N O W JACOBSON. Iowa S t a t e University

Transcription

1 THE CONTROVERSY OVER THE RELATIONSHIP OF ANIMAL FAT TO HEART DISEASE* N O W JACOBSON Iowa S t a t e University Much has been w r i t t e n on t h e r e l a t i o n s h i p o f d i e t t o heart disease and almost anything can be "proven" i f one s e l e c t s t h e appropriate references The b a s i c problem which ha8 p r e c i p i t a t e d the debate on d i e t a r y f a t and other r e l a t e d controversies is the extremely high m o r t a l i t y i n the United S t a t e s from cardiovascular d i s e a s e There are about 600,000 deaths annually f r o m complications of a t h e r o s c l e r o s i s and about 1,000,000 from a l l types of cardiovascular t r o u b l e It has been estimated t h a t i f we could eliminate cancer as a cause of death i n t h e US the average length of l i f e would be extended about 2 1/2 years, b u t if w e could eliminate cardiovascular disease, t h e average length of l i f e would be increased 8 t o 10 years These s t a r t l i n g s t a t i s t i c s have l e d t o a g r e a t p r o l i f e r a t i o n of research t o determine t h e cause of t h e i n o r d i n a t e l y high incidence of cardiovascular d i s e a s e i n the U S a s compared t o other populations and t o develop means whereby it can be reduced The following are some of the f a c t o r s which are o f t e n mentimed a s possible contributors t o our problem: 1 Heredity--most c e r t a i n l y a c o n t r i b u t i n g f a c t o r 2 Stress--Many believe t h i s i s a very important f a c t o r b u t early s e t t l e r s i n the US must have been stressed Germans and Norwegians c e r t a i n l y were s t r e s s e d during World War 11; yet coronary heart d i s e a s e was markedly reduced 3 Smoking ( e s p e c i a l l y c i g a r e t t e s ) --shown t o be involved, but people i n some countries with much l e s s coronary heart disease (0) smoke about as much a8 we do 4 Leck of exercise--relationship not c l e a r l y are strongly suggestive established but d a t a 5 Diet--some components which have been suggested as f a c t o r s are: t o o many c a l o r i e s, t o o much sucrose, t o o l i t t l e of c e r t a i n vitamins such as vitamins E and C, t o o l i t t l e of c e r t a i n minerals such as magnesium and chromium, t o o much s a l t (NaCl), t o o much f a t ( o r saturated f a t ) Data are a v a i l a b l e t o support o r c o n t r a d i c t (as you p r e f e r ) each of t h e s e suggested r e l a t i o n s h i p s and many o t h e r s 6 Hypertension--probably a contributing f a c t o r but c e r t a i n l y not only one * the Presented a t t h e 25th Annual Reciprocal Meat Conference o f the American Meat Science Association, 1972

2 239 7 Hypercholesteremia--associated with atherosclerosis but i s t h i s a cause and e f f e c t relationship? 8 Obesity--some relationship but not t h e principal f a c t o r The last three m i g h t be considered secondary ( i e, they themselves a r e abnormalities which have t h e i r own s e t of causes) I believe we i n the animal industry should be interested i n t h i s subject because of: 1 The t r a g i c number of deaths due t o CKD and other cardiovascular troubles, and 2 The need, in my opinion, f o r the a n a l industry t o be thoroughly knowledgeable so t h a t it can: a Refute unwarranted c r i t i c i s m of i t s products b Make appropriate a l t e r a t i o n s o f some of i t s products i f evidence ever shows d e f i n i t i v e l y t h a t such changes are needed O u r research group has, f o r many years, been engaged i n research related t o cardiovascular disease, with p a r t i c u l a r emphasis on the relationship of d i e t and exercise t o blood plasma cholesterol and the development of atheros c l e r o s i s Ruminants were chosen a s our principal models because of the s i m i l a r i t y of a r t e r i a l changes in some of these species t o a r t e r i a l changes i n humans, the a d a p t a b i l i t y of some of these species t o surgical a l t e r a t i o n s necessary f o r many of our studies, and several other advantages Now l e t us turn t o specifics, some of which I w i l l i l l u s t r a t e with slides One sometimes hears t h e statement that t h e reason we have s o many heart attacks i s that we l i v e longer and m u s t d i e of something The f a c t s are, hmever, t h a t people in m y other countries, with a much lower incidence of cardiovascular disease, l i v e longer than we Cardiovascular disease is a broad term and I want t o r e s t r i c t q y comments largely t o atherosclerosis ( l i p i d deposition and other degenerative changes i n the a r t e r i a l wall) In many species, as the animal grows older the walls of t h e arteries thicken, sometimes t o t h e point of s e r i m s l y r e s t r i c t i n g blood flow and of precipitating formation of thrombi I t has been amply demonstrated, w i t h experimental animals, t h a t degenep a t i v e changes i n the a r t e r i e s can be hastened by c e r t a i n d i e t a r y manipulations, p a r t i c u l a r l y when these changes a r e extreme Feeding high l e v e l s of cholesterol, accompanied by f a t, causes higher blood plasma cholesterol and increases l i p i d deposition in t h e w a l l s of t h e a r t e r i e s The maxjntum e f f e c t from a given amount of d i e t a r y cholesterol usually has been seen when t h e l e v e l of f a t is about 25 t o 30 times the l e v e l of cholesterol But, many such experiments have involved feeding cholesterol a t l e v e l s much higher than those usually encountered in n a t u r a l diets (eg, t h e equivalent, some

