Role of Dietary Saturated Fatty Acids on Lowering ...

Role of Dietary Saturated Fatty Acids on Lowering the Incidence of Heart Lesions in Male Rats1 E. R. FARNWORTH", J. K. G. KRAMER", B. K. THOMPSONt ANDA. H. CORNERJ 'Animal Research Centre, Agriculture Canada, Ottawa, Canada, Institute, \Animal Nepean,

K1A OC6, Â¡Engineering and Statistical Research Agriculture Canada, Ottawa, Canada K1A OC6; Diseases Research Institute, Agriculture Canada, Ontario, Canada, K2H 8P9.

INDEXING KEY WORDS; fatty acids â€¢growth

male rats

In 1960 KoinÃ¨et al. (1) reported that male albino rats fed semisynthetic diets containing 25 or 35% by weight of high erucic acid rapeseed (HEAR) oil developed myocardial ne crosis. Since that time, it has been shown that feeding other dietary oils (2-6), fats (7, 8), or fat-oil mixtures (8, 9, 10) can also result in myocardial necrosis in male rats. The fac tors responsible for the development of myo cardial necrosis have been elusive, since there does not appear to be any characteristic com mon to all the dietary lipids that could ac count for all the experimental observations. For example, attempts to explain the pro duction of myocardial necrosis as being due to erucic acid (7, 8), or oxidative products (11), or a non-triglyceride substance (5, 8, 12-14) have failed. Highly purified triglyc Ã©ridefrom soybean oil or low erucic acid

â€¢heart lesions

digestibility

rapeseed (LEAR) oil, when fed to male rats, resulted in a lesion incidence similar to that of rats fed the original vegetable oils, impli cating the fatty acids of the dietary oils (5, 14). A retrospective analysis of heart lesion data in which linear relationships between dietary fatty acid content and lesion incidence were demonstrated, further implicated the fatty acid pattern of the diets (15). This analysis showed that the incidence of heart lesions in male albino rats was negatively correlated with the level of saturated fatty acids, pal mitic (16:0), and stearic (18:0) in the diet, and positively correlated with the level of Q1982 American Institute of Nutrition. Received for publication 15 June 1981. 1Contribution number 1002 from Animal Research Centre and number 1-287 from Engineering and Statistical Research Institute. 231

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ABSTRACT Male weanling rats were fed soybean or low erucic acid rapeseed oils alone or in combination with cocoa butter (a source high in saturates) or triolein for 16 weeks. All diets contained 20% by weight of the test oils. The apparent digestibility of all diets and test oils increased with the age of the rat. The apparent digestibility of the saturated fatty acids was lower in rats fed the diets containing cocoa butter. The relative organ weights, however, were not affected by diet, but growth was improved by sup plementing the vegetable oils with cocoa butter. This growth difference was significant for the addition of cocoa butter to low erucic acid rapeseed oil. After 16 weeks all groups of rats developed myocardial necrosis. A dramatic lowering of myocardial lesion incidence was observed in rats fed diets enriched with saturated fatty acids. The results of the present experiment suggest that enriching a vegetable oil with saturated fatty acids affects both nutritional and cardiopathological properties of the oil. J. Nutr. 112: 231-240, 1982.

232

FARNWORTH

MATERIALS AND METHODS

Dietary oils and diets. Seven oil mixtures were formulated by including either a fully refined low erucic acid rapeseed (LEAR) oil Brassica napus cv. (Tower Cooperative Veg etable Oil Ltd., Altona, Manitoba) or soybean oil (Canada Packers Ltd., Toronto, Ontario) alone or in combination with either cocoa butter (Hershey Foods Corp., Smith Falls, Ontario), triolein (Nu Check Prep, Elysian, MN), linseed oil (donated by J. D. Jones, Agriculture Canada, Ottawa) or a mixture of long chain monoenes (table 1). The long chain monoene mixture was prepared by high vacuum distillation of methyl esters of high erucic acid rapeseed (HEAR) oil; the methyl esters were prepared by an alkali interesterification procedure (27). Gas chromatographic analysis showed that the long chain monoene mixture contained 79% 20:1, 20% 22:1 and 1% 24:1. The proportions of LEAR oil, soybean oil, cocoa butter, triolein, linseed oil, and long chain monoenes are given in table 1, which also contains the fatty acid analysis of the oil mixtures that was car ried out using methods and instruments de scribed elsewhere (28). Seven experimental diets were mixed, each containing a dry basal mixture (table 2) and 20% (by weight of the final diet) of the oil or oil mixtures. 125 kg of each diet was mixed at one time and then all diets were stored at â€”4Â° until required. The gross energy of a representative sample of each diet was de termined by bomb calorimetry (29). Animals, housing and feeding. A total of 350 male, weanling Sprague-Dawley rats (Bio-Breeding Laboratories, Ottawa, On tario), weighing between 50 and 60 g, were ear notched for identification, allocated ran domly to the seven dietary groups (50 per diet) and placed immediately on the exper imental diets. Two animals were housed in each cage which were suspended and equipped with stainless steel, wire mesh bot toms. Food and water were available ad li bitum. Individual body weights were mea sured every 2 weeks. Within each dietary group, aggregate food consumption data were obtained from five groups of 10 animals by a feed weigh back at the end of the ex periment. Care was taken throughout the experiment to ensure that the diets had re-


