Temple, Norman J.

Athabasca University Library Institutional Repository

Diet, blood lipids and coronary heart disease - currentcontroversiesNQ~N J. TEMPLEI t has been kno . wn for years that a high blood cholesterollevel is ca,-"uUv rdmed to coronary heart disease (CHD)This belief is based on several lines of evidence. Manystudies have dernonstrared 1:haI individual~ Vv'ith a relativelyhl~h blood dlOlesterol level are at increased risk of CHD.Si;;1ilarly, populations .or groups ~'hose customary diet CCltISC!;a high blood .cho!csl:crol level hav" a high risk of CHD.' Inseveral European COUntrie~ during the Second World Warthere was a marked:ccirop in the intake of :lil-t-ri"h [0 ods, whichwere replaced by carbohydrates and chNary fibre; the5e dietarychanges were followed by a sharp fall in CHD monality."SnLc.tie~ un non-human. p.rin1.ates h.a.v~ r~peatedly dcmonst.x'3(edthat atherosclerosis develops"s"consequence of a high bloodcholesterol leveLGrowing evidence has demonstrated that aLh~rosclerosis isreversible:. The ori.'cina] evidence for iliis cume fn.nn studie5 inanimals.. particularly prilnate!';.:J-- In recent years studies using;angiugruphy havr; demonstrated that atherosclerosis CHn .abobe reversed in humans.1! 'Ibis \ova!;; clearlv d~IIlon5trated in th~recent Sr Tl:l<..>m"" Atheron~a Regt"cossion Study (ST1\R$) inwhich diet i1lone reversed atherosclerosis in less th",o 3 yeaI"s.'It" therefore appears thataIhcroscleroticIt."':::iiollS are in dynamicequilibrium v.,.'ith lhe blood cholesterol (or, to be morC prccige,the lo~'-de:n~iry lipoprotein fraction thereat), Tht:::-e: is. a neutl'alpoint of about 4,2-4.)6 mmol/L Atherosclerotic lesions devel-op when the blood cholf!:sr~H')1 level is above this point andreverse whcn under it. !'v1oreover.) the rate of dt::velopnH~:nt ()rreversal is roughly proportional tu th~ d-ifference between theblood chl)lesl~rol1e\lel and the neutral point.N"um~rous. clinical trials have: tested the hYPDttH::}iis tharwhen the blood cholesterol level is lowered by dkt or drugs.,CHD .rnortalinT 1'ate~ are reduced. As Alec \Xt'aLker and II" hav~pointed out, j~tct'Vention does indeed pr~veJ11 C:HD} but toachieve a clinically meaningful impact on CRD occurrencethere Il1.USr he a f.iignificant reduction in blood cholesterol 1evel;The minimum should be about 6% but" c:uIlsiderably largerdecrease is preferable. B~aring in lU1.ud that n1.any trials haveachievcu onl~' a rn.inor d~crea5e in the blood cholc$tcrol level,it js hardly surprising that the impact on C:HI) 11,,1::;often beendisappointing.Davt::y SU1ith el at. JI recently analysed these trial~. They~~parated those rhat used drug,:> [rOIl} th~ orhen=:) almost all ofwhom used dietary tneans. Both typ~s of trial sho\vcd thatintervention to lov.