Human protein requirements: nitrogen balance response to graded levels of egg protein in elderly men and women1 2

Transcription

1 Humn protein requirements: nitrogen blnce response to grded levels of egg protein in elderly men nd women1 2 Ricrdo uy, MD, PhD, Nevin S Scrimshw, PhD, MD, nd Vernon R Young,3 PhD ABSTRAT Seven elderly men, ges 68 to 74 yers, nd seven elderly women, ges 7 to 84 yers, prticipted in short-term studies to determine nitrogen blnce response to grded intkes of whole egg protein within the sub-mintennce to ner-mintennce rnge of nitrogen intke After 1 week of consuming n dequte, free-choice diet, the subjects received protein-free diet for 1 dy to fcilitte dpttion to decresed level of dietry protein nd three rndomly ssigned levels of egg protein for 1 dys A 4-dy brek with norml diet followed ech 1-dy diet period The levels of egg protein intke tested (grm protein (N x 625) per kilogrm of body weight per dy) were: for women, 52, 65, nd 8 g nd, for men, 57, 7, nd 85 g All the women were in negtive nitrogen blnce t the 52 g level of protein intke, nd only two subjects chieved positive nitrogen blnce t the higher intkes Of the elderly men, four subjects were in positive blnce t the 57 nd 7 g levels, nd five were in positive blnce t the 85 g level The clculted men protein requirement for elderly women ws 83 g of protein per kilogrm per dy, or twice the level rrived t by the fctoril method (Scrimshw, NS, WDA Perer nd VR Young J Nutr 16: 665, 1976) The fctoril method thus fils to predict suitble protein llownce for the elderly It is concluded tht typicl S diet providing bout 12 to 14% protein clories should be dequte for the elderly Am I lin Nutr 31: , 1978 urrent dietry protein llownces for the elderly re bsed on extrpoltions of dt obtined from helthy young dults (1, 2) However, ge-relted chnges in body protein metbolism suggest tht dietry protein needs my chnge with dvncing ge in humns It is prticulrly importnt to exmine this possibility becuse of the growing number of elderly people in North Americ nd other industrilized regions (eg, Reference 3) A review of the studies concerned with ssessing the dietry protein needs for older people does not llow definitive conclusions concerning their requirements reltive to those of helthy young dults (eg, References 4 nd 5) Some investigtors hve concluded tht the elderly need more dietry protein thn younger people (6), wheres others hve concluded tht they require similr mounts (7, 8) or less (9) The discrepncies mong the vrious studies presumbly relte to differences in the types of subjects studied, the methods chosen to estimte needs, or the interprettion of the experimentl findings We hve begun systemtic investigtion of protein metbolism nd nutrition in helthy elderly subjects We first determined the obligtory urinry nd fecl nitrogen losses for helthy femles (1) nd mles (11) nd, by pplying the Food nd Agriculture Orgniztion/World Helth Orgniztion (FAO/WHO) fctoril method (2) with correction fctors for efficiency of utiliztion of dietry protein nd norml From the Deprtment of Nutrition nd Food Science nd linicl Reserch enter, Msschusetts Institute of Technology, mbridge, Msschusetts Supported in prt by Grnt AG475 from the Ntionl Institutes of Helth The linicl Reserch enter is supported by grnt (RR-88) from the Generl Reserch enters Progrm of the Division of Resources, Ntionl Institutes of Helth Address reprint requests to: Dr Vernon R Young, , MIT, mbridge, Mss 2139 Downloded from wwwjcnorg t Institute of Atmospheric Physics,AS on July 9, 211 The Americn Journl of linicl Nutrition 31: MAY 1978, pp Printed in SA 779

