Postprandial glycaemic response to berry nectars containing inverted sucrose

RESEARCH ARTICLE Pos p andial glycaemic esponse o be y nec a s con aining in e ed suc ose Rii a Tö önen 1 *, Ja kko Hells öm 2 , Pi jo Ma ila 2 and Kyllikki Kilpi 3 1 Depa men o Clinical Nu i ion, Ins i u e o Public Heal h and Clinical Nu i ion, Uni e si y o Eas e n Finland, PO Box 1627, FI-70211 Kuopio, Finland 2 New Business Oppo uni ies, Na u al Resou ces Ins i u e Finland, Mylly ie 1, FI-31600 Jokioinen, Finland 3 Finnsuga L d, Soke i eh aan ie 20, FI-02460 Kan ik, Finland (Recei ed 16 May 2016 –Final e ision ecei ed 29 Sep embe 2016 –Accep ed 28 No embe 2016) Jou nal o Nu i ional Science (2017), ol. 6, e4, page 1 o 7 doi:10.1017/jns.2016.44 Abs ac Suc ose is commonly used o swee ening be y p oduc s. Du ing p ocessing and s o age o be y p oduc s con aining added suc ose, suc ose is in e ed o glucose and uc ose. We ha e p e iously shown ha pos p andial glycaemic esponse induced by in ac suc ose is a enua ed when suc ose is consumed wi h be ies ich in polyphenols. I is no known how in e sion o suc ose a ec s glycaemic esponse. We in es iga ed pos p andial glycaemic and insu- linaemic esponses o blackcu an (Ribes nig um) and lingonbe y (Vaccinium i is-idaea) nec a s and a e e ence d ink (wa e ) swee ened wi h glucose and uc ose, ep esen ing comple ely in e ed suc ose. The nec a s and e e ence d ink (300 ml) con ained 17·5 g glucose and 17·5 g uc ose. Polyphenol composi ion o he nec a s was analysed. A o al o eigh een heal hy olun ee s pa icipa ed in a andomised, con olled, c oss-o e s udy. Blood samples we e collec ed a as ing and six imes pos p andially du ing 120 min. In e ed suc ose in he e e ence d ink induced glycaemic and insulinaemic esponses simila o hose p e iously obse ed o in ac suc ose. In compa ison wi h he e e ence, he blackcu an nec a a enua ed he ea ly glycaemic esponse and imp o ed glycaemic p ofile, and he lingonbe y nec a educed he insulinaemic esponse. The esponses induced by in e ed suc ose in he be y nec a s a e simila o hose p e iously obse ed o be y nec a s con aining in ac suc ose, sugges ing ha in e sion has no majo impac on glycaemic esponse o suc ose-swee ened be y p oduc s. The a enua ed glycaemic esponse a e he blackcu an nec a may be explained by inhibi ion o in es inal abso p ion o glucose by blackcu an an hocyanins. Key wo ds: Be ies: In e ed suc ose: Pos p andial glucose: Insulin: Polyphenols Be ies con ain an ioxidan i amins, mine als and fib e, and hey a e unique as ich sou ces o fla onoids and o he poly- phenols. Be ies and hei fla onoids, especially an hocyanins, ha e been associa ed wi h educed isk o CVD (1–4) , ype 2 diabe es (5–7) , he me abolic synd ome (8) ,inflamma ion (9–11) and cogni i e decline (12,13) , and hey may also con ibu e o heal hy ageing (14) and weigh main enance (15) . Thus, he scien- ific e idence o heal h benefi s is encou aging, and he No dic Nu i ion Recommenda ions (16) ad ise o inc ease consump- ion o be ies as pa o a balanced heal hy die . Due o low suga :acid a io and high con en o polyphenols, sou and bi e as e is ypical o many be ies. Suga , such as suc ose o high- uc ose co n sy up, is commonly used o inc ease accep abili y o be y p oduc s. Al hough suga helps o inc ease be y consump ion, i may comp omise he nu i- ional and heal h benefi s o be ies, e.g. by inducing pos p an- dial hype glycaemia. The e o e, i is impo an o unde s and he me abolic consequences o suga consumed wi h be ies. Ou p e ious s udies ha e shown ha be ies may imp o e pos p andial glycaemic con ol in heal hy subjec s when Abb e ia ions: i.d., in e nal diame e ; SGLT1, sodium glucose co- anspo e 