~er the blood cholcsn:roL It:\,'d is effective inpreventing death from CHD, However, treaUl1ent \vith drugsalso causes an incr~ase indeaths fron1 caus~s orner than CHD,such a5 stroke: and certain typ~s of cancer. All rypes of d:rugappear tohave this aCtion. Diet.. by (.:ontrasl, does not cause anincrease in non-CHD death~. Davey Sn~idi e.t al. 1) concludedthaL dn.J,t=;3 Hn: only VY'LlITarHed in subjects \vho arc at exception-ally hil':h risk for CHD, e.g. a person Wtth a blood cholesterollevel of over 6~5 mmoL'l plus clinical1y evident CIlD. For PC.L'-sons."'jth fl lo~ver I-Jsk ofCHD, drugs...vill cause a net iIlL:r~asein the number of deaths. At prcscnt (Hr rnOre: people are receiv-ing drug therapy than can he justified. Unless prescribing pr"c:-liCt:~s change, this nlay become: th~ next drugscandaLDietJ then., isthe treatment of choic~ f( IT lhe prevenrion ofCHD,. a~ it is bOlh safe and effective, l-Iowever" there has been111uch contT()Versy as to the most a.ppropriRle dif::!tary advice,The most common intervenlion is rh~ Step I Diet (far'" 30%of energy) ~alur;][cd fatty acids <: 100/"., cholestcrol ;: 300mg/day). Ho\vever) Ramsey.ec al.J2,'3 pointed nut that this diettypically causes only a 2% drop in h100d cholest~roj level. TillsFuc1,.I.1ty neScience., At.h.abasca Univer$lty~ A-chabHscn..Alberta, CanadaNORMAN J. TEMPLE, PH.D.30poor rcspon::;e is. i--u-obably du~} in the main, to insufficientcOl11pliancc. l\1..ore rigorous diets reduce tht:: iuL.tke of f~r to 20-30% of energy and thal o[ satUrnted far to 5-7%. Such dietsachicve a fall ill blood cholesterol level of 6~o to over 200/0. H,.5The dief is likely to be et1cclivc ~vhcn ~tr:ictly followed but,\-'\~hen the subjcct is }n:;;l.lfficiently nlotivated) rcsults may be dis-appoint.ing.J6The farthati, removed from the: dieL ,hould be rep1aced byfibre-rich carbohydrate foods. Sn1uble fibre, found In f'ruit andbeans., has a mudest hypochole~terola~mic effect.11 On tht:uc:c:"sion of Alcoe Walker's 80th birthday it is partieulttrly fittingto point out that back in 1955 h" wa~ the first pe«on to sug-gest a possiblt::" relationship hc:t~.een a high-fibre dietand pro-tectiun against C.HD.'AEvidence has appeared in recenl year~ that demonstt.atcsthe importance <..\fulher (1spect'" of dier. TIlere is growing evi-dence thar 'trans-fatty acids may increase th~ risk of CHD.TI~ese fats are fonned wh"n ve~eLable oils arc hydrogenatced inorderIO harden then) and extend theirshelf life. This igCOITl-rnon1y done in the production of margarine and the f.flts usedin products suchas bisc.uirs. caL{t;$ BnLl white bread.In a prospective ,'udy in the USA of 85 000 nurses, the1I1take of rrans-fatty acids \\.'as directly rel~Hed to the risk ofCUD; thc relative risk was I,'> when rhe highest and lowestquintiles \'>1~re cOl'npared.19 Similarly, a case-control study inGreece n~:p()rted an increased flsk for CHD in persons \vhoregulary used tnarga.rine fur LookitlR. 20 Then~: has been a trend1.1:1recent yeal'S in ;-.Jorth America for fast: tood restaurants LOuse pi1rtially hydrogenared vegetable {Jib in plnce Qf ht:ef tallo\,,,and tropical oils, lrunic(tlly~ this. subf.ritution may be having theopposite effect ofthar intended...