linolenic acid (18:3) in the diet, for oils con taining less than 7.4% erucic acid (22:1). Ear lier works combined tallow, palm oil, or lard/ corn oil mixtures with rapeseed oil and raised the level of dietary saturated fatty acids (8, 10, 16-18). Abdellatif and Vies (18) con cluded that palmitic acid, in addition to pro moting improved growth, exerted some pro tective effect against "erucic acid induced lesions" when fed to ducklings. Beare-Rogers (19), however, concluded that earlier data (8) did not demonstrate any beneficial effect of adding saturated fatty acids to rapeseed oil. The experiment reported here was de signed to test whether the incidence of heart lesions could be reduced by increasing the level of saturated fatty acids in the diet of male albino rats. Cocoa butter was chosen as a source of saturated fatty acids because of its high 16:0 and 18:0 content. By replacing part of the dietary oil with cocoa butter, the effect of increasing the level of dietary sat urated fatty acids could be studied. Two other diets were also formulated in which part of the dietary oil was replaced by triolein to ensure that any effect attributed to the addition of cocoa butter was not due to a dilution of a cardiotoxic agent (20). Triolein was chosen because oleic acid was shown to have a very weak correlation with heart le sion incidence (15). An additional diet was formulated to mimic the fatty acid pattern of LEAR oil by using a combination of soy bean oil, linseed oil, triolein, and long chain monoenes. The manipulation of the level of saturated fatty acids in the diet could have nutritional as well as pathological consequences. For ex ample, it has been shown that there is a re lationship between the level of saturated fat in the diet of rats and growth performance (21-23). Therefore, several nutritional pa rameters were measured to determine the effects of increasing the level of saturated fatty acids in the diet. The retrospective sta tistical analysis of heart lesion data was done only for the level of dietary fatty acids, and not for the amount of fatty acids actually digested (15). Therefore, we felt it would be informative to measure the apparent diges tibility of individual fatty acids to ensure that preferential absorption of certain fatty acids was not occurring (24-26).

ET AL.

FATTY ACIDS ON INCIDENCE

OF HEART

233

LESIONS

TABLE 1 Composition of dietary oils and their fatty acid analysis

LEAR oil Soybean oil Cocoa butter Triolein Linseed oil LCM2 (20:1 + 22:1 + 24:1}

LEAR

LEAR + cocoa butter

LEAR + triolein

20'

16

16

Soybean

20 4

Soybean + cocoa butter

16 4

Soybean + triolein

Soybean + triolein + LCM2

9.6

9.5

9.6 0.8

9.5 0.8

â€”

0.2

Fatty Acids

14:016:018:020:022:024:0Total16:118:120:122:124:1Total18:218:3TotalO.I34.41.50.80.30.17.20.457.51.90.60.160.522.010.332.30.18.27.50

mained homogeneous with respect to the oil content (30). The animal room was main tained at a temperature of 22 Â±1Â°and a humidity of approximately 50%. A regimen of 12 hour light (0800 hours to 2000 hours) and 12 hour dark (2000 hours to 0800 hours) was used throughout the experiment. Apparent digestibility determinations. During weeks 4, 8 and 12, feed consumption data and the feces excreted by the same ten animals (in five cages) per diet were obtained for two consecutive 48-hour periods. Feces from the two collection periods were then pooled, weighed, freeze dried and the lipids extracted by an acidic-hexane extraction pro cedure (31). The fatty acid content of the feces extract was determined by gas-liquid chromatography of the methyl esters ob tained after HCl-MeOH transesterification (32). The apparent digestibility of various

