Urinary sodium and blood pressure in vegetarians1

Transcription

1 rinry sodium nd blood pressure in vegetrins1 Bruce Armstrong,4 M B, B S, DPhil, FRA CP, Helen Clrke,5 Crig Mrtin,5 BSc (Hons), Willim Wrd,5 Neroli Normn,5 BMedSc (Hons), nd John Msrei,6 MD, FRCPA ABSTRACT rinry sodium, potssium, ure, cretinine, uric cid, plsm ure, cretinine, cholesterol, blood pressures, height, weight, nd skinfold thickness were mesured in some or ll of mtched pirs of vegetrins (minly Seventh-Dy Adventists) nd nonvegetrins Men blood pressures were lower in vegetrins (1419/889 mm) thn nonvegetrins (1480/909 mm) but the urinry excretion ofsodium ws higher, lthough not significntly, in the vegetrins (men of 1697 compred with 1612 mmole/dy) The vegetrins lso hd higher urinry potssium excretion (629 mmole/dy) thn the nonvegetrins (548 mmole/dy) thus giving them lower men sodium to potssium rtio (30 compred with 33) Both systolic nd distolic blood pressures correlted positively with plsm cholesterol levels which were less in vegetrins (60 mmole/liter) thn nonvegetrins (66 mmole/liter) They lso correlted positively with the urinry sodium to potssium rtio, but only in nonvegetrins It ws concluded tht dietry sodium does not explin the blood pressure differences between vegetrins nd nonvegetrins Am J Clin Nutr 32: , 1979 Recent studies hve reported lower blood pressure levels in vegetrins thn in nonvegetrins (1-3) No dequte explntion hs been offered for these observtions lthough it hs been suggested tht vegetrins my consume less sodium thn nonvegetrins (4, 5) or tht the blood pressure differences my be determined by differences in the blnce of dietry sturted nd unsturted fts (2, 6) Evidence for both of these suggestions is lcking t the present time This study ws undertken to estimte the dietry sodium intke of vegetrins from their urinry sodium excretion nd compre it with tht of nonvegetrins to provide cvidence for or ginst the first of the bove suggestions rinry potssium, ure, cretinine, uric cid, plsm ure, cretinine, cholesterol, height, weight, skinfold thickness, nd blood pressures were lso mesured nd re reported here Subjects nd methods Group 1 Fifty vegetrins ges 20 to 69 yers (25 men nd 25 women) nd 50 nonvegetrins mtched to the vegetrins by ge (in 5-yer ge groups) nd sex were selected rndomly from bout 500 Seventh-Dy Adventist vegetrins nd their friends nd neighbors who ttended crdiovsculr risk-ssessment progrm The vegetrins te no met, fish, or poultry while the nonvegetrins te flesh t lest once dily Complete dt were obtined from 3 1 pirs of subjects; the vegetrins hd men ge of 486 yers nd the nonvegetrins 479 yers Group 2 Twenty-six vegetrin students ges 17 to 3 I yers (20 men nd six women, of whom 18 were medicl students) were mtched by ge (within 2 yers), sex, smoking, lcohol-drinking, nd exercise hbits to 26 nonvegetrin medicl students selected rndomly from ll possible mtches in the totl popultion of medicl students in the niversity of Western Austrli The vegetrins te no met or poultry but two of them te smll mounts of fish The men ge of the vegetrins ws 219 yers nd of the nonvegetrins, 202 yers Ten of the vegetrins were Seventh-Dy Adventists Group 3 Fifty Seventh-Dy Adventist vegetrin postmenopusl women ges 50 to 79 yers were mtched by ge I From the Deprtments of Medicine nd Clinicl Biochemistry, niversity ofwestern Austrli, Nedlnds 6009, Austrli 2 Address reprint requests to: Dr B Armstrong, niversity Deprtment of Medicine, Queen Elizbeth II Medicl Centre, Nedlnds, 6009, Western Austrli 3 H C supported by vction scholrship of the Cncer Council of Western Austrli Senior Lecturer in Medicine Medicl Student 6 Associte Professor in Clinicl Biochemistry 2472 The Americn Journl ofc!inic! Nutrition 32: DECEMBER 1979, pp Printed in SA

