The American Journal of Clinicai Nutrition 42: AUGUST 1985, pp 190-197. Printed in USA© 1985 American Society for Clinical Nutrition

Plasma lipid and lipoprotein response of humansto beef fat, coconut oil and safflower oil13

Raymond Reiser, PhD, JL Probsifield, MD, Abraham Silvers, PhD, LW Scott, MA, RD,ML Shorney, RD. RD Wood, PhD, Barbara C O’Brien, PhD, AM Gotto, Jr. MD, D Phil,and William Insull, Jr, MD

ABSTRACT This study’s purpose was to evaluate the fasting human plasma lipid andlipoprotein responses to dietary beef fat (BF) by comparison with coconut oil (CO) and safflower

oil (SO), fats customarily classified as saturated and polyunsaturated. Nineteen free-living normo�lipidemic men aged 25.6 ± 3.5 yr consumed centrally-prepared lunches and dinners of commonfoods having 35% fat calories, 60% of which was the test fat. The test fats were isocaloricallysubstituted, and each fed for five weeks in random sequences with intervening five weeks ofhabitual diets. Plasma total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), andlow-density lipoprotein cholesterol (LDL-C) concentrations among individuals follows the same

relative rank regardless of diet. Triglycerides (TG) concentrations among individuals also maintaintheir relative rank regardless of diet but in a different order from that of the cholesterols. PlasmaTC, HDL-C, and LDL-C responses to BF were significantly lower and TG higher than to CO. Ascompared to SO, BF produced equivalent levels of TG, HDL-C, and LDL-C and marginally higherTC. Thus, the customary consideration of BF as “saturated” and grouping it with CO appearsunwarranted. Am J Clin Nuir l985;42:l90-l97.

KEY WORDS Diet fats, beef fat, safflower oil, coconut oil, saturated fat, polyunsaturated fat,

plasma cholesterol, triglyceride, high-density lipoprotein cholesterol, low-density lipoprotein cho-lesterol, plasma lipids, lipoproteins

Introduction

The effects of dietary beef fat (BF) uponplasma lipid and lipoprotein concentrationsare incompletely described although this is aprominent fat in the American diet, andmany diet investigations have described theeffects on plasma lipids of most other dietfats (1-4). BF is commonly considered to bea saturated fat, including it in a group withcoconut oil (CO), cocoa butter, hydrogenatedvegetable oils, butterfat, and swine fat, andattributing hypercholesterolemic effects to it.Of these fats, only CO appears to consistentlyelevate plasma cholesterol when comparedwith other fats (5). Nonetheless, dietary ad-visories recommend restricting consumptionof BF (6-7). The effects of BF on plasma

190

‘From the Department of Medicine (JLP, AS, LWS,MLS, AMG, WI), Baylor College of Medicine, Houston,TX; and Department of Biochemistry and Biophysics(RR, RDW, BCO), Texas A&M University, CollegeStation, TX.

2Add� reprint requests to: Raymond Reiser, PhD,Department of Biochemistry and Biophysics, Texas A&MUniversity, College Station, TX 77843.

3Supported in part by the Diet Modification Sectionof the National Heart and Blood Vessel Research andDemonstration Center, Baylor College of Medicine andthe Methodist Hospital, a grant-supported project of theNational Heart, Lung and Blood Institute, NationalInstitutes of Health, Grant No HL 17269, the ClinicalResearch USDHS Grant No 02-260-008 the Lipid Re-search clinics (LRC) Contract No HVI-2l56-L, the Na-tional Live Stock and Meat Board, the Texas CattleFeeders Association, and the Standard Meat Co of FortWorth, Texas.

Received July 16, 1984.Accepted for publication January 1, 1985.

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HUMAN LIPIDEMIC RESPONSES TO BEEF FAT

lipids and lipoproteins need to be defined toserve as a basis for rational recommendations.

The present study aims to define the effectsof BF more specifically by comparing theresponses of fasting plasma lipids and lipo-proteins to BF, CO. and safflower oil (SO)when fed to free-living normolipidemic men.

