Legumes in human nutrition

Transcription

1 Science & Reserch Overview Copyright! Peer-reviewed Mnuscript received: Mrch 15, 2017 Revision ccepted: June 28, 2017 Legumes in humn nutrition Nutrient content nd protein qulity of pulses Helmut F. Erbersdobler, Christin A. Brth, Gerhrd Jhreis Abstrct Using dt from the literture, we determined the nutrient content nd protein qulity of legumes (pulses), including pes, fb bens, sweet lupines, nd soybens. We clculted the Amino Acid Score (AAS) bsed on comprison of the mino cid vlues with those of stndrd protein tht ws determined bsed on the requirement vlues for children ged three yers nd bove, nd we clculted the Protein Digestibility Corrected Amino Acid Score (PDCAAS) bsed on the protein digestibility vlues. The vitmin nd minerl content of these legumes is reltively high, prticulrly for potssium nd clcium (in the cse of lupines nd soybens), mgnesium, iron, nd zinc, nd lso vitmin B1 (thimine) nd foltes. Soybens re good source not only of linoleic cid, but lso of α-linolenic cid. The remining legumes do not ply significnt role s sources of ftty cids due to their low ft content. Legumes hve very high dietry fiber content. The discchride nd oligoscchride levels in prticulr re remrkbly. In the cse of fb bens nd lupines, the sulfur-contining mino cids (methionine nd cystine) re limiting mino cids. The digestibility of the protein in ll legumes is very high, rnging from 89% to 96%. This mens tht the PDCAAS vlues rnge from 81 (lupines) to 96 (pes). These high vlues re comprble to those of niml proteins. Pes nd bens, nd to somewht lesser extent lupines, re good sources of lysine, which mens tht they re useful complement to cerel proteins, which re quite low in lysine. Lupine protein is lso rich in rginine. Keywords: legumes, pulses, pes, soybens, fb bens, sweet lupines, protein qulity, mino cids, minerls, vitmins, dietry fiber Cittion: Erbersdobler HF, Brth CA, Jhreis G (2017) Legumes in humn nutrition. Nutrient content nd protein qulity of pulses. Ernhrungs Umschu 64(9): ; 64(10): This rticle is vilble online: DOI: /eu Introduction Legumes re mong the foodstuffs for which regulr consumption is highly recommended. In ncient times nd in the Middle Ages, they were one of the most importnt sources of energy (strch) nd protein in the humn diet. Tody, they hve been replced in this role by cerels or pottoes nd foods of niml origin. Consequently, the verge consumption of legumes in Germny for instnce is now lower thn 1 kg per person per yer [1]. The resons for this lower consumption of legumes include their fltulescent (bloting) effect (especilly in the cse of bens), their simple nd rustic imge, nd the perception tht legumes (pulses) re frequently used s niml fodder. A further reson is the low level of cultivtion, which leds to lower supply. Lst but not lest, these dys, the cerel products nd potto products vilble re much more vried nd diversified thn legume-bsed products. However, ttitudes towrds legumes hve been improving for some time now, nd they re no longer consistently viewed s old-fshioned. The resons for this re the following: 1. The helth benefits of legumes re being incresingly recognized nd cknowledged (e.g. [2]). In study by Becerr-Tomás et l. [3] in 3,349 prticipnts with different intke levels of legumes (lentils, chick pes, bens, pes), 266 new cses of dibetes occurred within the four-yer study period. In the group with the highest qurtile of legume consumption (up to 35 g/dy), the risk of dibetes ws lower thn in the group with the lowest qurtile (9.5 g/dy). However, it should be noted tht the verge consumption of legumes in Germny is less thn 2 g/ dy. 2. There is n urgent need for more plnt-derived proteins tht cn be used in the humn diet, especilly in light of the growing world popultion. They re lso needed s n lterntive to diet tht is rich in crbohydrte nd ft. Legumes re reltively rich in proteins, 134 Ernehrungs Umschu interntionl 9/2017