1. *Co esponding au ho : R. Tö önen, email ii a. o onen@ue .fi © The Au ho (s) 2017. This is an Open Access a icle, dis ibu ed unde he e ms o he C ea i e Commons A ibu ion licence (h p://c ea i e- commons.o g/licenses/by/4.0/), which pe mi s un es ic ed e-use, dis ibu ion, and ep oduc ion in any medium, p o ided he o iginal wo k is p ope ly ci ed. JNS JOURNAL OF NUTRITIONAL SCIENCE 1 h ps:/www.camb idge.o g/co e/ e ms. h ps://doi.o g/10.1017/jns.2016.44 Downloaded om h ps:/www.camb idge.o g/co e. Na u al Resou ces Ins i u e Finland (Luke), on 09 Jun 2017 a 11:37:36, subjec o he Camb idge Co e e ms o use, a ailable a consumed wi h suc ose. The pos -meal fluc ua ion o blood glucose and insulin concen a ions induced by suc ose was alle- ia ed when suc ose was consumed wi h a mix u e o ou be - ies (bilbe ies, blackcu an s, c anbe ies and s awbe ies) (17,18) . In addi ion, blackcu an s and lingonbe ies, ei he as whole be ies o nec a s, imp o ed he pos p andial glycaemic and insulinaemic esponses o suc ose (19) . These esponses a e con- sis en wi h delayed diges ion o suc ose and/o slowe abso p- ion o glucose caused by be y polyphenols. Suc ose is a disaccha ide composed o glucose and uc ose. In he p esence o low pH and hea , suc ose is in e ed, i.e. he glycosidic linkage is hyd olysed in an i e e sible eac ion, eleasing glucose and uc ose. In ou p e ious s udies (17–19) , suc ose was added o he be y p oduc s jus be o e he p od- uc was consumed, o a oid in e sion. Howe e , du ing p o- cessing and s o age o be y p oduc s wi h added suc ose, in e sion o suc ose is likely o occu , due o he low pH o be ies. The e o e, unde s anding he e ec s o be ies on he glycaemic esponse induced by in e ed suc ose is o p ac- ical impo ance. The pu pose o his s udy was o in es iga e he pos p andial glycaemic and insulinaemic esponses o blackcu an (Ribes nig um) and lingonbe y (Vaccinium i is-idaea) nec a s con aining in e ed suc ose, added as glu- cose and uc ose, in heal hy subjec s. Me hods Pa icipan s Volun ee s we e ec ui ed by an announcemen in a local newspape in he a ea o Kuopio, Finland. The inclusion c i- e ia we e as ollows: heal hy men o women, age 25–69 yea s, BMI 20–28 kg/m 2 , no diabe es o o he ch onic disease, no smoking, no an ibio ic medica ion wi hin he pas 3 mon hs, and no blood dona ion wi hin he pas mon h. A he sc eening isi , hei heal h s a us and medical his o y was assessed by using a s uc u ed in e iew, and by an h opo- me ic and labo a o y measu emen s ( ou ine haema ological measu emen s, as ing plasma glucose, lipids, hy oid- s imula ing ho mone, alanine amino ans e ase and c ea inine). The s udy was conduc ed acco ding o he guidelines laid down in he Decla a ion o Helsinki and all p ocedu es in ol - ing human subjec s we e app o ed by he Resea ch E hics Commi ee o he Hospi al Dis ic o No he n Sa o (Finland). W i en in o med consen was ob ained om all pa icipan s. The s udy was egis e ed a clinical ials.go as NCT02743130. Tes p oduc s Blackcu an and lingonbe y nec a s we e p epa ed by Eckes-G anini Finland Oy Ab om indus ial juice concen- a es, wi h he final juice concen a ion o 50 %. Sodium benzoa e was added as a p ese a i e, and he nec a s we e pas eu ised and s o ed a +5°C. Suga composi ion was ana- lysed by HPLC. In he esea ch labo a o y, glucose (Glucosum anhyd icum Ph.Eu .; Vi abalans Oy) and uc ose (F uisana;, Danisco Swee ene s Oy) we e added o achie e final concen a ions o 17·5 g in 300 ml nec a (Table 1). Acco ding o Eu opean legisla ion, p oduc s ob ained by add- ing wa e and suga s o concen a ed ui juice a e defined as nec a s (20) . A e e ence d ink con ained 17·5 g glucose and 17·5 g uc ose