Methods

Experimental design

This study was divided into seven feeding periods offive weeks each, a duration sufficient to establish theeffect of each diet on lipids and lipoproteins (8). Thebaseline diet fed during the initial period and subsequentthree odd-numbered periods, consisted of the participants’habitual foods taken ad lib at a caloric level to maintainconstant weight. The study diets fed during the threeeven-numbered periods consisted of the foods containingone of the three study fats for lunch and supper, andlow fat, high carbohydrate foods for breakfast. Uponenrollment, the men were randomly assigned among sixtreatment groups which would have the three test dietsin different sequences in order to randomly distributeany bias in results due to the order of the test diets.

The initial period was to establish the control baselinevalues for plasma lipids and body weight, to determinethe characteristics of habitual diets, and to instruct andacclimate the participants to the operation of the study.The subsequent odd-numbered peiods were also with thehabitual diet to allow the effects of the preceding testdiets to dissipate and the plasma lipids to return tobaseline values, and to provide the subjects relief fromthe rigors of adherence to the test diet procedures.

Fasting bloods were drawn at the end of each of thelast two weeks of each diet period with measurementsof plasma total cholesterol (TC) and triglycerides (TG).The last plasma obtained in each time period was alsoanalyzed for the concentrations of high-density lipoproteincholesterol (HDL-C). The two successive measurementsof TC and TG were to determine that the lipid changeswere established. The mean values of the fourth andfifth weeks of each of these periods were used to evaluatethe final lipid changes. The intra-subject variance wasless than 3%. The intra-assay variance is 3% for cholesteroland triglycerides.

Subjects

Nineteen healthy volunteer male medical studentswere randomized among six treatment groups with dif-ferent test diet sequences and subsequently completed 2or 3 diets. All subjects had average normal values fortheir fasting plasma lipids during the study as evaluatedby the age- and sex-specific values observed in theAmerican population groups of the prevalence study ofthe Lipid Research Clinics. The subjects were recruitedfrom the Texas Medical Center community in Houston,Texas. Potential subjects were excluded if they weretaking plasma lipid-lowering medication or had significantorganic, psychiatric or metabolic disease, hyperlipidemia,alcoholism or hypertension.

The study was approved by the Baylor College ofMedicine Human Research Committee. All participantswere volunteers, were completely informed about thetrial, and signed informed consent forms at entry.

In order to guide food intake during the study, weightwas measured in the clinic and at home under standardconditions, without shoes and suitcoats.

Food preparation and distribution

Foods for two meals each day, lunch and supper,were prepared and provided by the central food serviceto each participant at no cost. These meals were composedof natural foods, with calories distributed as follows:protein 15%, carbohydrates 50% and fats 35%. Sixtypercent of the fat calories were from the test fats. Thesestudy fats (60% of total fat) were approximately 25% inthe meat dishes, 25% in bread spreads, 25% in filled icecream, and 25% baked in cookies. The non-study fat(40% of total fat) was distributed in the following pro-portions: 45% from fish, chicken or turkey, and skimmedmilk, 49% from a lard-based margarine, 3% from bakedgoods, and 3% from vegetables and grains. The propor-tions of fatty acids of this margarine were: 14:0-1.2%,16:0-29.1%, 17:0 less than 0.25%, 18:0-12.3%, 16:1-2.0%, 17:1 less than 0.25%, 18:1-46.7%, and 18:2-7.7%.

The food consisted of the main entrees of meat,poultry or fish, a major starch food, and green vegetables.Standard menus for ten different meals over five dayswere prepared, and these meals were served in consecutivecycles every five days to provide variety and to avoidcycling the same meals on the same days of the week.The prepared foods were dispensed twice weekly fromthe central source. The participants provided and con-sumed a standard breakfast according to their habits,largely carbohydrate and low fat. According to instruc-tions, they supplied and prepared their own beverages,fresh leafy vegetables, and fruit for snacks and desserts.Provisions were made for cold lunches when necessary.The test meals were modified by the use of various spicesduring the study to meet the taste preferences of thesubjects. Adherence to the test diets was judged to begood on the basis of self report and regular interviewswith the study nutritionists.

Test fats

The BF, CO, and SO were donated or purchased.(See Acknowledgements.) Their fatty acid composi-tions were determined by gas-liquid chromatography(Table 1).