3 240 cases, of t h e cholesterol intake of a man eating several dozen eggs d a i l y ) Certain d i e t a r y manipulations can lower plasma cholesterol a l s o Usually, but certainly not always, t h e "saturated" fats cause somewhat higher plasma rllolesterol than do t h e more unsaturated fats Why t h i s happens i s not c l e a r Some believe it involves only a redistribution of cholesterol i n the various t i s s u e s of the body We must be careful in manipulating d i e t s so t h a t w e do not create problems as great or greater than those w e are t r y i n g t o correct I n one study, death r a t e from complications of atherosclerosis w a s lowered by increasing unsaturated and decreasing saturated f a t s I n t h e d i e t of men but incidence of cancer was increased and the o v e r a l l death r a t e was not a l t e r e d Also, there i s s m e evidence that unsaturated fats may decrease longevity by hastening the aging process i n the t i s s u e s F u r t h e m r e, changing one d i e t a r y component may a f f e c t requirements f o r others For example, an increase in d i e t a r y unsaturated f a t t y acids g r e a t l y increases t h e requirement f o r vitamin E The proportion of unsaturated f a t t y acids i n m i l k, meat and eggs can be g r e a t l y increased, if desirable, by manipulation of t h e d i e t of the animal B u t some questions and problems a r e involved, not t h e l e a s t of which i s this: What i s t h e e f f e c t of feeding a d i e t high in unsaturated fats over a long period of time? Some animgl experiments suggest there may be some problems Certainly, t h e ultimate e f f e c t s of various major dietary manipulations on cardiovascular disease and other parameters is f a r from clear Let us now look a t a few other f a c e t s of this s i t u a t i o n According t o best estimates, the per capita consumption of saturated fats and cholesterol has changed very l i t t l e i n the U S during t h e p a s t 60 years Yet t h e i n c i - dence of deaths from coronary h e a r t disease has increased dramatically During t h e same period, consumption of unsaturated f a t s has increased Milk and meat have been c r i t i c i z e d because of t h e i r comparatively high content of saturated f a t t y acids but many countries which consume f a r more m i l k and milk products per capita than w e do have a lower incidence of coronary h e a r t disease And countries with both high and low meat consumption have less of this problem than we Atherosclerosis i s by no means r e s t r i c t e d t o humans It has been observed in many species (eg, swine, c a t t l e, deer, caribou, rabbits, pigeons, dogs, ducks, pheasants, sharks ) Whether it i s a common cause of death in any of these species, except under experimental conditions, i s not known An extensive comparison of I r i s h i n Ireland w i t h I r i s h in Boston was conducted cooperatively by personnel of t h e Harvard School of Public Health and the T r i n i t y College School of Medicine in Dublin A t o t a l of 1,994 middle aged men were involved, including about 500 pairs of brothers, one of whom lived i n Ireland and t h e other i n Boston I r i s h in Ireland had much l e s s atherosclerotic heart disease Brothers l i v i n g in Ireland consumed more calories, more complex carbohydrates, more b u t t e r (78$ of c a l o r i e s vs 2 8 i n Boston) mre magnesium, more f l u o r i n e ( i n t e a ), more m i l k, more