3 Fatty acid

dietary components was calculated using the composition data for the dietary oil and feces (33). Internal organs and cardiac pathology. At the end of 16 weeks, six randomly selected rats per diet group were killed by CO2 in halation and decapitation. The major internal organs were removed, weighed and exam ined for gross pathological abnormalities. The remaining 44 animals per diet were killed and their hearts examined for myocardial necrosis and fibrosis (11). Statistical analysis. Analyses of variance were calculated for weight gain, feed con sumption, organ weights, and apparent di gestibility data, using 1% as the level of sig nificance. Analyses of covariance adjusting for initial weights were carried out on the weight gain and feed consumption data. The least significant differences (LSD's) were ob-


1 Percent by weight of total diet. 2 LCM = longchain monoenes (79% 20:1, 20% 22:1, 1% 24:1). composition expressed as relative percent by weight. 4 tr = less than 0.1%. 5â€” not detected.

234

FARNWORTH ET. AL. TABLE 2 Percent composition of experimental diets' Ingredient

Casein2 Sucrose Cornstarch

Vitamin mix3

Salt mix*

20 20 30 1

4

Alpha floe Oil (or mixture)

5 20

tained from the pooled error estimates of the analyses of variance. Heart lesion data were analysed using approximate x2 statistics de scribed by Fienberg (34). RESULTS

A few rats in each diet group developed a transitory alopecia, an observation that has been reported before (35). Except for this,

TABLE 3 Weight gain, feed consumption, and feed efficiency of rats fed experimental diets DietLEARLEAR

Gaingirai361411371440Consumedgirai1636168416541709 Efficiency0.2210.2440.2240.257

butterLEAR + cocoa trioleinSoybean + Soybean + cocoa butter Soybean + triolein Soybean LCMLSD+ triolein + (1%)5F6Weight12

451 405 41023.2FÂ«Â«

26.9Feed13

1733 1712 168169.6F6,28

3.86Feed4

0.260 0.237 0.2440.0124F6M

22.5

' Experimental period of 113 days. 2Mean of 50 rats per diet group. 3 Mean of five groups of ten rats per diet group. 4Weight gain/feed consumed. 5 Least significant difference at 1% level, based on the pooled estimate from the analysis of variance. 6 Analysis of variance F statistic.


' Percent by weight of total diet. 2 Vitamin free casein (Teklad Test Diet Co., Madison, WI). 3 Ingredients (mg/kg diet): thiamin HC1 10; riboflavin 10; pyridoxine HC1 10; Ca pantothenate 30; inositol 500; niacin 50; p-aminobenzoic acid 100; biotin 0.2; vitamin B-12 20; cholinebitartrate 2000; folie acid 2; dry vitamin A palmitate (500,000 lu/g) 10;dry ergocalciferol (500,000 IU/g) 2; dry vitamin E acetate (500 lu/g) 200; menadione 5 (Teklad Test Diets Co., Madison, WI). 4U.S.P. XVII mineral mix (Teklad Test Diets Co., Madison, WI).

all animals appeared to adapt to the high fat diet. Table 3 shows the weight gains of the rats fed the experimental diets for 16 weeks. Gen erally, rats consuming the diets containing LEAR gained less weight than those fed the diets containing soybean oil. Adding cocoa butter to the LEAR resulted in significantly increased gains. Of the soybean oil-based diets, the groups receiving added triolein or triolein and long chain monoenes had sig nificantly smaller weight gains. An analysis of covariance indicated that the 16 week weight gains were unrelated to initial body weight of the rats. The patterns in feed consumption were less clear than the growth data. The differences among diets within the two groups (LEAR and soy) were not significant although there were significant differences among the seven diets. It may be noted that the groups fed cocoa butter supplemented diets had higher rates of consumption, albeit not significant, but there was little evidence of any effect from the addition of triolein. Unlike the weight gain data, the total feed consumption was related to the initial body weight of the rat, but adjustment of the means of table 3 by the analysis of covariance did not alter the general picture. The bomb calorimetry results for the ex perimental diets indicated that the differ-

