Plant Proteins in Relation to Human Protein - Young & Pellett - 1994

5/28/2018 Plant Proteins in Relation to Human Protein - Young & Pellett - 1994

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Am J C li,z N u tr 19 94:59(sup pl) :12 03S -l2 S . P rin ted in U S A . 19 94 A m er ica n S o cie ty for C lin ica l N u trition I 2 03 5

P lan t p ro te in s in re la tion to hum an p ro te inand am ino a c id nu tritio n 2Vernon R Young and P e ter L P e lle tt

A B S T R A C T P la n t pro tein fo ods con tribu te 6 5% ofth e p erc ap i ta su pp ly o f pro tein on a w o rld w id e bas is an d 32% in theN o rth A m e ric an re g io n . T hese sou rce s of p ro tein a re d isc ussedin re la tion to the ir am ino ac id co n ten t, hu m an am ino ac id re -q uirem ents, an d die tary p ro tein qu ali ty . M ix tures o f p lan t pro-te ins can serve as a com p le te and w ell-ba lanced source of am inoa cid s fo r m ee ting hu m an p hy sio log ical req u irem ents. T h is sh ortre v ie w end s w ith a list o f a se ries o f m yth s an d rea litie s c on-cern ing the re la tio nsh ip be tw een p lan t p ro te in and hu m an nu tri-t ion an d a lis t o f so m e n utr itio nal issu es o f con cern to the he althp rofess ion al an d info rm e d con sum er . Am J C /in N u ir1994;59 suppl : l203S- l2S.

K E Y W O R D S A m in o a c id s, req u irem en ts. p ro te in , co m p le -m en tation , n u tri tio nal q ual ity , n i tro gen , b ala nc e, am ino a cidscore , tim ing , d ig est ib il ity , lim iting am ino acid , lys ine

In tro d u c t io n

Plan ts a re th e predom inan t harves ters o f so la r energy and theycon stitu te a p rim ary reso urc e of ca rbo n , v i tam ins , m in era ls, p ro -te in , es sen tia l fa tty ac ids , a nd util iza b le en erg y for h um an fo odpro duc tio n . I t is n o t su rpr isin g , the refore , tha t p lan t food s hav ealw ays sup plied the g lo bal hou se hold w ith the b ulk o f its fo odenergy in take an d m ost o f its p ro te in needs. In deed , p lan ts havebeen m ajo r p layers in shap ing the course of hu m an h is to ry ( 1 ).Fur the rmore , it is an tic ip ate d th at be fore the turn of th e ne x tce n tu ry w e w ill b e using , d irectly or in d ire ctly , c rop pro duc tsth at hav e be en ta ilo red to m ark et sp ecifica tio ns by th e ad dit ion ,de le tion , o r m odifica tion of genes (2 , 3 ). W ith an increased un-de rsta nd ing o f the gen etic o rga n iz atio n and reg u la tion of g en esresp on sib le fo r en cod ing seed sto ra ge pro tein s it is like ly that th enu tritiona l value o f grain s, fo r e xam ple, w ill b e a m e nab le to ef -fe ctiv e m an ipu lation (4 ). A d dit ion ally , a n increased con trib u tionof p lan t foo ds in W es tern-ty pe d iets ha s bee n reco m m en ded as aw ay to redu ce the risk of chron ic d iseases 5 . F or these reason sit is p ert inen t to c on side r, in br ief , the ro le of p la n t food pro te insin h um an n utr itio n .

Q u a n tita tiv e im p o r ta n ce o f m a jo r p la n t cro p s

T hroug hou t h is to ry , hum ans have used som e 30 00 p lan t sp e-cies fo r food an d a t leas t I 50 spec ies have been cu ltiva ted fo rcom m erc ia l purpo ses . H o w ever, m os t o f the w orld s popu la tiondepen ds o n ap prox im ate ly 2 0 d iffe ren t p lan t c rop s, w hich are

ge nerally d iv ided in to ce rea ls, ve ge tab les (includ ing le gum es ),fru its , and n uts . In the con tex t of hu m a n p ro tein nu trition , th em ost im po rta n t g rou ps are ce rea l g ra ins a nd fo od le gum es , in -c lud ing oil-see d leg um es.

T he w orld sup p lies o f p ro tein tha t a re derived from eithe r p lan to r an im al so urc es a re d iffic u lt to est im ate , bu t th eir ap pro x im ateam ou nts a re g iven in T ab le 1 . O n a g lo b a l b a s is, p lan ts p rov id e6 5 o f th e w o r ld su p p ly o f e d ib le p ro tein . T he ce real gra ins,in p articu lar. a cco unt for a su bs tan t ia l p ortion o f th e w o rld s fo odpro tein (T a b le 2 ) a n d en erg y . O n th e o th er h a n d , a n im a l p ro d u c tsco n trib u te 3 5% o f the per cap ita ava ilab ility o f foo d pro te in .H ow ever, the re are m arked d isc repanc ies in per cap ita p ro te insupp lies fro m a nim al an d pro tein sources b etw een the d ev elo pedan d deve lop ing reg ions (T ab le I ; re f 6 ). F or exam ple . in N or thA m erica an im al p rod uc ts supp ly 70% of th e fo od pro te in .w hereas the equ iva len t figu re is 20 % for th e p opu la tions of theF ar E ast, and m ay appro ach m uch lo w er leve ls fo r m an y m di-v idu als in rura l are as of Ind ia a nd In do nes ia . In the U nited S tate s,food consum ption survey da ta (T ab le 3 ) show tha t the con tri-b ution m ad e b y p lan t pro tein to the es tim ate d dai ly pro te in in ta keis 3 0% fo r al l ag e g rou ps an d for th e po pulatio n a s a w h ole .A lso sho w n in T ab le 3 is the p atte rn ofin take ofthe ind ispensab le(essen t ia l) am ino a cid s lysine. su lfu r a m in o acid s, th reon in e, andtry p to pha n , w hic h is c ons tan t ac ros s al l age group s.

In part because liv es tock pro duc tion in vo lves a po ten tial lo sso f the energy an d av ailab le p ro te in of p lan ts tha t cou ld o therw isebe used to m ee t hu m an needs, it has been a pop u lar v iew , andone tha t w as echo ed a t the S econd In te rn ationa l C ongress onV ege ta rian N utrition , to recom m end sign ifican t red uc tio ns in theam ou nts o f c erea ls an d legu m e s use d fo r fe ed an d to increasethe ir d irect u se as fo od s for h um an s. F ur the rm ore , th e po ten t ia lhea lth benefits o f th is sh ift in the com position of hum an d ie tshave rece ived co nsiderab le a tten tion in recen t years an d th is top icw as also a m ajo r focus of in te rest a t the C ongress. T here fo re , thenu tritiona l asp ects o f p lan t food s and th e pro te in n u trition a l ad -e qua cy o f d ie ts b ase d m ain ly on pla n t sources de serve o ur con -siderat ion .T o assess the n u trition a l ro le o f p lan t p ro te ins in m eeting theneeds of h um an su b jec ts un der various cond itions w e shou ld firs t

I F rom th e C lin ica l R esearch C en te r and L abo ra to ry o f H um an N u tr i-tion , S c hoo l of S cien ce, M assach use tts Inst itu te o f T e chn olo gy ,C am bridge , and th e D ep artm en t of H u m a n N u tri tion , U n ive rsi ty o fM assac husetts a t A m h erst .

2 R ep rin ts no t ava ilab le . A d dress correspond en ce to V R Y oung , E I8 -6 13 , M assach use tts Ins titu te of T ec hn olo gy . C am bridge , M A 021 42 .



2 84 6 1 1 . 912 4 50 1 0 . 252 9 54 1 2 . 342 3 6 3 9 . 8 92 7 3 2 1 1 . 4 3

2 0 5 8 8 . 6 12409 1 0 . 0 83 4 17 1 4. 3 03 4 57 1 4. 4 63650 (1 5.27 )3 2 40 1 3. 5 62 7 1 0 1 1. 3 4

7 3 1 4 6 1 7 77 5 I I 5 9 8 16 7 1 7 7 8 7 87 2 1 2 5 8 7 96 5 2 9 6 8 5 7

7 6 9 5 2 8 37 4 1 1 5 8 8 15 3 6 1 10 4 425 1 6 0 1 0 3 4 24 8 7 3 1 1 0 3 45 0 66 9 8 336 7 2 5 7 1 6 5

7 .

12045 Y OUNG A ND PE L L E T T

B ased on F A O /A g ros ta t d ata ( re fe rence 6).

T A B L E 1E nergy an d p ro te in supp lie s per c ap i ta pe r d ay for selected ge ograph icand econ om ic reg io ns fo r 1989

R e gi o nDe v e l o p i n gFa r Ea s tM id dle E astA f r i c aL atin A m eri ca

E con om ic c lassL ea st d ev el op edL ow inco m eD e v e l o p e dW este rn E uro peNor th A m e r i c aOc e a n i aW o r l d

An i ma l T o t a l P l a n tE n erg y C a rbo hyd rate p ro tein p ro tein pro tein

k c a ( M ) g

B ased on F A O /A gros tat d ata (refe renc e 6).

tu rn our a tten tion to the estim ates o f requ irem en ts fo r to ta l p ro -te in (n itrog en ) and fo r the spec ific ind ispensab le am ino ac ids .T his su b ject h as bee n rev iew ed b y u s (8 , 9 ) an d o the rs (10 , 1 1)and so an abb rev ia ted accoun t o f som e of th e m ore im p ortan tissues re lev an t to p lan t pro teins w ill be prese n te d h ere .