2 78 AY T AL vrition to these results, sfe prcticl llownce for egg protein ws clculted The estimte for elderly mles ws 55 g of protein per kilogrm of body weight per dy, nd, for elderly femles, 42 g per kilogrm per dy If the 1973 fctoril pproch is pproprite, these intkes of either egg or milk protein should be sufficient to cover the needs of nerly ll helthy elderly subjects However, the ccurcy of this method depends upon the pplicbility to the elderly of the fctors ssumed for both efficiency of nitrogen use t requirement intkes nd individul vribility in requirements We hve conducted short-term metbolic studies in order to determine directly in elderly men nd women the nitrogen blnce response to grded intkes of egg protein within the sub-mintennce to ner-mintennce rnge of nitrogen intke Since we hve found tht the 1973 fctoril clcultion underestimtes long-term protein requirements in helthy young men (12, 13), these short-term studies in the elderly will be supplemented lter by long-term studies TABL 1 Initil chrcteristics of elderly mles nd femles studied for nitrogen blnce response to grded levels of egg protein intke Femles MG MF D RP LF MK A Men ±SD Mterils nd methods Seven mle ucsins, ges 68 to 74 yers, nd seven ucsin femles, ges 7 to 84, were selected from group of volunteers locted through newspper dvertisements or through locl chronic disese hospitl or nursing home Volunteers with identifible metbolic, infectious, or neoplstic disese - ssessed from medicl history, physicl exmintion, clinicl lbortory tests, chest x-ry, nd electrocrdiogrm - were not ccepted for study Subjects unble to give informed consent were lso excluded Tble 1 summrizes the initil chrcteristics of the subjects nd gives estimtes of their body cell mss nd energy intkes During the study, the subjects were inptients t the Msschusetts Institute of Technology s linicl Reserch enter nd received constnt medicl nd nursing supervision All signed written informed-consent forms, nd the experimentl protocol ws pproved by the MIT ommittee on the se of Humns s xperimentl Subjects, s well s by the xecutive nd Policy ommittees of the linicl Reserch enter Diets For t lest one week before the study begn, ll subjects received n dequte free-choice diet providing 1 g of high-qulity protein per kilogrm of body weight per dy nergy needs were estimted on the bsis of dietry history, s previously described (1,11) Subject Age Initil body weight Height Body cell mse yr ±23 kg ±57 cm ±39 kci/kg/dy ±61 kg ±155 Downloded from wwwjcnorg t Institute of Atmospheric Physics,AS on July 9, 211 Mles RM HS W JG ML HM PM Men ± SD ± ± ± ± ±27 stimted fr om whole body [4KJ (12)

3 PROTIN NDS IN TH LDRLY 781 The experimentl diets were prepred t the linicl Reserch enter nd consumed under supervision The subjects received four isocloric, isonitrogenous mels per dy s follows: 1) protein-free diet (1) ws provided on the first dy of ech dietry period to fcilitte dpttion to decresed level of protein intke; 2) the subjects then received formul-bsed diet tht provided grded levels of egg protein (whole dried egg ws the sole source of protein) For the femles, the lowest level of egg intke ws 52 g protein per kilogrm of body weight per dy, which corresponded to the 1973 FAO/WHO (2) sfe llownce for this protein source The higher levels studied were 65 nd 8 g per kilogrm per dy For mles, the lowest level of egg intke ws 57 g per kilogrm, which corresponded to the 1973 FAO/WHO (2) recommendtion for dult men The two higher levels chosen for study were 7 nd 85 g per kilogrm Nitrogen intke ws determined by nlyzing smples of ech experimentl diet At the lowest level of dietry protein, the egg ws incorported into liquid formul; t higher levels, it ws cooked s n omelette The grded intkes of egg protein were rndomly ssigned to ech subject The composition of the experimentl