the nitrate content in some green leafy vegetables with ... · the significanthighest average...

385

วารสารสาธารณสุขศาสตร์ ปีที่ 48 ฉบับที่ 3 (ก.ย.-ธ.ค. 2561)

J Public Health 2018; 48(3): 385-397

Articleinfo:ReceivedJuly6,2018;RevisedAugust9,2018;AcceptedAugust16,2018.

Correspondence:LinnaTongyonk.DepartmentofFoodandPharmaceuticalChemistry,FacultyofPharmaceutical

Sciences,ChulalongkornUniversity,Bangkok,10330.THAILAND.E-mail:[email protected]* DepartmentofFoodandPharmaceuticalChemistry,FacultyofPharmaceuticalSciences,Chulalongkorn

University.

The Nitrate Content in Some Green Leafy Vegetables with

Different Cultivation Methods in Thailand

Chatchada Petpiamsiri* Tippawan Siritientong* Kaew Kangsadalampai* Linna Tongyonk*

ABSTRACTHighnitratefoodproductswerereported

toincreaseriskofcancerandmanydiseases.Vegetableswerethemainsourcesofnitrateintakeinhuman.Theobjectiveofthisstudywastoinvestigatenitratecontents(NO3-N)offourgreenleafyvegetables,namelyChinesekale(Brassica oleraceavar.alboglabra),Chinesemustard(Brassica rapavar.parachinensis),Chinesecabbage(Brassica rapa var. pekinensis),andBokchoy(Brassica rapa var.chinensis) growninfourdifferentcultivationmethods(conventional,hygienic,organic,andhydro-ponicmethods).Thenitratecontents(NO3-N)wereanalyzedbyAOACbrucinecolorimetricmethodbetweenNovember,2017andFebruary,2018.Chinese kale,Chinesemustard, andChinesecabbagewerecultivatedwithhydro-ponicmethodthatcontainedhighernitratecompared to that of the other cultivationmethods(p<0.05).Bokchoycultivatedwithconventional method revealed statistically

highernitratecontentthanthatofvegetablescultivatedwithothermethods(p<0.05).Onlyhydroponic Chinese mustard (3,627 ± 900

mg/kg)andconventionalBokchoy(3,537 ± 817mg/kg)hadnitratecontentexceededtheEUstandardof3,500mg/kg.Among the fourcultivation methods, hydroponics had thesignificant highest average nitrate amount(2,994 ± 958mg/kg)(p<0.05).Withrespecttotypesofvegetables,Bokchoycontainedthesignificanthighestaveragenitrateamount(2,634 ± 1,071mg/kg)(p<0.05).Sincebothcultivation method and type of vegetableaffect nitrate accumulation of green leafyvegetables,consumingvariousvegetablesineachmealmayhelptoreducetheriskofover-exposureofnitratetohuman.

Keywords:nitrateaccumulation,greenleafyvegetable,organic,hygienic,hydroponics,conventional

386

Journal of Public Health Vol.48 No.3 (Sep-Dec 2018)

IntroductionNitrogen, an important component

necessarytoproducechlorophyll,protein,and

geneticmaterialsisanessentialnutrientforthe

growingofplants.Oneofthemainsources

ofnitrogentakenupbyplantsorvegetable

is come from nitrate containing fertilizer.

Providing an excess of this fertilizer may

resultinnitrateaccumulationinvegetables1,2.

Inhumandailydiet,vegetablesarerecognized

asanimportantsourceofnitrateintake.By

estimation,adailyamountconcentrationof

nitrateconsumedbymanisapproximately

75-100mg,ofwhichalmost80%comefrom

vegetables3-5. Suchdetails have raisedan

important concern because high level of

nitratecanbeconvertedtonitriteinhuman

bodybytheactionofbacteriaaswellas

mammalianenzymeslikesnitratereductase

found in saliva and gastric juice4, 6. This

nitritemayinteractwithaminoacids,amides,

andaminestoformN-nitrosocompounds.

Althoughnitrateisnotquitetoxic,itsproducts

suchasnitriteandN-nitrosocompoundsare

knowntobecarcinogenic4,6.Togetherwith

thepreviousstudiesshowingthattheplasma

levelofnitrateiscorrelatedwiththeriskof

severalcancers includinggastric7,prostate

cancer5 and bladder cancer8,thusthelevel

ofaccumulatednitrateindietaryvegetables

shouldbepreciselymonitored.