2 RINARY SODIM AND BLOOD PRESSRE IN VEGETARIANS 2473 (in 5-yer ge groups) to 50 nonvegetrin postmenopusl women resident in similr circumstnces (either in n ged-persons home or in their own home) The men ge of the vegetrins ws 68 yers nd of the nonvegetrins, 67 yers Aprt from documenttion of the met, poultry, nd fish intke of these three groups, no detiled informtion ws collected on other spects of their diet All the vegetrins te eggs nd diry products but dt on egg, milk, nd cheese consumption by subjects in group 3 did not suggest ny tendency for them to increse their consumption of these foods s mens of replcing dietry met It is likely, therefore, tht met ws replced by incresed consumption of vegetble foods s ws seen in previous detiled study ofdiet in Austrlin lcto-ovo-vegetrins (7) We hve no reson to believe tht the vegetrins differed gretly from the nonvegetrins with respect to cooking of vegetble foods or their use of processed or preserved vegetble foods Twenty-four-hour urine collections were obtined during the winter from ll subjects in group I nd 22 complete pirs in group 2 Twelve-hour (730 PM to 730 AM) urine collections were obtined during the summer from those in group 3 One subject in this group (with her mtched prtner) ws excluded from further urinry excretion nlyses becuse the 12-hr urinry volume ws less thn 100 ml Aprt from the creful instruction of ll subjects, no other mesures were tken to ensure completeness of the urine collections No dietry restrictions were in opertion during the collections except tht subjects in group 3 fsted from 900 PM of the night of the collection nd brekfst ws deferred until the collection ws complete rine smples were either nlyzed or deep frozen on the dy the collection ws completed Venous blood smples were obtined from most of the subjects In groups I nd 3, they were tken before 900 AM fter n overnight fst wheres in group 2, they were tken in the evening not less thn 2 hr fter the lst food ws eten All plsm nd urinry vribles reported here (sodium, potssium, ure, cretinine, uric cid, nd cholesterol) were mesured by stndrd utomted (Technicon Auto Anlyser) methods in one lbortory Single mesurements of blood pressures were mde with the subject seted, without prior rest, by use of stndrd mercury sphygmomnometer The distolic pressure ws recorded t the point of disppernce of sound The triceps skinfold thickness ws mesured, in subjects in group 3, with Hrpenden clipers The sttisticl significnce of correltion coefficients nd differences reported in the following section ws evluted by Student s t test TABLE I rinry excretion of sodium, potssium, ure, cretinine, uric cid, nd plsm ure, nd cretinine in vegetrins nd nonvegetrins rinry sodium (mmole/dy) rinry potssium (mmole/dy) Mens with SD in prentheses b p< 001 C p< 0001 dgroup I only Group 2 only P< 005 Results rinry excretion of sodium, potssium, ure, cretinine, uric cid, nd plsm ure nd cretinine concentrtions in vegetrins nd nonvegetrins re shown in Tble I nless stted otherwise, the levels re for ll three groups of subjects combined For the purpose of combining results the 12-hr excretion levels of subjects in group 3 were doubled There ws no pprecible difference between vegetrins nd nonvegetrins in the 24-hr urinry sodium levels The 24-hr urinry potssium levels, however, were significntly higher in vegetrins thn nonvegetrins with the result tht the urinry sodium:potssium rtio ws less in vegetrins (30) thn in nonvegetrins (33), but not significntly so (P = 0 13) Plsm nd unnry ure nd cretinine levels nd urinry uric cid levels were significntly less in vegetrins thn in nonvegetrins but the crctinine clernce (vilble for group 2 only) ws not different between the two dietry groups The differences between men urinry cxcretion levels in vegetrins nd nonvegetrins in the three groups combined were lso present (lthough not necessrily sttisticlly significnt) in the three groups nd the sexes seprtely (Tble 2) The men 24-h urinry potssium, cretinine, nd ure excretion levels in women from group 3 (twice the 12- hr levels) were pprecibly less thn in No of pirs Vegetrins Nonvegetrins (810) (262) (690) (258) rinry sodium:potssium rtio 30 (16) 33 (15) rinry ure (mmole/dy) 2753 ( 1) 3329 (1 168)c rinry cretinine (mmole/dy) 94 (38) (50)t rinry uric cid (mmole/dy) 3 l 39 (09) 49 (16) Plsm ure (mmole/iiter) ( 13) 59 ( 1 0) Plsm cretinine (mmole/liter) (145) 1006 (229) Cretinine clernce (ml/sec) 2Y 182 (036) 194 (043)