2 Copyright! with protein content of 20 40% in the dry mtter, wheres cerels for exmple only hve protein content of 10 15%. 3. Protein concentrtes nd isoltes re incresingly being used in specil diets, for exmple in nutrition of thletes. 4. There re incresing clls to reduce consumption of foods of niml origin nd replce them with plnt-derived proteins, both for helth resons nd for sustinbility resp. environmentl resons. A prospective cohort study of 131,342 prticipnts within the Nurses Helth Study concluded tht there my be positive correltion between high intke of foods of niml origin nd incresed crdiovsculr mortlity. Conversely, high intke of plnt-derived proteins is ssocited with lower overll mortlity nd lower crdiovsculr mortlity. This reltionship ws prticulrly mrked in people with t lest one risk fctor of lifestyle [4]. 5. Protein-rich foods tht cn provide high-qulity protein re urgently needed to supply the growing trend towrds vegetrin nd vegn diets. 6. Furthermore, new proteins with functionl properties tht re technologiclly useful, concerning solubility or the bility to form emulsions, foms or gels, etc. re constntly being sought [5, 6]. Some protein isoltes derived from vrious legumes meet these requirements. Legume flour nd specil products bsed on protein isoltes (nd sometimes lso strch isoltes) in prticulr therefore ply n incresingly importnt role in food technology. Consequently, it comes s no surprise tht there is growing trend towrds the cultivtion of legumes moving out of the kitchen grden nd into lrge res of rble lnd. This is why the nutrition nd food industry hve their focus set on niml fodder crops such s field pes, fb bens, nd sweet lupines. These developments rise the question of whether these products meet humn dietry requirements in terms of their nutrient content nd in terms of ny unfvorble substnces they my contin, nd whether they my even hve positive impct on humn helth. This rticle dels primrily with the most importnt nutrients, nd lso focuses on protein qulity due to the specil role of protein s nutrient. Methodology The most populr legume flours mde of field pes (Pisum stivum L.), fb bens (Vici fb), nd sweet lupines (Lupinus ngustifolius) were selected nd compred with soybens (Glycine mx). The pes tht were used were dehulled pes tht re very similr to grden pes. nippornnn/istock/thinkstock UrosPoteko/iStock/Thinkstock PicturePrtners/iStock/Thinkstock d chengyuzheng/istock/thinkstock b c victoriy89/istock/thinkstock Legumes/pulses The word legume is derived from the botnicl term Leguminose. Legumes re the dry seeds of ppilioncee. They re the third lrgest fmily mong the higher plnts. The most common legumes re soybens, fb bens, pes, green bens, lentils, lupines, nd chick pes. In terms of globl production, soybens re by fr the most commonly cultivted, followed by fb bens nd pes. Legumes hve prticulrly positive impct on soil fertility, not lest becuse their roots fix nitrogen out of the ir in the soil thnks to symbiotic reltionship with rhizobi, thus mking the nitrogen vilble to other plnts. ) Fb bens (Vici fb), b) Soybens (Glycine mx), c) Sweet lupines (Lupinus ngustifolius), d) Pes (Pisum stivum) Ernehrungs Umschu interntionl 9/

3 Science & Reserch Overview Copyright! Digestibility Digestibility is tested in experiments known s blnce studies. In these studies, the reltionship between N-excretion vi feces nd N-intke is investigted. True digestibility (TD) refers to digestibility vlues tht re corrected for endogenous losses in the feces. The endogenous losses re clculted in seprte tests, e.g. niml studies with protein-free feed. TD N = N-intke (N-excretion endogenous N-losses) N-intke This clcultion does not tke ccount of chnges in individul mino cids due to the microbiome in the cecum. This phenomenon is ttempted to be tken into ccount in clcultions by ilel digestibility, of mino cids s described below. Fb bens belong to the genus Vici (vetches) nd not to the genus Phseolus like green bens. The lupines referred to here re minly dehulled, blue-flowering sweet lupines. They re preferred in Germny over the white nd yellow-flowering vrieties becuse they re less susceptible to fungl diseses like nthrcnose. The differences in the nutrient content between the species re usully no greter thn the vritions within species, which depends on the