Recently, there isadramatic shift in

healthyfoodbusinessandthekeycomponents

ofhealthyfoodsarevegetables.Thereisa

contextofhypothesisthattheamountofnitrate

foundinvegetablesmayvarydependingon

vegetablespecies,harvestingtime,lightintensity,

ambienttemperature,nitrogenfertilization,and

thecultivationmethods1,however,according

to the previous report indicating that the

amount of nitrate in soil is the major factor

determiningthenitratecontentinvegetables2.

Thehypothesisofthisstudywasthatthe

cultivationmethodshouldbeamongthemost

impactingfactordeterminingnitratelevelin

vegetable products. Regarding vegetable

cultivationmethods,therearefourcultivation

methodscommonlyemployedincludingcon-

ventional,hygienic,hydroponic,andorganic.

In conventional cultivation, the vegetables

aregrown insoil, usingbothofchemical

fertilizersandpesticides9.Hygieniccultivation

isessentiallysimilartotheconventionalculture;

however,hygieniccultivationusestheshort

half-lifechemicalsandterminatesthechemical

fordetoxifiedperiodbeforeharvesting9. In

hydroponiccultivation,vegetablesaregrown

in the water supplemented with the suitable

nutrientsandfertilizer9.Theorganiccultivation

method cultivates vegetables in soil using

naturalfertilizersandavoidingchemicals9.

Asthetypesofvegetablesandcultivation

methodsmayvarythenitrateresidues,this

studyis,therefore,aimedatdeterminingthe

387


nitratescontentsindifferenttypesofvegetables;

Chinesekale(Thainame:Pak-ka-na),Chinese

mustard (Thainame:Pak-kwang-tung)and

Chinesecabbage(Thainame:Pak-kad-kao)

andBokchoy(Thainame:Pak-kwang-tung-

hong-tae) which were obtained from four

different cultivationmethodsasmentioned

previously.

Materials and MethodsSamples

Fourtypesofgreen leafyvegetables,

includingChinesekale(Brassica oleraceavar.

alboglabra),Chinesemustard(Brassica rapa

var.parachinensis),Chinesecabbage(Brassica

rapa var. pekinensis)andBokchoy(Brassica

rapa var.chinensis) infourcultivationtypes

(organic,hygienic,hydroponics,andconven-

tional)werepurchasedfromdifferentsources.

Conventionalvegetablesgrowninsoilusing

bothchemicalfertilizersandchemicalpesticides

werepurchasedfromfreshlocalmarketin

Bangkok.Hygienicvegetableswith“Qmark”

labelgrowninsoilusingtheshorthalf-life

chemicalswerepurchasedfromsupermarket

in Bangkok. The “Q mark” guaranteed

productionofhygienicvegetablesofgood

agricultural practice (GAP) standardwhich

certified by national bureau of agricultural

commodity and food standards (ACFS)9.

Organicvegetableswith“OrganicThailand”

labelgrown insoil usingnatural fertilizers

and natural pesticides were purchased from

supermarketinBangkok.The“OrganicThailand”

labelassuredproductionoforganicvegetables

whichcertifiedbydepartmentofagriculture9.

Hydroponicvegetablesgrownwiththesuitable

nutrientsolutionwereacquireddirectlyfrom

hydroponic farm in Sukhothai province,

Thailand. Total numbers of samples were

16samplesfrom4typesofvegetableswith

4differentcultivationmethods.Eachsample

wascollectedbetweenNovember,2017and

February,2018indifferentthreebatchesand

waspurchasedin300to500gramsquantities

per batch.

Samplepreparation

AccordingtoAOACmethod976.1410 with

modifications was employed for vegetable

extraction.Eachfreshvegetablewaswashed

withflowingwater,anddriedthoroughlywith

adsorbent paper trays. After removing the

non-ediblepart,theediblepartofvegetable

wasblendedtobefinepieces.Each50gof

finesamplewasaddedwith200mLdeionized

waterthenhomogenizedwithUltra-turraxT25

(IKA-Werke GmbH & Co. KG, Germany)

for5min.Themixturewasboiledonhot

waterbath(70-80°C)for15min.Whenthe

mixturewas cool, the solid insoluble part

wasseparatedbyfiltrationthroughWhatman

No.1withBuchnerfunnel.Thefinalvolumeof

filtratewasadjustedto200mLwithdeionized

waterandthisextractedsamplewaskeptin

a 4 °Cfornitratecontentanalyzingwithin

12 hours.

