Y khoa, dược - Chapter 7: Vitamins: vital keys to health

Chapter 7 Vitamins:Vital Keys to HealthUnderstanding VitaminsVitaminsNeeded in small amountsNot an energy sourceIndividual units rather than long chainsEssential for normal functioning, growth, and maintenance of the bodyUnderstanding VitaminsFat-soluble vs. water-solubleFat-soluble: Vitamins A, D, E, KAbsorbed with fat into lymphatic systemStored in larger quantitiesLess vulnerable to cooking lossesWater-soluble: B Vitamins and Vitamin CAbsorbed into bloodstreamStored in small amountsVulnerable to cooking lossesUnderstanding VitaminsFood preparation affects vitamins in foodsVitamins found in all food groupsFactors that determine amountsSource (animal vs. plant)SunlightMoistureGrowing conditionsPlant’s maturity at harvestPackaging and storageFood preparation affects vitamins in foodsEnrichment and fortificationEnrichment—replacing lost nutrients in processed foodsFortification—adding extra nutrients to foods that wouldn’t have them naturallySome is required by lawUnderstanding VitaminsFood preparation affects vitamins in foodsProvitaminsInactiveBody must change them to active formExample: beta-caroteneUnderstanding VitaminsVitamin A: The RetinoidsForms of Vitamin AActive forms (retinoids)RetinolRetinalRetinoic acidPrecursors (carotenoids)Vitamin A: The RetinoidsFunctionsVisionMaintaining healthy cellsFighting infections and bolstering immune functionPromoting growth and developmentCell development and healthVitamin AFunctions of vitamin AVision: night and dayChanges incoming light to visual imagesKeeps eye’s surface healthyAllows night and color visionVitamin AFunctions of vitamin ACell production and differentiationRegulates production of enzymes, blood carrier proteins, and structural proteins (like those in the skin)SkinNeeded to replace epithelial cellsVitamin AFunctions of vitamin AImmune functionProduce immune cellsReproductionKeep reproductive tracts healthyBonesHelps produce bone cells Required for bone remodelingVitamin ADietary RecommendationsRetinol activity equivalent (RAE)Sources of Vitamin AAnimal food sources (retinoids)Plant food (provitamin A carotenoids)Fortified foodsVitamin AVitamin A DeficiencyRare in North America and Western EuropeLeading cause of child blindness worldwideAffects eyes, body cell development, and immune functionVitamin AVitamin A DeficiencyThe EyesXerophthalmiaThe Skin and Other Epithelial CellsKeratinImmune functionVulnerable to infectionOther EffectsGrowth retardation, bone deformities, defective teeth, and kidney stonesVitamin AVitamin A ToxicitySymptomsFatigue, vomiting, abdominal pain, bone and joint pain, loss of appetite, skin disorders, headache, blurred or double vision, and liver damageVitamin AVitamin A ToxicityTeratogenCauses birth defectsDiscoloration of skinAcne treatmentRetin-A and AccutaneUse with cautionThe CarotenoidsPlant pigmentsMajor CarotenoidsAlpha-caroteneBeta-carotene (most common)LuteinZeaxanthinCryptoxanthinLycopeneThe CarotenoidsFunctions of carotenoidsNot technically essentialCan function as potent antioxidantsProtect visionLowers risk of certain cancersFood Sources, Absorption, and Storage of CarotenoidsGood sourcesOrange and yellow fruit and vegetables, dark green vegetablesBody absorbs 20–40% of carotenoids eatenDietary fat increases absorptionPhoto © PhotoDiscThe CarotenoidsVitamin DForms and formationsActivated in liver and kidney25-hydroxyvitamin D [25(OH)D]FunctionsEssential for bone healthProtects against certain cancers and other chronic diseasesHelps regulate insulin formation and secretionVitamin DSourcesExposure to sunlightFortified foodsMilkBreakfast cerealsSupplementsVitamin DDeficiencyRickets in childrenOsteomalacia and osteoporosis in adultsToxicityHypercalcemiaVitamin EFormsFamily of eight similar compounds Only alpha-tocopherol considered for human vitamin E requirementStored mainly in body fatFunctionsAntioxidantProtects cell membranes from free radicalsMay lower risk of some chronic diseasesVitamin EDietary RecommendationsRelated to intake of polyunsaturated fatty acidsRDA15 mg/day alpha tocopherol for adults19 mg/day for breastfeedingVitamin EFood SourcesNuts, seeds, vegetable oil, whole grain, wheat germ oil, fruit, vegetables, and animal productsVitamin EDeficiencyOccurs with fat malabsorption or rare genetic