vriety, the cultivtion conditions, the climte, etc. For some nutrients, reference is lso mde to white nd yellow lupines. For the ftty cids, the vlues of the three lupine species re compred (ccording to [7]). For the mino cid content, the vlues pply to ll three lupine species. Becuse the Germn food tbles provide little dt for field pes, fb bens nd lupines, nd since these products hve so fr minly been used in niml nutrition, vlues from feed tbles hve lso been used [8, 9]. As generl rule, dt from tbles is preferred becuse this dt is usully bsed on multiple nlyses, mking it more relible. There ws sufficient dt for the energy contributing nutrients, minerls, nd mino cids. However, there is little dt for vitmins, ftty cids, nd dietry fiber. In specific cses (especilly in the cse of pes), dt from food tbles on grden pes ws Min nutrients (per 100 g) Pes Fb bens Lupines, blue Soybens dry substnce g energy kj kcl 1, , , protein N x ft g strch utilizble sugr g g fiber g 10 b , Tb. 1: Energy contributing (min) nutrients present in the legumes (pulses) investigted from Souci et l., dried pes [10] b Jhreis et l [11] used [10]. The study by Jhreis et l. [11] served s the control, nd some individul vlues from tht study were used directly in this one (noted in the tbles). In order to ssess nutrient density, in Figure 1 the dt ws linked to the reference vlues for the supply of energy nd some nutrients, vitmins nd minerls provided in the EU Food Informtion to Consumers Regultion (EU-FIC) [12]. With the exception of folte, these vlues re pproximtely the sme s the D-A-CH reference vlues for 19 to 25-yer-old womn [13]. In order to clculte the protein qulity, the levels of indispensble mino cids (lso known s essentil mino cids) in the legumes were correlted with n idel protein bsed on the requirements for growing child of the ge of 3 yers or bove. The dt for children is considered the most relible vilble to dte. Furthermore, t this ge, mino cid requirements re high [14, 15], nd it is therefore prticulrly importnt to py ttention to them. This lso pplies to children on vegn diet. The vlues for dults re not yet sufficiently relible [14 16], but they re lower, which mens tht the biologicl vlue of the protein tht pplies to children is lso pplicble to dults. The United Ntions Food nd Agriculture Orgniztion (FAO) [14] therefore recognizes only three stges of mino cid requirement: 0 to 6 months, 6 months to 3 yers nd 3 yers nd up (including dults). Bsed on the comprison with reference protein, it is esy to determine which mino cids re low compred to the requirements. The indispensble mino cid with the lrgest deficit compred to the required vlue ( first limiting mino cid) determines the Amino Acid Score (AAS). Amino cid vlues bove the requirement, i.e. n pprent mino cid index of bove 100, re thus mde equl to 100 (science clls these truncted ). Exmple: In the cse of bens nd lupines, with 136 Ernehrungs Umschu interntionl 9/2017

4 Copyright! Minerls Pes Fb bens Lupines, blue Soybens potssium g clcium g mgnesium g iron copper zinc selenium µg Tb. 2: The most importnt minerls present in the legumes (pulses) investigted Jhreis et l [11] Vitmins Pes Fb bens Lupines, blue Soybens α-tocopherol γ-tocopherol thimine (vitmin B 1 ) riboflvin (vitmin B 2 ) pyridoxine (vitmin B 6 ) vlue of 2.1%, the sulfur-contining mino cids methionine + cysteine only rech 91% of the required vlue. The AAS is therefore 91. However, mino cid content is not the only fctor tht limits protein qulity. It is lso limited by the digestibility of the protein nd the biovilbility of the mino cids. This spect of protein qulity is most severely ffected by the presence of substnces tht hve negtive effect on protein digestibility. It is well-known fct tht legumes cnnot be eten rw. Some of them contin very lrge mounts of protese inhibitors, lectins (phytohemgglutinins), phyttes, tnnins, nd other such substnces. One well-known wy of reducing the effect of these substnces is moderte heting, such s tosting (of soy mel for exmple), extrusion, bking, steming, nd boiling. There is fine line between dequte heting nd overheting, nd it is essentil to find the