388


Nitratedetermination

Nitrate determination was achieved

accordingtoAOACofficialmethod973.50:

brucine colorimetric method. The brucine

method is based on nitrate determination

throughtheyellowcompoundfromthenitrate

ionreactswithbrucine-sulfanillicacidreagent

in acidic (H2SO4) and high temperature

condition(100°C)11.Foreachdetermination,

three replicates were performed. Absorbance

oftheyellowcompoundwasreadat410nm

againstareagentblankbyusingaspectro-

photometer(ThermoSpectronic,BecthaiBangkok

Equipment & Chemical Co.,Ltd., Thailand).

Nitratecontentexpressedasnitrate-nitrogen

(NO3-N)mg/L was calculated from the linear

regression equationof the standard curve

whichwasperformed in each experiment.

Theresultswerecontinuouslyinterpretedin

NO3-N mg/kg of fresh vegetable weight.

Totalnitratevalueswere9valuesfromthree

replicate of three different batches of each

sample.

Statistical analysis

Datawerepresentedasmeans ± SDof

triplicate experiments. The statistical tests

wereperformedbyusingIBMSPSSStatistics

22 (IBM, Inc.). Comparison of the nitrate

contentsinfourleafyvegetableswithfour

differentcultivationmethodswereperformed

byone-wayANOVAandpost-hoctest.The

significance of difference was defined at

p<0.05.

ResultsThe average nitrate contents of four

vegetable samples, namely Chinese kale,

Chinesemustard,Chinesecabbage,andBok

choycultivatedwithfourcultivationmethods

(organic,hydroponics,hygienic,andconven-

tional)areshowninTable1.Whenconsidering

theeffectofcultivationmethodonnitrate

levelinthesametypeofvegetable,itwas

foundthatthreeofthefourtypesofselected

vegetables,includingChinesekale,Chinese

mustard,andChinesecabbagewhichcultivated

byhydroponicmethodshowedhighernitrate

contentthanthosecultivatedbyothermethods

withstatisticallysignificant.Whilenosignificant

differenceswereobservedinnitratecontentof

Bokchoygrownwiththecultivationofhydro-

ponics,hygienic,andconventionalmethods,

it was apparent that the nitrate level of

organicBokchoywaslowerthanconven-

tional Bok choy. In addition, the nitrate

contentsofsampleswerecomparedamong

eachtypeofvegetablewhichcultivatedby

the same cultivation method. By organic

methodtherewerenosignificantdifferences

innitrate level in fourtypesofplants.By

hygienicmethod, Bok choy contained the

highestaveragenitratelevel,similartowhat

wasfoundinconventionalgrowingvegetables.

389


Table 1 NitrateContentsinChinesekale,Chinesemustard,ChinesecabbageandBokchoy

ProducedbyDifferentCultivations;Organic,Hygienic,Hydroponic,andConventional

Methods.

Typeofvegetable

NO3-Ncontentoffreshweight(mg/kg)Average ± SD(range)

Organic Hygienic Hydroponics Conventional

Chinesekale

(Pak-ka-na)

1,906 ± 454a †

(1,413-2,400)

1,269 ± 912a †

(530-2,413)

2,757 ± 462b †‡

(2,558-3,049)

1,883 ± 361a †

(1,512-2,132)

Chinese mustard

(Pak-kwang-tung)

1,912 ± 1,391a †

(194-2,905)

1,289 ± 1,066a †

(573-2,695)

3,627 ± 900b †

(2,797-4,386)

1,500 ± 770a †

(499-2,104)

Chinesecabbage

(Pak-kad-kao)

1,363 ± 739a †

(661-2,313)

953 ± 383a †

(571-1,391)

3,211 ± 633b †‡

(2,687-3,674)

1,409 ± 900a †

(624-2,538)