Filled ice cream

Ice cream mixes were prepared at the Dairy ScienceSection, Department of Animal Science, Texas A&MUniversity and were to contain 40.76% total solids, 16of which was of the test fats. Fat consisted of BF, SO,or CO.

Other diet constituents

The remainder of the fat in the test diets consisted offat from poultry, fish, and dairy foods. TC intake wasapproximately 450 mg/day, one half of an egg yolk beingadded/day to the CO and SO diets. With this addition,the TC in the diets equals the amount in the BF diet.

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192 REISER ET AL

TABLE 1Fatty acid composition of diet test fats

Diet fat

Fatty �ids

14:0 14:1 16:0 16:1 17:0 17:1 180 18:1 18:2

%

Beef fatSafflower oilCoconut oil

2.1T

19.9

0.4-

-

24.76.28.0

2.1T

-

1.0-

-

0.5-

-

18.61.71.8

48.510.9

5.5

2.180.3

1.4

T = Denotes detectable quantities less than 0.25%.* = Other fatty acids present are 8:0, 3.2%; 10:0, 4.8%; and 12:0, 55.4%.

The diet was balanced in composition and nutritionallyadequate. Standard menu plans were established for allfeeding periods. The amount of food for each individualwas quantitatively adjusted to maintain a constant bodyweight according to caloric requirements as determinedby pre-study dietary histories They varied from 1700 to5000 calories/day, with a mean of 3400. Alcoholicbeverages were permitted provided that the intake wasmoderate and kept constant throughout the study at theparticipant’s customary level.

Clinical laboratory tests

Plasma lipid and lipoprotein determination

Plasma lipid and lipoprotein concentrationswere measured after a twelve-hour fast usingstandardized blood-letting techniques. Deter-minations of TC, TG, and HDL-C were donein the Lipid Research Clinical Laboratoryaccording to previously reported methodology

(9) using the regularly monitored qualitycontrol by the Center of Disease Control(CDC). Plasma low-density lipoprotein cho-lesterol (LDL-C) was calculated by themethod of Fnedewald and colleagues (10).

Data management and analysis

Statistical analysis on the 19 subjects usedthe 4 and 5 wk TC and TG values and theirmeans, and 5 wk HDL-C values. The 5 wkLDL-C values were calculated. The data wereassembled by fat regardless of diet sequence.The analysis assumed that a) the 5 wk dietperiod is long enough to eliminate carryovereffects, and b) there is no long-term trend inthe response variable br any of the subjects.

In order to utilize the habitual diet lipidvalues to obtain the within-subject variance,randomized block analysis of variance wasperformed upon the total cholesterol andtriglyceride values for the three test fat dietsand their respective preceding habitual diets,

with individuals as blocks and 6 diet periodsas treatments. These analyses were not pos-sible on the HDL-C and LDL-C because toomany values were missing.

Analyses of all plasma lipids were per-formed upon values for the three test fatdiets. The model for these analyses of variancewas also that of a randomized block, with

individuals as blocks and test diets as treat-ments. Due to the lack of balance of treat-ments (12 men completing all the test diets,16 men completing the SO diet and 17 eachcompleting the CO and BF diets), a generallinear model analysis was performed. In ad-dition to significant tests for diets in general,so-called adjusted mean treatment meanswere produced (least square means in SAS).Also produced by the analysis are tests ondifferences between adjusted treatment meansof individual diets. Since these were notpreplanned comparisons, the statistical sig-nificance of the individual comparisons aresomewhat overstated.

Results

All subjects had normal lipid values duringthe periods of habitual diets and the diets oftest fats (Table 2). Twelve men completedthe study with all three diets Additionally,three men completed the BF and CO, twomen the BF and SO, and two men the COand SO diets, 19 in all. Seventeen mencompleted the BF and CO diets, and 16 theSO diet.