hppy medium in order to obtin optimum protein qulity. In order to tke digestibility into ccount, in this evlution the Protein Digestibility Corrected Amino Acid Score (PDCAAS) [14 19] ws used. In this scoring system, the AAS is multiplied by the true digestibility quotient of the protein (s mesured in niml tests on rts). It ws estblished in previous tests tht the digestibility vlues mesured in rts re lso lrgely pplicble to humns [16, 19]. For exmple, if the AAS of fb bens is 91% nd the true digestibility quotient is 0.95, then the PDCAAS would be This vlue is pproximtely equivlent to the biologicl vlue of the protein. One often cited disdvntge of the PDCAAS is tht it overestimtes the protein qulity of strongly heted foods becuse the biovilbility of some mino cids (lysine in prticulr) is impired in such cses [14, 17]. For these resons, it is suggested giving preference to the Digestible Indispensble Amino Acid Score (DIAAS) s mesure of protein qulity over the ilel mino cid digestibility [14, 20]. The gut contents (chymus) of the ileum (usully from the pig) re removed by mens of fistul nd nlyzed. Chnges in the indigestible protein components of the food in the cecum re thus circumvented. This method is used in niml nutrition nd it is lso promising method for use in humn nutrition. In humn nutrition, however, this method, which is more time-consuming nd mteril-intensive thn PDCAAS, hs so fr not become estblished, especilly since there is still not sufficient dt vilble on ilel mino cid digestibility [14]. Results nd discussion Preprtion nd use 0.11 b b n. d. Legumes re n estblished food. Some of them hve been used s food for thousnds of yers nd their preprtion methods re well known. Essentilly, they require 1.1 b 15.3 b 6.5 b 23.0 b b b foltes µg Tb. 3: The most importnt vitmins present in the legumes (pulses) investigted from Souci et l., dried pes [10] b Jhreis et l [11] n. d. = not determined sufficient heting, which not only dectivtes detrimentl substnces, but lso increses digestibility, nd especilly the digestibility of the protein portion, through denturtion. Until now, dried fb bens hd never been commonly eten foodstuff in Centrl Europe. They re sometimes found s n ingredient in muesli or bred, nd this set to occur more often now in light of the current trend towrds vegetrin nd vegn diets. The use of lupines in humn nutrition is lso reltively new phenomenon, especilly since low-lkloid sweet lupines hve only been cultivted since the beginning of the 20 th century. Energy-supplying nutrients In pes nd fb bens, strch is the min component ( Tble 1). Prior to the introduction of the potto, pes were n importnt source of strch, Ernehrungs Umschu interntionl 9/

5 Science & Reserch Overview Copyright! *" Fol B6 )" B2 (" '" B1 +,-./012/3" Zn &" %" Fe $" Mg #" C energy!" soybens lupines bens pes % +,-./012/3" Fig. 1: Reltive levels of the most importnt minerls nd vitmins per 100 g, with reference to the dily reference vlues Reference vlues for the supply of energy nd some nutrients, vitmins nd minerls provided in the EU Food Informtion for Consumers Regultion [12] solid line = in the cse of 100% reference vlues dshed line = reltive energy contribution of 100 g reltive to the forementioned reference vlue for energy B 1 = thimine; B 2 = riboflvin; B 6 = pyridoxine; C = clcium; Fe = iron; Fol = foltes; Mg = mgnesium; Zn = zinc long with cerels. Soybens re low in utilizble crbohydrtes, but they hve substntil ft content. Lupines re prticulrly high in dietry fiber. In soybens, nd lso often in lupines, protein is the lrgest component. It is therefore no surprise tht these legumes (first soybens, then lter lso lupines) re used to mke protein concentrtes nd isoltes for nutritionl nd technologicl purposes. White lupines tend to contin somewht more protein thn blue nd yellow lupines, but they hve less strch [21]. White lupines re the highest in ft nd hve somewht lower crude fiber content, mking this lupine species prticulrly useful in niml nutrition. Dietry fiber Dietry fiber content vries gretly. It depends lrgely on whether the seeds re dehulled. In the non-dehulled seed, most of the