Bokchoy

(Pak-kwang-tung-hong-tae)

2,007 ± 726a †

(1,326-2,927)

2,609 ± 887ab ‡

(2,210-3,458)

2,382 ± 1,266ab ‡

(731-3,302)

3,537 ± 817b ‡

(2,925-4,577)

Note:Numberofsamples(n)=9(onesamplehad9values,triplicatenitratevaluesfrom

threedifferentbatches)

Differentletters(a,b)indicatethedifference(p <0.05)betweencultivationmethods

ofeachvegetable

Differentsymbols(†,‡)indicatethedifference(p <0.05)betweentypesofvegetables

ofeachcultivation

Thedistributionofnitratecontentvalues

of vegetable grouping by vegetable types

andcultivatedmethodsisshowninFigure1.

Figure1Aexhibitsthe36valuesofnitrate

contentforeachtypeofvegetablecollected

fromfourdifferentcultivationmethods.The

meanvaluecalculatedfromthenitratecontents

ofthese36sampleswasalsodetermined.

Accordingtotypeofvegetables,Bokchoy

hadthehighestaveragenitratecontent(2,634

± 1071mg/kg)(p<0.05)butnosignificant

differenceswereobservedinaveragenitrate

content among Chinese mustard, Chinese

kale,andChinesecabbage.Plotofnitrate

contentsofvegetablevs.cultivationmethod

isshowninfigure1B.Eachcultivationmethod

consistedof36valuesofnitratecontents

from four types of vegetables. The data

showedthatvegetablesgrownbyhydroponic

methodhadthehighestaveragenitratecontent

(2,994 ± 958mg/kg)(p<0.05)comparedto

the mean values obtained from those of

other methods.

390


Figure1TheDistributionofNitrateContentofAllVegetablesVariedin(A)TypeofVegetable

and(B)CultivationMethod

Note:Eachcolumnofgraphwasplottedfromthesinglenitratevalueofalldifferentsamples

(n=36,onesampleshad9valuesfrom4typesofvegetablesor4methodsof

cultivations)

Meanofnitratecontentswererepresentedinmg/kgoffreshweight,differentletters

(a-c)indicatedthemeandifference(p<0.05)

Thenitratecontent inoneportionof

serving(80g)ofeachfreshvegetable12 was

determined and the data are shown in

Table2.Forinformationondecisionmaking

forconsumer,thepricesperkilogramofeach

vegetablewerealsocalculated.Theresults

wereshowninbracketsinTable2.Itwas

foundthatvegetablesgrownbyhydroponic

method showed a tendency to have high

nitrate contents.

391


Table 2EstimatedAmountsofNitrateContent(mg)inOneServing(80g)ofEachVegetable

Consumption12ofSelectedVegetableswithDifferentCultivations.

Typeofvegetable Nitratecontentoffreshvegetableweighta(price:baht/kg)

Organic Hygienic Hydroponics Conventional

Chinesekale(Pak-ka-na) 153(200) 102(152) 219(400) 151(63)

Chinesemustard(Pak-kwang-tung) 153(178) 103(112) 290(400) 120(50)

Chinesecabbage(Pak-kad-kao) 109(200) 76(92) 257(400) 113(40)

Bokchoy(Pak-kwang-tung-hong-tae) 161(220) 209(193) 191(400) 283(150)

AcceptableDailyIntake(ADI)ofnitrate(3.7mg/kg/bodyweight/day,expressedasnitrateion)18

ADIofnitrateforThaimale=255mg/dayandThaifemale=211mg/day(basedonthe

averageweightofThai69-kgmaleadultandThai57-kgfemaleadult)19

a1servingofvegetable=80g12

DiscussionThere is no standard set for nitrate

contentinThailand.Theresultsofthisstudy,

socomparingwiththelegallimitestablished

byEuropeanUnion(EU)legislationoffresh

spinachwhichisnotexceed3,500NO3-N

mg/kg13.ThenitratecontenthigherthanEU

standardvaluewasfoundinChinesemustard

plantingbyhydroponicmethod.Wangand

Li1alsofoundthatmustardfamilyvegetables

tendedtohavehigh levelsofnitrate.Bok

choygrowingbyconventionalmethodhad

nitratecontentslightlyhigherthanthestandard

value.However,theamountsofnitrateinmost

vegetable samples in this studywere not

exceedthelimitssetbytheEU.Theresult

isconsistentwiththestudyofPrasadand

Chetty14.Theyfoundthatnitratecontentin

cabbageinFijiwas2,487 ± 381NO3-Nmg/kg14.