Comparisons between 4 and 5 wk valuesfor TC and TG for each test fat diet periodand each habitual diet period showed nosignificant differences. This indicated that thetest periods were of sufficient duration toachieve stable treatment effects, and that the

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HUMAN LIPIDEMIC RESPONSES TO BEEF FAT 193

TABLE 2Plasma lipids and lipoprotein cholesterol concentrations of men, twenty-six years old, consuming habitual dietsand test diets with 21% of calories as coconut oil, beef fat,or safflower oil for 5 weeks*

Totelt

cholesterolHDL-q

obeerved means LDL.q Triglyceridest

mg/dI ± SEM

Habitual:pre-B9 (17)1 157 ± 9.0 44 ± 3.2 99 ± 10.7 83 ± 8.9pre-CO�(l6) 158± 5.3 45±3.0 96± 5.8 80± 7.5pre-SO�(l7) 152±6.7 42±2.7 96± 7.2 88±9.6

Test:BF(l7) 155±3.0 40±1.2 98± 4.5 88±3.5CO(16) 168±3.0 46±1.1 110± 4.1 78±3.6SO(l7) 141±3.1 40± 1.2 90± 4.7 72±3.7

p value&’

BF vs CO 0.01 0.01 0.08 0.01BF vs SO 0.01 0.07 0.24 0.06CO vs SO 0.01 0.02 0.01 0.39

* 12 completed all 3 diets, 2 the BFand SO diets, 2 the CO and SO diets, and 3 the BFand CO diets; 17 completed

the BF, 17 the CO, and 16 the SO diets.

t Average of fourth and fifth weeks on the diets. There was no significant difference between the two.f Fifth week values.§ BF = beef fat, Co = coconut oil, SO = safflower oil.tSee section on Data Management. p values> 0.05 are not significantly different.I Values in parentheses represent number of participants.

plasma lipid effects of the habitual diets werenot changing significantlyduring each obser-vation period. Comparisons of plasma lipidvalues among the habitual diet periods priorto each test fat diet showed no significant

differences (Table 2).These observations sub-stantiated the design assumptions that thepretreatment habitual diets were not differentin their lipid effects, and that there were nosignificant carryover effects from previousdiets of test fats.

The ingestion of CO compared to SOresulted in significant differences in all plasmalipids except TO, respectively: TC 168 and141 mg/dl; HDL-C 44 and 40 mg/dl; LDL-

C 110 and 90 mg/dl; TO 75 and 80 mg/dl(Table 2). Analyses of test diet responsesusing the habitual diet values similarly showeda significant difference for TC, p <0.05, butno significant TO difference. The lower cho-lesterol levels with SO were due to lowervalues of both LDL-C and HDL-C.

The ingestion of BF compared to COshowed significant differences for all lipidsexcept LDL-C. TC and HDL-C were lowerwith BF, 155 versus 168 mg/dl and 36 versus44 mg/dl respectively, and TO higher,

89 versus 75 mg/dl. The LDL-C concentra-tion was insignificantly lower, 98 versus

110 mg/dl.The ingestion of BF compared to SO

showed only TC to be significantly different,155 versus 141 mg/dl respectively. This wasaccompanied by insignificantly higher LDL-C, HDL-C, and TO.

Tables 3 and 4 show that the concentrationsof the plasma lipids and lipoproteins continuein the same relative rank regardless of changesin absolute values affected by dietary manip-ulation. The rankings are not all perfect indirection of changes in magnitude, probablydue to variations in metabolic response andsome crossovers among the quartiles.

The tables also show that TC, HDL-C andLDL-C concentrations follow one order, Ta-ble 3, and TG a different order, Table 4.

The values in the tables cannot be averagedand compared to Table 2. There are only 17participants represented in Table 3, insteadof all 19 who consumed 2 or 3 diets, becausethe BF values were used to establish rankand subjects 4 and 10 did not eat the BFdiet. Furthermore, since subjects 14 and 35did not participate in the CO diet, those

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194 REISER ET AL

columns also represent only 17 subjects. Also,participants 16, 18, and 33 did not participatein the SO diet.

Discussion

The present study was designed to describethe response of humans to diet BF becauseof the importance placed on ruminant fatand meat in diet recommendations by variousgovernmental agencies and public healthgroups, its prominent role in the Americandiet, and the paucity of human studiesof BF.

