CHAPTER OVERVIEW k
10: MACRONUTRIENT METABOLISM MICRONUTRIENTS
k k k
Thekmacronutrientkmetabolismkvitaminskandkmineralskare:kThiamin,kRiboflavin,kNiacin,kPantothenickAcid,kVitaminkB6,k Biotin,kVitamink
B12,k VitaminkC,kIodine,kManganese,kandkMagnesium.kAllkbutkthreekofkthesekwillkbekcoveredkinkthisksection.
10.1 :kIODINE
10.2 :kMANGANESE
10.3 :kTHIAMIN
10.4 :kRIBOFLAVIN
10.5 :kNIACIN
10.6 :kPANTOTHENICkACID
10.7 :kVITAMINkB₆
10.8 :kBIOTIN
,10.1 :kIodine
Whykiskiodinekfirstkinkthiskchapter?kPartlykbecausekitkiskakmineralk(butksokiskmanganese),kbutktherekiskalsokakconnectionkbetweenki
odinekandkseleniumk(lastkantioxidantkinkthekpreviouskchapter).kIodine'skonly,kyetkcritical,kfunctionkiskthatkitkiskrequiredkfork thyroi
dkhormoneksynthesis.kThekfigurekbelowkshowskthatkthekthyroidkglandkiskakbutterfly-
shapedkorgankfoundkinkthekneck.kThekparathyroidkglandskarekalsokfoundkwithinkthekthyroidkgland.
Figurek10.1.1:kLocationkofkthyroidk andkparathyroidkglands1
Iodinekiskfoundkinkfoodskprimarilykaskiodidek(I−),ksomekbreadkdoughkhaskiodatek(IO−3)kaddedktokhelpkwithkglutenkcross-
linking2.kThiskusedktokbekmorekcommonlykusedkinkthekpastkthankitkisknow.kLikekselenium,kiodidekconcentrationskofktheksoilkvaryk
greatly,kcausingkfoodkconcentrationsktokgreatlykfluctuate.kSeakwaterkiskhighkinkiodine,kthuskfoodskofkmarinekorigin,ksuchkaskseawe
edkandkseafood,karekgoodkdietaryksourceskofkiodine.kDairykproductskalsoktendktokbekgoodksourceskofkiodidekbecausekitkiskaddedktok
cattlekfeed.kCattlekreceivekiodine-containingkmedications,kandkiodide-
containingksanitizingksolutionskarekusedkinkdairykfacilities3,4.
ForkmostkAmericans,kwekconsumekamplekiodinekthroughkthekconsumptionkofkiodizedksalt.kConsumptionkofk1/2kteaspoonkofkiodiz
edksaltkmeetskthekRDAkforkiodine.kTherekiskakglobalklogokforkiodizedksalt.kHowever,kIkmustkadmitkthatkIkdoknotkrecallkeverkseeingk
itkmyself.
Thekotherklinkkbelowkisktokakpagekthatkcontainskakscorecardkmapkthatkdepictskaccessktokiodizedksaltkworldwide.kItkalsokcontainskak
Youtubekvideokthatkdisplayskthekreductionkinkiodinekdeficiencykoverktheklastk2kdecades.
WebkLink
GlobalkIodizedkSaltkIconkGlob
alkIodinekScorecard
Saltkiskiodizedkwithkeitherkpotassiumkiodidek(KI)korkpotassiumkiodatek(KIO3k).kThekpositiveskofkeachkare:kPotassiu
mkiodide
+kLesskexpensive
+kHigherkiodinekcontentk(76%kvs.k59%kforkKIO3k)
+kMoreksolublekPotassiu
mkIodate
+kMorekstable
ThekU.S.kuseskpotassiumkiodide,kbutkthekform,kandkamount,kusedkvarieskfromkcountry-to-
country.kMostkAmericans’ksaltkintakekcomeskfromkprocessedkfoods,kmanykofkwhichkarekmadekwithknon-
iodizedksalt.kIodinekiskwellkabsorbedk(~90%).kSomekdietarykcompoundsk interferek withk thyroidk hormonek productionk ork utilizatio
n.k Thesek compoundsk arek knownk ask goitrogens.k However,k itkisknotkbelievedkthatkgoitrogenskarekofkclinicalkimportancekunlesskthe
rekiskakcoexistingkiodinekdeficiency5.