P ro te in and am in o ac id requ irem en ts and pro te inqu ality co nside ra tio ns

T he requ irem en ts fo r to ta l p ro te in , a t v ar io us stages du ring th elife cy c le o f hum ans , w ere rev iew ed and eva lua ted recen tly by ajo in t pane l o f th e Fo od and A gr icu ltu re O rgan ization , the W orldH ea lth O rgan iza tion , and the U nited N ations U nivers ity (F A O /W H O /U N O ) (1 1). In T ab le 4 , th e sa fe in tak es o f h ig h qua litypro te ins , de fined in the F A O IW H O /U N U (1 1) report as tho sef rom eggs , m ea t, and m ilk , a re g iven fo r d iffe ren t age g roups .T hese da ta w ere derived la rge ly from grow th and m etabo lic n i-tro gen b alance stud ies an d , w h en expressed per kg body w eig h t,they rev ea l an age-re la ted dec lin e in d ie ta ry pro te in needs fo rm ain tenance of adequa te p ro te in nu tritio na l sta tus .

T A B L E 2R ela tive im p ortance o f variou s food grou ps in average w orld da ily perc ap ita in tak e for 198 9

E nergyPercen t

o f energy Pro te inPercen t

o f p ro te ink c a l ( k J ) g

T ota l p lan t 2277 (9 526) 84 4 6 . 1 6 5C ereals 1 385 (5 794) 51 33 .7 47P u lses , nu ts, o il c rop s 109 (456 ) 4 6 .0 8S ta rchy roo ts 141 (5 90) 5 2 .0 3O ther vege tab les 46 ( 192) 2 2 .5 4Fru i ts 65 (2 72) 2 0 .8 1T ota l an im al 433 (1 8 11) 16 25 .0 35T o t a l 2 7 1 0 1 1 3 3 9 1 0 0 7 1 . 1 1 0 0

T A B L E 3P ro te in c on sum ption an d a m ino ac id p atte rn for va rio us a ge group s(fem ale ) in the U nited S ta tes

T o t a l

P rote ins A m ino ac ids2

M ea t, p ou ltry . G r a i nA g e g ro up prote in P lan t fish produc ts L y S aa T h r Tr y

gid gld Png g prote in7 5 y 5 9 3 2 4 8 1 9 0 6 8 3 4 3 8 1 2

B ase d on U S D ep artm e nt of A gricu lture F ood C onsum ption D a ta (refe renc e L y. ly sin e: S a a, su lfur a m ino ac ids : T hr. thre onine : T ry . try p top han .

T he req u irem en t fo r d ie ta ry pro te in cons ists o f tw o com po-nen ts : the requ irem en t fo r the n u trition ally ind ispensab leam in o ac ids (h istid ine , iso leuc ine , leuc ine , lys ine , m eth io n ine ,pheny la lan ine , th reon ine , tryp to phan , an d va lin e) und er a ll co n-dit ion s an d for co nditio nally in d ispen sab le a m ino acid s (cy stin e ,ty ros in c, tau rine , g lyc ine , a rg in ine , g lu tam ine , p ro line ) underspec ific phys io log ica l and pa tho log ica l con d ition s and 2 th e re -qu irem en t fo r non spec ific n itrogen fo r the syn th es is o f th e nu tri-tion a lly d ispensab le am ino ac ids (aspartic acid , asparag ine , g lu -tam ic ac id , a lan ine , se rine ) an d o ther ph ysio log ica lly im portan tn itro gen-con ta in ing com po unds su ch as nu c le ic ac ids , c reatine ,and p orphy rin s. W ith respec t to the firs t com p onen t, it is usua llyaccep ted tha t the nu tritive va lu es o f various fo od pro te in so urcesa re to a la rge ex ten t de te rm ined by th e co ncen tra tion and ava il-ab ility o f the ind iv id ua l in d ispensab le am ino ac ids . H ence , thee fficiency w ith w hich a g iven source of fo od pro tein is u tilizedin su pp ort o f an ad equ ate sta te of nu trit ion al he alth dep en ds b oth

T ABL E 4S afe pro te in in tak es as p rop osed in 198 5 by F A O /W HO /U N U A ge grou p M ales F em ales2

gpro te in k g d3-6m o 1 .85 1 .8 56-9m o 1 .65 1 .6 59 -l2 m o 1.50 1 .50l - 2 y 1 . 2 0 1 . 2 02-3 y 1.15 1 .153 - S y 1 . 1 0 1 . 1 0S - 7 y 1 . 0 0 1 .007- lOy 1 .00 1 .00

l0 -12y 1 .00 1 .0012-14y 1 .00 0 .951 4-l6y 0 .94 0 .90l6 -l8y 0 .88 0 .8 0A dults 0 .75 0 .75

A d ap ted from refe ren ce 1 1 V alue s are un co rrec ted fo r nu trit ion alva lue (am ino ac id scores) o f m ix ed d ieta ry pro te ins fo r in fan ts and ch il-d ren and d igestib ility fo r all g roups .

Safe pro te in in takes fo r p regnan t fem ales , in takes in tab le 6 g: forlacta ting fem ales (0 -6 m o ), in takes in tab le + 17 .5 g ; an d fo r lac ta t ingfem ales (6 m o), in takes in tab le 13 g .



PL A N T PR O T E IN S 1 2 0 5 5o n th e p h y sio lo g ical req u irem en ts f o r th e in d isp en sab le am in oac ids and total n itro gen and o n the c on cen tration of sp ecif icam in o ac id s in th e so u rce o f in te re st.

T h is raise s the que stio n o f the c ontent an d b alance of indis-p en sab le am in o acid s in p lan t an d an im al p ro te in f o o d s. T h ereare ex ten s iv e d ata o n th e am in o ac id co m p o s itio n o f f o o d s (1 2 ,1 3 ). Fo r p resen t su m m ary p u rp o ses , Table 5 g iv es th e am ou n tsin d if f e ren t f o o d so u rces o f th o se in d isp en sab le am in o ac id s th atare lik e ly to b e th e m o st lim itin g in p lan t p ro tein f o o d s . A ssh o w n , th e in d isp en sab le am in o ac id ly sin e is co n s is ten tly at am u ch lo w er co n cen tratio n in all m ajo r p lan t-f o o d p ro tein g ro u p sth an in an im al f o o d s. In ad d itio n , th e su lf u r-co n tain in g am in oacid s are distin ctly low er in leg um es and f ru its and th reon in e islo w er in cereals co m p ared w ith am o u n ts f o u n d in p ro tein s o fan im al o rig in . A m o re ex ten siv e su rv ey o f th e lim itin g am in oacid and th e am ino acid sco re f or v ariou s plant p rote in f o ods isp resen ted in T ab le 6 .

G iv en th ese co m p ariso n s o f am in o ac id co n ten t am o n g p lan tan d an im al p ro te in s. it is n o w re lev an t to ask ab o u t th e ir n u tri-tio n al sig n if ican ce in re f e ren ce to m ee tin g th e n eed s o f h u m anp ro te in n u tritio n . H en ce, w e in tro d u ce th e to p ic o f p ro te in n u tri-tio n al q u ality . V ario u s ap p ro ach es h av e b een u sed to assess th eco m p arativ e n u tritio n al v alu e o f f o o d p ro tein s se e re f 1 5 f o rrev iew ). O n e ex am p le is th e rat b io assay p ro ced u re te rm ed th ep ro te in e f f ic ien cy ratio (PE R ), w h ich h as b een in w id esp read an do f f ic ial u se sin ce f irst p ro p o sed in I 9 1 9 ( 1 6) . H o w ev er, th is p ro -ced u re d o es n o t n ecessarily p red ic t satis f ac to rily th e n u tritio n alv alu e o f all p lan t p ro te in f o o d s in ten d ed f o r d irec t h u m an co n -su m p tio n (1 7 , 1 8 ). T h is is p articu larly so f o r leg u m e an d o il-seedpro teins. A lte rnativ e pro ced ure s th at w ou ld be m o re d ire ctly ap-p licab le to h u m an p ro te in an d am in o acid n u tritio n h av e b eenp ro p o sed an d d ev e lo p ed .

T h e p ro ced u re th at w as ad o p ted b y a recen t FA O /W H O E x p ertC o n su ltatio n ( 1 9 ) o n p ro tein q u ality ev alu atio n is b ased o n th eco n cep t o f an am in o ac id sco re . T h is co n cep t w as f irs t in tro d u cedin I 94 6 b y B lo ck an d M itch e ll (2 0 ), w h o o b serv ed a lin ear re -latio n sh ip b etw een th e b io lo g ical v alu e o f p ro te in s an d th e co n -ten t o f th e ir lim itin g am in o ac id . T h e am in o acid sco re is d e f in edas the c onc entration of th e lim iting am ino ac id in the f oo d pro teinan d is ex p ressed as a p ro p o rtio n o r p ercen tag e o f th e co n cen tra-tio n o f th e sam e lim itin g am in o ac id in a stan d ard o r ref eren ceam in o ac id p atte rn (1 5 ). H en ce , a p articu larly c ritical an d im -p o rtan t issu e b eco m es th e ch o ice o f th e am in o ac id ref eren cep atte rn to b e u sed f o r assessin g n u tritio n al q u ality o r f o r calcu -latin g an am in o ac id sco re f o r a f o o d p ro te in o r m ix tu re o f p ro -tein s of in tere st. W he n B lock an d M itch ell (2 0) pro po sed thissco rin g p ro ced u re , th e am in o ac id co m p o sitio n o f eg g p ro te in sw as u sed as a stan d ard . It w as late r d e te rm in ed th at th e re lativ e lyhig h am o un ts o f ind isp ensable am in o acids in e gg p rotein s un-d erv alu ed m an y p ro te in s f o r h u m an n u tritio n , w h ich led to th eu se o f es tim ate s of hu m an am ino ac id requ ire m e nts as a b asis f o rsu b seq u en t sco rin g sy s tem s (1 1 , 2 1 , 22) .