FATTY ACIDS ON INCIDENCE OF HEART LESIONS

235

TABLE 4 Apparent digestibility of total diet and total lipid at weeks 4, 8, and J2' dietwk

lipidwk

490.791.291.292.090.291.791.31.412.90Total 890.188.892.489.289.090.490.22.912.87wk 1293.990.093.793.091.392.890.03.313.93wk 495.493.496.595.790.096.996.31.8925.8Total 896.192.596.895.291.797.296.82.4512.5wk 1297.894.497.797.694.398.096.81.491 LEARLEAR +LEAR buttertriolein+ +SoybeanSoybeanSoybeanSoybeanDietcocoa butter+ cocoa triolein+ LCMLSD triolein + (%)2F 8 6.24wk

enees in feed consumption could not be attributed to differences in the gross energy content of the diets. The gross energy contents of the seven experimental diets were found to be very similar (5.02-5.13 kcal/g). The seven experimental groups showed a calculated feed efficiency ratio pattern similar to the weight gain data. The animals eating the LEAR and LEAR plus triolein diets had the lowest ratios, and adding cocoa butter increased the ratio. The low weight gains

of the soybean plus triolein and soybean + triolein + long chain monoenes groups, resuited in their feed efficiencies being lower than for the soybean and the soybean plus cocoa butter groups. The apparent digestibility data for the total diet and the total lipid in the diet, for the three sampling periods (4, 8, and 12) are given in table 4. Over the period of the expÃ©riment,the apparent digestibilities of the total diet and total lipid were consistently

TABLE 5 Apparent digestibility of palmitic (16:0) and stearic (18:0) acids at weeks 4, 8, and 12'

492.282.292.587.6 1294.181.694.286.8 8 wk

472.864.579.972.5 875.960.486.464.9 1280.471.289.182.8

LEARLEAR butterLEAR + cocoa trioleinSoybean + Soybean + cocoa butter Soybean + triolein Soybean LCMLSD+ triolein + (1%)2V 3r

74.6 79.5 93.4 94.5 93.54.148.6Amount94.75.423.8â€”

86.0 96.0 94.73.823.9v

58.2 64.5 75.9 80.2 79.174.313.57.5,wk 85.7 78.810.69.918:0wk 77.711.84.2of

6.2-Iwk

amount excreted96.086.695.793.1 ingested16:0wk innwk based on the pooled estimate from the analysis of variance.

3Analysis of variance F statistic.

1 (P.

la

,Ã¬


Amount ingested â€”amount excreted : X 100 Least significant difference at 1%level, amount ingested based on the pooled estimate from the analysis of variance. 3Analysis of variance F statistic. Apparent digestibility =

236

FARNWORTH

ET. AL.

TABLE 6 Relative organ weights' Diet

Heart

Liver

Kidneys

Spleen

Adrenals

Testes

LEARLEAR butterLEAR + cocoa trioleinSoybean + Soybean + cocoa butter Soybean + triolein Soybean LCMLSD + triolein +

2.59 26.927.2 5.75 1.46 0.10 6.81 2.34 5.84 1.37 0.11 7.36 2.500.374.025.326.226.425.4 27.25.50.86.855.986.935.86 6.090.874.81.291.231.271.30 1.250.415.290.140.120.110.11 0.110.050.68.176.807.976.69 5.931.862.3

(1%)"F 4 6.52.692.412.862.27

1 (organ weight/body weight) X IO3. 2 Mean of six animals per diet group. 3 Least significant difference 1% level, based on the pooled estimate from the analysis of variance. 4 Analysis of variance F statistic.

the case of LEAR + triolein). The addition of 18:1 to the diet did appear to enhance the digestibility of 18:0 in either the soybean or LEAR based diets. The relative organ weights for the six rats TABLE 7