Somekexampleskofkfoodskthatkcontainkgoitrogenskare3,4,6:
,Cassava
Thek cassavak plantk isk cultivatedk ask ank annualk cropk ink tropicalk andk subtropicalk regionsk fork itsk ediblek starchyk tuberousk root.k Itk isko
ftenkcalledkyucakinkSpanishkAmericakandkinkthekUnitedkStates.
Figurek10.1.2:k(left)kCassavakplantskarektypicallykgrownkinktropicalkandksubtropicalkenvironments.6k(center)kThekcassavakrootsk
arekwhatkarektypicallykeaten,kbutkfirstktheykmustkbekpeeled.kThesekarekunprocessed7k(right)kPeeledkcassavakroots8
Millet
MilletkiskankimportantkcropskinktheksemiaridktropicskofkAsiakandkAfricak(especiallykinkIndia,kMali,kNigeria,kandkNiger).
Figurek10.1.3:k(left)kMilletkgrowingkinkakfield9k(right)kMillets10
Cruciferousk Vegetablesk (broccoli,k cabbage,k Brusselsk sprouts)
Cruciferousk vegetablesk arek vegetablesk ofk thek familyk Brassicaceaek withk manyk speciesk beingk raisedk fork foodk productionkincl
uding
BriankLindshieldk 10.1.2 https://med.libretexts.org/@go/page/21024
k 10/6/2021
, OnionskGar
lickSoybea
nskPeanuts
Thyroidk Hormone
Thekthyroidkaccumulateskmostkabsorbedkiodine,kkeepingkitkforkusektoksynthesizekthyroidkhormone.kThekfollowingkvideokshowsk t
hekthyroidkandkdescribeskitskfunction.
Videok10.1.1:kInk thisk animationk thyroidk gland,k itsk structurek andk functionk alongk withk thek hormonesk producedk arek describe
d.khttps://www.youtube.com/watch?v=xKQa-MbZUPY
Askmentionedkinkthekvideo,kthektwokprimarykformskofkthyroidkhormonekarektriiodothyroninek(T3)kandkthyroxinek(T4).
Figurek10.1.4:k(left)kThekstructurekofktriiodothyroninek(T3)11kandk(right)kThekstructurekofkthyroxinek(T4)12
T4kiskthekprimarykcirculatingkform,kandkiskreallykakprohormonekthatkiskconvertedktokthekactivekT3kform.
Thekenzymeskthatkmetabolizekthyroidkhormoneskarekknownkaskdeiodinases.kTherekarekthreekdeiodinasesk(TypekIk,kTypekII,kTypekI
II)kthatkarekselenoenzymeskwhoseklocationkandkfunctionkareksummarizedkinkthektablekbelow.
Tablek10.1.1:kLocationkandkfunctionkofkthekthreekdeiodinases13
Enzyme Tissues Function
DeiodinasekTypekIk(DI1) Liver,kkidney,kthyroidkgland PlasmakT3kproduction
DeiodinasekTypekIIk(DI2) Brain,kpituitary,kbrownkadipose LocalkT3kproduction
DeiodinasekTypekIIIk(DI3) Brain,kplacenta T3kdegradation
Thyroidkhormonekregulateskthekbasalkmetabolickratekandkiskimportantkforkgrowthkandkdevelopment.kThyroidkhormonekiskparticula
rlykimportantkforkbrainkdevelopment,kbutkhypothyroidismk(lowkthyroidkhormone)kalsokleadsktokdecreasedkmusclekmasskandkskelet
alkdevelopment13.
Iodinek Deficiencyk &k Toxicity
Therekarektwokiodinekdeficiencykdisordersk(IDD):kgoiterkandkcretinismk(alsokknownkaskcongenitalkhypothyroidismkandk congenit
alkiodinekdeficiencyksyndrome).kGoiterkiskakpainlesskdeficiencykconditionkthatkresultskfromkthekenlargementkofkthek thyroidktokhel
pkincreasekitskabilityktoktakekupkiodine.kAkcouplekofkpictureskofkgoiterkarekshownkbelow.