in 300 ml ap wa e . Polyphenols (an hocya- nins, p oan hocyanidins, fla onols and phenolic acids) in he nec a s we e analysed be o e addi ion o he suga s. Re e ence s anda ds o an hocyanins (delphinidin-3- glucoside, delphinidin-3- u inoside, cyanidin-3-galac oside, cyanidin-3-glucoside, cyanidin-3-a abinoside, cyanidin-3- u inoside, pe unidin-3-glucoside, peonidin-3-glucoside, mal idin-3-glucoside) we e pu chased om Ex asyn hese. T iplica e samples we e weighed and dilu ed wi h a mix u e o me hanol, ace ic acid and wa e (65:4:31) p io o HPLC analysis. An hocyanins we e sepa a ed on a 150 mm, 4·6 mm in e nal diame e (i.d.), 5 µm, Gemini C18 column wi h a C18 gua d column using a g adien elu ion o ace oni ile in o 5 % o mic acid acco ding o Hells öm e al. (21) . De ec ion wa eleng h was se a 518 nm and UV spec um was eco ded be ween 190 and 600 nm. Iden ifica ion was based on e e ence s anda ds, UV spec a and li e a u e. Au hen ic s anda ds we e used o quan ifica ion when a ail- able; i no , he co esponding an hocyanidin-3-glucoside was used (e.g. pe unidin-3- u inoside was quan ified as pe unidin-3-glucoside). Re e ence s anda ds o p oan hocyanidins (ca echin, epica- echin and p ocyanidin B2) we e pu chased om Ex asyn hese. P ocyanidin oligome s (deg ee o polyme isa- ion 3–10) we e om Plan a Analy ica; he pu i y was de e - mined wi h hiolysis (22) . T iplica e samples (10 ml) we e pu ified wi h polyamide Supelco Disco e y DPA-6S (Sigma-Ald ich Chemie Inc.) (22) . HPLC analyses we e ca ied ou wi h an Agilen 1100 se ial de ice using a Phenomenex Luna HILIC column (250 mm, 4·6 mm i.d., 5 µm) wi h diol phase. The elu ion sol en s we e ace oni ile + ace ic acid = 98 + 2 (A), me hanol + ace ic acid + wa e = 95 + 2 + 3 (B) and dime hyl o mamide + ace ic acid + wa e = 85 + 2 + 13 (C). P oan hocyanidins we e sepa a ed a he flow a e o 1 ml/min acco ding o he ollowing e na y g adien : 95 % A and 5 % B as ini ial condi ions; changing o 40 % A and 60 % B in 45 min; isoc a ic elu ion (40 % A and 60 % B) o 5 min; changing o 60 % B and 40 % C in 1 min; changing o 20 % B and 80 % C in 2 min; isoc a ic elu ion (20 % B and 80 % C) o 7 min; changing o 80 % A and 20 % B in 4 min; changing o 95 % A and 5 % B in 1 min. Equalising ime be ween he injec ions was 10 min. Fluo escence de ec- ion wi h exci a ion wa eleng h o 280 nm and emission wa e- leng h 323 nm was used o he de e mina ion. Table 1. Suga composi ion o he es p oduc s Re e ence d ink Blackcu an nec a Lingonbe y nec a Glucose, na u al (g) 4·68 4·50 Glucose, added (g) 17·50 12·82 13·00 F uc ose, na u al (g) 5·07 3·81 F uc ose, added (g) 17·50 12·43 13·69 Juice (ml) 300 300 Wa e (ml) 300 2 jou nals.camb idge.o g/jns h ps:/www.camb idge.o g/co e/ e ms. h ps://doi.o g/10.1017/jns.2016.44 Downloaded om h ps:/www.camb idge.o g/co e. Na u al Resou ces Ins i u e Finland (Luke), on 09 Jun 2017 a 11:37:36, subjec o he Camb idge Co e e ms o use, a ailable a Fla onol glycosides we e hyd olysed by efluxing he sam- ples in 1·2M-HCl in 50 % aqueous me hanol o 1 h acco ding o He og e al. (23) . Fla onol aglycones we e iden ified and quan ified using an Agilen 1100 Se ies HPLC equipped wi h a diode a ay de ec o . The analy ical column was a No a Pak C18 (150 mm, 3·9 mm i.d., 4 µm, Wa e s) p o ec ed wi h he manu ac u e ’s p ecolumn. The mobile phase con- sis ed o 0·05 M-phospha e bu e (A) a pH 2·4 and me hanol (B) (5–60 % B in 50 min ollowed by 60–90 % B in 6 min). Iso hamne in, kaemp e ol, my ice in and que ce in we e quan- ified a 370 nm. Fo iden ifica ion pu poses, UV/ isable spec a we e eco ded a 190–600 nm. Re e ence s anda ds o phenolic acids (ca eic acid, e ulic acid, p-couma ic