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Transcript
Chapter 7 The Vitamins Nutrition: Concepts & Controversies, 12e Sizer/Whitney Learning Objectives List the fat-soluble and water-soluble vitamins, and describe how solubility affects the absorption, transport, storage, and excretion of each type. Explain how vitamins and minerals work in combination to maintain the health of the bones. Name some functions of vitamin D not associated with the bones. Learning Objectives Define the term antioxidant, and name the vitamins that act as antioxidants in the body. Discuss the roles of B vitamins in body tissues, and explain in a general way how B vitamins assist with energy metabolism. Present arguments both for and against vitamin fortification of foods. Learning Objectives Suggest foods that can help to ensure adequate vitamin intakes without providing too many calories. Justify this statement: “It is better to get vitamins from food than from supplements.” List some valid reasons why supplements may be required by some people. Definition and Classification of Vitamins Vitamin Essential, noncaloric, organic Role of vitamins Vitamin precursors Classes Absorption Roles Vitamin Names Characteristics of the Fat-Soluble and Water-Soluble Vitamins The Fat-Soluble Vitamins A, D, E, and K Food sources Storage Toxicity Deficiency Roles within the body Vitamin A Precursor Beta-carotene Active forms in the body Retinol Retinal Retinoic acid Food sources Vitamin A – Roles and Deficiency Gene regulation Retinoic acid Eyesight Process of light perception Maintenance of healthy cornea Rhodopsin molecule An Eye Vitamin A – Roles and Deficiency Night blindness Deficiency Xerophthalmia and blindness Keratinization Deficiency Cell differentiation Immune function Growth Vitamin A – Deficiency and Toxicity Deficiency Worldwide problem Blindness HIV Toxicity Symptoms food sources Liver Vitamin A – Deficiency and Toxicity Toxicity Supplements Higher risk groups Recommendations DRI recommendation based on body weight Food sources Animal origin Liver Plant origin Vitamin A Deficiency and Toxicity Vitamin A – Snapshot Beta-Carotene Plant-based foods Colorful groups Macular degeneration Dietary antioxidant Measuring beta-carotene Retinol activity equivalents (RAE) Toxicity Food sources Excess Beta-Carotene Symptom: Discoloration of the Skin Vitamin D Body can synthesize all it needs Sunlight Transformation Liver and kidneys Estimated deficiency prevalence Vitamin D – Roles Bone integrity Hormone Dangers with deficiency Vitamin D – Too Little, Too Much Deficiency Rickets Recommendations for prevention Osteomalacia Recommendations Toxicity Signs of toxicity Rickets Vitamin D Ultraviolet B light rays Cholesterol Sunbathing risks Sunscreen Exposure times Intake recommendations Food sources Factors Affecting Vitamin D Synthesis Vitamin D - Snapshot Vitamin E Roles of vitamin E Antioxidant Deficiency Symptoms Toxicity Dietary intake vs. supplemental intake Recommendations Food source Free-Radical Damage and Antioxidant Protection Vitamin E – Snapshot Vitamin K Roles Blood clotting Bone proteins Deficiency Toxicity Jaundice Requirements Sources Vitamin K – Snapshot The Water-Soluble Vitamins Dissolve in water Absorption Transport Excretion Sources Food Supplements Vitamin C Roles Connective tissues Collagen Antioxidant Protects iron Prooxidant Deficiency symptoms Scurvy Scurvy Symptoms – Gums and Skin Vitamin C Toxicity Safe doses Recommendations Tobacco use Physical stressors Food sources Destruction of vitamin C Vitamin C – Snapshot The B Vitamins in Unison Function as part of coenzymes Combines with enzyme to activate it Coenzyme shape Roles in metabolism Help the body use the energy-yielding nutrients for energy Cell multiplication Coenzyme Action Some Roles of the B Vitamins in Metabolism: Examples The B Vitamins in Unison Deficiencies Every cell is affected Symptoms Rarely are isolated deficiencies Thiamin Energy metabolism of all cells Nerve cell membranes Deficiency Beriberi Alcohol abuse DRI recommendation Food sources Thiamin Snapshot Riboflavin Role in energy metabolism of all cells Deficiencies Examples Destruction of vitamin UV light Irradiation Heat Riboflavin Snapshot Niacin Participates in energy metabolism Deficiency Pellagra Toxicity Physician administration “Niacin flush” Niacin Snapshot Folate Helps synthesize DNA Normal metabolism of several amino acids Deficiency Causes Outcomes of deficiency Anemia, diminished Immunity, abnormal digestive function Cancer risk Interaction with medications Folate Birth defects Neural tube defects (NTD) Toxicity UL Recommendations Food sources of folate Destruction of folate Incidence of a Common NTD, Spina Bifida, Over Time Folate Snapshot Vitamin B12 Closely related to folate Helps maintain sheaths around nerve fibers Deficiency May be masked by folic acid intake Pernicious anemia Vitamin B12 absorption Intrinsic factor Food sources Vitamin B12 Snapshot Vitamin B6 Roles Participates in over 100 reactions Additional roles Deficiency General symptoms Toxicity Intake recommendations Food sources Vitamin B6 Snapshot Biotin and Pantothenic Acid Important for energy metabolism Biotin Cofactor for enzymes Gene expression No UL Pantothenic acid Key coenzyme Non-B Vitamins Choline Nonvitamins Carnitine Inositol Lipoic acid Vitamin Supplements: Do the Benefits Outweigh the Risks? Controversy 7 Some Valid Reasons for Taking Supplements Arguments Against Taking Supplements Food rarely causes nutrient imbalances or toxicities Toxicity Supplement contamination Lift-threatening misinformation Unknown needs False sense of security Whole foods are best Can Supplements Prevent Heart Disease or Cancer? Oxidative stress Vitamin C Population studies Animal studies Cell studies Intervention studies Vitamin E Beta-carotene Supplements Safety and Risks Safety Food and Drug Association (FDA) Risks Dangers for your body Selecting a Supplement Choose type Read labels Target your needs Choosing doses Quality Avoid marketing traps