The American Heart Association (AHA)(11), the Senate Select Committee on Nutri-tion and Human Needs (7), the US Depart-ment of Agriculture (USDA) and Departmentof Health, Education and Welfare (12), andthe Office of the Surgeon Oeneral (13), haverecommended the partial substitution ofpoultry and fish for ruminant and swinemeats. This recommendation has been madebecause BF is said to be saturated, to giverise to hypercholesterolemia, and therefore,is expected to increase the risk of coronaryheart disease. Our data suggest that BF maynot raise plasma cholesterol.

The hypothesis that saturated fats are hy-percholesterolemic is based mainly on studieswith CO and polyunsaturated vegetable oil,and on regression equations which appear torelate plasma cholesterol levels to diet levelsof saturated lauric, myristic, and palmiticacids on one hand, and polyunsaturated fattyacids on the other, with a factor for cholesterol(14). Saturated acids of 18 carbons or more,of 10 carbons or less, and of monoenoicacids are said to be neutral. Both the resultsof the studies with saturated fats other thanCO. such as hydrogenated vegetable oils (5),and the use of regression equations (4, 14),have been challenged (15).

There appear to be no well-defined humanstudies testing BF, but there are some usingbeef tissue, the results of which can be as-cribed to its constituent fat. Thus, Hodges,et al (2), found that university students withserum cholesterol of about 150 mg/dl main-tained that value when consuming normalor polyunsaturated beef. Students with serumcholesterol of about 190-195 mg/dl re-sponded to normal beef with cholesterol levels

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HUMAN LIPIDEMIC RESPONSES TO BEEF FAT 195

TABLE 4Plasma triglyceride responses to beef fat, coconut oil and safflower oil arranged by quartiles of triglyceride responseto habitual diet

Subjects

D�a

Habitual’ BP C0 S0

mg/d!

3, 5, 28, 32, 34 (5)1 61 (5) 68 (5) 58 (5) 531, l8,* 20, 33, 35� (5) 81 (5) 86 (4) 83 (4) 5911, 144 l6,� 19, 30 (5) 91 (5) 101 (4) 93 (4) 814,t l0,t 27, 31 (4) 125 (2) 112 (4) 85 (4) 101weighted means 88 88 78 72

* BF = beef fat; CO = coconut oil; SO = safflower oil.

t Did not participate in BF diet.f Did not participate in CO diet.§ Did not participate in SO diet.“Includes all baseline and between-diet values.#{182}Values in parentheses represent numbers of participants.

of 210 mg/dl and to polyunsaturated beefand dairy products with values around 165mg/dl.

In a study comparing the effect of beefwith fish and poultry, no difference wasfound in plasma cholesterol (16). Six subjectswere involved in a study comparing normaland polyunsaturated ruminant fats, includingmilk products (1). The normal fats produced0, 5.5, 6.0, 8.0, 12 and 14% higher serumcholesterol levels respectively in the six sub-jects. In a 1957 study BF at 40% of caloriesproduced an average serum cholesterol of 20mg/dl higher than corn oil, 180 mg/dl vs 161mg/dl (8). Prolonged consumption of COwas reported for two groups of native Po-lynesians who consumed 63% and 34% re-spectively of their food energy from CO (17).The respective average serum cholesterol val-ues (males plus females ages 15-64 years)were 209 mg/dl and 172 mg/dl. The authorsobserved, however, that “Vascular disease isuncommon in both populations and there isno evidence of the high saturated fat intakehaving a harmful effect in these populations.”

The three fats tested did have some signif-icantly different effects on the plasma con-centrations, especially BF vs CO, and SO vsCO. Increases or decreases from the concen-trations were observed with the habitual dietsbefore and between the CO and SO diets.However, there was no significant differencebetween the BF and habitual diet values.

In the present study BF, compared withCO, was associated with significant differences

in the concentrations of almost all the lipidstested: TC was lower by 13 mg/dl (8%),HDL-C lower by 8 mg/dl (18%), and TOhigher by 14 mg/dl (19%). Only the differencein LDL-C, lower by 12 mg/dl (11%), was not

significant. Clearly BF was different fromCO. BF when compared with SO was asso-ciated with significantly higher TC levels by14 mg/dl (10%), but not significantly different

with respect to HDL-C, LDL-C, or TO.The study subjects showed the anticipated

responses to the reference fats, CO and SO.BF, though intermediate between the COand SO reference fats in its effects on TC,affected insignificant differences in its effecton LDL-C, HDL-C, and TG as comparedto SO.