diet is given in Tble 2 xperimentl design nd nlyses After 1 week of stndrdiztion with norml freechoice diet, the subjects received the protein-free diet for one dy nd then one of three rndomly ssigned levels of egg protein for 1 dys A 4-dy brek, during which norml diet ws consumed, followed ech of the 1-dy experimentl periods omplete urine collections were mde dily throughout the study for ech subject, nd liquots were nlyzed for cretinine, ure, nd nitrogen s previously described (14) Fecl smples were pooled for the lst 8 dys of ech experimentl dietry period nd nlyzed for totl nitrogen (14) Subjects were weighed dily under stndrdized conditions: t 8 AM, fter voiding, before brekfst, nd with miniml clothing Body cell mss ws estimted from whole body [4K] mesurements (15) mde t the end of ech 1-dy diet period Blood smples for biochemicl nlyses were drwn when the subjects were dmitted to the linicl Reserch enter nd on the lst dy of ech dietry period; the results will be reported elsewhere Dt nlysis Nitrogen blnce ws clculted from mesured nitrogen intke, urinry nitrogen output for the lst five dys of ech dietry period, nd men fecl nitrogen losses Integumentl nd miscellneous nitrogen losses were ssumed to be 5 mg of nitrogen per kilogrm of body weight per dy, s proposed in the 1973 FAO/WHO report (2) Nitrogen blnce ws expressed s milligrms of nitrogen per kilogrm of body weight per dy, bsed on men body weight during the lst five dys of ech period Becuse fecl nitrogen output is reltively constnt for vrious levels of egg protein intke in the ner-mintennce rnge (14), ech subject s men fecl nitrogen loss for ll three diet periods ws used s the best estimte of fecl nitrogen output vlution of the dily vrince in cretinine excretion llowed us to estimte the prob- TABL 2 omposition of experimentl diet Dietry components Amount Ingredients of formul (6% protein) Whole dried egg5 1 Dextrose mltosec 15 orn oil 1 Vnille 3 Lemon juice 9 Nl 2 ellulose 1 (OH)2(P4)6 1 K2HPO4 35 Wter 4 Totl 7965 Nonprotein foods to meet energy needs rbonted beverges Vrible Sucrose soft drinks Vrible ornstrch dessert Vrible Protein-free cookies9 Vrible Vitmin nd minerl1 supplements The level of protein intke ws regulted by modifying the mount of formul given nd/or by providing given mount of the dried egg mixed with wter nd cooked s n omelette (testing of cooked product for nitrogen content showed 99% recovery) bspry dried, psteurized whole egg powder ws purchsed from the Osklcos Food Products orp, Oskbcos, Iow ompound (mltose, 56%; dextrose, 42%) ws obtined from Med Johnson Lbortories, vnsville, md d Pure Mzol orn Oil ws obtined from P Products, nglewood liff, NJ e Pure vnill extrct B-41 ws from Mcormick nd o, Inc, Bltimore, Md Juice ws obtined from Golden rown itrus o, vnston, III ompositions hve been described (14) ch subject received one cpsule dily of Multivitmins with Iron (Miles Lbortories, lkhrt, Indin) which contined: vitmin A cette, 5 I; thimine nitrte, 15 mg; riboflvin, 17 mg; nicinmide, 2 mg; pyridoxine hydrochloride, 2 mg; cynocoblmine, 6 g; folic cid, 4 mg; scorbic cid, 6 mg; tocopherol cette, 15 I; vitmin D, 4 I; iron, 18 mg The dily trce minerl supplement provided: 6599 mg MgO (3985 mg Mg); 179 mg ul22h2o (67 mg u); 146 mg ZnSO47H2 (332 mg Zn); 512 mg MnSO4H2O (166 mg Mn); 21 mg N2MoO42H2O (83 mg Mo); 17 mg r2(so4)315h2o (168 mg r); 8 mg NSeO3 (37 mg Se); 283 mg A1KSO412H2O (161 mg Al) Subjects were lso given one 1-g tblet of Nl dily nd one 5-mg tblet of diclcium phosphte dily Subjects with history of prtil gstrectomy received 1 tg of vitmin B12 per month intrmusculrly during the study Subjects on diuretics received potssium supplements Subject H S, who took Isonizid, received pyridoxine supplement g Downloded from wwwjcnorg t Institute of Atmospheric Physics,AS on July 9, 211