A co m m o n f eatu re o f m o s t o f th e am in o ac id sco rin g sy stem sp ro p o sed b e f o re 1 9 8 5 , w h en th e FA O /W H O IU N U rep o rt o n en -erg y an d p ro te in req u irem en ts w as p u b lish ed , w as th at a s in g leref eren ce am in o ac id p atte rn w as u sed f o r stu d ie s o n all ag es,d esp ite p u b lish ed am in o ac id req u irem en t d ata th at g en erallysh o w ed th at in f an ts n eed ed w 3 5 % o f th e ir to tal am in o acid s inth e f o rm o f in d isp en sab le am in o ac id s w h ereas ad u lts ap p aren tlyn eed ed o n ly 1 5 % o r le ss (1 1 , 2 2 ).

T ABL E SS u rv ey o f th e am in o ac id co n ten t o f d if f e ren t f o o d p rote in sources

Su l f u rF o o d source L y sin e am ino acids T h reo nin e Tryptophan

mg/g pro tein

L e g u m e s 64 1 0 2 5 3 3 8 3 1 2 4C ere als 31 1 0 3 7 S 3 2 4 1 2 2Nu t s s e e d s 4 5 1 4 4 6 1 7 3 6 3 1 7 3F r u i t s 4 5 1 2 2 7 6 2 9 7 1 1 2A n im al f o o d s 8 5 9 3 8 4 4 12

1 S D . B ased o n d ata f ro m FA O (re f e ren ce 1 2 ) an d U S D ep artm en to f A gricu ltu re (re f e ren ce 1 3 ).

T h e 1 9 8 5 FA O IW H O IU N U es tim ate s o f th e am in o ac id re -q u irem en ts in v ario u s ag e g ro u p s an d th e estim ate s p ro p o sed b yU S au th o ritie s (1 0 ) are sh o w n in T ab le 7 . Fo r am in o ac id sco rin gp u rp o ses, if th e v alu es g iv en in T ab le 7 f o r th e co n cen tratio n o fessen tial am in o ac id s in re latio n to th e to tal p ro te in n eed s o fad u lts w ere ad o p ted , th e n u tritio n al v alu e o f a p ro te in f o r ch ild renw o u ld b e o v eres tim ated . In co n trast, ad o p tio n o f th e ch ild p atte rnw o u ld u n d eres tim ate th e v alu e o f a p ro te in f o r ad u lts.

W h en th e FA O /W H O IU N U (1 1 ) am in o ac id req u irem en t e s-tim ate s f o r th e adult, w h ich are ex p ressed per unit o f p roteinn eed , are co m pared s ee T a b le s 5 an d 7 ) w ith th e am in o ac idpattern o f v ariou s plant and an im al prote in so urc es, it sh ou ld beev id en t th at th e am o u n ts o f am in o ac id s in th ese f o o d so u rces ism u ch h ig h er (p er u n it o f p ro tein ) th an req u ired . A s a resu lt, allo f th e in d isp en sab le am in o ac id s, in c lu d in g th e su lf u r am in o ac -ids, in so y p rotein s and ly sine in c ere al pro teins are p red icte d tob e in co n sid erab le ex cess o f ad u lt n eed s . T h u s, all u su al f o o dp ro te in s w o u ld read ily m ee t an d ev en ex ceed th e req u irem en t f o rth e in d isp en sab le am in o ac id s, p ro v id in g th at th e d ie tary p ro te insu p p ly w as eq u al to o r ab o v e th e saf e p ro te in in tak es (T ab le 4 ).

O n th e ab o v e b as is it w o u ld b e co n c lu d ed th at th ere is littlereaso n to b e f u rth er co n cern ed w ith an assessm en t o f th e n u tri-tio n al q u ality o f p lan t p ro te in s in ad u lts . It co u ld also b e co n -c lu d ed th at o u r atten tio n sh o u ld b e f o cu sed o n ch ild ren an d in -f ants , particu larly be cau se th ey m ight b e giv en d iets con tain in ga sin g le f o o d p ro te in so u rce o r a lim ited n u m b er o f p ro te inso u rces, f o r ex am p le , in f an ts f ed a d ie t o f a p ro p rie tary f o rm u la,p o ss ib ly su p p lem en ted w ith s train ed f o o d s. H o w ev er, th ere isin cre asing ev ide nce th at th e c urre nt in tern ational FA O IW H O /U N U (I I) and n ational (1 0) re qu irem en t estim ates f or m ost in-d isp en sab le am in o ac id s in ad u lts are f ar to o lo w (9 , 2 3 , 2 4 ).S ev eral g ro u p s (2 5 -2 7 ) are seek in g to f u rth er su b stan tiate th isev id en ce , w h ich w o u ld stren g th en th e case f o r th e in ad eq u acy o fth e in te rn atio n al reco m m en d atio n s an d w o u ld h av e im p o rtan t im -p lic atio ns f or the approac hes to be tak en to co m p reh ens iv e ly as-sess th e ro les of b oth p lan t and anim al f o od p rotein so urc es inh um an n u tritio n.

T h e sp ecif ic s o f th is n ew research o n h u m an am in o ac id re -q u irem en ts w ere p rev io u s ly rev iew ed b y u s (9 , 2 3 , 2 4 ). H o w ev er,f ro m m o re recen t d ata w e h av e arriv ed at a n ew , ten tativ e se t o fe stim ates f o r th e am in o ac id n eed s o f ad u lts . T h ese v alu es aresh o w n in T ab le 8 , an d are co m p ared w ith th e I 98 5 estim ate sm ad e b y FA O /W H O /U N U f o r th e ch ild ren ag ed 2 -5 y .

It can b e seen th at, ex cep t f o r a lo w er th reo n in e an d s lig h tlylo w er ly sin e co n ten t, o u r p ro p o sed ad u lt p atte rn is q u ite s im ilar



T ABL E 6P ro te in concen tra tion , lim itin g am in o ac id (L A A ) sco re and lysinescore fo r se lec ted p lan t foods

LA A score L ys ineP ro te in (am ino acid ) sco re

T A BL E 6 (C on tinu ed)

Pro te inL AA s c o r e

(am ino ac id )L y s i n e

score%

V eg eta ble s (c on tin ue d)T urn ipY amFruitsA pp lesAvoc a dosB ananasF igsO rangeP e a c hPearP ineapp leP lan ta inP lum

0. 91 5

0. 22.01 .00. 80. 90 . 70. 40. 41. 30. 8

53 (A aa)66(L ys)75 (A aa)82 (L ys)80 (L ys)67 (L eu , L ys)37 (L eu)5 7 L y s62 (L ys)74 (L eu)69 (L eu )37 (L ys )

6966

10 9828069865 762

11 18037

%

1 4 . 512 .513 .31 2 . 2

9. 41 1 . 016 .9

7. 97. 1

14 .811 .313 .212 .613 .710 .312 .8

21 .923 .619 .323 .528 .121 .536 .223 .92 5 . 821 .736 .529 .7

20 .414 .315 .3

3. 38. 0

14 .914 .341 .024 .517 .72 2 . 8

89 (L ys)6 4 L y s8 7 (L ys)48 (L ys)49 (L ys)33 (L ys)72 (L ys)6 6 L y s62 (L ys)71 (L ys)35 (L ys)48 (L ys)46 (L ys)38 (L ys)38 (L ys)33 (L ys)

10 010 010 010 0

86 (Saa)9 5 (Saa)78 (S a a)83 (Saa)62 (L ys)91 (Saa)

10 010 0

5 8 (L ys)6 5 L y s92 (L y s)76 (L y s)65 (L y s)

10 047 (L y s)88 (L y s)

10 055 (L ys)7 1 (L y s)

C erea lsA ma r a n t hBa r l e yB u c k w h e a tB ulgurC ornMil le tOa t sR ice brow nR ice w hiteRy eS o r g h u mTriticaleW hea t hardW hea t du rumW heat flou rSpaghe t t i

L e g u m e sB ean w hiteB ean k idn eyC h ick peakC o w peaL en t i lL im a beanL up ineM u n g b e a nPeanu tP igeon peaSoybeanW ing bean

N u ts and S eedsA l m o n dB raz i lC a s h e wC oconu tPecanP is tach ioW a l n u tC o t t o n s e e dP u m p k i n seedSesam e seedSun flow er seed

V ege tab lesB ea n (g re en )B rocco l iC abbageCa r r o t sC a s s a v aO k r aO nionPe a s g r e e nP epper sw ee tP o t a t oSpinachSquashS wee t po ta toT a r oT o ma t o

896 4874 849337 2666262354846383833

11 811 811 511 712 011 6

9212 0

6212 111 512 4

586 592766 5

10 74788

12 95571

838281675 67082

1 17 7

10 510 5

958 57 76 4

L y s, lys ine ; Saa , su lfu r am ino ac id s; L eu , leuc ine ; A aa , a rom aticam ino ac ids. B ased o n F A O /W H O IU N U d ata ( re fe rence 1 1 ) an d re fe r-ences 12 , 13 , and 1 4 .