Myocardial lesions in male rats fed the experimental diets


high, and generally increased from 4 to 8 to 12 weeks. The nature of the dietary oil did have some effect on the apparent digestibil ities. The diets containing cocoa butter tended to have lower (in some cases significantly lower) digestibilities compared to the diets containing only LEAR or soybean oil. There appeared to be no effect on the apparent digestibility when triolein was added to the LEAR or soybean diets. Table 5 contains the apparent digestibility data for the individual saturated fatty acids 16:0 and 18:0. The digestibility of 18:1, 18:2, 18:3, and 20:1 + 22:1 were also determined (but not tabulated). The apparent digestibil ities of 18;1, 18:2, and 18:3 were all greater than 96% for all diets at all three collection periods, whereas the digestibility of 20:1 + 22:1 ranged from 80-88%. As was the case with the apparent digestibility of the total lipid component of the diet, the apparent digestibility of the individual fatty acids was greatest during the 12th week sampling pe riod. The addition of cocoa butter to the diet had a marked effect on the digestibility of some fatty acids. In particular the apparent digestibilities of 16:0 and 18:0 were lower (in some cases significantly) in the diets con taining LEAR + cocoa butter, than those for the corresponding acids in the diet contain ing only LEAR oil. There were no significant differences in the apparent digestibilities of 18:1 for any of the diets, in spite of the large differences in the percent of 18:1 in the diets (24.3% in the case of soybean, and 64.2% in

at

Inci dencen = 4461365557345955Severity101728201929182011081110111616

DietsLEARLEAR

butterLEAR + cocoa trioleinSoybeanSoybean + butterSoybean + cocoa trioleinSoybean + + triolein + LCM% Analysis d.f. Entire severity table

12

23.24"

Incidence(0 >1)Diets versus 1 and versusoriginal with cocoa butter oilsDiets versusoriginal with triolein oilsDegree severity(1 of versus >1)611613.04'10.15b0.2010.21 1 Numbers of rats with 0, one, or more than one lesion per three sections of heart. " Significant at 5% level. b Significant at 1% level.


237

of experimental animals (18,36,37). By com paring oils high in erucic acid (HEAR) to â€¢Thit work those low in erucic acid (LEAR), it was con cluded that the observed growth depression in rats fed HEAR oils was due to the presence of erucic acid, lower digestibility, prolonged absorption time, and inefficient energy uti lization (38). The results of this present ex periment indicate that both the total LEAR oil and its constituent fatty acids were highly digestible (tables 4 and 5). Indeed, all the dietary lipids used in this study were highly digestible, and therefore the experimental results could not be attributed to lowered fat Â»DIETARY16:0+ 18:0 digestibility. Fig. 1. A plot of the level of dietary 16:0 and 18:0 It has been suggested that the relative fatty acids versus the incidence of invocan liai lesions. amounts of saturated and mono-unsaturated fatty acids may also affect the nutritional per diet group that were examined at the end quality of dietary oils (21, 22). Beare et al. of 16 weeks are presented in table 6. In most (23) showed that increasing the level of di cases, the differences between groups were etary saturated fatty acids in HEAR resulted found not to be significant. Also, it was dif in improved weight gains. The old as well ficult to establish any trends in the relative as the new varieties of rapeseed oils are char organ weights that could be attributed to the acteristically low in saturated fatty acids. The dietary oil. For example, rats on the LEAR removal of erucic acid led to an increase of plus cocoa butter diet had lower relative 18:1, but the level of saturates was not af heart, kidneys, spleen, adrenals and testes fected. When the nutritional quality of LEAR weights, than animals receiving only the was tested in a short term feeding trial, it LEAR oil. On the other hand the soybean was concluded that the addition of saturated plus cocoa butter group had larger relative fatty acids to LEAR did not improve heart, liver, spleen and testes weights com growth (39). pared to the soybean group. In the present experiment, rats receiving Myocardial lesions were found in rats from a diet containing LEAR oil supplemented all diet groups irrespective of the dietary with saturates from cocoa butter gained sig lipid (table 7). There was a very significant nificantly more weight after 16 weeks than reduction in the incidence of lesions when rats receiving only LEAR oil (table 3). The effect was not seen, however, when soybean cocoa butter was added to the diets, as re flected by the large x2 statistic representing oil was supplemented with cocoa butter. The differences between diets with added cocoa LEAR oil with 7.2% saturated and 60.5% butter and the original oils. The addition of monounsaturated fatty acids may have pre triolein or triolein plus long chain monoenes sented the rat with a pattern of fatty acids did not affect the incidence of the myocarthat was too imbalanced for optimal growth. dial lesions in either the LEAR or soybean The soybean oil with 16.2% saturated and 25% monounsaturated fatty acids, may have groups. Analysis of the severity data showed the a pattern more conducive to optimal growth. overall \z to be non-significant and, there By adding cocoa butter to LEAR oil, the sat fore, no further analyses were carried out. urated fatty acid level was raised to 16.6% and the animals gained more weight. The fatty acid pattern of the LEAR plus cocoa DISCUSSION butter mixture may more closely approxi mate a pattern needed for optimal growth. The oil from older varieties of rapeseed The present experiment demonstrated the high in erucic acid were shown to have a low nutritional value when fed to several species nutritional benefits of increasing the level of a Beare-Rogers et al. 1974