4 782 AY T AL ble completeness nd consistency of urine collection (Tble 3) Whenever the coefficient of vrition exceeded 2 %, the nitrogen blnce dt were not included in the summry clcultions - c N e N O - n 2) 2 in in Results Tble 3 presents summry of the nitrogen blnce dt for the seven elderly femles receiving grded levels of egg protein As expected, urinry nitrogen excretion incresed s the level of dietry protein incresed All subjects were in negtive nitrogen blnce t the 52 g of egg protein level of intke At the higher intkes, only two subjects (RP nd MK) chieved positive nitrogen blnce Tble 4 summrizes the nitrogen blnce responses of the elderly mles At the lowest level of protein intke, 57 g per kilogrm, three subjects were in negtive nitrogen blnce At the highest level of intke, 85 g per kilogrm, five subjects were in positive nitrogen blnce, while two (RM nd HM) were still in slightly negtive blnce Subjects HS, HM, nd PM hd ech received prtil gstrectomy s tretment for peptic ulcer Although two of them (HM nd PM) hd higher men fecl nitrogen outputs thn the other subjects, they were close to body nitrogen equilibrium t the 85 g of protein per kilogrm per dy level of intke Figure 1 depicts the men nitrogen blnce results for both the men nd the women For the femles, the regression of nitrogen blnce on nitrogen intke ws s follows: Y = 3X - 393; where X nd Y re nitrogen intke nd nitrogen blnce, respectively (mg nitrogen per kilogrm of body weight per dy) The correltion coefficient r is 6 (P < 5) From this reltionship, the men intke required for nitrogen equilibrium is 133 mg of nitrogen per kilogrm of body weight per dy (or 83 g of protein (N x 625) per kilogrm per dy) In contrst to the findings with femles, the nitrogen blnce response in elderly mles ws more vrible nd showed less of n improvement with incresed nitrogen intke becuse most subjects were in positive nitrogen blnce t the lowest level of c 2 = N - O NOO in co m coon cn - m m O eicr-ooo r ri r l in - ( in in in N e In n in r m z_ NO OONr l in N t r N OO in - z TT i L N Nr1r l N N NrNO- n 4N n c m in N ci - ci ,L in 1f - = +1 >, 6 o oi e #{176} cj o - 5 o u & flo L o I!II e - ) = fill 2Z 2 8: Downloded from wwwjcnorg t Institute of Atmospheric Physics,AS on July 9, 211

5 PROTIN NDS IN TH LDRLY o - 5 =2) 2 o I- o -Z2 4 4 in in in m -- d io N in 4inm- O inc in - in N 4 ri ri -- cfl OOin cfl N N m in in r c i in c m m in - r t N ri - o ocoo o o-rn N Z - N I in in - N O N N N inm N ri en oo en -- N N eeneninr -io\n, r i I;; enenriin z- - I ++++ L N-en en en - r N N N in N en intke studied ither stble or incresed nitrogen retention t the highest level of intke ws observed in the subjects who showed positive blnce when consuming 57 g of protein per kilogrm per dy The subjects in negtive nitrogen blnce t the lower intke levels responded dequtely to incresed nitrogen intkes Becuse dily cretinine excretion t the 85 g of protein per kilogrm level fluctuted widely for subject ML, his dt for this period hve not been included in the summry nlysis For the results shown in Tble 4, it ppers tht dily protein intke of between 7 nd 85 g per kilogrm would be sufficient to mintin body nitrogen equilibrium in most elderly men during short-term blnce periods Discussion Studies of the protein nd nutrient requirements of elderly subjects re confounded by biologicl nd methodologicl problems, some of which hve been reveled in this study Subjects defined s elderly on the bsis of chronologicl ge re heterogeneous in terms of body composition, energy needs, cretinine excretion, nd most of the other biochemicl prmeters mesured in these experiments The diminished cpcity of some elderly