to the pa tte rn recom m en ded by F A O IW H O IU N U (1 1 ) fo r p re -school and ear ly sch oo l-age ch ild ren (2 -S y). I f th ese re v isedestim ates o f am ino ac id requ irem en ts in adu lts are ra tion al, a s w ebe liev e they are fo r reasons d iscussed e lsew h ere (9 , 23 , 24 ), thenu tritio na l va lue of d iffe ren t p ro te in so urces w ou ld no t be af-fected as m arked ly by the age of the con sum er. T h is is in co n trastto the p osition ad op ted in the 198 5 F A O /W H O /U N U report.B ased on th e rev ised estim atio ns o f am ino ac id requ irem en ts tha ta re g iven in T ab le 8 , it fo llow s th a t fo r eva lua tion of d ie ta rypro te in q ua lity in h um an nu tr ition it is on ly n ece ssa ry to rec -om m end use o f tw o am ino ac id requ irem en t, o r sco ring , pa tte rn s.T he firs t pa tte rn w ould be th at fo r th e in fan t, w h ich accord ing toF A O /W H O /U N U (1 1) sho uld b e based on the am in o ac id c om -pos ition of b reast m ilk ; the second , as sh ow n in T ab le 8 , w ou ldbe the am ino ac id requ irem en t p atte rn fo r ages 2-5 y , w hichw o uld be app lied to a ll g roups abo ve 2 y o f ag e. T his v iew isn ow reflec ted in the recom m enda tions m ade b y the expert g roupcon vened by FA O /W H O (19), w hich p roposed tha t the 19 85F A O /W H O IU N U a m in o acid req u irem ent for the g rou p ag ed 2-5 y be u sed to assess th e pro tein qua lity o f foods in re feren ce toy oung ch ild ren , o ld er ch ild ren , and also ad u lts.

FA O /W H O (1 9) pro posed , fo r sco r in g purp oses , the so -ca lledp ro te in d iges tib ility -co rrec ted am ino ac id score (PD C A A S),w hich can be defined as fo llow s:

A m ino acid con ten tP D C A A S (m g /g p ro tein ) in foo d pro tein x d ig es ti bi li ty

A m ino acid con ten t in 1985FA O /W H O /U N U p atte rn fo r ages 2-5 y

It shou ld b e no ted tha t d iges tib ility is inc luded in th is am ino ac idsco ring p rocedure , to a llow for d iffe rences in the d iges tib ility o fthe d iffe ren t foo d-p ro te in sources. W e w ill refer spec ifica lly tothe d ig estib ility o f p lan t p ro te in food s be low .

A m ino acid score and plant protein qualityT he am ino ac id scor in g procedure ap pears like ly to be adop ted

by the U S govern m ent as the offic ia l p rocedure fo r food p ro te in

1 .8 83 (L ys)3 .0 6 7 (L eu)1 .2 7 3 ( S aa)1 58 (Saa)1 .3 4 4 (L eu)2 .0 70 (L ys)1 .2 5 3(L eu )5 4 85 (Saa)0 .9 77 (L ys , L eu)2 . 1 9 1 L . e u2.9 1 0 01 .2 70 (T hr)1 .7 85 ( L ys)1 . 5 77(L ys)0 .9 56 (L eu)

1 206S Y O U N G A ND P E L L E U



PL A N T PR O T E IN S 1 2 0 7 5T A B L E 7E stim ates o f am ino ac id re qu irem en ts o f pre sch oo l children, o lder childre n, an d adults

In tak e f o r w t In tak e b y p ro te in

Preschool S ch o o lch ild ren 2 A d u lts Presch o o l S ch o o lch ild ren 2 A d u l t s A m in o acid (2-S y ) (10 -1 2 y ) ( 18 y ) (2 -S y ) (1 0-1 2 y ) ( 1 8 y )

mg kg body wt d mg/g p r o teinHi s t i d i n e 8 1 2 16Iso leu cin e 31 .0 2 8.0 1 0.0 28 28 13L e ucine 73 .0 4 4 .0 1 4 .0 6 6 4 4 1 9L y sin e 6 4 .0 4 4 .0 12.0 58 4 4 16M ethionine and cy stine 27 .0 2 2.0 1 3.0 25 22 17Ph en y lalan in e an d ty ro sin e 6 9 .0 2 2 .0 1 4 .0 6 3 2 2 1 9Threonine 37 .0 2 8.0 7 .0 34 28 9T ry p to p h an 1 2 .5 3 .3 3 .5 1 1 9 5V alin e 3 8 .0 2 5 .0 1 0 .0 3 5 2 5 1 3T o tal (-h is tid in e) 3 5 2 .0 2 1 6 .0 8 4 .0 3 2 0 2 1 6 1 1 1

A d ap ted f ro m re f e ren ce 1 1. B ased o n N R C d ata (ref eren ce 1 0 ).

q u ality ev alu atio n an d q u ality co n tro l o f p ro te in f o o d s . B ecau sew e h av e arg u ed in f av o r o f th is p o licy (2 8 ) it m ig h t b e w o rth w h ileto b rie f ly co m p are so m e h u m an m etab o lic d ata w ith p red ic tio n sb ased o n th e PD C A A S .

In T ab le 9 w e co m p are th e am in o ac id co m p o sitio n o f co m -m o n h y b rid an d h ig h -ly s in e m aiz e an d h av e calcu lated th ePD C A A S f o r th ese d if f e ren t cu ltiv ars . T h e p red ictio n is th at th en utri tion al v alu e o f the high- ly s ine v ariety is sup erior to th at o fth e h y b rid m aiz e an d th is h as b een co n f irm ed in m e tab o lic s tu d ie sin ch ild ren , as su m m ariz ed by B ressani (2 9). A low er b iolo gic alv alu e f o r n o rm al m aiz e co m p ared w ith tw o v arie ties o f h ig h -ly sin e m aiz e w as also rep o rted (2 9 ). H o w ev er, w h e th er an y sig -n if ican ce sh o u ld b e g iv en to th e d if f e ren ce b etw een th e v alu e f o rth e sco re o f 0 .6 3 (T ab le 9 ) an d th e n u m erical e stim ate s f o r th eb io lo g ical v alu e o f th e h ig h -ly sin e m aiz e as d eriv ed f ro m th em e tab o lic stu d ie s is d if f icu lt to ju d g e . T h e re lativ e d if f e ren cesb etw een th e sco res an d th e m e tab o lically d eriv ed , b io lo g ical v al-u cs f o r th e h y b rid an d h ig h -ly s in e m aiz e s are sm all. If th e ly sin eco n ten t o f th e FA O IW H O IU N U (1 1 ) am in o ac id re f e ren ce p at-

TABLE 8N ew , te ntativ e am ino ac id re qu irem en t es tim ate s f or adults an dc orresp ond ing requ irem en t pattern f o r pre sch oo l c hildre n

A m in o ac id

A d u l tten ta t ive

req u iremen t

A d u l tam in o ac id

pattern2

Presch o ol ch ildam in o ac id

pattern2

mg kg d mg lg pr o te in mg/g pr o teinI so leu c in e 2 3 3 5 28L eu c in e 4 0 6 5 6 6L y s ine 3 0 5 0 58S u lf u r a m in o ac id s I 3 2 5 2 5A ro m atic am in o ac id s 3 9 6 5 63Th r e o n i n e I S 2 5 3 4T ry p to p h an 6 1 0 1 1V a l in e 2 0 3 5 3 5

B ased o n d ata f ro m re f e ren ce 2 3 .2 A d ap ted f ro m re f e ren ce 1 1.

te rn f o r ch ild ren ag ed 2 -5 y is set to o h ig h th en th is w o u ld g iv eth e p ro te in a lo w er n u m erical v alu e f o r th e sco re th an w o u ld b eo b tain ed v ia a f eed in g -m e tab o lic stu d y . B ecau se ly s in e is m o s tlik e ly to b e th e f irs t lim itin g am in o ac id in d ie ts th at are b asedp red o m in an tly o n cereal g rain s (3 0 ) it is im p o rtan t to d ete rm in em o re accu rate ly th e ly s in e co n ten t o f th e re f e ren ce am in o ac idreq u irem en t p atte rn .

T h e re f e ren ce am in o ac id p atte rn u sed to arriv e at th ePD C A A S p red ic ts th at in ad d itio n to cereals , w e ll-p ro cessed so yp ro te in p ro d u c ts , su ch as iso lated so y p ro te in s 1 8), w o u ld h av ea h ig h n u tritio n al v alu e . W e h av e rev iew ed th is to p ic in d e tailan d h av e co n c lu d ed th at so y f lo u r an d so y iso late s, w h en th eyare th e so le o r m ajo r so u rce o f p ro te in in d ie ts co n tain in g ad e -q u ate en erg y an d o th er essen tial n u trien ts, are f u lly cap ab le o fp ro m o tin g ad eq u ate g ro w th in y o u n g in f an ts (1 7 , 1 8 ). Fo r cx -am p le , T o ru n (3 1 ) g av e g rad ed am o u n ts o f o n e o f tw o so y -p ro -

T A B L E 9In d isp en sab le am in o ac id co n ten t an d am in o ac id sco re o f n o rm al an dh igh -ly sin e m aiz e

M a i z e A min o acid score1 9 9 1

H igh - FA O IW H OA m ino ac id N orm al ly sin e patte rn2 N orm al H igh -ly s ine

m g g m g gL y s i n e 177 25 6 363 0 .44 0 .63I so leucine 2 06 193 175 >2 .00 0 .98L e uc i n e 8 2 7 5 0 7 4 1 3 > 1 0 0 > 1 0 0S ulf ur am ino acid s 1 88 1 88 15 6 > I .00 >1.0 0A rom atic am in o acids 505 50 2 39 4 > I . 00 > I . 00T hr e o n i n e 21 3 19 9 2 1 3 0 8 9 0 8 3T ry ptoph an 3 5 78 68 > I . 00 > I . 00Va l i n e 2 9 2 2 9 8 2 1 9 >1 .00 >1.00L e uc ine-Iso leu cine 4 .0 1 2 .6 3 2 .36 >1 .00 >1.00

A dap ted f ro m ref eren ce 2 9 . A dap ted f ro m ref eren ce 1 9 .3 C orrec ted f or d ige stib ility , assum in g a v alu e o f 0 .89 re lativ e to re f -

e re nc e p ro te in s.



