dia care-2012-cooper-1293-300

A Prospective Study of the AssociationBetween Quantity and Variety of Fruitand Vegetable Intake and IncidentType 2 DiabetesANDREW J. COOPER, MPHIL1

STEPHEN J. SHARP, MSC1

MARLEEN A.H. LENTJES, MSC2

ROBERT N. LUBEN, BSC2

KAY-TEE KHAW, FRCP, PHD3

NICHOLAS J. WAREHAM, FRCP, PHD1

NITA G. FOROUHI, FFPH, PHD1

OBJECTIVEdThe association between quantity of fruit and vegetable (F&V) intake and riskof type 2 diabetes (T2D) is not clear, and the relationship with variety of intake is unknown. Thecurrent study examined the association of both quantity and variety of F&V intake and risk ofT2D.

RESEARCHDESIGNANDMETHODSdWe examined the 11-year incidence of T2D inrelation to quantity and variety of fruit, vegetables, and combined F&V intake in a case-cohortstudy of 3,704 participants (n = 653 diabetes cases) nested within the European ProspectiveInvestigation into Cancer and Nutrition-Norfolk study, who completed 7-day prospective fooddiaries. Variety of intake was derived from the total number of different items consumed in a1-week period. Multivariable, Prentice-weighted Cox regression was used to estimate hazardratios (HRs) and 95% CIs.

RESULTSdA greater quantity of combined F&V intake was associated with 21% lower hazardof T2D (HR 0.79 [95%CI 0.621.00]) comparing extreme tertiles, in adjusted analyses includingvariety. Separately, quantity of vegetable intake (0.76 [0.600.97]), but not fruit, was inverselyassociated with T2D in adjusted analysis. Greater variety in fruit (0.70 [0.530.91]), vegetable(0.77 [0.610.98]), and combined F&V (0.61 [0.480.78]) intake was associated with a lowerhazard of T2D, independent of known confounders and quantity of intake comparing extremetertiles.

CONCLUSIONSdThese ndings suggest that a diet characterized by a greater quantity ofvegetables and a greater variety of both F&V intake is associated with a reduced risk of T2D.

Diabetes Care 35:12931300, 2012

Type 2 diabetes (T2D) is one of themost common noncommunicablediseases worldwide and is a leadingcause of premature mortality (1), morbid-ity (2), and health care expenditure (3).Lifestyle intervention trials that includedietary changes have been shown to beeffective in preventing the developmentof T2D (4). However, it is still largely un-known which aspects of the diet conferthis benecial effect.

A World Health Organization expertconsultation recommended a minimumintake of 400 g or ve portions (based onan average portion weighing 80 g) ofcombined fruits and vegetables (F&V)per day for the prevention of several ma-jor noncommunicable diseases, includingT2D (5). In addition, the ve-a-day pro-gram in the U.K. and similar programs inother countries (e.g., the U.S.) (6) recom-mend consuming a variety of different

F&V, thereby ensuring adequate intakeof micronutrients, dietary ber, and amultitude of other important bioactivecompounds (7). Yet, the specic role of va-riety in F&V intake and T2D has not beenexamined. Additionally, as studies havegenerally used a food frequency question-naire (FFQ) to assess F&V intake, which issuitable for ranking individuals accordingto their relative but not absolute intake (8),there is also an absence of research on theimportance ofmeeting the ve-a-day quan-tity recommendation for F&V intake. Theuse of a prospective food diary offers amore precise measure of dietary intakeand can overcome some of the limitationsof the FFQ (9), but so far no studies haveused this dietary assessment method in re-lation to T2D risk.

In order to develop effective dietarypublic health strategies for T2D preven-tion, it is essential to clarify the contribu-tion of both quantity and variety of F&Vintake to T2D risk. The aim of this studywas therefore to evaluate the associationbetween the quantity and variety of fruit,vegetables, and combined F&V consump-tion, as assessed using a prospective 7-dayfood diary, and incident T2D.

