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Nutrition: Concepts & Controversies, 12e Sizer/Whitney
Chapter 7 The Vitamins Nutrition: Concepts & Controversies, 12e Sizer/Whitney
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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.
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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.
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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.
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Definition and Classification of Vitamins
Essential, noncaloric, organic Role of vitamins Vitamin precursors Classes Absorption Roles
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Vitamin Names
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Characteristics of the Fat-Soluble and Water-Soluble Vitamins
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The Fat-Soluble Vitamins
A, D, E, and K Food sources Storage Toxicity Deficiency Roles within the body
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Vitamin A Precursor Active forms in the body Food sources
Beta-carotene Active forms in the body Retinol Retinal Retinoic acid Food sources
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Vitamin A – Roles and Deficiency
Gene regulation Retinoic acid Eyesight Process of light perception Maintenance of healthy cornea Rhodopsin molecule
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An Eye
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Vitamin A – Roles and Deficiency
Night blindness Deficiency Xerophthalmia and blindness Keratinization Cell differentiation Immune function Growth
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Vitamin A – Deficiency and Toxicity
Worldwide problem Blindness HIV Toxicity Symptoms food sources Liver
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Vitamin A – Deficiency and Toxicity
Supplements Higher risk groups Recommendations DRI recommendation based on body weight Food sources Animal origin Liver Plant origin
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Vitamin A Deficiency and Toxicity
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Vitamin A – Snapshot
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Beta-Carotene Plant-based foods Macular degeneration
Colorful groups Macular degeneration Dietary antioxidant Measuring beta-carotene Retinol activity equivalents (RAE) Toxicity Food sources
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Excess Beta-Carotene Symptom: Discoloration of the Skin
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Vitamin D Body can synthesize all it needs Transformation
Sunlight Transformation Liver and kidneys Estimated deficiency prevalence
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Vitamin D – Roles Bone integrity Hormone Dangers with deficiency
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Vitamin D – Too Little, Too Much
Deficiency Rickets Recommendations for prevention Osteomalacia Recommendations Toxicity Signs of toxicity
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Rickets
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Vitamin D Ultraviolet B light rays Sunbathing risks Sunscreen
Cholesterol Sunbathing risks Sunscreen Exposure times Intake recommendations Food sources
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Factors Affecting Vitamin D Synthesis
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Vitamin D - Snapshot
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Vitamin E Roles of vitamin E Deficiency Toxicity Recommendations
Antioxidant Deficiency Symptoms Toxicity Dietary intake vs. supplemental intake Recommendations Food source
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Free-Radical Damage and Antioxidant Protection
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Vitamin E – Snapshot
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Vitamin K Roles Deficiency Toxicity Requirements Blood clotting
Bone proteins Deficiency Toxicity Jaundice Requirements Sources
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Vitamin K – Snapshot
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The Water-Soluble Vitamins
Dissolve in water Absorption Transport Excretion Sources Food Supplements
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Vitamin C Roles Deficiency symptoms Connective tissues Antioxidant
Collagen Antioxidant Protects iron Prooxidant Deficiency symptoms Scurvy
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Scurvy Symptoms – Gums and Skin
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Vitamin C Toxicity Recommendations Food sources
Safe doses Recommendations Tobacco use Physical stressors Food sources Destruction of vitamin C
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Vitamin C – Snapshot
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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
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Coenzyme Action
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Some Roles of the B Vitamins in Metabolism: Examples
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The B Vitamins in Unison
Deficiencies Every cell is affected Symptoms Rarely are isolated deficiencies
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Thiamin Energy metabolism of all cells Nerve cell membranes Deficiency
Beriberi Alcohol abuse DRI recommendation Food sources
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Thiamin Snapshot
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Riboflavin Role in energy metabolism of all cells Deficiencies
Examples Destruction of vitamin UV light Irradiation Heat
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Riboflavin Snapshot
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Niacin Participates in energy metabolism Deficiency Toxicity Pellagra
Physician administration “Niacin flush”
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Niacin Snapshot
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Folate Helps synthesize DNA Deficiency Interaction with medications
Normal metabolism of several amino acids Deficiency Causes Outcomes of deficiency Anemia, diminished Immunity, abnormal digestive function Cancer risk Interaction with medications
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Folate Birth defects Toxicity Recommendations Food sources of folate
Neural tube defects (NTD) Toxicity UL Recommendations Food sources of folate Destruction of folate
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Incidence of a Common NTD, Spina Bifida, Over Time
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Folate Snapshot
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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
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Vitamin B12 Snapshot
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Vitamin B6 Roles Deficiency Toxicity Intake recommendations
Participates in over 100 reactions Additional roles Deficiency General symptoms Toxicity Intake recommendations Food sources
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Vitamin B6 Snapshot
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Biotin and Pantothenic Acid
Important for energy metabolism Biotin Cofactor for enzymes Gene expression No UL Pantothenic acid Key coenzyme
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Non-B Vitamins Choline Nonvitamins Carnitine Inositol Lipoic acid
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Vitamin Supplements: Do the Benefits Outweigh the Risks?
Controversy 7
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Some Valid Reasons for Taking Supplements
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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
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Can Supplements Prevent Heart Disease or Cancer?
Oxidative stress Vitamin C Population studies Animal studies Cell studies Intervention studies Vitamin E Beta-carotene
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Supplements Safety and Risks
Food and Drug Association (FDA) Risks Dangers for your body
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Selecting a Supplement
Choose type Read labels Target your needs Choosing doses Quality Avoid marketing traps
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