T y p e I

A. PssmB. Corn

I I I I

T yp e if

T yp e III

A. CornB. So y F lo ur

I I I I

T y p e

A. Soy ProteinB. Beef Protein

I I I I

l208S YOUNG N PELLETTtein isolates to chi ldren w ho had recovered f rom earl ier protein-energy m alnutri t i on and com pared ni trogen-balance responsesw i th those obtai ned using m i l k as the ref erence protei n. I nterpre-tati on of the ni trogen-balance data show ed that the nutri t i ve valueof the i solated soy protei n tested w as 86- 107 that of m i l k ,depending on the speci f i c cri teri on used f or com pari son. H ence,the protei n nutri t ional value of the w el l -processed isolated soyproteins so f ar exam ined in y oung chi l dren i s essential l y cquiv -al ent to that of m i l k protei n.

R esul ts of studies on the nutri ti onal qual i ty of speci f ic soy -protein products i n adul ts have al so been rev iew ed prev iousl y( I 7, 1 8). I n sum m ary . the nutri t i onal value of an i solated soyprotei n (Supro-620, Ral ston Puri na C o. St. L oui s, M O ), based onan anal ysis of the ni trogen-balance data, w as high f or heal thyadults, 80 of the nutri t ional value of egg protei n. T he truedigestib i l i ty of the soy i sol ate w as also high (97 ) and w ascom parable w i th that f or egg protei ns.

Of parti cul ar im portance f rom the f i ndings in these v ar iousm etabol i c studies, w as the observati on that the protein value ofth is soy i sol ate w hen tested i n chi l dren and adul ts w as consid-erabl y higher than w hat w ould be predicted f rom the PER assaycarri ed out i n rapidl y grow ing rats. T he latter assay seri ouslyunderestim ates the nutri ti onal qual i ty of the soy i solate f or chi l -dren and adul ts. Perhaps the di screpancy betw een rat and human data al so ex plains w hy there appears to be a l i ngeri ngv iew held by som e prof essi onals as w el l as consum ers that soyprotei ns arc of poor qual i ty . C learl y the m ore recent, d i rect hu-m an m etabol ic data reveal that they can be and are of hi gh nu-tr i ti onal v alue.

Parenthetical l y , the questi on of the need f or m ethi oninc sup-plem entati on em erges here. From our ow n studies and those ofothers ( 17, 1 8), m ethionine supplem entation of soy protei ns i scl earl y unnecessary in adul ts. Soy protei ns, consum ed as isolatesor concentrates, are excel l ent sole sources f or m eeti ng ni trogenand al l am ino acid needs w hen consum ed at physiol ogi cal ly im -por tant i ntakes of total protei n. M ethi onine supplem entati on ofsoy -based inf ant f orm ulas m ay , how ever, be desi rable, al thoughthe m ethioninc addi ti on requi red to achieve high uti l i zati on ofsoy protein appears m odest ( 1 8, 32) and i s considerabl y l ow erthan w ould have been predi cted f rom rat PER assay data.

M ore than 30 y have passed since the 1 957 report of the f i rstFA O protei n requi rem ents com m i ttee (2 1 ), w ho selected protei n,or am ino acid, scori ng as an of f ici al basi s f or assessing the nu-tr i ti onal value of protei ns f or m eeti ng hum an nutri ti onal requi re-m ents. Prov ided that an adjustm ent i s m ade f or the digesti bi l i tyof i ngested protei ns (or the avai l abi l i ty of the indispensableam ino acids i n the protei n), the conclusi on m ade by thi s group that the concept of a desi rable pattern of essential am ino acidhas a great adv antage and by com pari son, w i th such a pattern,data on the am ino acid content of i ndi v i dual f oods and f ood com -binati ons can be apprai sed f or a w ide range of si tuati ons, w i threspect to evaluati on of the nutri t ional qual i ty of the diet and ofm ethods of im prov ing i t rem ains val id. I n addi ti on, the recentrecom m endations m ade by FA OI W H O ( 1 9) are enti rel y consi s-tent w i th thi s v i ew .

A ddi tional i ssuesC omplementa tio n a n d timing o f ing estion of p r o teins

I m por tant di f f erences am ong and betw een f ood products ofv egetable and anim al ori gi n are the concentrations of protei ns

and indispensable am ino acids that they contai n. T he concentra-ti on of protei n and the qual i ty of the protei n i n som e f oods ofvegetable ori gi n m ay be too low to m ake them adequate, solesources of protei ns w hen consum ed in thei r tradi ti onal m anner,parti cul arl y f or inf ants and chi ldren. H ow ev er, chi ldren canthri ve on as w el l as recover f rom severe m alnutri t i on i f gi venw el l -f orm ulated diets based enti rel y on plant f ood sources. T hus,pl ant f oods, i n appropr iate am ounts and com binati ons are able tosuppl y the essential nutri ents requi red f or m aintenance of ade-quate heal th and f uncti on.

M ix tures of pl ant protei n f oods m ay be of potenti al ly hi ghnutri t i onal qual i ty . For exam ple. al though the soybean i s low insul f ur-contai ni ng am ino acids, cottonseed, peanut and sesam ef l our, and cereal grai ns are def i ci ent m ainl y i n l ysi ne. This m di-cates that oi l -seed protei ns, in parti cular, soy protei n. can be usedef f ecti vely i n com binati on w i th m ost cereal grai ns to im prove theov eral l qual i ty of the total protei n i ntak e. A com binati on of soyprotei n, w hi ch i s hi gh in l ysi ne, w i th a cereal that contai ns arel ativ el y good concentrati on of s-am ino acids resul ts in a nutri -t ional com plem entati on; the protei n qual i ty of the m ix ture i sgreater than that f or ei ther protei n source alone.

T hi s concept of protein, or am ino acid, com plem entati on i sperti nent to a di scussion of pl ant f oods. V ari ous nutri t i onal re-sponses are observed w hen tw o dietary proteins are com bined.T hese hav e been classi f ied by B ressani et al (33) i nto one of f ourtypes (T y pes I , I I , I I I , and I V ) as show n in Figure 1.

T y pe I i s an exam ple w here no protein com plem entary ef f ecti s achieved. For example, thi s occurs w i th combinations of pea-

14

0

0

PR O T E IN C OM P L EM E N T A T IO N

A 1 8 O 60 40 20 0 10080 60 40 20 0 0 20 40 60 80 100 0 20 40 60 80 100

P R O T E IN D IS T R IB U T IO N IN D IE TFI G 1 Four ty pes of response, assessed in term s of an i ndex of bio-

l ogi cal v alue or protein qual i ty , ari sing f rom mi x ing of tw o food proteinsources. A dapted f rom reference 33.



PL A N T PR O T E IN S 1 2 0 9 5T A B L E 1 0D iges tib ilities of d if f erent sou rce s of f oo d p rotein in hu m ans

T ru edigestibility

D ig es tib ility re lativ e tore fe re nc e p ro te in s

% %R ef eren ce p ro te in s

Eg g97 {247}32

10 0M ilk , che ese 95 3 10 0M eat, f ish 94 3 10 0

P lan t p ro te in sM a i z e 8 5 6 8 9Po lish ed rice 8 8 4 93W h o le w h eat 8 6 5 90Oa tmea l 86 7 90B e a n s 7 8 8 2M aiz e , b ean s 7 8 8 2In d ian rice d iet 7 7 8 1B raz ilian m ix ed d iet 78 82Filip in o m ix ed d ie t 8 8 9 3U S m ix ed d ie t 9 6 10 0

A d ap ted f ro m re f e ren ce 1 1.2 {247} S D .

n u t an d co rn , w h ere each o f th e p ro te in so u rces h av e a co m m o nan d q u an titativ e ly s im ilar ly sin e d e f ic ien cy an d are b o th also d e -f ic ien t in o th er am in o ac id s. T y p e II re sp o n se is o b serv ed w h enco m b in atio n s are m ad e o f tw o p ro te in so u rces th at h av e th e sam elim itin g am in o ac id , b u t in q u an titativ e ly d if f e ren t am o u n ts. C o rnan d co tto n seed f lo u r, f o r ex am p le , are b o th lim itin g in ly s in e b u tco tto n seed is re lativ ely le s s in ad eq u ate th an is co rn .