RESEARCH DESIGN ANDMETHODS

Study populationThe Norfolk component of the EuropeanProspective Investigation into Cancer andNutrition (EPIC-Norfolk) study recruited25,639men andwomen aged 4079 yearsat baseline in19931997.TheEPIC-Norfolkstudy was initiated to investigate the rela-tionship between diet and cancer but hassince broadened its scope to include a rangeof chronic diseases, including T2D. The re-cruitment procedures, collection of ques-tionnaire data, and anthropometric anddietary measures have been described indetail elsewhere (10,11). In brief, partici-pants residing in Norfolk, England, wererecruited from age-sex registers of generalpractices and attended a baseline healthcheck. Follow-up of participants constituted

c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c

From the 1MRCEpidemiologyUnit, Institute ofMetabolic Science, Addenbrookes Hospital, Cambridge, U.K.;the 2Department of Public Health and Primary Care, Strangeways Research Laboratory, MRC Centre forNutritional Epidemiology in Cancer Prevention and Survival, University of Cambridge, Cambridge, U.K.;and the 3Clinical Gerontology Unit, University of Cambridge School of Clinical Medicine, AddenbrookesHospital, Cambridge, U.K.

Corresponding author: Nita G. Forouhi, [email protected] 8 December 2011 and accepted 16 February 2012.DOI: 10.2337/dc11-2388 2012 by the American Diabetes Association. Readers may use this article as long as the work is properly

cited, the use is educational and not for prot, and thework is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details.

care.diabetesjournals.org DIABETES CARE, VOLUME 35, JUNE 2012 1293

E p i d e m i o l o g y / H e a l t h S e r v i c e s R e s e a r c hO R I G I N A L A R T I C L E

a postal questionnaire at 18 months, a sec-ond health check in 19982000, and a fur-ther postal questionnaire in 20022004.

From the 25,639 participants inEPIC-Norfolk at baseline, we ascertainedincident cases of T2D (n = 892) andselected a random subcohort of 4,000participants. This subcohort was repre-sentative of the entire EPIC-Norfolk co-hort in terms of age, BMI, education level,physical activity level, smoking status,and total energy intake (data not shown).Among the subcohort, there were 143 in-dividuals who developed incident T2Dduring follow-up. Of the 4,749 partici-pants, we excluded those with unknowndiabetes status (n = 1) or prevalent diabe-tes at baseline (n = 121), those with fewerthan 7 days of diary data (n = 435) or whodid not return a diary (n = 15), or thosewith missing information on potentialconfounding variables (n = 73). Partici-pants with prevalent myocardial infarc-tion, stroke, or cancer were also excluded(n = 400). The nal sample for analysisconsisted of 653 incident T2D casesand a subcohort of 3,166 individuals (in-cluding 115 incident T2D cases). All vol-unteers gavewritten informed consent, andthe study was approved by the Norwichdistrict ethics committee.

Case ascertainmentWe ascertained incident T2D cases by self-report of doctor-diagnosed diabetes fromthree follow-up health and lifestyle ques-tionnaires, i.e., answering yes to Has adoctor ever told you that you have diabe-tes? or diabetes medication that was self-reported or brought to the second healthcheck. In addition, external sources of in-formation through record linkage includedlisting of any EPIC-Norfolk participant inthe general practice diabetes register, localhospital diabetes register, hospital admis-sions data with screening for any diabetes-related admissions among study participants,and Ofce of National Statistics mortalitydata with coding for diabetes. Participantswho gave a self-report of history of diabetesthat could not be conrmed against anyother sources of ascertainment were notconsidered as a conrmed case of T2D.Follow-up was censored at the date of di-agnosis of T2D, 31 July 2006, or the dateof death, whichever came rst.

Assessment of diet and lifestylevariablesAt the baseline medical examination,participants were instructed by trainedinterviewers on how to complete the

7-day food diary (11,12). The food diaryconsisted of 45 color pages containingfood portion photographs and detailedinstructions on how to record and describepreparation methods and quantities offoods eaten at main meals, snacks, and be-tween meals. Completed diaries were re-turned by post to the coordinating centerat the University of Cambridge. The fooddiary has been validatedwithweighed foodrecords, 24-h urine collections, and bloodbiomarkers (13).

Intake of F&V (including tinned anddried) was calculated from food diary datato give average daily quantity of intake foreach participant. In order to preciselyquantify the actual intake of F&V con-sumed alone or from dishes (in accordancewith the U.K. ve-a-day public healthguidelines) (14), all recorded foods anddishes were disaggregated into their com-ponent parts. Composite dishes containingfruits and/or vegetables included home-made and shop-bought desserts, vegetablebakes, stews, pies, and soups, for example.The F&Vquantity and typewas derived forthe composite dishes by using recipes fromMcCance and Widdowson as previouslydescribed (12) and by using ingredientslisted on the packages of products andready-made meals. Potatoes were not in-cluded as a vegetable because they differfrom vegetables regarding energy andcarbohydrate content and are frequentlyused as a substitute for cereals (15). F&Vjuices were also not included becausethey differ from their source of origin interms of food matrix and ber content,and as such may be dissimilarly associatedwith diabetes (16). Variety of fruit, vegeta-bles, and combined F&V intake was de-rived by calculating the total number ofdifferent items consumed at least oncein a 1-week period, irrespective of quantityof intake. The groupings of items included58 different fruit items (range 058), 59different vegetable items (range 059),and hence a total of 117 different F&V itemsconsumed over a 1-week period, as recor-ded in the 7-day food diary.