-\..nother important finding lu t:nlel'ge in recent years is theprotective effc<;t of anti-nxid;1nts. Gc::y el a.1.1.1 rcvic\.vcd theresults from an -interpopulationstudy, a case-control study anda pl"ospective study. In each there WHS fin increased risk ofCHD at low plasma levels or anti-oxidants, with the fOllowingrank order: viu.unin E » carotene ~ vitamin C. -11l1s UI,l.Uer--liIle~ the great }mportance, of fruit and vegetable'd in a healthydiet. First> these foods are the so1e !o;(Hlt'Ce: of carotene and'~ta-min C1 aud a $ignificant SOurce of vitamin E. Second, the:::senutrients also have the same prott:ctiv~ t."1Iec[ ngainst ~troke.Third, fruir and vegetables ~uh"tantiallv lower the risk of mosttypes of cancer,2"2 - ~Gl.o~'ing cvidenee dc:mUilstfate.s that fis.h is protectiveagainsl CHD, Severu1 prospective studies have indicated thatfish consumption is negatively related to risk of CHD." In onera.ndon1.ised trial, fish or fish uil W"lS fed to 1TI~n \\'ith CHDY"This redut;e:u CHD lTIortaliry by 33% but there was no reduc:-don in non-futal CHD. TI~e .principal route via whic:h this pro-Lt::'ction QCcur$;, appears to be reduction of th~ It:ndency todevefop throInbosis"J~ Ho\.veveI") t1sh also induces a modestreductiun in blood pr~ssl.1.rc~ particularly .in hypertensiv~H. 25The active ingredient in fish appt:Hrs to be th~ long-chainonlcga-3 fany acids.The evidence ptese:ntcd here sh.o~'s that diet can drall1.ati-cally rcoducc me risk of CHD.-'v\.o" impOI,ant is the loweringof the blood choLt>sterol level. This requires a reduction in theinrak~ of f>:lturated fat and cholesterol to tl level far beloVo' ~vhatis. rypical1y consumed by we~re:y.njsed populations. It is ironicL.h.:H \vbile': IllDny poorer populations, e,g. the bh.u..:ks of SouthAfrica, strive for a \X.Testern lifestyle, our end~nVOllrs f:ncouragethe bCtter-o.tT pupul.nrions to move in the oppositc directioD, atleasr in respect of di~t.\Xlhilc modification of bloud c:hole:s.tC!:["nl level must be thefirst consideration v,lith n:gay"d to reduction of CHD, other fac~tor':! u1so have an in1.portant impact. Briefly revie~C!:d are theeffecrs of trans-fatty acids, anti-oxidums and fish. Each of-rhesecan potential1y reduc:" Lite risk of CI-ID by 20% or m.ure ifSUPPLEMENT TO SAMJ, JULY 1994intake is oprirnised. In addition, a nluch reduced salt: intakecan have a sitnilnrly hene:ficial effect (and an even greater effect.on.th~ risk of stroke). ~6...:.,..n~~~~:~~~:~J.~: ?~\!!~~~:-:P?:~:':~:\:i~..pr:~.:.~~t~F}~~J:P2:,if.~c .~i~~e~~avei.l'.we1"e .ll)st :';>;..q.t~;:':".'~~:::~:::~,:r:!>:.;:'.~J:O\I[,~eY~!".;.>}::')::{~~:c.ri~~.,-'i):rioreruBy in a formcorii)rigbook/.:-'ti~'-iar~e:'b:"'<J.~~:~'~~{:~~y.i4~?:8~'~compelsthe conclUS10n that t.he chang~s' to diet and other. aspe'ctS oflifestyle required to prevent CI-ID are essentially t.hesaIne Qfo;lho8e r~quired to prevent other W't:"stern dj~eases, such asstroke, diabcr~s, obesiry and cuucer of the colon and breast.This benefil has the great advantage of facilinning (h~ task ofin1.plementing a population strategy fnr the prevention ofCHD. ,'\fter all when p~uple calculate the cost/bcndit ratio.,they ur~ much nl0r~ ,)'i.