acid, cinnamic acid) we e pu chased om Sigma-Ald ich. T iplica e samples we e fil a ed and analysed by Agilen 1290 Infini e UHPLC equipped wi h a diode a ay de ec o . Phenolic acids we e sepa a ed a a flow a e o 0·4 ml/min on a 50 mm, 2·1 mm i.d., 1·8 µm, Zo bax Eclipse Plus C18 column using a g adien elu ion o ace o- ni ile (B) in o 50 mM-phospho ic acid (pH 2·5, A): 95 % A and 5 % B as ini ial condi ions; isoc a ic elu ion o 1·2 min; changing o 85 % A and 15 % B in 4·05 min; changing o 80 % A and 20 % B in 5·75 min; changing o 50 % A and 50 % B in 5 min; isoc a ic elu ion o 1·2 min; changing o 95 % A and 5 % B in 0·8 min. De ec ion wa eleng hs we e 280 nm and 329 nm, and UV spec um was eco ded a 190–400 nm. Phenolic acids we e iden ified acco ding o hei UV spec a and quan ified as he co esponding aglyconic o ms. S udy design The andomised, con olled, c osso e s udy was ca ied ou single-blinded o he labo a o y pe sonnel and analyses. Each subjec pa icipa ed in h ee 2 h es s on sepa a e isi s, a leas 3 d apa . The es p oduc s we e se ed in a ando- mised o de . The pa icipan s we e ins uc ed o keep hei die , body weigh and li ing habi s cons an du ing he s udy, abs ain om alcohol o 2 d be o e he es , and o e ain om in en- si e physical ac i i y o 12 h be o e he es . The day be o e he s udy isi , hey we e ad ised no o consume any be ies o be y p oduc s. In he e ening be o e he isi , hey we e ins uc ed o consume a meal o choice and epea ha meal be o e e e y isi . Body weigh was measu ed a e e y isi . The es s we e ca ied ou in he mo ning a e a 10–12 h o e nigh as . Fo collec ion o enous blood samples, an in a- enous ca he e (BD Venflon™P o 18GA, 1·3 × 32 mm; Beck on Dickinson) was inse ed in an an ecubi al ein o he o ea m. Baseline blood samples we e d awn a as ing (0 min) and o he samples a 15, 30, 45, 60, 90 and 120 min a e s a ing o consume he es p oduc . The samples o plasma glucose measu emen s we e collec ed in ci a e–fluo ide ubes and o plasma insulin measu emen s in EDTA ubes kep on ice. Plasma was immedia ely sepa a ed by cen i uga ion a +4°C and s o ed a −70°C. Glucose concen a ions we e analysed wi h he hexokinase me hod using Konelab Sys em eagen s and a Konelab 20 XTi clinical chemis y analyse (The mo Fishe Scien ific). The in a- and in e -assay CV we e 2·7 and 1·8 %, espec - i ely. Insulin was measu ed wi h a chemiluminome ic immuno- assay using Liaison® Insulin eagen s (DiaSo in Inc.) and a DiaSo in Liaison® analyse (DiaSo in Deu chland GmbH). The in a- and in e -assay CV we e 3·7and3·8 %, espec i ely. Calcula ions and s a is ical analyses The da a we e analysed by using IBM SPSS S a is ics o Windows, e sion 21.0 (IMB Co p.), and a e exp essed as means and s anda d de ia ions o s anda d e o s, as indi- ca ed. Linea mixed-e ec s modelling was used o compa e he e ec s o he es p oduc s. His og ams we e used o checking he no mali y o model esiduals. Values o P< 0·05 we e conside ed o be s a is ically significan . The s a is ical significance o he p oduc × ime in e ac ion was es ed in he mixed-model analysis using pa icipan as a andom ac o and p oduc × ime and hei main e ec s as fixed ac o s. When he p oduc × ime in e ac ion was s a is- ically significan , he di e ences be ween he e e ence d ink and be y nec a s a indi idual ime poin s we e es ed by pos hoc analysis wi h Sidak adjus men o mul iple compa isons. The maximum inc eases om he baseline concen a ions we e calcula ed by sub ac ing he as ing alue om he high- es alue. G aphPad P ism 5.03 o Windows so wa e (G aphPad So wa e, Inc.) was used o calcula ion o he gly- caemic p ofile o each subjec and es p oduc acco ding o Rosén e al. (24) , by di iding he ime (min) du ing which he plasma glucose was abo e he as ing concen a ion wi h he inc emen al peak alue (mmol/l). The inc emen al AUC we e calcula ed by using G aphPad P ism so wa e, igno ing he a ea below he baseline (0 min) concen a ion. The di e - ences be ween he e e ence and be y nec a s we e es ed using pa icipan as a andom ac o and p oduc as a fixed ac o in he mixed-model analysis. Resul s A e sc eening wen y-six olun ee s, hi een emale and fi e male pa icipan s we e en olled o he s udy, and hey all com- ple ed he h ee isi s. The a e age ime be ween isi s was 7·6 ( ange 3–17) d. The basic cha ac e is ics o he pa icipan s a e p esen ed in Table 2. The body weigh s emained s able Table 2. Basic cha ac e is ics o he pa icipan s (n13 emale and n5 male) (Mean alues, s anda d de ia ions and anges) Mean SD Range Age (yea s) 59 7 40–68 Weigh (kg) 66·99·453–86 BMI (kg/m 2 )23·92·220–28 Fas ing plasma glucose (mmol/l) 5·40·34·9–6·1 Fas ing plasma o al choles e ol (mmol/l) 5·30·83·9–7·1 Fas ing plasma LDL-choles e ol (mmoll/l) 3·00·91·7–5·7 Fas ing plasma HDL-choles e ol (mmol/l) 2·10·41·2–2·8 Fas ing plasma TAG (mmol/l) 0·90·30·5–1·6 3 jou nals.camb idge.o g/jns h ps:/www.camb idge.o g/co e/ e ms. h ps://doi.o g/10.1017/jns.2016.44 Downloaded om h ps:/www.camb idge.o g/co e. Na u al Resou ces Ins i u e Finland (Luke), on 09 Jun 2017 a 11:37:36, subjec o he Camb idge Co e e ms o use, a ailable a h oughou he s udy pe iod. The mean body weigh s we e 67·5( SD 9·6), 67·6(SD 9·5) and 67·3(SD 9·3) kg o he e e - ence, blackcu an nec a and lingonbe y nec a isi s, espec i ely. The e we e no di e ences in he imes spen d inking he es p oduc s. The e e ence d ink was inges ed in 2:36 (SD 0:59), blackcu an nec a in 2:37 (SD 1:04) and lingonbe y nec a in 2:31 (SD 0:59) min:s. Glucose esponse Since one pa icipan had an abno mal glucose esponse cu e, he glucose a iables ha e been calcula ed o se en een pa i- cipan s. The pos p andial glucose esponses a e p esen ed in Fig. 1. The p oduc × ime in e ac ion was s a is ically signifi- can (P=0·003). In compa ison wi h he e e ence, inges ion o he blackcu an nec a esul ed in lowe glucose concen a- ions a 15 and 30 min and a highe concen a ion a 60 min. A e he blackcu an nec a , he maximum inc ease om baseline was a enua ed by 33 %, and he glycaemic p ofile was imp o ed by 84 % (Table 3). The lingonbe y nec a had no s a is ically significan e ec on he glucose a iables. Insulin esponse The pos p andial insulin esponses a e p esen ed in Fig. 2. The p oduc × ime in e ac ion was highly significan (P<0·001). In compa ison wi h he e e ence, lowe insulin concen a ions we e obse ed a 15 min o bo h nec a s and a 30 min o he lingonbe y nec a . A 60 min, he insulin concen a ion emained highe a e he blackcu an nec a . In compa ison wi h he e e ence, he maximum inc ease om he baseline was a enua ed by 21 % a e he lingonbe y nec a (Table 3). A e he blackcu an nec a , he maximum inc ease om he baseline was 13 % smalle han a e he e e ence, bu he di e ence is no s a is ically significan . Polyphenol composi ion An hocyanins and p oan hocyanidins we e he majo polyphe- nols in he nec a s, and fla onols (que ce in) and phenolic acids (p-couma ic, ca eic and e ulic acids) we e de ec ed in smalle quan i ies (Table 4). The con en o an hocyanins was much highe in he black- cu an nec a (57·9 mg/100 g) han in he lingonbe y nec a (4·5 mg/100 g) (Table 4). The an hocyanin p ofile o he blackcu an nec a was domina ed by u inosides o delphini- din and cyanidin ollowed by glucosides o he same an hocya- nidins. Ru inosides o pe unidin and peonidin we e iden ified as mino an hocyanins. In he lingonbe y nec a , cyanidin-3- galac