T h e th ird ty p e o f re sp o n se (T y p e II I) d em o n s trate s a tru e co m -p lem en tary e f f ec t b ecau se th ere is a sy n erg istic e f f ec t o n th eo v erall n u tritiv e v alu e o f th e p ro te in m ix tu re; th e p ro te in q u alityo f th e b es t m ix ex ceed s th at o f each co m p o n en t alo n e . T h is ty p eo f re sp o n se o ccu rs w h en o n e o f th e p ro te in so u rces h as a co n -s id erab ly h ig h er co n cen tratio n o f th e m o s t lim itin g am in o ac idin th e o th er p ro te in . A n ex am p le o f th is re sp o n se , b ased o n s tu d -ie s in ch ild ren (3 3 ), is o b serv ed w h en corn an d so y f lo u r arem ix ed so th at 6 0 % o f th e p ro te in in tak e co m es f ro m co rn an d th erem ain d er f ro m so y a p ro te in .

Fin ally , th e T y p e IV resp o n se o ccu rs w h en b o th p ro te insou rces hav e a com m on am ino acid de f icienc y . T he p ro tein co m -p o n en t g iv in g th e h ig h est v alu e is th e o n e co n tain in g a h ig h erco n cen tratio n o f th e d e f ic ien t am in o ac id . C o m b in atio n s o f so m etex tu red so y p ro te in s an d b ee f p ro te in f o llo w th is ty p e o f re-sp o n se (3 4 ).

T h ese n u tritio n al relatio n sh ip s h av e b een d ete rm in ed f ro m ratb io assay stu d ie s . H o w ev er, th e m o re lim ited resu lts av ailab lef ro m h u m an s tu d ies w ith so y an d o th er leg u m es co n f irm th e ap -p licab ility o f th is g en eral co n cep t in h u m an n u tritio n . T h isk no w le dg e h elp s u s to un de rstand an d ev alu ate h ow nu trit ion allye f f ec tiv e co m b in atio n s o f p lan t p ro te in f o o d s can b e ach iev ed .

O u r reaso n f o r d iscu ss in g am in o ac id co m p lem en tatio n is toin tro d u ce th e q u estio n o f tim in g o f in g es tio n o f co m p lem en taryp ro te in s. T h ere is so m e co n cern , at leas t at th e co n su m er lev e l,ab o u t th e n eed to in g es t d if f e ren t p lan t p ro te in s at th e sam e tim e ,o r w ith in th e sam e m eal, to ach iev e m ax im u m b en e f it an d n u tri-tio n al v alu e f ro m p ro te in s w ith d if f e ren t, b u t co m p lem en tary ,am in o acid p atte rn s. T h is co n cern m ay also ex ten d to th e q u estio n

o f th e n eed to in g es t a sig n if ican t am o u n t o f p ro tein at each m eal,o r w h e th er it is su f f ic ien t to co n su m e p ro te in in v ariab le am o u n tsat d if f e ren t m eals as lo n g as th e av erag e d aily in tak e m ee ts o rex ceed s th e reco m m en d ed o r saf e p ro te in in tak es.

A cco rd in g to FA O /W H O IU N U (1 1 ), e s tim ate s o f p ro tein re-q u irem en ts re f e r to m e tab o lic n eed s th at p ersist o v er m o d eratep erio d s o f tim e . A lth o u g h p ro te in an d am in o acid req u irem en tsare co n v en tio n ally ex p ressed as d aily rate s (o f in tak e ) th ere is n oim p licatio n th at th ese am o u n ts m u st b e co n su m ed each an d ev eryd ay . T h eref o re , it is n o t e ssen tial, at least in ad u lts, th at d ailyin tak es o f p ro te in , o r p resu m ab ly o f each in d isp en sab le am in oacid , m u st eq u al o r ex ceed th e p h y sio lo g ical req u irem en t; it isap p aren tly su f f ic ien t f o r th e av erag e in tak e o v er a n u m b er o f d ay sto ach iev e th is lev el. T h is p atte rn o f in tak e w o u ld allo w m ain -ten an ce o f an ad eq u ate p ro te in n u tritio n al s tate .

T h ere is a lim ited d atab ase th at w e can co n su lt to m ak e ad e f in itiv e co n c lu sio n o n th e tim in g o f co n su m p tio n o f co m p le -m entary p rotein s or of spec if ic L -am ino acid su pplem ents f or p ro-te in s th at are d e f ic ien t in o n e o r m o re am in o ac id s . E arlie r w o rkin rap id ly g ro w in g rats su g g ested th at d e lay in g th e su p p lem en -tatio n o f a p ro te in w ith its lim itin g am in o ac id red u ces th e v alu eo f th e su p p lem en t (3 5 -3 8 ). S im ilarly , th e f req u en cy o f f eed in go f d ie ts su p p lem en ted w ith ly s in e in g ro w in g p ig s af f ec ts th eo v erall e f f ic ien cy o f u tiliz atio n o f d ie tary p ro te in (3 9 , 4 0 ). T h ereare f ew d ata av ailab le f ro m h u m an stu d ie s to assess th e s ig n if i-can ce o f th ese f in d in g s. H o w ev er, th e re lev an ce o f rat an d p igstu d ie s can b e q u estio n ed in v iew o f th e p ro f o u n d ly d if f e ren tq u alitativ e an d q u an tativ e ch arac te ris tic s o f p ro te in m etab o lismin rats an d p ig s co m p ared w ith h u m an su b jects (4 1 ). O u r stu d ie sin h u m an ad u lts sh o w ed th at o v erall d ie tary p ro te in u tiliz atio nw as sim ilar w h eth er th e d aily p ro te in in tak e w as d is trib u teda m o n g tw o o r th ree m eals (4 2 ). H o w ev er, th e su p p lem en tary e f -f ec t in ch ild ren o f th e ad d itio n o f Phaseolus vulgar is to a m aiz e -b ean d ie t w as so m ew h at les s w h en th e su p p lem en t w as g iv en atin terv als of > 6 h (R B ressan i an d D W ilso n , p erso n al co m m u -n icatio n , 1 9 9 2 ).

W e b e liev e th at f o r u su al co n d itio n s o f h ealth y liv in g it is n o tn ecessary to co n su m e co m p lem en tary p ro tein s at th e sam e tim ean d th at sep aratio n o f th e p ro te in s am o n g m eals o v er th e co u rseof a d ay w o u ld still p e rm it th e n u tritio n al b en e f its o f co m p le -m en tatio n . T h ere are also p h y s io lo g ical d ata to su p p o rt th is co n -ten t io n .

B ecau se ly s in e is m o st lik e ly to b e th e lim itin g am in o ac id ina d ie t b ased p red o m in an tly o n cereal g rain s (3 0 ), it is o f in te re s tan d re lev an ce th at in th e sk ele tal m u scu latu re th ere is a s iz eab lep o o l in th e in tracellu lar sp ace o f f ree am in o ac id s , p articu larly o fly s in e . T h e siz e o f th is p o o l re sp o n d s to ch an g es , b o th acu te an dch ro n ic , in th e am o u n t o f ly sin e in g ested (4 3 ). B ased o n th e d ataof B erg strom et al (44 ), w e calcu late that af ter a pro te in -rich m eal(p ro v id in g 5 0 g b o v in e seru m alb u m in ) 6 0 % o f th e ad u lt d ailyreq u irem en t f o r ly s in e m ay b e d ep o s ited in th is in trace llu lar p o o lw ith in 3 h . H en ce , a p ro tein w ith a relativ e ly lo w ly sin e co n ten t(m aiz e ) cou ld be in gested som e ho urs later than a com plem en-tary , h ig h er ly s in e -co n tain in g p ro te in (eg , so y p ro te in ) an d th ef ree -ly sin e p o o l in th e m u sc le w o u ld b u f f e r th e lo w ly sin e co n ten to f th e am in o acid m ix tu re d eriv ed f ro m th e d ig es tio n o f m aiz e.O v erall, th e nu trition al q uality o f th e c om bin ed m e als w ou ld b eh ig h .

W e co nc lude th at it is n o t n ecessary to b alan ce th e am in o ac idpro f ile at each m eal, e sp ec ially und er cond itions w here in tak eso f to tal p ro te in su bstan tially ex ceed m in im um phy sio log ical re -



1 2 1 0 S Y O U N G A N D P E L L E T T A B L E I IP lan t p ro te in s in hu m an nu trition : m yths and rea litie s

M y t h Reali tyI Plan t p ro teins a re incomplete (ie lac k spec ific am in o ac ids)2 l nt pro teins a re no t as good as an im a l p ro tein s

3 Pro teins from diffe ren t p lan t foods m u st be consum ed toge ther inth e sam e m eal to ach ieve h igh nu tritio na l va lue

4 ) A nim al b ioassay p rocedures a re sa tisfac to ry index es of thehum an nu tritio na l va lue of fo od pro teins

5 P lan t p ro te ins a re no t w ell d ig es ted6 ) P lan t p ro te ins a lone are no t su fficien t to ach ieve an adequa te d ie t

(p ro te in in tak e)7 ) P lan t p ro te ins a re imbalanced and th is lim its the ir n u trition al

va lue

1 U sual d ie tary co m b ina tio ns of p ro tein s are c om ple te: sp ecif icfo od p ro te ins m ay b e lo w in spec ific am ino a cid s

2 Q uality depen ds on the source and d ie ta ry m ix tu re o f p lan tp ro te ins : can be equ iva len t to h igh-qu ality an im al p ro te in s

3 P ro te ins do n ot nee d to be c onsum ed a t th e sa m e tim e, th eba lance over a d ay is o f g rea te r im po rtan ce