~ely to become motivated to s\.\.'ilCh to ah~althier diet if the pr~mjsed beD~fit is [he p!'e"~ention not onlyof CHD, but ofrnQsl Western diseases. To use the Americanphra.." 'TIley get." bigger bang for the buck.'In this review, the relationshIp b~tween blood cholesteroland CHD is dis{::us::ied briefly. Pre,,-enrion of the disea.se neces-sitates reducing the fat content of the diet to 20 - 30% and-satul'ated fat (0- 5-70/0 of energy requiren"lents, with a greatly:increased intake of fonds rich ill carbohvdrate and dietar"fi:br~. \Vith a sufficienr faU in blood cholt:~tt~rl)l level, athero-sclerosis can SlOp progressing and can start reversing, Drugtrcaunent of u hi.~h blood cholesterol level is only justified in ilsnI311 'minority of subjects, because of tht:': re~ul tin~ increase innon-CHD deaths. Otht!r aspects of diet arc also discussed,namely trans-fatty acids) ant1-\.'")xidant nutrients and fish.RCFEF.J2NCES':-<K~Y'I A. Corollary he-;u:t discas~ in :!Icvc-n C'O\.LPtrit"s. t:trt:ulari07'l 1979", 41~:s.u"pl 11 1.41<}fi';;':'.s';hl!:.'t'd.~r G.. CJll1'd;.ova cular di-..ca~c. dun.l.)'~ and aft~r '~'/or-ld '\':J(.'ar II' n c.nm.p~r~~onofthc.Fcdera[ ,R~plJh1ic: nf{:rer"r1LOI.uy Wilh other C.urop~an CQt]nrl"ic~.I.7~':j.l!!Ii:.! 1979; 8: 581-590.-<: Malin.os H. The Ic:lation of nutrjt:io" to health: a 5ta1.h.t\.-.;.,:d ~lu;.iv of the.crtc.ct ~fwat.timi: on ..n:t:nu$t;l~rQsi'So, cudiosckro.sis, ttlh~rcu~osi~ awl Jia-~~t~!!.>1~r..:! Mll.-fSc.andSuppI19~O, 246; r:n.l~O...~:<:~tt9.Ql::j':i.., l~.n~e'!1 R:\. .\tonalilY [ruu), (..iLculator)-' diseases :in NOTWIi'IY 1i)1()-:::::::L~4.5.::~~x'l= 1951; 1: 126-12~.''i;,'~t,:L:{.:nrRW (heLoscJ.crosis rcg:r-i':,,~ion in animal Iw.}d~\:;. c.uut:;nt: conce.ptS'~d:'GO!h'lI~"t:and..biQt.:he1n1cal mecha.oisffis. A-c% Cardi()nn.~r. [)i.~ t 9H3,j 26; 109.!.32.6. Armsrrong MLt Wuruex: ED"C()nnor \X/E. Rcgre~sicn of (',om-onry o.uu:ro-matosi! in ;l:"b~su$ monkeys. G;;.-c: 1<(15lY'/O; 1.7: 59-Q7.7. C1.:.a-ksoD. TD, Dond MG, fhJJ!.")ck BC, ~\1.cLa.ugh!in KJ, Sa-wyc:r TK. A :itUdyof athl::rQs.;JeJ;osis r~gression in M.ac8CQ mula['t[l. 1:::xp A1Qt ecu;JwI 19.84: 4;1.96 Jl8..8 WM.e~ D, Le~peIa1.lC;f: J. ReKl'~~$ion of cOronary 8.therQsclero51s: an ac]u-t:V,""4L~,;!':goal? R~vic~:w (jf rc5ulc5 t!'om Icccnt clin.ical trials. Am J AllUi 1091; 91::.u-ppl J.B, J 05-1 7S.9.'1~"ll:i: OF, LCV\T1:sD, Brunt JNH, et al. E![t:Cl:i 011 .COI'OlUJ."y artt:ry. ch$ea.se-;:oi.jlpid-lowctlnJijl: diet, o.r diet plus Cho'~9Tyrnm1ne, In the St..'Thol11a{' .At:herQsclero~n~ KeI,.>re'ilS1OJ.lSru.dy ($T~'\.n.S). 1.."l'/'1a.z 19Q2.i 339; 563-569.: :: :10 Ternp1~ NJ, 'Walk~r AR1.:J. .HI00Q c:h.olcst.