An explanation for the lower plasma TOaccompanying CO ingestion may be foundin differences in the transport and relativerates of deposition and catabolism of theconstituent fatty acids (18-20). CO containsabout 8% of partially water-soluble 8 and 10carbon acids, 55% and 20% of intermediate12 and 14 carbon acids respectively, 8% of16 carbon palmitic acid, and only 5.5% oleicand 1.4% linoleic acids. It has been shownthat the water-soluble acids are absorbed viathe portal system (2 1-22) and are quicklycatabolized or elongated (18). The 12 and 14carbon acids are deposited to only a slightdegree in adipose tissue; and the 16 carbonpalmitic, even if fed at a high level, does notgreatly increase levels of palmitic in adiposetissue, possibly being elongated and desatu-

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196 REISER ET AL

rated to oleic acid. Oleic and linoleic acidscan accumulate to very high levels.

The data in Tables 3 and 4 demonstratethat the levels of plasma lipids and lipopro-teins among individuals reasonably maintaintheir relative rank regardless of diet, a ho-meostatic phenomenon related to the previ-ously identified intrinsic characteristic (23).However, it is a new observation that TCand the cholesterol-containing lipoproteinsfollow one rank order, but that TO followsa different order.

Of the 19 subjects, only 2 may be said tohave experienced lipidemic changes from be-nign to marginally high risk levels by con-sumption of BF or CO. Thus, subject 32 hadTC concentrations of 155, 198, and 222 mg/dl during the consumption of SO, BF, andCO respectively. The corresponding valuesfor subject 33 were 191 (estimated), 215, and226 mg/dl. The highest other values duringSO, BF and CO consumption were 156, 197,and 196 mg/dl in subject 34, and 175, 184,and 188 mg/dl respectively in subject 19.

The common classification of BF togetherwith CO, cocoa butter, hydrogenated vege-table oils, and butter fat as hypercholester-olemic saturated fats appears inappropriate.BF in this study clearly had significantlydifferent effects on various plasma lipids

compared to the common reference saturatedfat,CO, but had very similar effects comparedto SO. Oiven the present state of knowledgeof diet and plasma lipoprotein metabolism,with different effects on coronary risk attrib-uted to LDL-C and HDL-C, each dietary fatshould be evaluated on the basis of its effectson individual lipoproteins. The classificationof dietary fats solely as saturated, unsaturated,or hypercholesterolemic is misleading, andmay obscure a complex of significant meta-bolic effects (18, 24).

Further studies of BF and its effects onlipids and lipoprotein metabolism are neededto more clearly define the effects and establisha rational perspective on BF in the Americandiet. Studies of BF should include the follow-ing: 1) comparison of BF with the variety ofcommon dietary fats to establish the relativemagnitudes of its various lipoprotein effects,2) comparison of the effects of various pro-portions of BF in the diet to establish amount-response relationships, 3) controlled feeding

investigations comparing BF with other di-etary fats in populations of other ages andsexes to establish the general applicability ofthe results of the present study, 4) studies todefine the effects of BF compared to otherdietary fats upon the proportions and com-position of the subclasses of the HDL-C, and5) studies of BF to differentiate between theeffects of its fatty acid composition and itssterol content.

An overlooked area of fat metabolism basicto the diet-heart theory is the possible meta-bolic pathways and mechanisms by whichindividual fatty acids or glycerides may con-trol the levels of plasma cholesterol andlipoproteins.

The authors are indebted to the following colleagues:Mr Mauro Nava and Dr Gosta Dahien for their perfor-mance of the lipid and lipoprotein cholesterol assays, DrCharles W Dill for his preparation of the filled ice cream,Ms Grace Lin and Dr Ri Freund for the statisticalanalysis, and Ms D McLain for preparation of sandwichesand dinner entrees.

The authors gratefully acknowledge the gifts of saf-flower seed oil by the Pacific Vegetable Oil Co ofRichmond, California, and of coconut oil by the Ander-son-Clayton Foods of Richardson, Texas�

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HUMAN LIPIDEMIC RESPONSES TO BEEF FAT 197

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