3 2474 ARMSTRONG ET AL V n, women expected from from groups the known 1 nd diurnl 2, s would vrition be in L #{149} L r 0 - ri their urinry excretion (8) These differences l do not invlidte the combined group corn- 8 u pnsons, however, becuse of the mtched- 0 z t IrIO0r1 t8 pirs study design n r 0 Men thickness, blood pressures, nd plsm height, cholesterol weight, levels skin- fold Q - r r in vegetrins Tble 3 Bothnd systolic nonvegetrins nd distolicre shown blood t8 pressures were less in vegetrins thn non- i : Li r4 -irs0ri- #{228} 0 O - oo vegetrins, the former significntly so This 50 r s#{228} ws true in ech group of subjects nd in r1 mles nd femles seprtely except tht in R :: group 2 femles men systolic nd distolic 0 r, blood pressures in vegetrins were essen-, 3 tilly identicl to those in nonvegetrins The lrgest differences were in group 2 mles s 2 0 O en rn (men blood pressures 1329 systolic nd 854 z r i r ;g distolic in vegetrins nd 1440 systolic nd en 898 distolic in nonvegetrins; P < 001 for v difference The vegetrins in systolic were pressures) lso ;; r O lighter (on v- 8 #{182} erge 28 kg; P = 003, one-tiled test) thn 0, 2 t the nonvegetrins There were no ppreci- 2 > #{176}-: sq 0 ble differences between the two dietry Do 2 r1 groups lfl men height, Quetelet s index - (weight/height2) or triceps skinfold thickness 2 As would be expected, the plsm cholesterol level in vegetrins ws less thn in nonveg- r oeioo t NO 2 ) S 8rilfO! t-i ri - o - etrins (9) E ) ci) The correltions between systolic nd di- g so 0 rs stolic blood pressure levels nd vlues of the 0 z_:rri;r: - vribles mesured in ll three groups were fi : et exmined trins In systolic both nd vegetrins distolic nd blood nonvegepressures 2 (S,O 1 00 correlted positively with the plsm choles- 8 - g 0 terol level (simple correltion coefficient, r0, t6 z, i r* C oo i r- etrins only, systolic nd distolic blood c, from 023 to 032 with P < 0001) In nonveg- 2 r1 n r- - i8 pressures were significntly correlted neg- tively with height nd urinry potssium, crcc8 tinme, nd ure, (r0 from to -037, P t < 005 to < 0001) nd positively with the E 0 ll 9 S;:; - Cs urinry 026, sodium:potssium < 0001 for rtio systolic (r0 nd 030 distolic nd P, ts-i_ E _ pressure, respectively) but not with urinry - 2 g E E #{176} sodium lone (r0 < 0 13 in ech cse) C! Discussion r%4 EllE!: E m ; 2 2 Z The use of urinry sodium excretion s <c )0r# F- mesure of dietry sodium ws chosen for this study becuse of its simplicity compred

4 RINARY SODIM AND BLOOD PRESSRE IN VEGETARIANS 2475 TABLE 3 Blood pressure, height, weight, skinfold thickness, nd plsm cholesterol in vegetrins nd nonvegetrins N o of pirs vegetries Nonvegetrins Systolic blood pressure (mm) Distolic blood pressure (mm) Height (cm) Weight (kg) Quetelet s index (g/cm2) Triceps skinfold thickness (mm) Plsm cholesterol (mmole/iiter) Mens with SD in prentheses b p < 005 C Group 3 only (2l4) (159) (105) (1 16) (045) (57) ( 1 5) d p < (192) (121) (104) (120) (039) (48) ( I 5)( with the most vlid lterntive, the nlysis of smples tken from weighed dietry portions As virtully ll ingested sodium is cxcreted in the urine (in the bsence of profuse perspirtion), dily excretion should reflect dily intke firly ccurtely Both 24-hr nd overnight urinry sodium excretion levels correlte highly with men dily sodium cxcretion mesured over 3 dys (10) In this study sodium loss through perspirtion ws minimized in groups I nd 2 by conduct of the study in winter Group 3 ws studied in the summer but ws very sedentry group If it is ccepted, s rgued bove, tht urinry sodium ccurtely reflects dietry sodium, then this study provides evidence ginst the hypothesis tht vegetrins et less sodium thn nonvegetrins nd tht this explins their lower men blood pressures (4) The combined smple size of this study (Tble 1) ws such s to suggest tht the true men 24-hr urinry sodium excretion in vegetnns is unlikely (P = 005) to be greter thn 1 10 mmole/dy (7%) less thn tht in nonvegetrins, nd is more likely to be the sme or more thn tht in nonvegetnns The vegetrins did hve