~rol anrl c.nrnoary hea~ dis~se.: .11. ~:~e~nfn~i~~~~~~~~g {:~sS::,~~d 4 ~~tl:~1~~'~;1~~iloweIing and m.orta1i~~~h<:: Il'niX'rtanc~ of ('on,id~ring initiall~vt:l of Il~k. HMJ lIJY:J, 306: 13-67.1373.12. RnmMY Lb.'I'cu WW, Jack50n rI't. Dietary rc.c1uciion of senlIU \,;hQl~te(ol.concc:t:ltt'9rinn~ time LU th~.uk aij:ail~. DM.7 199J; 303: 953-9~7.1"j n.arr..s~y I.'F., Yeo \VW, JBcksun 1-'1<.,H<:uue chokst.(:rol t~st:i.n.g. LaYtcu: ] 9()~j341: 3JJ-314.\4. l<.ns-.uthe:-rton PM, Krummel D, RusseU J\1.J:::;, 81 ;4;. Th.e effect -of di~t Qnvlu:sma hpids) )-ipoprOtein9. and c.oronary he an di~t:"si:. j Am DIll: .-4.1'.1'01..1C')R~; RR: 1.373.1400.15. Connor SI., Connor WE, COJ.-cnary heart disease: prevenrion and 'tT.e~rmenrby nutritional changf'!. Tn: Carroll KK, ed. Di.~,~ NI~tTit£c» and He.alrh.l\.lonucaL 1\'kGUI-Qt1cr:n"::; Ul1iy~r:iilY Pn:1f.;h 1989; 3:).Y().16. Ku.~hn~r 1{T-'. Long.tc::rm cQmplianci' wirh a hpid-lowt!:r.ill~ diet. Nulr Rev1993; 51, 16-1".)7, Anderson~',D~akinio DA, l'!oor~ L'I." Smith RM. Whids SE. Die.'t3ryfibc-.r Rnd cOronary heart diSII::.ltoc:. C'nt RIif"l.1FCQd-Sd l.luz,' 1990; 29: 9'"i-147.18. Walker ARP. Dier Ilnd arheros(.:h:ru~is. Lc.l,j'~I 1 ~~~, I: 565-5661 SI. ~'il1~t1: \X7C. SC!i1T1pfer tvI], 1-.-1..m::sulJJE. to' !:.Ii. Int<Akc of tram f:atty a.cid, an.dJ:l~k of coronary hCl1.rt dis~a5i~ nmong wom~n. Lanul 1993; 341: 5!:::11.~!:$S.20. Tzonuu A, Kal;ul.didi A. Trichoponlo"l i\, e.I ai. Dict und o;;OTQUil.ryhc;~'t d18-~~f~ra. ~a~~-~I)J)trol study il"a.Athens, Greece-, Epid~l,"t'Ql"fJY 1<)9~j 4: 5] 1-21. Gt"Y KF, MO'9cr GK, Jordan P, tJl "l. lil.cJ:c=:asce-d.r:l!ok of cardiovasc\J.1ar diseas.e~c ~uboptima.i pla5mo\ c:on~C":ntrBtjnns of essenci3.J anl14JXitl;jll~S: an epidernJ.o-!l:JIitH.:;:t1update- with s.pecial Olttcnr:iQn ro C"RrOI:'f".oeand ViI.aIDm C. .-im:J (;J1nNu.lr- 1993j 57: 787S-797S.22. RInck Gt Pa(lt:I'~l)uB":Su.bar A. rn.!it, vC!'I;c:tiitbks, .and can(.;~r pr.~vf':nTi()n: areview of ~pidem10Iog1c.a) eVH1en{.;~. fo..'U~TCQJU.'1111992; 18: 1-2923. D"..Irr ML. Fish Ancl i.qchaemk ht:an dl$e.ase, In: Simopoulos !\P, ~d.NULnlJ07J a1'.d Fi~,ltu.J~'tJ Hu~lf;" and DiSC":HC. Ba~el: KaI~t:r~ 1 \}I», 49-60.24. Burr 1\lL. rl:.hiJy Al'vi. Gilb~rt: JF. u a.l. F.rT£':c.r~ of chYng~";3 in till, tish andt,hre inUdkc.s QU death and myocardial rc:1nfftrCfion: dier and reint3.t'l:tlunrrial (DART). Lancut lc)f:l9; 2: P:>-I-~t61.25. A:ppel LJ. Milif~r P.!{, .seidJ~r AI. '.,);ihelton PK. Do~s $uppkmt-ntlltion ofd!c.t wi.th 'fis,h oil' rC'dlJC:C: h]nod pre::i:.;urt:? A ,U:.ieta-analysis of contc:oUcd din.-l~yl tn.a.ls. An;;h 1m.m i'v1."a I ~93; 153! 14-?:9 11 ~R.26.~~;~~o~r~~~~~;:~?~:i~i :j~l~~ls.1~v.rQ~~1~~O~e;ri~t;t~7 s;rTltr~~~~~;~~~BM71~~I; 302, 819-82<1.~7. "Temple NJ, Burkin DP, f."ct~. Wl>swm DiH~Q~.~'; 'TIlt/i.T D~e:ary PU'V~l1rio'1 QYldRf'-ver:.;~bmLY. Totowa., NT: HUI!'\aI1f1. Prl!!;~ (in pres~). -SUPPI.EMENT TO SAMJ. JULY 1994 ::j,1:

Diet, blood lipids and coronary heart disease: current controversies

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Diet, blood lipids and coronary heart disease: current controversies

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