subjects, reltive to young dults, to follow rigorous experimentl protocols imposes further compliction Moreover, the concept of helthy elderly subject is difficult to define While the effects of life history of series of clinicl problems my not be pprent, the cumultive effect of pst episodes my influence individul responses to stndrdized experimentl nd nutritionl tretments For exmple, the three mle volunteers who hd hd prtil gstrectomies were in pprent good helth nd nutritionl sttus t the beginning of the study, but their fecl nitrogen losses were considerbly higher thn those of the other subjects If dditionl fctors tht might directly or indirectly ffect nutritionl nd metbolic responses hd been considered in the ptient selection process, we might hve obtined more consistent dt However, this would hve dded difficulties, nd its Downloded from wwwjcnorg t Institute of Atmospheric Physics,AS on July 9, 211

6 784 AY T AL z -J z> o os- - ZZ > -j o -2 z mg N/kg/dy) 5 75 (g protein/kg/dy) GG PROTIN (NITROGN) INTAK FIG 1 Nitrogen blnce dt for seven elderly men nd seven elderly women receiving grded mounts of egg protein within the sub-mintennce to mintennce rnge prcticl significnce would be questionble Although the sme fcilities nd personnel were used in both series of studies, the dt obtined for the elderly femles pper to be methodologiclly more stisfctory thn those obtined for the mles becuse of both the lower vrition in dily cretinine excretion nd the more consistent responses of urinry nitrogen excretion to chnges in nitrogen intke From the pooled liner regression of nitrogen blnce on egg nitrogen intke for the elderly femles, the Y intercept represents men vlue of 39 mg of nitrogen per kilogrm s the estimted obligtory nitrogen loss, vlue identicl to tht mesured directly by Scrimshw et l (1) in similr group of elderly women nfortuntely, the present dt for elderly men re ll too close to blnce to permit relible clcultion of Y intercept The men protein requirement clculted in the present study for elderly women is 83 g per kilogrm of body weight per dy, or essentilly twice tht rrived t by the fctoril method (42 g per kilogrm) (1) This discrepncy my be explined in prt by the fct tht the erlier study (1) involved higher energy intkes, which would tend to reduce the pprent requirement for protein (eg, References 13, 16, nd 17) However, this difference is not sufficient to ccount for the degree of discrepncy observed It seems likely, therefore, tht dietry nitrogen utiliztion by elderly femles t requirement levels of intke is considerbly less thn tht ssumed by the 1973 FAO/WHO report (2) The dt obtined with elderly mles re more vrible for both dily cretinine excretion nd urinry nitrogen response to protein intke Furthermore, since most of the subjects were in positive nitrogen blnce, the correltion between nitrogen losses nd nitrogen intke ws not significnt However, not ll subjects were in nitrogen equilibrium when consuming 57 g of protein per kilogrm of body weight per dy, level tht the fctoril estimtion of protein llownces predicted to be dequte for ll subjects (11) Thus, our dt for the elderly suggest tht the fctoril method, s proposed by FAO/WHO (2) nd including corrections for efficiency of nitrogen utiliztion nd subject vribility, fils to predict suitble protein llownce for the elderly of either sex Whether these requirements differ significntly from those estimted for young dults is difficult to sy becuse of our evidence tht the fctorilly derived llownce for young dults is too low for long-term min- Downloded from wwwjcnorg t Institute of Atmospheric Physics,AS on July 9, 211