KaleinCroatiaintheautumnwas1,182 ± 700

NO3-Nmg/kg15.

Consideringthemeanvalueofnitrate

content in each vegetable regardless of

cultivationmethod, itwas found thatBok

choyhadthehighestnitratecontentamong

fourvegetablesamples.Thedifferentparts

of a plant are the one factor that affects

thenitrateaccumulationinvegetable.Some

studies showed that the nitrate concentration

inpetiolewashigher than in leaf1, 3. The

characteristicofBokchoyhas largerand

thickerpetiolesthanothervegetableswhile

othervegetableshavelargeleavesbutsmall

petioles. This is probably the reasonwhy

bok choy had higher nitrate content than

othervegetables.

392


Normally, roots of vegetables absorb

nitrogen from the fertilizer toproduce the

aminoacidsintheformofnitrateions.Nitrate

accumulation in vegetables occurs when

vegetables absorb nitrate more than they

require for their sustainable growth14. The

maximummeanvalueofnitratecontentwas

found in vegetables grown by hydroponic

method.Inhydroponiccultivation,vegetables

aregrowninthewatersupplementedwith

thesuitablenutrientsandfertilizer9. With this

characteristic the roots of the plant are

exposedtoachemicalsolutiondirectlyand

excessivesubstancesmaybeabsorbedby

therootsandaccumulatedinthebodyof

plant14. Phupaibul16alsofoundthattheaverage

amountofnitrateinhydroponicChinesekale

inThailandhadthehighestnitratecontent

4,529.3NO3-Nmg/kgamongtheirsamples.

Nowadays,therearenostudiesaboutthe

suitable amount of nitrate that should be

addedintohydroponicfertilizertominimize

theaccumulationofnitrateinvegetables.In

conventional cultivation, vegetables were

cultivatedinsoilculturesandfarmersused

chemicalfertilizers.Nitratenitrogenofchemical

fertilizerdissolveseasilyinwaterandmoves

quicklyinsoils17. Concentrated nitrate ions

ofchemicalfertilizerareeasilyabsorbedby

vegetables.Organicfertilizerrequiresbacteria

insoiltoconvertammoniaintonitrateions

forabsorptionbyvegetables.Therefore,the

exactamountofnitratecontentinthistype

of fertilizer cannot bemeasured17. As the

resultofthisstudy,thevegetablesgrownin

conventional cultivation had higher nitrate

contentthanthatoftheorganicvegetables.

Althoughfarmersusedchemicalfertilizersin

hygieniccultivationassameasinconventional

cultivation,farmersstoppedusingthechemicals

during pre-harvest period9. Therefore, it is

possiblethathygienicvegetablesmaybeable

toeliminatenitrateoutduringthispre-harvest

period.Thismaycausehygienicvegetables

hadlessnitratecontentsthanthoseofgrown

withothercultivationmethods.

Inthisstudyallvegetablesampleswere

found to contain nitrate residue in different

quantitiesandsomevegetableshadnitrate

contentshigherthanstandardlevelofEU.

Obtainingnitratefromeatingalotofvegetables

maycauseadversehealtheffects.Acceptable

dailyintake(ADI)ofnitrate(3.7mg/kgbody

weight/day, expressed as nitrate ion) was

reported by the Joint FAO/WHO Expert

CommitteeonFoodAdditives18.Basedon

the average weight of Thai populations,

69-kgformaleand57-kgforfemale19,thus

the maximum safety daily level of nitrate

consumptions for Thaimales and females

are 255 mg and 211 mg, respectively.

Accordingtothepresentstudy,theamount

ofnitratein1servingor80gofvegetables

werecalculated.Thisoneservingofvegetable

393


thatisequivalentto80giscalculatedby

theNationalHealthService(NHS)choices12.