BriankLindshieldk 10.1.3 https://med.libretexts.org/@go/page/21024
k 10/6/2021
10: MACRONUTRIENT METABOLISM MICRONUTRIENTS
k k k
Thekmacronutrientkmetabolismkvitaminskandkmineralskare:kThiamin,kRiboflavin,kNiacin,kPantothenickAcid,kVitaminkB6,k Biotin,kVitamink
B12,k VitaminkC,kIodine,kManganese,kandkMagnesium.kAllkbutkthreekofkthesekwillkbekcoveredkinkthisksection.
10.1 :kIODINE
10.2 :kMANGANESE
10.3 :kTHIAMIN
10.4 :kRIBOFLAVIN
10.5 :kNIACIN
10.6 :kPANTOTHENICkACID
10.7 :kVITAMINkB₆
10.8 :kBIOTIN
,10.1 :kIodine
Whykiskiodinekfirstkinkthiskchapter?kPartlykbecausekitkiskakmineralk(butksokiskmanganese),kbutktherekiskalsokakconnectionkbetweenki
odinekandkseleniumk(lastkantioxidantkinkthekpreviouskchapter).kIodine'skonly,kyetkcritical,kfunctionkiskthatkitkiskrequiredkfork thyroi
dkhormoneksynthesis.kThekfigurekbelowkshowskthatkthekthyroidkglandkiskakbutterfly-
shapedkorgankfoundkinkthekneck.kThekparathyroidkglandskarekalsokfoundkwithinkthekthyroidkgland.
Figurek10.1.1:kLocationkofkthyroidk andkparathyroidkglands1
Iodinekiskfoundkinkfoodskprimarilykaskiodidek(I−),ksomekbreadkdoughkhaskiodatek(IO−3)kaddedktokhelpkwithkglutenkcross-
linking2.kThiskusedktokbekmorekcommonlykusedkinkthekpastkthankitkisknow.kLikekselenium,kiodidekconcentrationskofktheksoilkvaryk
greatly,kcausingkfoodkconcentrationsktokgreatlykfluctuate.kSeakwaterkiskhighkinkiodine,kthuskfoodskofkmarinekorigin,ksuchkaskseawe
edkandkseafood,karekgoodkdietaryksourceskofkiodine.kDairykproductskalsoktendktokbekgoodksourceskofkiodidekbecausekitkiskaddedktok
cattlekfeed.kCattlekreceivekiodine-containingkmedications,kandkiodide-
containingksanitizingksolutionskarekusedkinkdairykfacilities3,4.
ForkmostkAmericans,kwekconsumekamplekiodinekthroughkthekconsumptionkofkiodizedksalt.kConsumptionkofk1/2kteaspoonkofkiodiz
edksaltkmeetskthekRDAkforkiodine.kTherekiskakglobalklogokforkiodizedksalt.kHowever,kIkmustkadmitkthatkIkdoknotkrecallkeverkseeingk
itkmyself.
Thekotherklinkkbelowkisktokakpagekthatkcontainskakscorecardkmapkthatkdepictskaccessktokiodizedksaltkworldwide.kItkalsokcontainskak
Youtubekvideokthatkdisplayskthekreductionkinkiodinekdeficiencykoverktheklastk2kdecades.
WebkLink
GlobalkIodizedkSaltkIconkGlob
alkIodinekScorecard
Saltkiskiodizedkwithkeitherkpotassiumkiodidek(KI)korkpotassiumkiodatek(KIO3k).kThekpositiveskofkeachkare:kPotassiu
mkiodide
+kLesskexpensive
+kHigherkiodinekcontentk(76%kvs.k59%kforkKIO3k)
+kMoreksolublekPotassiu
mkIodate
+kMorekstable
ThekU.S.kuseskpotassiumkiodide,kbutkthekform,kandkamount,kusedkvarieskfromkcountry-to-
country.kMostkAmericans’ksaltkintakekcomeskfromkprocessedkfoods,kmanykofkwhichkarekmadekwithknon-
iodizedksalt.kIodinekiskwellkabsorbedk(~90%).kSomekdietarykcompoundsk interferek withk thyroidk hormonek productionk ork utilizatio
n.k Thesek compoundsk arek knownk ask goitrogens.k However,k itkisknotkbelievedkthatkgoitrogenskarekofkclinicalkimportancekunlesskthe
rekiskakcoexistingkiodinekdeficiency5.