7 PROTIN NDS IN TH LDRLY 785 tennce (eg, Reference 13) However, the elderly need higher dietry rtio of protein to energy becuse their energy requirements decrese with ge (2), nd protein requirements re either the sme or higher for this ge group thn for young dults According to the nitrogen blnce dt presented here, level of egg protein intke of bout 8 g per kilogrm of body weight per dy would be more nerly dequte for the helthy elderly popultion s whole thn the level of 57 g of egg or milk protein per kilogrm suggested for dults of ll ges in the FAO/WHO report (2) The men energy intke of bout 3 kcl per kilogrm per dy received by the subjects in our study is close to the intke recommended by the S Food nd Nutrition Bord (1) These findings give dietry protein energy-to-totl energy rtio for helthy elderly subjects of 1 for egg or milk protein Assuming 75% efficiency of nitrogen use for the mixed proteins of the S diet (1), diet providing 12 to 14% protein clories should be suitble for the elderly This is higher thn the mount suggested by the most recent Recommended Dily Allownces of the Food nd Nutrition Bord (1) The uthors thnk the nursing nd dietetic stff of the Msschusetts Institute of Technology linicl Reserch enter: Ms Rose Mrie Holmes, RD; Mrs Betty Kene, RN; Dr H Zys-Bzn; Ms Bilmzes; nd Mr R Leighton for their help in crrying out these studies The kind nd willing coopertion of the elderly volunteers is gretly pprecited References 1 Food nd Nutrition Bord, Ntionl Reserch ouncil Recommended Dietry Allownces, (8th ed) Wshington, D : Ntionl Acdemy of Sciences, Joint FAO/WHO d hoc xpert ommittee nergy nd protein requirements World Helth Orgniztion Technicl Report Series No 522 Genev: World Helth Orgniztion, BROTMAN, H B Popultion projections Prt 1 Tomorrow s older popultions Gerontologist 17: 23, YONG, V R, W D PRRA, J WINTRR AND N S SRIMSHAW Protein nd mino cid requirements of the elderly In: Nutrition nd Aging, edited by M Winick New York: John Wiley nd Sons, 1976, p 77 5 YONG, V R, R AY, J WINTRR AND N S SRIMSHAW Protein metbolism nd needs in elderly people In: Nutrition, Longevity nd Aging, edited by M Rockstein nd M Sussmn New York: Acdemic Press, 1976, p 67 6 KONTZ, W B, B L HOFFSTATFR AND P G AKRMANN Nitrogen blnce studies in four elderly men J Gerontol 6: 2, WATIN, D M The ssessment of protein nutrilion in ged mn Ann N Y Acd S 69: 92, HORWrFr, M K Dietry requirements of the ged J Am Dietet Assoc 29: 443, ALBANS, A A, R A HIGGANS, B VSTAL, L STPHANSON AND M MALSH Protein requirements of old ge Geritrics 7: 19, SRIMSHAW, N S, W D A PRRA AND V R YONG Protein requirements of mn: obligtory urinry nd fecl nitrogen losses in elderly women J Nutr 16: 665, AY, R, N S SRIMSHAW AND V R YONG Humn protein requirements: obligtory urinry nd fecl nitrogen losses nd the fctoril estimtion of protein needs in elderly mles J Nutr 18: 97, GARZA,, N S SRIMSHAW AND V R YONG Humn protein requirements: the effect of vritions in energy intke within the mintennce rnge Am J lin Nutr 29: 28, GARZA,, N S SRIMSHAW AND V R YONG Humn protein requirements: long-term metbolic nitrogen blnce study in young men to evlute the 1973 FAO/WHO sfe level of egg protein intke J Nutr 17: 335, YONG, V R, Y S M TAYLOR, W M RAND AND N S SRIMSHAW Protein requirements of mn: efficiency of egg protein utiliztion t mintennce nd submintennce levels J Nutr 13: 1164, YONG, V R, AND N S SRIMSHAW ndogenous nitrogen metbolism nd plsm free mino cids in young dults given protein-free diet Brit J Nutr 22: 9, INO, G, Y FJITA AND Y NHYAMA Studies on protein requirements of young men fed egg protein nd rice protein with excess nd mintennce energy intkes J Nutr 13: 1673, ALLOWAY, D H Nitrogen blnce of men with mrginl intkes of protein nd energy J Nutr 15: 914, 1975 Downloded from wwwjcnorg t Institute of Atmospheric Physics,AS on July 9, 211