Biological evaluation of hydrogenated rapeseed oil

A 91-day feeding study evaluated soybean oil, rapeseed oil, fully hydrogenated soybean oil, fully hydrogenated rapeseed oil, fully hydrogenated superglycerinated soybean oil and fully hydrogenated superglycerinated rapeseed oil at 7.5% of the diet in rats; a 16-wk feeding study evaluated soybean oil and the three rapeseed oils or fats at 15% of the diet. Each fat was fed to 40 rats as a mixture with soybean oil making up 20% of a semi-synthetic diet. No significant differences in body weight gains or diet-related pathology were seen in the 91-day study although the rats fed liquid rapeseed oil had slightly heavier hearts, kidneys and testes than the others. The rats fed the four fully hydrogenated fats ate more feed and had lower feed efficiencies than those fed oils but no differences were seen among the four hydrogenated fats. In the 16-wk feeding study, no pronounced pathology related to the diet was seen although the rats fed liquid rapeseed oil had a slightly higher incidence of histiocytic infiltration of cardiac muscle than the rats in the other groups. The female rats fed the three rapeseed oil fats gained significantly less weight and the females fed liquid rapeseed oil had enlarged hearts compared to the other groups. The absorbabilities of the six fats were measured in the 91-day study when fed as a mixture with soybean oil and as the sole source of dietary fat in a separate 15-day balance study. The four fully hydrogenated fats were poorly absorbed and the absorption of behenic acid from the two hydrogenated rapeseed oils was found to be 12% and 17% in the balance study and 8-40% in the feeding study. The adverse biological effects of unhydrogenated rapeseed oil containing erucic acid as reported in the literature do not occur with fully hydrogenated rapeseed oil. In addition, the low absorbability of the fully hydrogenated rapeseed oil is an added factor in its biological inertness.     

Exacerbation of heart and liver lesions in rats by feeding of various mildly oxidized fats

Groups of 40 male Charles River rats were fed diets containing cottonseed oil, olive oil, corn oil, soybean oil, coconut oil, chicken fat, beef fat, butter oil, lard and saturated medium chain triglycerides. The fats were fed fresh and after 40 hr aeration at 60 C, which hardly changed peroxide values. In addition, fresh and aerated soybean oil and lard were fed to W/Fu rats. Body weights and life span were significantly influenced by the kind of fat fed, but not by aeration. Many hearts exhibited unspecific focal myocarditis and focal fibrosis. The latter was graded in a blind test, which revealed highly significant differences in the incidence of severe lesions; those fed corn oil had the most, followed by cottonseed oil, soybean oil, olive oil, beef fat, saturated medium chain triglycerides, butter, chicken fat and lard, in that order. Feeding of aerated fat resulted in an increased incidence with six of the eight fats. The W/Fu rats had lower incidences, but those fed soybean oil had more than those fed lard, and aeration led to a higher incidence. Some heart sections stained with Light Green SF Yellowish revealed areas of muscle fibrils that did not accept the stain, probably as a consequence of cellular damage. Higher incidences of this lesion were associated with the same fats as was severe fibrosis, and feeding of aerated fats led to higher incidences. Many livers revealed marked proliferation of bile ducts. The groups fed cottonseed, soybean, olive and corn oils had higher incidences of severe lesions, and feeding of the oxidized oils led to still higher incidences. None of the results appeared to be associated with the fatty acid composition of the fats, which suggested that these long term effects may have been due to minor constituents in the individual fats. One of seven papers presented in the symposium “Biological Significance of Autoxidized and Polymerized Oils,” JOCS-AOCS Joint Meeting, Los Angeles, April 1972.     