OneservingofhydroponicChinesemustard

orhydroponicChinesecabbageorconven-

tionalBokchoywillresultinexcessnitrate

intakeoverADI.Anappropriatepracticeto

reducedailyconsumptionofnitrate intake

should be performed by incorporation of

various vegetables intomeals in order to

reachthe5servingsor400gperdayas

healthyportionsofvegetablesrecommended

bytheFood-baseddietaryguidelinesThailand20.

Theconsumptionofhighnitrategreenleafy

vegetables along with other low-nitrate

vegetablesmayhelptoreducetheriskof

over-exposure of nitrate. Literature review

showsthatvegetableswithlow-nitratelevels

are easily found, for instance, asparagus,

garlic, onion, potato, mushroom, tomato,

broccoli, cucumber and carrot3, 6. Another

factor that should be concerned is the price.

Ifconsideredonly theprice, regardlessof

thechemicalresidues,hydroponicvegetables

are the most expensive and conventional

vegetablesarethecheapest.

Foodswithhighnitratelevels,suchas

sausages,cancausetoxiceffectsonhuman

health;similarly,vegetableswithhighnitrate

levelsmaybelikelytohavesomeimpacton

humanhealthaswell.Especiallyinthegroup

ofpeoplewhoarevegetarians,eatingplenty

vegetables ismore likely tobeat riskof

toxicityofnitratethannormalpeople.However,

green leafy vegetables also containmany

vitaminsandantioxidantsthathelptoreduce

the incidence of human cancer, such as

vitaminC.VitaminCcanreducenitritebefore

forminganitrosaminesandisothiocyanates

that were found as a natural substance in

greencruciferousvegetables.Isothiocyanates

caninhibitDNAmethylationandearlyand

latestageofcarcinogenesis21.Sulforaphane

isthemostpotentchemopreventiveagent

among isothiocyanates that can prevent

cancer from many mechanisms such as

anti-inflammatoryorpro-apoptotic22.Vegetables

areprocessedbyfermentationandboilingthat

reduces the amount of nitrate accumulated

invegetables5,14.

ConclusionsThefindingsshowedthatthegreenleafy

vegetablesgrownwithhydroponicmethod

seemedtoaccumulatehighernitrateinthe

vegetablesthanthosegrowninsoil.According

totypesofvegetables,Bokchoyhadthe

highest average nitrate content. Thus, if

consumerwouldliketoeatvegetableswith

highnitrateaccumulation,theyshouldalso

consumeotherlow-nitratevegetableswithin

thesamemealtoprovideagoodvarietyof

nutrients and also to reduce the risk of

ingestingexcessivenitrates.Itwouldbeof

interesttostudyontheproportionofnutrients

394


and the appropriate amount of nitrate in

solutionofhydroponicfertilizertominimize

nitrateaccumulationofgreenleafyvegetables

growingunderhydroponicmethod.Alsosince

nitratecanbeconvertedtonitriteinhuman

bodybytheactionofsalivarybacteria,further

investigationisneededtodeterminetheriskof

carcinogenicnitrosamine/nitrosamideformation

inthegastrointestinaltract.

AcknowledgementsThis research work was supported

by budget revenue of Graduate School,

ChulalongkornUniversity(GCUGR1225602030M).

Theauthorsacknowledgehydroponicvegetables

supportfromcommunityenterpriseofhydro-

ponicfarmatKohTaLiengdistrict,Sukhothai

province.

References1.Wang Z, Li S. Effects of nitrogen and

phosphorusfertilizationonplantgrowth

andnitrateaccumulationinvegetables.

JPlantNutr2004;27(3):539-56.

2.LucariniM,D’EvoliL,TufiS,GabrielliP,

Paoletti S, Ferdinando SD, et al.

Influenceofgrowingsystemonnitrate

accumulationintwovarietiesoflettuce

andredradicchioofTreviso.JSci

FoodAgric2012;92(14):2796-9.

3.HordNG,TangY,BryanNS.Foodsources

ofnitratesandnitrites:thephysiologic

contextforpotentialhealthbenefits.

AmJClinNutr2009;90(1):1-10.

4.Shao-tingD,Yong-songZ,Xian-yongL.

Accumulationofnitrateinvegetables

and its possible implications to human

health. Agr Sci China 2007; 6(10):

1246-55.