oside was he mos abundan , and cyanidin-3-a abinoside and cyanidin-3-glucoside we e p esen in smalle amoun s. In addi ion, aces o delphinidin and mal idin de i a i es we e de ec ed, p obably o igina ing om con amina ion o he lingonbe y juice concen a e wi h bilbe y. The lingonbe y nec a con ained mo e p oan hocyanidins (71·5 mg/100 g) han he blackcu an nec a (37·1 mg/100 g) (Table 4). Oligome ic p oan hocyanidins (deg ee o poly- me isa ion 2–10) domina ed in he lingonbe y nec a , and 35 % o he dime s we e A- ype (could no be es ima ed o o he oligome s). On he o he hand, 90 % o he Fig. 1. Plasma glucose concen a ions a e inges ion o he es p oduc s: e - e ence (▲); blackcu an nec a (●); lingonbe y nec a (○). Values a e means (n17), wi h s anda d e o s ep esen ed by e ical ba s. P=0·003 o p od- uc × ime in e ac ion in he mixed-model analysis. Mean alue o he black- cu an nec a was signi ican ly di e en om ha o he e e ence a an indi idual ime poin : * P<0·05, ** P<0·01 ( pos hoc analysis wi h Sidak adjus men ). Table 3. Glucose and insulin a iables a e consump ion o he es p oduc s (Mean alues and s anda d de ia ions) Re e ence Blackcu an nec a Lingonbe y nec a Mean SD Mean SD Mean SD Mixed model analysis: P Glucose† Fas ing (mmol/l) 5·30·35·30·35·10·4>0·05 Maximum inc ease (mmol/l) 2·41·01·6** 0·92·20·50·007 AUC (mmol/l × min) 73·337·755·234·573·929·50·055 Glycaemic p o ile (min/(mmol/l)) 25·27·246·4*** 22·829·76·4<0·001 Insulin‡ Fas ing (mU/l) 5·02·05·73·45·42·8>0·05 Maximum inc ease (mU/l) 27·912·624·314·221·9* 12·10·040 AUC (mU/l × min) 1089 492 1117 482 958 436 0·090 Mean alue was signi ican ly di e en om ha o he e e ence: * P<0·05, ** P<0·01, *** P<0·001 (pos hoc analysis wi h Sidak adjus men ). †n17. ‡n18. To con e insulin in mU/l o pmol/l, mul iply by 6·945. 4 jou nals.camb idge.o g/jns h ps:/www.camb idge.o g/co e/ e ms. h ps://doi.o g/10.1017/jns.2016.44 Downloaded om h ps:/www.camb idge.o g/co e. Na u al Resou ces Ins i u e Finland (Luke), on 09 Jun 2017 a 11:37:36, subjec o he Camb idge Co e e ms o use, a ailable a p oan hocyanidins in he blackcu an nec a we e highly poly- me ised (deg ee o polyme isa ion >10). Discussion Suc ose is commonly used o swee ening be y juices and o he be y p oduc s. When he me abolic e ec s o suc ose-swee ened be y p oduc s a e e alua ed, in e sion o suc ose should be conside ed. In his s udy we in es iga ed he e ec s o be y nec a s swee ened wi h glucose and uc- ose, ep esen ing comple ely in e ed suc ose, on pos p andial glucose me abolism. Ou esul s show ha he ea ly pos p an- dial glycaemic esponses induced by in e ed suc ose in he be y nec a s a e simila o hose obse ed in ou p e ious s udies (18,19) whe e in e sion o suc ose was a oided. The e a e e y ew s udies compa ing he glycaemic e ec o suc ose and in e ed suc ose. The s udy o Ellwood e al. (25) ound no significan di e ence in he glycaemic esponse be ween a load o suc ose o in e ed suc ose. Compa able glycaemic esponses ha e also been epo ed o suc ose and high- uc ose co n sy up, a swee ene consis ing o ee uc- ose and glucose (26–29) . Howe e , i is possible ha suc ose gi en in he o m o a be e age in hese s udies was hyd o- lysed, as epo ed by Le e al. (29) . The p esen s udy shows ha in e ed suc ose induces pos p andial glucose and insulin esponses compa able wi h hose o in ac suc ose. The esponse cu es o he e e ence d ink con aining 17·5 g glu- cose and 17·5 g uc ose a e p ac ically simila o hose epo ed p e iously o 35 g suc ose (18,19) . The maximum inc eases om he baseline we e 2·4 and 2·3 mmol/l o glu- cose and 27·9 and 33·4 mU/l o insulin in his s udy and in he p e ious s udy (19) , espec i ely. The alues o he