4) A nim al b ioassay pro ced ures can be u sefu l bu t they m ayun de rest im ate p lan t pro tein nu trit ion al q ua lity for hu m ans

5 D ige stib ility ca n v ary a cco rd in g to sou rce an d foo d prep ara tio n :d ige stib ili ty can be h ig h

6 ) T h e in takes an d ba lance o f in takes o f in d ispen sab le a m in o ac idsand n itrog en are c ru c ia l and can be adequ ate ly m et from p lan to r p lan t and an im al so urces

7 ) T h ere is n o e v id enc e that am ino ac id im ba lan ces p er se areim por tan t: pos sib le im balanc es ca n b e create d by in app ro pria team in o a cid su pp lem en tation , bu t th is is n o t a pra ctical p ro b le m

qu irem en ts . C onsum ption of co m plem en ta ry pro te ins a t d iffe ren tm ea ls over the co urse of th e day sh ou ld assu re th e ach ievem ento f an adeq ua te s ta te o f n itro gen (p ro te in ) re ten tion and u tiliza tion .T here fo re, an undu e em ph asis on am ino ac id ba lance at eachm ea l is inapp ropria te in th e co n tex t o f usu al d ie ts in hea lthy pop-u la t ions .Protein digesti bi l i ty and amino acid as ai l abi l i r s

T he nu tritiona l va lue of a d ieta ry pro te in so urce m ay no t b epred ic ted w ith prec ision from a de term in ation of its am ino ac idcon ten t alon e; severa l o the r fac to rs can affec t the u tiliza tion ofp ro te ins . A n im p ortan t fac to r, w h ich is frequ en tly c ritica l in thefeed ing of s im ple -stom ached fa rm lives tock , is the d igestib ilityand ava ilab ility o f the pro te in and ind iv id ua l am in o ac id s.

In genera l, th e d igestib ility o f vege tab le p ro teins in th e ir na t-u ra l fo rm is low er than tha t o f an im al p ro te ins . T ab le 10 sum -m arizes resu lts fo r the d ig estib ility in hum an sub jec ts o f variou sp lan t sources and of d ie ts b ased on m ixed p lan t-fo od so urces.P lan t p ro te ins a re o ften con sum ed on ly afte r u ndergo ing som edegree of p repara tion or p rocessing . A lthoug h the effec ts o f p roc-ess in g on pro te in q ua lity and av ailab ility w ill no t b e rev iew edh ere , th is fac to r deserves a tten tion in an ov erall a ssessm en t o fp lan t foods fo r h um ans. For exam ple , o il-seed flours m ay b ep roduc ts o f p ro cesses des ig ned to econo m ica lly recover the o ilfrom th e seed . Such processes d o no t necessa rily favor the ef fi-c ien t recovery of h igh -qua lity p ro te in . C erea ls and legum es in -tend ed fo r hum an feed ing are cooked or p rocessed to enhancethe ir pa la tab ility and accep tance . F or exam ple , w hea t is used p ri-m arily in bread , pas ta , and breakfas t-ce rea l-type foods . T herm alp rocess in g m ethods tha t use h igh -tem p eratu re, sho rt-tim e p roc-essing con d itio ns, such as ex trus ion , m ic row ave hea ting , puffing ,an d spray dry ing , have been w ide ly ad op ted . H ow ever, as a resu lto f such trea tm en ts , the nu tritive va lue of the pro tein m ay be e ith e renhanced o r redu ced to an ex ten t tha t depends on the pro te incom pon en ts in the food and fac to rs such as the tem pera tu re , du -ration of h ea ting , an d the presence or absence of m oistu re . B o il-ing in w ate r genera lly im pro ves pro tein qua lity , w hereas to astingo r d ry hea tin g redu ces pro te in qua lity . H ence , it is d if ficu lt tod raw bro ad genera liza tion s concern ing the effec ts o f v ario usprocess in g and prepara tion cond itions on the pro teins and the

in d iv idua l am ino ac ids o f p lan t foods . M ore b asic w ork is neededon the chem ica l and p hys ica l changes tha t occur in pro te ins und erthese con d ition s an d the ir nu tritio na l e ffec ts to deve lop . in th elon g-te rm , o p tim u m procedures fo r the u tiliza tion of p lan t foodpro te ins .

M an y p lan ts con ta in num ero us com po unds tha t m ay cause un -favorab le p hys io lo g ical and c lin ica l responses w hen ea ten . in -c lud ing d im in ished d ig es tib ility . M an has lea rned to avo id tho sefoods tha t p rodu ce im m edia te ill e ffec ts o r has dev ised m eans ofelim inating the un de sira b le co m p oun ds fro m o the rs. O ften p roc -ess ing , or co oking , resu lts in the de stru ction , in act ivat ion , o r less -en ing of these tox ic com poun ds (an tinu tr itiona l facto rs), b u t th eym ay no t be su ffic ien tly reduced to e lim ina te the hea lth p rob lemen tire ly , pa rticu la rly if n ove l p lan t foods are ea ten m o re fre -quen tly and o ver lon ger p er io ds of tim e . E xam ples o f so m e ofth e fac to rs p resen t in various legum e-seed pro tein sources andtheir p oss ib le m e tab o lic and phy sio log ic sig n if ica nce are: am y-la se inh ib ito rs , w h ich are found in m ost legum es and m ay in te r-fe re w ith s ta rch d ig es tio n ; cyano gen . w hich is fo und in lim abeans an d m ay cause resp ira to ry fa ilu re : and tan n ins, w h icharc p heno lic com pou nds found in m o st legu m es and m ay formless d ig estib le com plexes (45). In p ro duc ts th at a re com -m erc ia lly ava ilab le these fac to rs do no t pose any nu tritiona l o rc lin ica l p rob lem s . N everthe less, they are im p ortan t to cons id erin th e course of deve lo p ing new and im prov ed sources o f p lan tp ro te in , fo r exam p le , as in th e case of new varietie s an d uses o fso rgh um (46).

S u m m a r y and conclusionsIn th is b rie f rev iew w e have h igh ligh ted the va lue of p lan t

p ro te in s in re la tion to hum an pro te in nu tritio n . W e b eg an w ith ab rie f cons ide ra tion o f the con tribu tion m ade by p lan t p ro teins tothe pro te in com p onen t o f d ie ts on a w orldw id e bas is and a lsow ith in the U nited S ta tes . W e then d iscussed the requ irem en ts fo rp ro te in and fo r ind isp ensab le am ino ac ids in hu m ans a t variou sages , toge ther w ith a sh ort su rvey of the am in o ac id com po sitiono f d ifferen t p lan t-fo od pro te in sources. T here is a large variationin the con trib u tio n m ade by p lan t p ro teins to the av a ilab ility andin take of to ta l d ie ta ry pro te in am o ng pop u la tion s bo th w ith in the



P L A N T P R O T E I N S 12115tech n ically ad v an ced reg io n s o f th e w o rld an d b etw een th ese an dd ev e lo p in g reg io n s . It can b e sh o w n f ro m co n s id eratio n s o f th eam in o ac id co m p o s itio n o f th e m ajo r f o o d p ro tein so u rces th atp lan t p ro te in s are a m ajo r d e term in an t o f th e ly sin e co n ten t o fd ie ts w o rld w id e (2 9 , 3 0 ) . T h is in d isp en sab le am in o ac id m ig h tw e ll b e lim itin g , o r m arg in al, in d ie ts o f so m e co u n trie s w h erecereals, f o r ex am p le , w h eat, are th e p red o m in an t so u rce o f th eto tal d ie tary en erg y su p p ly . H o w ev er, m o d est am o u n ts o f h ig h er-ly sin e p ro te in f o o d s su ch as leg u m es o r an im al p ro te in s, can h av ea m ajo r an d f av o rab le im p ac t o n th e p ro te in n u tritio n al q u alityo f su ch d iets (3 0 ). O v erall it can b e co n c lu d ed th at m ix tu res o fp lan t p ro te in s can serv e as a co m p le te an d w e ll-b alan ced so u rceo f am in o ac id s th at ef f ectiv e ly m ee t h u m an p h y sio lo g ical re -q u iremen ts .

W e presen t in T able 11 a list o f m y th s and realities concern ingp lan t p ro te in s in h u m an n u tritio n . W e h av e in clu d ed in th is lis ta re f e ren ce to am in o ac id im b alan ce (n o . 7 ) th at w e d id n o t co n -sid er in an y d e tail earlier, larg e ly b ecau se w e d o n o t co n sid er th isis su e to b e an im p o rtan t p ro b lem in p ractice (4 7 ). C o n s id erab lean d in te re s tin g ex p erim en tal d ata h av e d e f in ed th e n atu re an dm ech an ism s o f d ie tary am in o ac id im b alan ces (4 8 ) an d th e u n -to w ard p h y s io lo g ical co n seq u en ces o f an im b alan ce h av e b eeno b serv ed in ch ild ren d u rin g am in o ac id su p p lem en tatio n trials o fd ie tary p ro te in (4 9 ). H o w ev er, th e su g g es tio n th at h ig h leu c in ein tak es, as su p p lied b y so rg h u m in reg io n s o f In d ia, m ig h t b ee tio lo g ically sig n if ican t in th e p e llag ra th at ex is ts in th ese areas(5 0 ) h as n o t b een su b stan tiated b y co n sid erab le ad d itio n al in v es-tig atio n (4 7 ). T h u s, w e co n c lu d e th at co n su m ers d o n o t n eed tob e at all co n cern ed ab o u t am in o ac id im b alan ces w h en th e d ie taryam in o ac id su p p ly is f ro m th e p lan t-f o o d p ro tein s th at m ak e u po ur usu al d ie ts. M ix tu res o f p lan t pro te ins can b e f u lly adequ atef o r m ee tin g h u m an req u irem en ts . Fro m th e s tan d p o in t o f th eco m p o sitio n o f a h ealth f u l d ie t, th ey serv e as a d esirab le v eh ic lef or carry ing nitrog en and ind ispensable am ino acid s to m eet bo tho u r n eed s an d w an ts (T ab le 1 1 , reality n o . 6 ). El

R e f e r e n c e s1 . H o b h o u se H . S eed s o f ch an g e . N ew Y o rk : H arp er an d R o w , 1 9 8 7 .2. V oelk er T A, W orrell A C, A nd erso n L , e t al. Fatty acid b io sy n th es is

red irected to m ed iu m ch ain s in tran sg en ic o ilseed p lan ts. S c ien ce1991;257:72-4 .