At recruitment, participants com-pleted a detailed health and lifestyle ques-tionnaire. Participants self-reported theireducation level (low, O level, A level, ordegree), occupational social class (manualor nonmanual), smoking status (current,former, or never), and baseline history ofmyocardial infarction, stroke, and cancer(yes or no). Area deprivation was assessedfrom residential postal codes using theTownsend Deprivation Index, which pro-vides amaterial measure of deprivation and

disadvantage based on unemployment, carownership, home ownership and house-hold overcrowding. A higher TownsendIndex score indicates greater deprivation(17). A validated, four-point physical activ-ity index was derived, incorporating occu-pational and leisure-time components ofphysical activity (18). Trained nurses mea-sured height, weight, and waist circumfer-ence according to standardized protocols(10). BMI was calculated as weight dividedby height (kg/m2). Venous blood sampleswere taken by trained study nurses. Hemo-globin A1c (HbA1c) was measured halfwaythrough the baseline health check (19951997) and was available in approximatelyhalf of the EPIC-Norfolk cohort. HbA1cwas measured using high-performanceliquid chromatography on a Bio-Rad Dia-mat (Bio-Rad, Richmond, CA), on a sampleof EDTA-anticoagulated blood.

Statistical analysisBaseline characteristics were summarizedby tertiles of combined F&V quantity andvariety among the subcohort participants,using means with SDs, medians with in-terquartile ranges (IQRs), or frequencies(where appropriate).

Multivariable, Prentice-weighted Coxregression (19) was used to estimate theassociations between quantity and varietyof fruit, vegetables, and combined F&Vintake and hazard of diabetes, with intakedened as tertiles (with the lowest tertileas the reference category). To check theproportional hazards assumption of themodels, interactions between quantityand variety of fruit, vegetables, and com-bined F&V intake and current age (i.e.,the underlying timescale) were tested.The proportional hazards assumptionwas not violated for quantity and varietyof fruit, vegetables, or combined F&V in-take (all P values $0.32). Hazard ratios(HRs) and 95% CIs were estimated usingthe following modeling strategy. Age wasused as the underlying timescale in allmodels. Model 1 was adjusted for sex.In Model 2, we additionally adjusted forBMI (continuous), waist circumference(continuous), education level (low, O level,A level, or degree), Townsend DeprivationIndex (continuous), occupational socialclass (manual or nonmanual), physical ac-tivity level (inactive, moderately inactive,moderately active, or active), smoking sta-tus (current, former, or never), family his-tory of diabetes (yes or no), total energyintake (continuous), and season of diarycompletion (December, January, February =winter; March, April, May = spring; June,

1294 DIABETES CARE, VOLUME 35, JUNE 2012 care.diabetesjournals.org

Fruit and vegetable intake and diabetes risk

July, August = summer; and September,October, November = autumn). In Model3, in order to estimate the association be-tween quantity of F&V consumption andhazard of diabetes independent of the ef-fect of variety, we additionally adjusted forvariety of F&V intake and vice versa forthe analysis of variety in intake. We exam-ined multicolinearity in Model 3 using thevariance ination factor.

In sensitivity analyses, the associationbetween F&V quantity and variety andthe hazard of diabetes was also investi-gated by including other potentially con-founding variables in Model 3, includinghypertension (yes or no), dairy intake(continuous), total ber intake (continu-ous), red and processed meat intake (con-tinuous), and percentage energy fromcarbohydrate (continuous), protein (con-tinuous), fat (continuous), and alcoholintake (continuous). Analyses were alsorepeated after additionally excludingparticipants who 1) developed diabeteswithin the rst 2 years of follow-up(n = 26), 2) had a baseline HbA1c level$6.5% (n = 15) in the subsample withHbA1c data available (n = 1,333), and3) were in the top and bottom 1% of theratio of energy intake to energy expenditure.Multiplicative interaction terms wereadded to Model 3 for quantity and varietyof combined F&V intake to examine effectmodication by sex, age (,60 or $60years), BMI (normal weight ,25 kg/m2,overweight/obese$25 kg/m2), and smok-ing status (never smoker or ever smoker)by using theWald test. Additionally, splineregression was used to demonstrate thecontinuous association between quantityand variety of combined F&V intake andthe HR (95% CI) of diabetes with knotsplaced at quartiles of the distribution (20).