5.WuT,WangY,HoS-M,GiovannucciE.

Plasmalevelsofnitrateandriskof

prostatecancer:aprospectivestudy.

CancerEpidemBiomar2013;22(7):

1210-8.

6.SantamariaP.Nitrateinvegetables:toxicity,

content, intake and EC regulation.

JSciFoodAgric2006;86(1):10-7.

7.ErogluA,DemirciS,AyyildizA,Kocaoglu

H,AkbulutH,AkgulH,etal.Serum

concentrationsofvascularendothelial

growthfactorandnitriteasanestimate

ofinvivonitricoxideinpatientswith

gastric cancer. Br J Cancer 1999;

80(10):1630-4.

8.Mohsen M, Hassan A, El-Sewedy S,

Aboul-AzmT,MagagnottiC,Fanelli

R,etal.BiomonitoringofN-nitroso

compounds,nitriteandnitrateinthe

urine of Egyptian bladder cancer

patients with or without Schistosoma

haematobiuminfection.IntJCancer

1999;82:789-94.

395


9.Thai Health Organization. What is the

differencebetweenorganicvegetable

and other vegetable? Available at:

http://resource.thaihealth.or.th/system/

fi les/documents/sooklibrary18_

ekstrinthriiy_final.pdf,accessedMay

5,2017.

10.AOACinternational976.14.AOACofficial

method976.14.Officialmethodsof

analysisoftheassociationofofficial

analyticalchemists.16th ed. Gaithers-

burg,MD,USA.AOACInternational,

1997.

11.AOACInternational973.50.AOACofficial

method973.50:nitrogen(Nitrate)in

water,brucinecolorimetricmethod,first

action1973In:GeorgeW.,LatimerJr.,

editors.Officialmethodof analysis

ofAOACinternational.19thed.USA.

AOACinternational,2012:11.

12.NHS choices. Rough guide-Fruit &

vegetableportionsizes.Availableat:

https://www.nhs.uk/Livewell/5ADAY/

Documents/Downloads/5ADAY_portion

_guide.pdf,accessedJune6,2018.

13.TheEuropeanUnion.Commissionregulation

(EU)No1258/2011ofDecember2,

2011amendingRegulation(EC)No

1881/2006asregardsmaximumlevels

fornitratesinfoodstuffs.Officialjournal

oftheEuropeanUnion.Availableat:

https://eur-lex.europa.eu/legal-content/

EN/ALL/?uri=CELEX%3A32011R1258,

accessedMay5,2018.

14.PrasadS,ChettyAA.Nitrate-Ndetermi-

nationinleafyvegetables:studyof

theeffectsofcookingandfreezing.

FoodChem2008;106:772-80.

15.BrkicD,BošnirJ,BevardiM,Bošković

AG,MilošS,LasićD,etal.Nitratein

leafygreenvegetablesandestimated

intake.AfrJTraditComplementAltern

Med2017;14(3):31-41.

16.PhupaibulP,SoiklomS,BourngamW.

Analysis of nitrate accumulation in

freshvegetables.Availableat:http://

www.lib.ku.ac.th/KUCONF/data52/KC

4701038.pdf,accessedJune6,2018.

17.Allance. What are different types of

fertilizer? Available at: https://www.

fertilizer-machine.net/solution_and_

market/types-of-fertilizer.html,accessed

July28,2018.

18.World Health Organization. Evaluation

ofcertain foodadditives:fifty-ninth

reportoftheJointFAO/WHOExpert

CommitteeonFoodAdditives.Available

at:https://www.ncbi.nlm.nih.gov/pubmed/

12677645,accessedJune7,2018.

19.SizeThailand.Thainationwideshapesurvey

results.Availableat:http://www.size

thailand.org/region_all.html,accessed

June6,2018.

396


20.FoodandAgricultureOrganizationofthe

UnitedNations.Food-baseddietary

guidelines Thailand. Available at:

http://www.fao.org/nutrition/education/

food-based-dietary-guidelines/regions/

countries/thailand/en/,accessed2018,

June6.

21.SteinmetzKA,PotterJD.Vegetables,fruit,

andcancer:II.Mechanisms.Cancer

CauseControl1991;2:427-42.