238

FARNWORTH ET AL.

on the incidence of heart lesions. The expla nation that the reduction in myocardial le sion incidence by the addition of cocoa butter to the diet is due to the dilution of a cardiotoxin is not tenable since the addition of triolein did not affect the lesion incidence. This lack of effect of triolein had been anticipated since the level of dietary oleic acid had been shown to be weakly correlated with heart lesion incidence (15). The factor linking fatty acid intake and development of heart lesions is still not clear. Fatty acids entering the heart are either esterified to form triglycÃ©ridesand phospholipids or are oxidized to produce energy. The in vivo control of fatty acid metabolism in the heart encompasses regulation of plasma levels of fatty acids, triglycÃ©ridesand other substrates by extramyocardial tissues, as well as local control of specific enzyme systems involved in myocardial fatty acid utilization (41). Kramer (28) has shown that the com position of cardiac lipid classes is relatively insensitive to dietary fatty acid changes. The cardiac phospholipids of rats fed a large spec trum of dietary oils were found to have very constant levels of saturated, total polyunsaturated and C22 polyunsaturated fatty acids. As a result, Kramer (28) speculated that some in vivo regulation mechanism was working to maintain an ideal membrane composition. Closer examination of the polyunsaturated fatty acids data showed that as the level of 18:3 n-3 in the diet was increased, so did the proportion of n-3 C22 polyunsaturated fatty acids in cardiac phosphatidylcholine and phosphatidylethanolamine. The mechanism involved in membrane synthesis appears to be very effective at pro ducing a membrane with an ideal composi tion, from a large spectrum of dietary fatty acids. But, as has been demonstrated in this experiment, the fatty acid pattern of the diet does affect the incidence of myocardial le sions, regardless of the source of the oil. ACKNOWLEDGMENTS

The helpful comments of S. Mahadevan, F. D. Sauer, and H. L. Trenholm concerning the experimental design and interpretation of the data are appreciated. Technical assis tance was provided by A. M. Honkanen,


saturates and a dramatic lowering of heart lesion incidence (table 7) in rats fed diets enriched with saturated fatty acids (from 7 to 17% and 16 to 28%). Beare-Rogers et al. (8) formulated diets with levels of saturated fatty acids varying from 4.5 to 31.9%. If the data from their 16-week feeding trials using weanling animals are plotted as shown in fig ure 1, there is a good correlation (â€”0.77)be tween the level of saturated fats in the diet and the level of heart lesions. When the re sults of this study (table 7) are superimposed on those of Beare-Rogers et al., the agree ment is excellent. The relationship of satu rates to heart lesions was pointed out by Hu Ã-anet al. (40). The effect of high levels of saturated fatty acids could be used to explain why BeareRogers and Nera (9) observed a lowering of heart lesion incidence when LEAR oil was hydrogenated to an iodine level of 77, since the level of saturates was raised from 7.9% to 17.4%. Feeding unhydrogenated oil, or partially hydrogenated oil (to an iodine value of 97) resulted in a high lesion incidence due to the combined effects of low levels of sat urated fatty acids and the presence of 18:3. Similarly, McCutcheon et al. (3), could only partially explain their results by changes in the linoleic/linolenic acid ratio. But their data showed that when rats consumed di etary oils which contained higher levels of saturated fatty acids, the heart lesion inci dence was lowered. Several investigators have suggested that individual fatty acids or the overall dietary fatty acid pattern could be influencing the incidence of myocardial lesions in male al bino rats (2,3,6,7,14,40). Early speculations as to which fatty acids were important in the etiology of heart lesion incidence were sub stantiated when saturates (16:0 and 18:0) and linolenic acid (18:3) were found to be neg atively and positively (respectively) corre lated with heart lesion incidence for oils low in 22:1 (15). This present study clearly shows that increasing the level of dietary saturated fatty acids lowers heart lesion incidence for male rats. This effect was evident even though the diets contained substantial amounts (4.9% to 10.3%) of 18:3. The presence of low levels of long chain monoenes, did not appear to have any effect


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