3 . Jo n es JL . G en etic en g in eerin g o f c ro p s: its relev an ce to th e f o o din d u s try . T ren d s Fo o d S ci T ech n o l 1 9 9 2 ;3 :5 4 -9 .

4. B en ne r M S . Ph illips R L , K irihara J A , M ess in g JW . G en e tic an aly se so f m eth io n in e -rich s to rag e p ro te in accu m ulatio n in m aiz e . T h eo rA p p l G en e t 1 9 8 9:7 8 :7 6 1 -7 .

5 Fo o d an d N u tritio n B o ard , N atio n al R esearch C o u n c il. D ie t an dh ealth : im plicatio n s o f red u c in g ch ro n ic d isease risk . W ash in g to n ,D C : N atio n al A cad em y Press, 1 9 8 9 .6 . Fo o d an d A gricu ltu re O rg an iz atio n /A gro stat. C o m pu teriz ed in f o r-m atio n serie s N o 1 . Fo o d b alan ce sh eets . R o m e: Fo o d an d A gricu l-tu re O rg an iz atio n , 1 9 9 1 .

7. C onsum er N u tri tion D iv is ion , H um an N utritio n In f orm ation S er-v ice . Fo o d in tak es in in d iv id u als in 4 8 s tate s . Y ear 1 9 7 7 -1 9 7 8 .H y attsv ille , M D : U S D ep artm en t o f A g ricu ltu re , 1 9 8 3 . (R ep o rtn o 1 -1 .)

8 . Y ou ng VR , Pe lle tt PL . Pro te in in tak e an d req u irem en ts w ith re f e r-en ce to d ie t an d h ealth . A m J C lin N utr 1 9 8 7 ;4 5 :1 3 2 3 -4 3 .

9 . Y ou n g V R . Pro tein an d am in o ac id req u irem en ts in h u m an s: m e ta-b o lic b as is an d cu rren t reco m m en d atio n s. S can d J N utr 1 9 9 2 ;3 6 :4 7 -56 .

1 0 . Fo o d an d N utritio n B oard , N atio n al R esearch C o u n c il. A ssessm en to f p ro te in n u tritu re . W ash in g to n , D C : N atio n al A cad em y Press,1 9 7 4 .

I 1 . Fo o d an d A gricu ltu re O rg an iz atio n /W orld H ealth O rg an iz atio n !U n ited N atio n s U n iv ers ity . E n erg y an d p ro te in req u irem en ts . R ep o rto f jo in t FA O /W HO /U N U ex p ert co n su ltatio n . G en ev a: W orldH ealth O rg an iz atio n . 1 9 8 5 . WH O T ech rep se r n o 7 2 4 .)

1 2 . Fo o d an d A gricu ltu re O rg an iz atio n . A m in o ac id co n ten t o f f o o d sand b io lo g ical d ata o n p ro te in s. R o m e: Fo o d an d A g ricu ltu re O r-gan iz ation . 1 98 5. (FA O nu trit ion al stu die s no 24 .)

1 3 . U S D ep artm en t o f A g ricu ltu re . A g ricu ltu ral h an d b o o k n o . 8 -1(1 9 7 6 ); 8 -2 (1 9 7 7 ); 8 -5 (1 9 7 9 ) ; 8 -6 (1 9 8 0 ), 8 -8 (1 9 8 2 ); 8 -9 (1 9 8 2 );8 -1 0 (1 9 8 3 ); 8 -1 1 (1 9 8 4 ); 8 -1 2 (1 9 8 6 ) an d 8 -1 4 (1 9 8 6 ). W ash in g to n ,D C : A gricu ltu re R esearch S erv ice.

1 4 . Pe lle tt PL , S h ad arev ian S . Fo o d co m p o s itio n tab le s f o r u se in th eM id d le E as t. 2 n d ed . B e iru t: A m erican U n iv ers ity o f B e iru t, 1 9 7 0 .

15 Pe lle tt PL , Y ou n g y R . N u tritio n al ev alu atio n o f p ro te in f o o d s.T o k y o : T h e U n ited N atio n al U n iv ers ity . 1 9 8 0 (Pu b licatio n N oW H T R - 3 I U N U P - 1 2 9 .)

1 6 . O sb o rn e T B , M en d el L P, Ferry E L . A m e th o d o f ex p ressin g n u -m erically th e growth p ro m o tin g v alu e o f p ro te in s. J B io l C h em1 9 1 9 ;3 7 :2 2 3 -9 .

1 7. Y ou ng y R . Pro tein nu trit ion al v alue of so y p rote ins in ad ult h um an s.In : S te in k e FH , W ag g le D H , V o lg arev M N , ed s . N ew p ro te in f o o d sin h u m an h ealth : n u tritio n , p rev en tio n an d th erap y . B o ca R ato n , FL :C R C P re ss , 1 99 1;1 07 -1 9.

1 8 . Y ou n g y R . S o y p ro te in in re latio n to h u m an p ro tein an d am in o ac idn u tritio n . J A m D ie t A sso c 1 9 9 1 ;9 1 :8 2 8 -3 5 .

1 9 . Fo o d an d A gricu ltu re O rg an iz atio n /W orld H ealth O rg an iz atio n . Pro -tein q u ality ev alu atio n . R ep o rt o f a jo in t FA O/W HO ex p ert co n su l-tatio n . R o m e: Fo o d an d A gricu ltu re O rg an iz atio n , 1 9 9 1 . (FA O f o o dand n u tritio n p ap er N o 5 1 .)

2 0 . B lo ck R i, M itch e ll H H . T h e co rre latio n o f th e am in o -ac id co m p o -si tion o f pro tein s w ith their nutritiv e v alu e. N utr A bs tr R ev1 9 4 6 ; 1 6 : 2 4 9 7 8

21 . Fo o d an d A gricu ltu re O rg an iz atio n . Pro te in req u irem en ts . R o m e:Fo o d an d A gricu ltu re O rg an iz atio n , 1 9 5 7 . (FA O N utritio n S tu d ie sN o 1 6 .)

2 2. Food an d A g ricu ltu re O rganiz atio n/W orld H ealth O rganiz atio n . E n-erg y an d p ro tein req u irem en ts . R ep o rt o f a jo in t FA O IW HO ad h o cex p ert co m m ittee . G en ev a: W orld H ealth O rg an iz atio n , 1 9 7 3 .( W H O Te c h Re p 5 c r n o 522.)

2 3. Y o ung y R . B ier DM , Pe llett PL . A th eo re tical b as is f o r in creas in gcu rren t es tim ate s of the am ino acid re quirem en ts in adult m an, w ithex perim en tal su p p o rt. A m J C lin N utr 1 9 8 9 ;5 0 :8 0 -9 2 .

2 4. Y o un g V R , M arc hin i JS . M e chanism s an d n utritio nal s ign if ic anc eo f m etab o lic re sp o n ses to alte red in tak es o f p ro tein an d am in o acid s ,w ith ref eren ce to n u tritio n al ad ap tatio n in h u m an s. A m J C lin N u tr1 9 9 0 ; 5 1 : 2 7 0 8 9

2 5 . M arch in i JS , C o rtie lla J, H iram atsu T , C h ap m an T E , Y ou n g y R .R eq u irem en ts f o r in d isp en sab le am in o ac id s in ad u lt h u m an s:lo n g er-te rm am in o ac id k in e tic stu d y w ith su p p o rt f o r th e ad eq u acyo f th e M assach u se tts In stitu te o f T ech n o lo g y am in o ac id req u ire -m en t p atte rn . A m J C lin N utr 1 9 9 3 ;5 8 :6 7 0 -8 3 .

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2 9. B re ssan i R . N utritiv e v alue of hig h ly sin e c ere als In: E jita G , M ertzE T , R o o n ey L , S ch af f e rt R , Y o h e J, ed s . Pro ceed in g s o f th eIn tern atio n al C o n f e ren ce o n S o rg h u m N u tritio n al Q u ality . W estL af ay e tte , IN : Pu rdu e U n iv e rsity , 19 92:50 -74 .



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am in o ac id n eed s in ad u lts an d th e ir im plicatio n s f o r in te rn atio n alp lan n in g . Fo o d N utr B ull 1 9 9 0 ;1 2 :2 8 9 -3 0 0 .

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Plant Proteins in Relation to Human Protein - Young & Pellett - 1994

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Transcript of Plant Proteins in Relation to Human Protein - Young & Pellett - 1994