gly- caemic p ofile in hese s udies we e 25·2 and 29·6 min/ (mmol/l), espec i ely. Blackcu an in he o m o a nec a (50 % juice) signifi- can ly a enua ed he in e ed suc ose-induced pos meal ise o plasma glucose concen a ion and imp o ed he glycaemic p ofile, whe eas he e ec on insulin esponse was less p o- nounced. The lowe glycaemic esponse was e iden du ing he ea ly pos p andial phase, and in he la e phase he declines o he glucose and insulin concen a ions we e less s eep han a e he e e ence. These esul s a e iden ical o hose de ec ed p e iously o suc ose added o a simila blackcu an nec- a (19) . The maximum inc ease o glucose concen a ion om he baseline (1·6 mmol/l o bo h) and he alues o he glycaemic p ofile (46·4 and 46·1 min/(mmol/l)) we e simi- la in his s udy and in he p e ious s udy. The glycaemic esponse induced by in e ed suc ose in he lingonbe y nec a did no di e om he e e ence. Also in he p e ious s udy (19) , suc ose in he lingonbe y nec a had no e ec on he ea ly glucose esponse. Howe e , in ac suc ose in he lingonbe y nec a p oduced a mo e sus ained la e -phase glucose esponse, p e en ed he suc ose-induced la e pos p andial hypoglycaemia and he eby imp o ed he gly- caemic p ofile (19) . These e ec s we e no obse ed in he p e- sen s udy. Fu he s udies a e needed o e i y and explain his di e ence. In e ed suc ose in he lingonbe y nec a signifi- can ly dec eased he ea ly insulin esponse. A enua ion o pos p andial insulin esponse by lingonbe ies, wi h li le o no e ec on glucose esponse, was p e iously obse ed when whole-be y pu ée was consumed wi h suc ose o whi e whea b ead (19,30) . We ha e p e iously sugges ed ha be ies may modula e he pos p andial glycaemic esponse o suc ose by educing diges- ion o suc ose and/o abso p ion o glucose, and ha Fig. 2. Plasma insulin concen a ions a e inges ion o he es p oduc s: e - e ence (▲); blackcu an nec a (●); lingonbe y nec a (○). Values a e means (n18), wi h s anda d e o s ep esen ed by e ical ba s. P<0·001 o p oduc × ime in e ac ion in he mixed-model analysis. Mean alue o he blackcu - an nec a was signi ican ly di e en om ha o he e e ence a an indi idual ime poin : ** P<0·01, *** P<0·001 (pos hoc analysis wi h Sidak adjus men ). Mean alue o he lingonbe y nec a was signi ican ly di e en om ha o he e e ence a an indi idual ime poin : †P<0·05, †† P<0·01 (pos hoc analysis wi h Sidak adjus men ). To con e insulin in mU/l o pmol/l, mul iply by 6·945. Table 4. Polyphenol con en s in he nec a s (mg/100 g) (Mean alues and s anda d de ia ions o iplica e analyses) Blackcu an nec a Lingonbe y nec a Mean SD Mean SD An hocyanins, o al con en 57·90·84·50·2 Delphinidin-3-glucoside 5·93 0·09 0·18 0·02 Delphinidin-3- u inoside 28·50·40 – Delphinidin de i a i es (as D-3-Glc) –0·84 0·05 Cyanidin-3-galac oside –2·19 0·09 Cyanidin-3-glucoside 2·63 0·04 0·45 0·02 Cyanidin-3-a abinoside –0·65 0·03 Cyanidin-3- u inoside 19·50·30 – Pe unidin-3- u inoside 1·01 0·04 – Peonidin-3- u inoside 0·33 0·03 – Mal idin-3-glucoside –0·17 0·01 P oan hocyanidins, o al con en 37·10·671·53·0 P1 0·50 0·014 3·43 0·19 P2 0·67 0·021 9·49 0·24 P3 0·49 0·039 7·53 0·22 P4–P6 1·26 0·13 15·20·6 P7–P10 0·72 0·061 6·78 0·65 >P10 33·50·529·11·4 Fla onols, o al con en 1·70·14·00·1 Que ce in 1·70·14·00·1 Phenolic acids, o al con en 1·72 0·02 1·17 0·01 Ca eic acid 0·741 0·011 0·24 0·001 Fe ulic acid 0·22 0·002 0·17 0·001 p-Couma ic acid 0·76 0·010 0·37 0·006 Cinnamic acid –0·39 0·002 P, deg ee o polyme isa ion. 5 jou nals.camb idge.o g/jns h ps:/www.camb idge.o g/co e/ e ms. h ps://doi.o g/10.1017/jns.2016.44 Downloaded om h ps:/www.camb idge.o g/co e. Na u al Resou ces Ins i u e Finland (Luke), on 09 Jun 2017 a 