All statistical analyses were perfor-med using Stata/SE 11.1 (Stata-Corp,College Station, TX). Statistical signi-cance was set at P , 0.05.

RESULTSdThe median (IQR) dura-tion of follow-up was 10.9 (9.811.8)years. The median quantity of combinedF&V intake was 3.7 (2.55.0) portionsper day and the mean (SD) variety ofcombined F&V intake was 11.7 (3.9)items/week. Fewer than 26% of studyparticipants reported consuming at leastve portions of F&V per day. There wasnearly a threefold difference in quantityand in excess of a twofold difference invariety of combined F&V consumptionbetween the highest versus lowest tertilesof F&V intake (Table 1). Participants who

consumed higher quantities and a greatervariety of combined F&V hadmore favor-able lifestyle, anthropometric, and dietaryproles. Baseline characteristics by tertilesof quantity and variety of fruit and vege-table intake separately showed similar re-sults (data not shown). The Pearsoncorrelation coefcient between quantityof fruit and quantity of vegetable intakewas 0.29, and between variety of fruit andvariety of vegetable intake was 0.30.Quantity of combined F&V intake wasstrongly positively correlated with varietyof combined F&V intake (0.60).

As shown in Table 2, quantity of fruit,vegetables, and combined F&V intakewere all inversely associated with inci-dent T2D (Model 1). Further adjustmentdid not appreciably alter the HRs (Model2). After additionally adjusting for the ef-fects of variety of intake, an inverse asso-ciation with quantity of vegetable intakeremained, but the associations for quan-tity of fruit and quantity of combinedF&V intake with T2D were attenuated,such that fruit was no longer associatedand F&V intake was borderline inverselyassociated with T2D. Further adjustmentfor hypertension, dairy intake, total berintake, percentage energy from carbohy-drate, protein, fat, and alcohol intake, andred and processed meat intake did notchange our results (data not shown). Thosemeeting the recommendation to consumeat leastve portions of F&Vper day did notdiffer from those not meeting this recom-mendation in hazard of T2D, excludingand including variety of intake (HR 0.85[95% CI 0.701.02] and 0.98 [0.801.21], respectively). As shown in Table 3,greater variety in fruit, vegetables, and com-bined F&V intake was inversely associatedwith incident T2D in adjusted analyses andalso when accounting for quantity of in-take. The relative reduction in the hazardof T2D with every additional two-item in-crease in F&V variety per week was 8%(0.92 [0.870.97]). The mean estimatedvariance ination factor was ,1.9 (,1.6for both F&V quantity and F&V variety),indicating that colinearity of the variablesincluded in Model 3 was low.

Figure 1 shows the continuous asso-ciation between quantity and variety ofcombined F&V intake and T2D.As shown,the HR for T2D decreased between an in-take of ;3.57.0 portions per day (Fig.1A), and this association was largely un-changed after accounting for the effects ofvariety of F&V (Fig. 1B). For variety, con-suming$12 different F&V items per weekwas associated with a decreased HR of T2D

(Fig. 1C), and this association was largelyunaffected after accounting for the effects ofquantity of F&V intake (Fig. 1D). The per-centage of participants achieving a quantityof .3.5 portions per day was 53.2%, andthe percentage achieving a variety of .12different F&V items per week was 40.3%.

Results were unaffected in sensitivityanalyses after excluding participantswho 1) developed T2D within the rst 2years of follow-up, 2) had a baselineHbA1c level of $6.5% in the subsamplewith HbA1c data, and 3) were in the topand bottom 1% of energy intake to energyexpenditure (data not shown). We foundno evidence of interaction between eitherquantity or variety in F&V intake withsex, age, BMI, or smoking status and in-cident diabetes (P . 0.10).

CONCLUSIONSdIn this prospectivestudy of nearly 4,000 men and womenwith dietary information from prospective7-day food diaries, we observed thata greater quantity of vegetable intake anda greater variety of fruit, vegetables, andcombined F&V intake may independentlybe benecial for reducing the risk of T2D.After accounting for potential confoundingfactors and the effects of quantity of intake,each different additional two item per weekincrease in variety of F&V intake was asso-ciated with an 8% reduction in the inci-dence of T2D.