significntly higher urinry potssium levels thn the nonvegetrins nd the urinry sodium:potssium rtio ws less in them (but not significnily so) The possibility tht high dietry potssium in vegetrins might exert protective effect ginst sodium-induced hypertension cnnot, therefore, be ruled out (1 1, 12) Blood pressures in this study correlted positively with the urinry sodium: potssium rtio in nonvegetrins but not in vegetrins Absence of n effect in vegetrins could be explined if their level of potssium intke ws such s to exceed the level tht would blnce their sodium intke Both plsm nd urinry ure nd cretinine levels (but not cretinine clernce) were significntly less in vegetrins thn in nonvegetrins It is likely tht these differences re determined by differences between vegetnns nd nonvegetnns in their intke of the dietry precursors of ure nd cretinine (13) It is possible, however, tht the lower cretinine levels in vegetrins re due in prt to lower verge len body mss in them becuse urinry cretinine is highly correlted with len body mss (14) This would be consistent with evidence from this study of body weight difference between vegetrins nd nonvegetrins with no pprent difference in diposity (s mesured by Quetelet s index nd skinfold thickness) In ny cse, this is ofdoubtful relevnce to the blood pressure differences between the dietry groups becuse in previous study these differences were not explined by the lower men body weight in vegetrins (2) Both systolic nd distolic blood pressures (the former most strongly) correlted posilively with the plsm cholesterol levels in vegetrins nd nonvegetrins in this study These ssocitions would be expected if the blood pressure differences between vegetrins nd nonvegetrins were due in some wy to dietry differences in the blnce of sturted to unsturted fts (2, 6) but could lso occur if blood pressures were ffected by some other component of dietry met tht would be correlted with sturted ft intke This study suggests tht dietry sodium differences do not explin the blood pressure differences between vegetrins nd nonvegetrins It does not, however, detrct from the hypothesis tht sodium intke my be mjor determinnt ofvrition ofblood pressure in the popultion t lrge Dietry potssium could be the explntory vrible lthough the evidence from this study is in-

5 2476 ARMSTRONG ET AL conclusive The possible roles ofother dietry fctors in explining the blood pressure difference cnnot be inferred from this study tents II: 5, FREIS, E D Slt, volume nd the prevention of hypertension Circultion 53: 589, IACONO, J M, M W MARSHALL, R M DOGH- ERTY, M A WHEELER, J F MACKIN AND J J CANARY Reduction in blood pressure ssocited with high polyunsturted ft diets tht reduce blood cholesterol in mn Prevent Med 4: 426, HITCHCOcK, N E, AND R M ENGLISH A comprison of food consumption in lcto-ovo-vegetrins nd non-vegetrins Food Nutr Notes Rev 20: 141, STANBRY, S W, AND A E THOMSON Diurnl References I SACKS, F M, B ROSNER AND E H KASS Blood pressure in vegetrins Am J Epidemiol 100: 390, ARMSTRONG, B, A J VAN MERWYK AND H COATES Blood pressure in Seventh-Dy Adventist vegetrins Am J Epidemiol 105: 444, ANHOLM, A C The reltionship of vegetrin diet to blood pressure Prevent Med 7: 35, GARFIELD, E The vegetrin lterntive Curr Con- El vritions in electrolyte excretion Clin Sci 10: 267, HARDINGE, M G, AND F J STARE Nutritionl studies of vegetrins 2 Dietry nd serum levels of cholesterol J Chin Nutr 2: 83, PIETINEN, P, T W FINDLEY, J D CLASEN, F A FINNERTY, JR AND A M ALTSCHL Studies in community nutrition: Estimtion of sodium output Prevent Med 5: 400, DAHL, L K, G LEITE AND M HEINE Influence of dietry potssium nd sodium-potssium molr rtios on the development of slt hypertension J Exptl Med 136: 318, LANGFORD, H G, AND R L WATSON Electrolytes nd hypertension In: Epidemiology nd Control of Hypertension, edited by 0 Pul New York: Strtton, l975,p BLEILER, R E, AND H P SCHEDL Cretinine excretion: vribility nd reltionships to diet nd body size J Lb Clin Med 59: 945, FORBES, G B, AND G J BRINING rinry cretmine excretion nd len body mss Am J Clin Nutr 29: 1359, 1976