22.MokhtariRB,BaluchN,HomayouniTS,

MorgatskayaE,KumarS,KazemiP,

et al. The role of sulforaphane in

cancerchemopreventionandhealth

benefits:amini-review.JCellCommun

Signal2018;12(1):91-101.

397


ปริมาณไนเตรทของผักใบเขียวบางชนิดที่ปลูกด้วยวิธีที่แตกต่างกันในประเทศไทย

ชัชฎา เพชรเปี่ยมศิริ* ทิพวรรณ ศิริเฑียรทอง* แก้ว กังสดาลอำาไพ* ลินนา ทองยงค์ *

บทคัดย่ออาหารที่มีไนเตรทสูงเพิ่มความเสี่ยงของโรค

มะเร็งและโรคตา่งๆ และผกัเปน็แหลง่ทีม่าหลกัของ

การได้รับไนเตรทเข้าสู่ร่างกายการศึกษาน้ีมีวัตถุประสงค์

เพือ่ศกึษาปรมิาณไนเตรทของผกัใบเขียว4ชนดิคอื

ผักคะน้า ผักกวางตุ้ง ผักกาดขาว และผักกวางตุ้ง

ฮ่องเต้ท่ีปลูกด้วยวิธีการปลูกท่ีแตกต่างกัน(วิธีด้ังเดิม,

วิธีอนามัย,วิธีอินทรีย์และวิธีไฮโดรโปนิกส์)ด้วยวิธี

วิเคราะห์บรซีูนในช่วงเดือนพฤศจกิายนพ.ศ.2560

ถึงเดือนกุมภาพันธ์ พ.ศ. 2561 พบว่า ผักคะน้า

ผักกวางตุ้งและผักกาดขาวท่ีปลูกด้วยวิธีไฮโดรโปนิกส์

มีปริมาณไนเตรทสูงกว่าผักเหล่านี้ท่ีปลูกด้วยวิธีอื่น

อย่างมีนัยสำาคัญทางสถิติ (p<0.05)ผักกวางตุ้ง

ฮ่องเต้ที่ปลูกด้วยวิธีดั้งเดิมมีปริมาณไนเตรทสูงกว่า

ผักกวางตุ้งฮ่องเต้ที่ปลูกด้วยวิธีอื่นอย่างมีนัยสำาคัญ

ทางสถิติ(p<0.05)ผกักวางตุ้งไฮโดรโปนกิส์(3,627

± 900 มก./กก.) และผักกวางตุ้งฮ่องเต้ที่ปลูกด้วย

วิธีดั้งเดิม (3,537 ± 817มก./กก.)มีค่าไนเตรทสูง

เกินกว่ามาตรฐานของสหภาพยุโรป(≤3,500มก./กก.)

เมื่อเปรียบเทียบวิธีการปลูก4วิธีพบว่าผักที่ปลูก

ด้วยวิธีไฮโดรโปนิกส์มีค่าเฉลี่ยปริมาณไนเตรทสูงสุด

(2,994 ± 958 มก./กก.) อย่างมีนัยสำาคัญทางสถิติ

แต่เมื่อเปรียบเทียบระหว่างผักท้ัง 4 ชนิด พบว่า

ผักกวางตุ้งฮ่องเต้มีค่าเฉลี่ยปริมาณไนเตรทสูงสุด

(2,634 ± 1,071มก./กก.)อย่างมีนัยสำาคัญทางสถิติ

เนือ่งจากท้ังวิธีการปลกูและชนดิของผกัสง่ผลกระทบ

ต่อการสะสมไนเตรทในผักใบเขียวดังน้ันการบริโภคผัก

ที่หลากหลายชนิดในแต่ละมื้ออาจช่วยลดความเสี่ยง

ที่มนุษย์จะได้รับสารไนเตรทในปริมาณที่มากเกินไป

คำาสำาคัญ: การสะสมของไนเตรท,ผักใบเขียว,อินทรีย์,

อนามัย,ไฮโดรโปนิกส์,ดั้งเดิม

วารสารสาธารณสุขศาสตร์ 2561; 48(3): 385-397

* ภาควิชาอาหารและเภสัชเคมีคณะเภสัชศาสตร์จุฬาลงกรณ์มหาวิทยาลัย