Previous epidemiological studieshave reported inconsistent ndings foran association between quantity of F&Vintake and risk of T2D. Two separatemeta-analyses have reported no overallassociation between fruit, vegetables, andcombined F&V intake and diabetes risk,although there was signicant heteroge-neity of association between the includedstudies (21,22). The meta-analysis byCarter et al. (21) did however nd a sig-nicant inverse association betweengreen leafy vegetable intake and risk ofT2D (HR for highest vs. lowest intakegroup 0.86 [95% CI 0.770.97]). Al-though low heterogeneity in F&V con-sumption may be one explanation for thenull ndings in some study populations,our current results suggest that it mayalso be due to differences in the assessmentmethods used for measuring F&V intake.Most epidemiological studies have used anFFQ to assess quantity of F&V intake.Although FFQs can be used to rank indi-viduals according to their relative intake(8), they are less suitable for the assess-ment of absolute intake (11,23), whichthey tend to overestimate. For example,


Cooper and Associates

Table1d

Descriptive

characteristicsat

baselin

eby

combinedF&Vqu

antity

andvarietytertilesin

3,16

6subcohortpa

rticipan

tsin

theEPIC-N

orfolk

stud

y

Median(IQR)qu

antity

ofintake

(portion

s/day)or

mean(SD)variety

ofintake

(no.

items/week)

Tertilesof

combinedF&

Vqu

antity

Pvalue

Tertiles

ofcombinedF&

Vvariety

Pvalue

Low

Medium

High

Low

Medium

High

2.1(1.6

2.5)

3.7(3.3

4.0)

5.7(5.0

6.8)

8.06

1.8

12.06

0.8

16.36

2.3

N1,05

51,05

61,05

51,26

592

797

4Age

atrecruitm

ent(years)

58.5

(9.8)

59.1

(9.2)

59.8

(9.0)

0.00

258

.8(9.7)

59.3

(9.4)

59.3

(8.9)

0.24

Men,n

o.(%

)52

3(49.6)

437(41.4)

408(38.7)

,0.00

163

7(50.4)

393(42.4)

338(34.7)

,0.00

1Edu

cation

level,no

.(%)

,0.00

1,0.00

1Lo

w45

0(42.7)

351(33.2)

345(32.7)

525(41.5)

325(35.1)

296(30.4)

Olevel

97(9.2)

118(11.2)

103(9.8)

123(9.7)

98(10.6)

97(10.0)

Alevel

411(39.0)

443(42.0)

426(40.4)

498(39.4)

369(39.8)

413(42.4)

Degree

97(9.2)

144(13.6)

181(17.2)

119(9.4)

135(14.6)

168(17.3)

Occupation

alsocialclass,no

.(%)

,0.00

1,0.00

1Manual

476(46.2)

432(41.6)

355(33.9)

584(47.2)

352(38.6)

327(33.9)

Non

manual

555(53.8)

606(58.4)

692(66.1)

653(52.8)

561(61.5)

639(66.2)

Tow

nsendDeprivation

Index

22.0(2.2)

22.2(2.1)

22.2(2.1)

0.30

21.9(2.3)

22.2(2.1)

22.3(2.0)

0.00

3BM

I(kg/m

2)

26.2

(3.7)

26.1

(3.7)

26.2

(3.9)

0.52

26.4

(3.8)

26.1

(3.8)

26.0

(3.7)

0.00

2Waistcircumference

(cm)

88.4

(11.9)

87.3

(12.2)

86.8

(12.3)

,0.00

188

.9(12.2)

87.2

(11.8)

85.9

(12.3)

,0.00

1Ph

ysicalactivity

level,no

.(%)

,0.00

10.00

1Inactive

358(33.9)

279(26.4)

270(25.6)

409(32.3)

264(28.5)

234(24.0)

Mod

eratelyinactive

278(26.4)

319(30.2)

329(31.2)

335(26.5)

288(31.1)

303(31.1)

Mod

eratelyactive

207(19.6)

255(24.2)

254(24.1)

273(21.6)

199(21.5)

244(25.1)

Active

212(20.1)

203(19.2)

202(19.2)

248(19.6)

176(19.0)

193(19.8)

Smok

ingstatus,n

o.(%

),0.00

1,0.00

1Currentsm

oker

191(18.1)

89(8.4)

71(6.7)

201(15.9)

84(9.1)

66(6.8)

Form

ersm

oker

425(40.3)

446(42.2)

436(41.3)

539(42.6)

374(40.4)

394(40.5)

Never

smok

er43

9(41.6)

