabolism • Convert vitamin B12 to coenzyme form • Synthesize DNA • Regenerate methionine from homocysteine

  31. The B Vitamins – Folate

  32. The B Vitamins – Folate • Folate disposal • Secretion by liver into bile • Enterohepatic circulation • Vulnerable to GI tract injuries • Recommendations • Bioavailability of folate • Synthetics vs. food sources • Increased need

  33. The B Vitamins – Folate • Neural tube defects • Supplement use • 1 month before conception • Through first trimester • Fortified grain products • Congenital birth defects • Safety concerns with fortification • Mask a vitamin B12 deficiency

  34. The B Vitamins – Folate • Heart disease • Breakdown homocysteine • Blood clots and atherosclerotic lesions • Risk for heart attacks, stroke, or death from cardiovascular causes • Cancer • Type of cancer • Timing of supplementation

  35. The B Vitamins – Folate • Deficiency • Impairs cell division and protein synthesis • Red blood cells and GI tract cells falter • Anemia • GI tract deterioration • Primary deficiencies • Secondary deficiencies • Drugs

  36. The B Vitamins – Folate • Toxicity • Naturally occurring from food sources • Fortified foods or supplements • UL has been established • Food sources • Heat and oxidation destroy folate

  37. The B Vitamins – Folate

  38. The B Vitamins – Vitamin B12 • Vitamin B12 and folate depend on each other for activation • Regeneration of methionine, synthesis of DNA, and synthesis of RNA • Individual roles of vitamin B12

  39. The B Vitamins – Vitamin B12 • Digestion and absorption • Stomach • Small intestine • Intrinsic factor • Transported in blood by specific binding proteins • Enterohepatic pathway • Deficiency is rare

  40. The B Vitamins – Vitamin B12 • Recommendations • Deficiency • Inadequate absorption • Lack of hydrochloric acid or intrinsic factor • Pernicious anemia • Vegan diets • Anemia of folate deficiency • Symptoms of vitamin B12 deficiency

  41. The B Vitamins – Vitamin B12

  42. The B Vitamins – Vitamin B12 • Toxicity • No adverse effects • No UL • Food sources • Found almost exclusively from animal products • Bioavailability • Fish and milk • Destruction

  43. Vitamin-Like Compounds • Choline • Manufactured from methionine in body • Conditionally essential nutrient • Adequate intake (AI) • Common sources • Deficiencies are rare • Roles in the body

  44. Vitamin-Like Compounds • Inositol • Part of cell membrane structures • Carnitine • Transports long-chain fatty acids for oxidation • Both can be made by body • No recommendations established • Both are widespread in foods

  45. The B Vitamins – In Concert • Each B vitamin coenzyme is involved in energy metabolism • Directly • Indirectly • Deficiencies • Single B-vitamin deficiencies seldom show up in isolation • Beriberi and pellagra

  46. The B Vitamins – In Concert

  47. The B Vitamins – In Concert • Toxicities • Excess eliminated through urine excretion • Homeostasis disruption • Toxicities develop • Food sources • First choice should be foods rather than supplements

  48. Vitamin C – Roles • Antioxidant • Defends against free radicals • Loses electrons easily • Vitamin C recycling • Protects tissues from oxidative stress • Disease prevention • Enhances iron absorption

  49. Vitamin C – Roles

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