11:37:36, subjec o he Camb idge Co e e ms o use, a ailable a polyphenols may be he ac i e compounds (17–19) . In he small in es ine, suc ose is hyd olysed o glucose and uc ose by α-glucosidase, which is known o be inhibi ed by be y ex ac s and polyphenols in i o (31–33) . In he p esen s udy, howe e , α-glucosidase ac i i y plays no ole, because suga was inges ed as ee glucose and uc ose. The e o e, he lowe glycaemic esponse obse ed a e consump ion o he blackcu an nec- a canno be explained by inhibi ion o α-glucosidase ac i i y. Inhibi ion o glucose abso p ion om he small in es ine is ano he po en ial mechanism o glycaemic con ol a e a meal. The in es inal abso p ion o glucose is mainly media ed by wo anspo e s, he sodium glucose co- anspo e 1 (SGLT1) in he apical memb ane and GLUT2 in he basola e al memb ane o en e ocy es (34,35) . Polyphenols and polyphenol- ich ex ac s a e known o in e ac wi h hese anspo e s and may he eby egula e he a e o glucose abso p ion (36,37) . In acco dance wi h p e ious s udies (38–41) , he polyphenol p ofile o he blackcu an nec a was cha ac e ised by he abundance o an hocyanins, especially by u inosides and glu- cosides o delphinidin and cyanidin, and highly polyme ised p oan hocyanidins, while lingonbe y nec a was cha ac e ised by oligome ic and polyme ic p oan hocyanidins, wi h lowe con en s o an hocyanins and fla onols. Ou p e ious (19) and p esen esul s show ha an hocyanin- ich blackcu an is mo e po en han lingonbe y in lowe ing pos -meal gly- caemia p oduced by in ac o in e ed suc ose, espec i ely. The e a e no p e ious s udies on he in e ac ion o blackcu - an o i s componen s wi h glucose abso p ion. Howe e , in i o s udies ha e demons a ed ha o he an hocyanin- ich be - ies a e able o influence in es inal glucose anspo . In human in es inal Caco-2 cells, s awbe y ex ac inhibi ed glucose up ake om heapicalsidein o hecellsand heGLUT2- acili a ede flux on he basola e al side (42) . Pela gonidin-3-glucoside, he main an hocyanin in s awbe y, was esponsible o 26 % o he o al inhibi ion. Mo eo e , an hocyanin- ich be y ex ac dec eased bo h Na-dependen and Na-independen glucose up ake and educed SGLT1 mRNA and GLUT2 mRNA exp ession in Caco-2 cells (43) . In e es ingly, cyanidin-3-glucoside and cyanidin-3- u inoside we e ound o inhibi bo h ypes o glucose anspo . These compounds and delphinidin glycosides we e he main an hocyanins o he blackcu an nec a o ou s udy. A maquibe yex ac ichindelphinidinglycosidesando he an ho- cyaninsdec easedpos p andialglucoseandinsulinconcen a ions a e s a ch consump ion, and SGLT1 inhibi ion by delphinidin was sugges ed o be he p ima y mechanism (44) . In conclusion, he pos p andial glycaemic and insulinaemic esponses induced by in e ed suc ose a e simila o hose obse ed p e iously o in ac suc ose. Modula ion o he ea ly glycaemic esponse by be y nec a s is p ac ically simila o in ac and in e ed suc ose, sugges ing ha in e sion has no majo impac on glycaemic esponse o suc ose-swee ened be y p oduc s. The a enua ed glycaemic esponse o he blackcu an nec a con aining in e ed suc ose may be explained by inhibi ion o in es inal abso p ion o glucose by blackcu an an hocyanins. In u u e s udies, he e ec s o o he an hocyanin- ich be ies, such as bluebe ies, bilbe ies and chokebe ies, on suc ose-induced pos p andial glycaemia should be in es iga ed. Acknowledgemen s The au ho s would like o hank he s udy pa icipan s o hei ime and e o , Hannele Heinonen and Ee a Lajunen o hei skil ul echnical assis ance in he clinical s udy, and Eckes-G anini Finland Oy Ab o p o iding he nec a s. R. T. and K. K. designed he esea ch, R. 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