521(49.3)

548(51.9)

525(41.5)

469(50.6)

514(52.8)

Totalenergy

intake

(kcal/d

ay)

1,86

7(1,559

2,27

1)1,91

8(1,628

2,27

9)1,93

2(1,641

2,27

4)0.00

61,88

2(1,562

2,28

5)1,90

4(1,621

2,29

4)1,92

9(1,657

2,24

2)0.04

Alcoh

olintake

(%totalenergy)

1.7(0.0

6.4)

2.1(0.0

5.6)

2.1(0.0

6.0)

0.48

1.6(0.0

5.6)

1.9(0.0

5.8)

2.5(0.5

6.4)

,0.00

1Variety

incombinedF&

Vintake

(no.

items/week)

8.8(2.9)

11.9

(3.0)

14.3

(3.6)

,0.00

1d

dd

dVariety

infruitintake

(no.

item

s/week)

2.3(1.5)

3.9(1.5)

5.3(2.0)

,0.00

1d

dd

dVariety

invegetableintake

(no.

items/week)

6.5(2.4)

8.0(2.6)

9.1(2.7)

,0.00

1d

dd

Quantityof

combinedF&

Vintake

(portion

s/day)

dd

dd

2.5(1.8

3.5)

3.7(2.9

4.8)

5.0(4.0

6.3)

,0.00

1Quantityof

fruitintake

(portion

s/day)

dd

dd

1.1(0.5

1.9)

1.9(1.1

2.8)

2.7(1.8

3.7)

,0.00

1Quantityof

vegetableintake

(portion

s/day)

dd

dd

1.3(0.9

1.7)

1.8(1.4

2.3)

2.3(1.8

2.9)

,0.00

1Dataaremeans

(SD),medians

(IQR),and%

forcategoricalvariables.P

values

arefrom

thetestfortrendforcontinuo

usvariablesandthex2testforcategoricalvariables.



in the EPIC-Norfolk study,mean consump-tion of F&V was much higher when as-sessed by FFQ (6.5 portions per day)than by a food diary (3.8 portions perday) (11). For this reason, FFQs are notideal for examining adherence to, or for

informing, public health guidelines. Fur-thermore, FFQs are based on perceptionsof habitual intake, whereas food diaries arebased on self-report of foods and amountsactually consumed in real time (8). Addi-tionally, because FFQs contain only a

limited list of precoded food items, whichtend to be grouped together, unlike thefood diary, which is open ended, theymay not be as suitable as food diaries forassessing variety of food intake. Despitethe fact that variety in F&V intake has

Table 2dHRs (95% CIs) of incident diabetes for quantity of fruit, vegetables, and combined F&V intake in the EPIC-Norfolk study

Low Medium High P for trend

Tertiles of quantity of fruit intakeCase subjects/total (n) 261/1,269 193/1,214 199/1,221Median (IQR) intake (portions/day) 0.6 (0.30.9) 1.8 (1.52.1) 3.4 (2.94.4)Model 1 1 (Reference) 0.72 (0.590.86) 0.77 (0.640.93) 0.004Model 2 1 (Reference) 0.72 (0.590.87) 0.75 (0.610.91) 0.003Model 3 1 (Reference) 0.81 (0.651.00) 0.91 (0.711.16) 0.46

Tertiles of quantity of vegetable intakeCase subjects/total (n) 245/1,260 229/1,236 179/1,208Median (IQR) intake (portions/day) 1.1 (0.81.3) 1.7 (1.61.9) 2.6 (2.33.1)Model 1 1 (Reference) 0.91 (0.761.06) 0.72 (0.590.87) 0.001Model 2 1 (Reference) 0.88 (0.731.06) 0.72 (0.580.87) 0.001Model 3 1 (Reference) 0.91 (0.741.11) 0.76 (0.600.97) 0.03

Tertiles of quantity of combined F&V intakeCase subjects/total (n) 268/1,277 188/1,206 197/1,221Median (IQR) intake (portions/day) 2.1 (1.62.5) 3.7 (3.34.0) 5.7 (5.06.8)Model 1 1 (Reference) 0.70 (0.580.84) 0.72 (0.600.87) ,0.001Model 2 1 (Reference) 0.68 (0.560.82) 0.68 (0.560.83) ,0.001Model 3 1 (Reference) 0.73 (0.600.90) 0.79 (0.621.00) 0.04

Data are HRs (and 95%CIs) estimated using Prentice-weighted Cox regression, with age as the underlying timescale variable. Adjustment for covariates was performedusing multivariable, Prentice-weighted Cox proportional analyses. Model 1 was adjusted for sex. Model 2 was adjusted for the same covariates as Model 1 plus BMI,waist circumference, education level, Townsend Deprivation Index, occupational social class, smoking status, physical activity, family history of diabetes, energyintake, and season. Model 3 was adjusted for the same covariates as Model 2 plus fruit variety for fruit quantity, vegetable variety for vegetable quantity, or combinedF&V variety for combined F&V quantity.