4 241 s t o u t and more beer and had more physical a c t i v i t y b u t l e s s coffee, l e s s whiskey, and l e e s gin, and less unaaturated f a t (4596 of c a l o r i e s v s 14@ f o r Boston) There w8s no s i g n i f i c a n t d i f f e r e n c e in serum cholesterol, blood pressure, c i g a r e t t e emking o r proportion of c a l o r i e s from f a t Body weight and t h e number of abnormal electrocardiograms were higher i n t h e Boston Irish Autopsies shuwed much earlier a t h e r o m t o u s involvement in t h e coronaries and a o r t a s of the Boston I r i s h One of t h e key differences, if not t h e p r i n c i p a l one, seemed t o be t h e much greater physical a c t i v i t y of t h e men in I r e l a n d Much must yet be learned before t h e shocking death r a t e f r D m cardiovascular disease i n the U S can be reduced t o a more acceptable l e v e l Any attempt t o a t t r i b u t e the problem t o only one f a c t o r i s u n r e a l i s t i c and misleading; many f a c t o r s undoubtedly a r e involved It would, however, seem prudent t o exercise great caution in promoting major changes in t h e American d i e t (except t o p r a c t i c e moderation ) In nny opinion, two of the major c o n t r i b u t o r s t o our problem in t h e US are (1)overindulgence in food and drink, and ( 2 ) underindulgence i n physical exercise We need t o g e t t h e s e back i n balance Furthermore, many more l i b e r t i e s can be taken i n t h e d i e t i f it is counterbalanced by appropriate physical a c t i v i t y A M MULLINS: Zadies and Gentlemen your conference chairman w a s kind enough t o l e t me introduce some people t h i s morning before t h e conference program g e t s under way F i r s t, I would l i k e t o introduce t h e new d i r e c t o r s t o you The names w e put on t h e board yesterday The new d i r e c t o r s f o r the American Meat Science Association f o r next year are James A C h r i s t i a n Jim, are you i n t h e audience? Jim's a hard worker and a l a t e s l e e p e r Fred P a r r i s h, Fred i s up i n t h e v i s u a l a i d stand i n the back a n d D r Warren Tauber, Union Carbide, Warren where are you? I n t h e back and up i n t h e right hand corner Congratulations t o a l l of y m gentlemen, We've introduced t h e incumbent d i r e c t o r s previously There's one o t h e r man i n t h e audience that I would l i k e t o introduce and I know most of you know t h i s man by name but I ' m s u r e that t h e r e are a lot of people i n the audience t h a t haven't had t h e p r i v i l e g e of meeting him personally and that i s D r J L Lush of t h e I D w a S t a t e University, a renowned animal breeder and g e n e t i c i s t We're delighted t o have you with us t h i s morning, D r Lush I s a w you in t h e audience Monday and d i d n ' t have the opportunity t o introduce you a t that time C E ALLEN: The next r e p o r t i n g t h i s morning i s the Meat Cookery Committee, and t h e chairman of t h i s committee i s M i s s Reba Staggs, from t h e National Live Stock and Neat Board, and I t h i n k r a t h e r than do b e t t e r than Dave Stroud d i d yesterday i n introducing Reba, I'll only say t h a t she i s widely laown throughout t h e United S t a t e s, and of course we a l l know her through h e r a c t i v i t i e s a t t h e National Live Stock and Meat Board, so, Reba, we're looking forward t o hearing from your committee, And I see t h e y ' r e a l l i n t a c t up here i n f r o n t, so you can have t h e program

5 242 REBA STAGGS: Thank you, D r Allen The Meat Cookery Committee members a r e l i s t e d on page 12 i n your program I ' m not going t o c a l l t h e i r name8 but I do want t o make t h i s public announcement--that each one on the committee has made a very important contribution I n deciding the subjects t o be discussed t h i s morning, it was not so d i f f i c u l t t o rind a great number of subjectr: i n t h i s area, but was more c h a l l e n g b g t o decide just w h a t subjects w e would discuss We hope that a f t e r the program t h i s morning you w i l l f e e l an inroad has been made in your thinking and that the two areas a r e not only important t o meat processing but a l s o t o meat as prepared i n the home Since we don't eat meat raw, it would seem t h a t both presentations should be of i n t e r e s t t o a l l of us We w i l l have the two presentations and, as indicated i n your program, following them there w i l l be a question and answer period O u r f i r s t speaker t h i s morning i s a member of this organization H e holds membership in many very prominent organizations, but I'm not going t o take your time t o n a m e a l l of them because that would take h i s time f o r speaking H e took h i s BS degree at Ohio S t a t e i n Food Technology, h i s further academic training a t t h a t university Fn biochemistry, he has been associated with the Hy-Grade Packing Company as a food technologist i n t h e research deprtment, he has been a professor, and associate professor o f biochemistry a t Purdue University, and he i s currently employed by Peter Eckrich & Sons, Inc H e went t h e r e in 1965 as a chemist i n the Research Department;, is currently t h e Manager of' the Basic Research of that organization I present t o you, D r Ned Draudt D r Draudt w i l l speak on "Changes Fn Meat During Cooking"