Somekexampleskofkfoodskthatkcontainkgoitrogenskare3,4,6:
,Cassava
Thek cassavak plantk isk cultivatedk ask ank annualk cropk ink tropicalk andk subtropicalk regionsk fork itsk ediblek starchyk tuberousk root.k Itk isko
ftenkcalledkyucakinkSpanishkAmericakandkinkthekUnitedkStates.
Figurek10.1.2:k(left)kCassavakplantskarektypicallykgrownkinktropicalkandksubtropicalkenvironments.6k(center)kThekcassavakrootsk
arekwhatkarektypicallykeaten,kbutkfirstktheykmustkbekpeeled.kThesekarekunprocessed7k(right)kPeeledkcassavakroots8
Millet
MilletkiskankimportantkcropskinktheksemiaridktropicskofkAsiakandkAfricak(especiallykinkIndia,kMali,kNigeria,kandkNiger).
Figurek10.1.3:k(left)kMilletkgrowingkinkakfield9k(right)kMillets10
Cruciferousk Vegetablesk (broccoli,k cabbage,k Brusselsk sprouts)
Cruciferousk vegetablesk arek vegetablesk ofk thek familyk Brassicaceaek withk manyk speciesk beingk raisedk fork foodk productionkincl
uding
BriankLindshieldk 10.1.2 https://med.libretexts.org/@go/page/21024
k 10/6/2021
, OnionskGar
lickSoybea
nskPeanuts
Thyroidk Hormone
Thekthyroidkaccumulateskmostkabsorbedkiodine,kkeepingkitkforkusektoksynthesizekthyroidkhormone.kThekfollowingkvideokshowsk t
hekthyroidkandkdescribeskitskfunction.
Videok10.1.1:kInk thisk animationk thyroidk gland,k itsk structurek andk functionk alongk withk thek hormonesk producedk arek describe
d.khttps://www.youtube.com/watch?v=xKQa-MbZUPY
Askmentionedkinkthekvideo,kthektwokprimarykformskofkthyroidkhormonekarektriiodothyroninek(T3)kandkthyroxinek(T4).
Figurek10.1.4:k(left)kThekstructurekofktriiodothyroninek(T3)11kandk(right)kThekstructurekofkthyroxinek(T4)12
T4kiskthekprimarykcirculatingkform,kandkiskreallykakprohormonekthatkiskconvertedktokthekactivekT3kform.
Thekenzymeskthatkmetabolizekthyroidkhormoneskarekknownkaskdeiodinases.kTherekarekthreekdeiodinasesk(TypekIk,kTypekII,kTypekI
II)kthatkarekselenoenzymeskwhoseklocationkandkfunctionkareksummarizedkinkthektablekbelow.
Tablek10.1.1:kLocationkandkfunctionkofkthekthreekdeiodinases13
Enzyme Tissues Function
DeiodinasekTypekIk(DI1) Liver,kkidney,kthyroidkgland PlasmakT3kproduction
DeiodinasekTypekIIk(DI2) Brain,kpituitary,kbrownkadipose LocalkT3kproduction
DeiodinasekTypekIIIk(DI3) Brain,kplacenta T3kdegradation
Thyroidkhormonekregulateskthekbasalkmetabolickratekandkiskimportantkforkgrowthkandkdevelopment.kThyroidkhormonekiskparticula
rlykimportantkforkbrainkdevelopment,kbutkhypothyroidismk(lowkthyroidkhormone)kalsokleadsktokdecreasedkmusclekmasskandkskelet
alkdevelopment13.
Iodinek Deficiencyk &k Toxicity
Therekarektwokiodinekdeficiencykdisordersk(IDD):kgoiterkandkcretinismk(alsokknownkaskcongenitalkhypothyroidismkandk congenit
alkiodinekdeficiencyksyndrome).kGoiterkiskakpainlesskdeficiencykconditionkthatkresultskfromkthekenlargementkofkthek thyroidktokhel
pkincreasekitskabilityktoktakekupkiodine.kAkcouplekofkpictureskofkgoiterkarekshownkbelow.
BriankLindshieldk 10.1.3 https://med.libretexts.org/@go/page/21024
k 10/6/2021