Table 3dHRs (95% CIs) of incident diabetes for variety of fruit, vegetables, and combined F&V intake in the EPIC-Norfolk study

Low Medium High P for trend

Tertiles of variety of fruit intakeCase subjects/total (n) 355/1,744 197/1,247 101/713Mean intake (no. items/week) 2.0 6 1.0 4.4 6 0.5 6.9 6 1.2Model 1 1 (Reference) 0.74 (0.620.88) 0.67 (0.540.84) ,0.001Model 2 1 (Reference) 0.72 (0.600.86) 0.71 (0.560.89) ,0.001Model 3 1 (Reference) 0.72 (0.590.87) 0.70 (0.530.91) 0.002

Tertiles of variety of vegetable intakeCase subjects/total (n) 348/1,759 172/1,004 133/941Mean intake (no. items/week) 5.5 6 1.4 8.5 6 0.5 11.4 6 1.5Model 1 1 (Reference) 0.85 (0.711.02) 0.68 (0.560.84) ,0.001Model 2 1 (Reference) 0.85 (0.701.03) 0.73 (0.590.89) 0.002Model 3 1 (Reference) 0.87 (0.721.07) 0.77 (0.610.98) 0.03

Tertiles of variety of combined F&V intakeCase subjects/total (n) 321/1,530 193/1,084 139/1,090Mean intake (no. items/week) 8.0 6 1.8 12.0 6 0.8 16.3 6 2.3Model 1 1 (Reference) 0.83 (0.690.99) 0.57 (0.470.70) ,0.001Model 2 1 (Reference) 0.88 (0.731.06) 0.60 (0.490.74) ,0.001Model 3 1 (Reference) 0.88 (0.731.07) 0.61 (0.480.78) ,0.001

Data are HRs (and 95%CIs) estimated using Prentice-weighted Cox regression, with age as the underlying timescale variable. Adjustment for covariates was performedusing multivariable, Prentice-weighted Cox proportional analyses. Model 1 was adjusted for sex. Model 2 was adjusted for the same covariates as Model 1 plus BMI,waist circumference, education level, Townsend Deprivation Index, occupational social class, smoking status, physical activity, family history of diabetes, energyintake, and season. Model 3 was adjusted for the same covariates as Model 2 plus fruit quantity for fruit variety, vegetable quantity for vegetable variety, or combinedF&V quantity for combined F&V variety.



been advocated by many national and in-ternational bodies (57), no studies thatwe are aware of have explored associationsbetween variety in intake and risk of T2D.Our current ndings suggest that quantity(at least 3.5 portions of F&V per day) andvariety (at least 12 different F&V items perweek) in F&V intake are both inverselyand independently associated with T2D.However, only;50% and 40% of the par-ticipants reported meeting these thresh-olds for quantity and variety of intake,respectively.

There are several unique strengths ofour study, including the large sample size,prospective study design, use of a 7-dayprospective food diary with disaggregatedF&V data, thorough assessment of newcases of T2D with self-report informationsupplemented by external sources, andcomprehensive information on covariates,

thus minimizing sources of bias and con-founding. Another strength of our studywas that we had HbA1c data availableon a subsample of participants and werethus able to demonstrate that our ndingswere unlikely to have been inuenced bythe presence of previously undiagnosed ca-ses of T2D at baseline. However, severalpotential limitations of our study merit dis-cussion. First, because of the observationalnature of the study, we cannot exclude thepossibility of residual confounding or con-founding by unmeasured factors. Second,we used baseline dietary consumptiondata to characterize individuals and didnot take into account possible misclassi-cation with respect to changes in con-sumption patterns over time. However,as this type of misclassication is likelyto be nondifferential, the effect wouldbe to attenuate the observed HRs toward

the null, suggesting that the true associa-tions between quantity and variety inF&V intake may be stronger than reportedin the current study. We were also not ableto adjust for lifestyle factors (e.g., smokingand physical activity) thatmay have changedduring follow-up. Finally, our populationis predominantly of European-Caucasianorigin (99.1%) and middle aged. Thus,the generalizability of our ndings to otherpopulations may be limited. Nevertheless,in comparison with the general populationof England, EPIC-Norfolk participants arecomparable with respect to characteristicsincluding anthropometry, blood pressure,and lipids (10).