disordersToxicityNontoxic and adverse effects have not been foundCan interfere with blood clottingVitamin KFunctionsBlood clottingBone healthDietary RecommendationsMen 120 mg/dayWomen 90 mg/dayVitamin KFood sourcesGreen vegetables, plant oils, intestinal bacteriaVitamin KDeficiencyRare in healthy peopleNewborn babies at riskToxicityRare Can interfere with anticoagulant medicationsThe Water-Soluble VitaminsEight B VitaminsAct primarily as coenzymes in energy metabolismVitamin CAntioxidantCan stabilize Vitamin EThiaminFunctionsCoenzyme in energy metabolismPart of the coenzyme thiamin pyrophosphate (TPP)Helps break down glucose, make RNA and DNA; helps power protein synthesisHelps synthesize and regulate neurotransmittersThiaminDietary recommendationsMen 1.2 mg/dWomen 1.1 mg/dPregnancy 1.4 mg/dBreastfeeding 1.5 mg/dFood sourcesPork, legumes, nuts and seeds, fish and seafood, enriched grain productsCooking reduces contentThiaminDeficiencyBeriberi: Overall profound muscle weakness and nerve destructionMilder symptoms: Headache, irritability, depression, and loss of appetiteToxicityNo reports of thiamin toxicityRiboflavinFunctionsCoenzyme in energy metabolismSupports antioxidantsFood sourcesMilk and dairy productsEnriched grains, eggsRiboflavinDeficiencyAriboflavinosisOccurs most often in chronic alcoholismToxicityNo reported casesNiacinFunctionsCoenzyme in energy metabolismSupports fatty acid synthesisNiacinFood sourcesCan be made from amino acid tryptophanWhole and enriched grainsMeat, poultry, fish, nuts, and peanutsNiacinDeficiencyPellagra“Four Ds”: Dermatitis, diarrhea, dementia, and deathToxicity and Medicinal usesHigh doses used to treat high blood cholesterolSide effects: skin flushing, liver damageVitamin B6FunctionsCoenzyme in protein and amino acid metabolismSupports immune systemHelps to lower blood levels of homocysteineVitamin B6Food sourcesMeat, fish, poultry, potatoes, fortified meat substitutes, bananas, sunflower seedsVitamin B6DeficiencyMicrocytic hypochromic anemiaToxicity and Medicinal UsesCan cause subtle neurological damage, upset stomach, headache, sleepiness, and a tingling, prickling, or burning sensationFolateFunctionsCoenzyme in DNA synthesis and cell divisionNeeded for normal red blood cell synthesisReduces neural tube defectsFolateFood sourcesFortified cereals, enriched grainsGreen leafy vegetables, orange juice, sunflower seeds, and legumesFolateDeficiencyAnemia and diarrheaMegaloblastic anemiaBirth defectsSpina bifidaHeart diseaseToxicityCan mask vitamin B12 deficiencyHypersensitive people may suffer hives or respiratory distressVitamin B12FunctionsNeeded for normal folate functionDNA and red blood cell synthesisMetabolize homocysteineMaintains myelin sheath around nervesVitamin B12Food sourcesOnly animal foods: meats, liver, milk, eggs, some fortified foodsVitamin B12Absorption Requires adequate stomach acid and intrinsic factorDeficiencyCan lead to pernicious anemia, resulting in nerve damageToxicityNo UL setPantothenic AcidFunctionsComponent of coenzyme AFood sourcesWidespread in foodsReduced by freezing, canning, and refiningDeficiency and toxicity are rareBiotinFunctionsCoenzymeAmino acid metabolismFatty acid synthesisRelease of energy from fatty acidsDNA synthesisFood sources Cauliflower, liver, peanuts, cheeseProtein avidin (raw egg whites) binds biotin and prevents absorptionDeficiency and toxicity are rareCholine: A Vitamin-Like SubstanceFunctionHelps metabolize homocysteineFood sourcesMilk, liver, egg yolk, and peanutsOverall abundant in foodDeficiencyUnlikely in healthy peopleToxicityDiarrhea, falling blood pressure, and fishy body odorVitamin CFunctionsAntioxidantNeeded for collagen synthesisOther rolesMakes other essential compoundsEnhances the absorption of iron from plant foodsVitamin CFood sourcesFruits: citrus, strawberries, kiwi, fortified juiceVegetables: broccoli, tomatoes, potatoes, cabbage, leafy green, peppersVitamin CDeficiencyScurvyToxicityMay cause GI distress in high dosesConditional NutrientsBody makes most substances needed for lifeMay need to get from diet due to illness or inherited metabolic errors—thus conditionalExamplesInositolCarnitineTaurineLipoic acidBogus VitaminsUnnecessary substances found in some supplementsMay be marketed as “vitamins” and “health boosters”ExamplesHesperidinPangamic acidRutin