fiber is insoluble fiber, including high proportion of cellulose [22]. After dehulling of the seeds, it is predominntly soluble fiber tht remins [23]. This rticle dels with these dehulled seeds. The lignin content is low [6]. It is worth noting the reltively high levels of triscchrides nd oligoscchrides (stchyose + rffinose %, smll mounts of verbscose). Lupines nd soybens lso contin ciceritol t levels of bout 0.65% nd 0.08% respectively [22]. These oligoscchrides cuse fltulence (intestinl wind) becuse they re fermented in the cecum in mnner similr to tht of soluble dietry fibers. These substnces cn be reduced through queous to slightly lcoholic extrction, nd het tretment prtilly destroys them. However, it is importnt to ber in mind tht they cn lso hve prebiotic effects. For further informtion regrding the helth benefits of the dietry fiber in legumes, we refer the reder to the work of Jhreis et l. [11]. The sme pplies to the question of llergenicity. In the EU-FIC, soybens nd lupines re listed mong the 14 llergenic foods tht must be shown on pckging [12]. Minerls nd vitmins The levels of the most importnt vitmins nd minerls re listed in Tble 2 nd Tble 3. Figure 1 shows the reltive levels for the most importnt minerls nd vitmins, reltive to the reference vlues for the supply of energy, some nutrients, s well s vitmins nd minerls provided in EU-FIC [12]. At the sme time, the energy content is shown s percentge of the reference vlue. Thus, the figure gives n ide of the nutrient density of legumes. Reltive nutrient content vlues bove the reltive energy vlue men high nutrient density. Vlues below indicte low nutrient density for this food. 138 Ernehrungs Umschu interntionl 9/2017

6 Copyright! As indicted in Figure 1, the reltive nutrient contents re bove the reltive energy contents in lmost ll of the cses shown, mening tht legumes cn generlly be considered high in vitmins nd minerls. The vlues for mgnesium nd iron, thimine (vitmin B 1 ), nd foltes re remrkbly high, nd in the cse of lupines nd soybens, the clcium vlues s well. Even the trce element levels re reltively high in the cse of iron, zinc nd copper, but the selenium content is only of note in soybens (there is generlly little dt for this) ( Tble 2). The biovilbility of the minerls from legumes vries nd is determined by the minerl content, by minerl-minerl interctions, nd by the levels of phytic cid nd tnnic cid. Phytic cid levels vry little between different types of cerels nd legumes. Overll, they depend more on the cultivtion conditions which cn cuse them to vry widely. With phytic cid content of > 2%, soybens hve the highest levels, followed by fb bens nd pes [11, 23]. Trinidd et l. [24] used the dilysbility of minerls s mesure of biovilbility. The biovilbility of iron from legumes ws reduced prticulrly drsticlly by high level of tnnic cid. The phytic cid nd tnnic cid levels in legumes did not ffect the vilbility of zinc. Generlly, the biovilbility of clcium nd zinc ws high, wheres the biovilbility of iron ws limited. The riboflvin levels (vitmin B 2 ) nd pyridoxine levels (B 6 ) (the ltter lso in pes) were lso high. The vitmin E content ws only of note in the ft-rich soybens. Some nutrients not listed, such s vitmins B 12, A, nd C, were present only in smll quntities or were bsent. Continution of this rticle, including the references, in the next issue of Ernährungs Umschu (issue 10/2017) Conflict of Interest Prof. Erbersdobler nd Prof. Brth re members of the Specil Committee for Humn Nutrition within the Union for the Promotion of Oil nd Protein Plnts e. V., nd Prof. Jhreis is the Chir of this committee. Other thn those stted bove, the uthors declre no conflict of interest. Prof. Dr. Helmut F. Erbersdobler 1 Prof. Dr. Christin A. Brth 2 Prof. Dr. Gerhrd Jhreis 3 1 ehemls Institut für Humnernährung und Lebensmittelkunde Christin-Albrechts-Universität zu Kiel E-Mil: h-erbersdobler@t-online.de 2 Professor für Ernährungsmedizin n der Universität Potsdm Wissenschftlicher Direktor Deutschen Instituts für Ernährungsforschung (DIfE) i. R. 3 Institut für Ernährungswissenschften der Friedrich-Schiller-Universität Jen DOI: /eu