The biological mechanisms for theinverse associations of F&V intake anddiabetes risk are not clear. Our ndingssuggest that F&V may be inversely asso-ciated with diabetes through two distinct

Figure 1dThe upper percentile of the rst tertile for quantity and variety of F&V intake was used as the reference category. A: The associationbetween quantity of F&V intake and HR (95% CI) of diabetes adjusted for sex, BMI, waist circumference, education level, Townsend DeprivationIndex, occupational social class, physical activity level, smoking status, family history of diabetes, total energy intake, and season. B: Same as A butadditionally adjusted for variety of F&V intake. C: The association between variety of F&V intake and HR (95% CI) of diabetes adjusted for sex,BMI, waist circumference, education level, Townsend Deprivation Index, occupational social class, physical activity level, smoking status, familyhistory of diabetes, total energy intake, and season. D: Same as C but additionally adjusted for quantity of F&V intake.



but complementary pathways. A plausi-ble biological mechanism to explain thebenecial effect of quantity of F&V intakeon T2D is via the low energy and high bercontent of F&V, and as such their ability toreduce the overall energy content of thediet. It has previously been demonstratedthat those who consume the highest quan-tity of F&V, in comparison with low con-sumers, have a lower risk of weight gain(24,25), a major risk factor for diabetes(26). A decreased risk of T2D with increas-ing quantities of vegetable intake in partic-ular may be explained by the fact thatvegetables are generally consumed withother foods as part of a meal and thereforemay displace or buffer the harmful effectsof deleterious foods from the diet, such asenergy-dense foods or foods that increasethe risk of T2D. Alternatively, higher con-sumption of specic vegetables, particu-larly green leafy vegetables, might reducethe risk of T2D due to the presence of rel-atively high concentrations of potentiallybenecial bioactive compounds (21). Thebiological mechanisms for the inverse asso-ciations of variety of F&V intake with T2Dare not clear but may be attributable to in-dividual or combined effects of the manydifferent bioactive phytochemicals con-tained in F&V (e.g., vitaminC and caroten-oids) (27,28). Thus, consumption of awidevariety of F&V will increase the likelihoodof consuming these phytochemicals. As thecurrent study was not designed to examinemechanisms of association, future studieswill be required to investigate this further.

In conclusion, using the prospective7-day food diary to assess F&V intake, wefound that a greater variety of fruit, vegeta-bles, and combined F&V intake is associ-ated with a reduced risk of T2D, whereasfor quantity, only greater vegetable, but notfruit intake, was associated with a reducedrisk. These ndings support current publichealth recommendations encouraging con-sumption of F&V as part of a balanced dietand place particular emphasis on the im-portant and independent role that bothquantity and variety in F&V intake mayplay in helping to prevent the developmentof T2D.

AcknowledgmentsdThis study was sup-ported by grants from the Medical ResearchCouncil, the Food Standards Agency, CancerResearch UK, and the British Heart Foundation.No potential conicts of interest relevant to

this article were reported.The sponsors did not participate in the de-

sign or conduct of this study; in the collection,management, analysis, or interpretation of data;

in the writing of the manuscript; or in the prep-aration, review, approval, or decision to submitthe manuscript for publication.A.J.C. conceived and designed the study,

analyzed and interpreted the data, drafted themanuscript, and had full access to all the datain the study and takes responsibility for theaccuracy of the data analysis. S.J.S. analyzedand interpreted the data. M.A.H.L. analyzeddata and contributed to the discussion. R.N.L.acquired the data. K.-T.K. obtained fundingand acquired the data. N.J.W. obtained fund-ing, acquired the data, and conceived and de-signed the study. N.G.F. conceived and designedthe study and analyzed and interpreted the data.All authors critically revised the manuscript forimportant intellectual content and approved thenal version. N.G.F., N.J.W., and K.-T.K. are theguarantors of this work and, as such, had fullaccess to all the data in the study and takeresponsibility for the integrity of the data and theaccuracy of the data analysis.The authors thank the EPIC-Norfolk par-

ticipants and the EPIC-Norfolk team for theircontributions. The authors also thank AmitBhaniani (University of Cambridge) for helpwith data and Anna Rickard and Soren Brage(Institute of Metabolic Science) for helpfuldiscussion in earlier stages of this work.

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