Effects of fresh and used hydrogenated soybean oil on reproduction and teratology in rats

Groups of 25 pairs of two generations of male and female rats were fed diets containing 15% of either fresh hydrogenated soybean oil (iodine value, 107), a similar fat used 56 hr for deep frying or an unhydrogenated mixture of fats and oils with a fatty acid composition similar to the hydrogenated soybean oil. The first two litters of each generation were permitted to be born naturally. During the third pregnancy of each generation, one-half of the females were sacrificed on day 13 of gestation and inspected for early embryonic death. The remaining females were sacrificed on day 21 of gestation, and the fetuses were examined for either skeletal or softtissue abnormalities. There was no evidence of any deleterious effects on the reproductive parameters nor any teratogenic effects due to either hydrogenated soybean oil, a similar oil used for frying foods for 56 hr or an unhydrogenated mixture of fats and oils.     

Effects of fresh and used hydrogenated soybean oil on reproduction and teratology in rats

Groups of 25 pairs of two generations of male and female rats were fed diets containing 15% of either fresh hydrogenated soybean oil (iodine value, 107), a similar fat used 56 hr for deep frying or an unhydrogenated mixture of fats and oils with a fatty acid composition similar to the hydrogenated soybean oil. The first two litters of each generation were permitted to be born naturally. During the third pregnancy of each generation, one-half of the females were sacrificed on day 13 of gestation and inspected for early embryonic death. The remaining females were sacrificed on day 21 of gestation, and the fetuses were examined for either skeletal or softtissue abnormalities. There was no evidence of any deleterious effects on the reproductive parameters nor any teratogenic effects due to either hydrogenated soybean oil, a similar oil used for frying foods for 56 hr or an unhydrogenated mixture of fats and oils.     

Melting behavior of blends of milk fat with hydrogenated coconut and cottonseed oils

The melting behavior of milk fat, hydrogenated coconut and cottonseed oils, and blends of these oils was examined by nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). Solid fat profiles showed that the solid fat contents (SFC) of all blends were close to the weighted averages of the oil components at temperatures below 15°C. However, from 15 to 25°C, blends of milk fat with hydrogenated coconut oils exhibited SFC lower than those of the weighted averages of the oil components by up to 10% less solid fat. Also from 25 to 35°C, in blends of milk fat with hydrogenated cottonseed oils, the SFC were lower than the weighted averages of the original fats. DSC measurements gave higher SFC values than those by NMR. DSC analysis showed that the temperatures of crystallization peaks were lower than those of melting peaks for milk fat, hydrogenated coconut oil, and their blends, indicating that there was considerable hysteresis between the melting and cooling curves. The absence of strong eutectic effects in these blends suggested that blends of milk fat with these hydrogenated vegetable oils had compatible polymorphs in their solid phases. This allowed prediction of melting behavior of milk-fat blends with the above oils by simple arithmetic when the SFC of the individual oils and their interaction effects were considered.     

Effects of level and type of dietary fat on incidence of mammary tumors induced in female sprague-dawley rats by 7,12-dimethylbenz(α) anthracene

Female Sprague-Dawley rats on semisynthetic diets containing 10% and 20% by weight of corn oil developed more mammary adenocarcinomas after treatment with a single oral dose of 7,12-dimethylbenz(α)anthracene than similar rats on diets containing only 0.5% or 5% corn oil. Experiments with 10 different fats and oils fed at the 20% level indicated that unsaturated fats enhance the yield of adenocarcinomas more than saturated fats. Fibroadenomas and adenomas were also found in small numbers in all dietary groups but the yield did not seem to be influenced by level or type of dietary fat. The possible relevance of these findings to the incidence of breast cancer in humans is discussed. Presented at the ISF-AOCS World Congress, Chicago, September 1970.     

Cardiopathogenicity of rapeseed oils and oil blends differing in erucic,linoleic, and linolenic acid content

Male Wistar rats were fed semipurified diets containing 20% fat for 25 weeks. Ten different oils or oil blends were employed, including rapeseed oils, simulated rapeseed-type oils, and modified rapeseed-type oils. Safflower, soybean, and hydrogenated coconut oils served as control oils. Histopathological examination of the cardiac tissue was conducted at the end of the study and an incidence-severity rating assigned to the lesions induced by each fat. Oils containing high levels of erucic acid (26–30%) induced the most severe cardiac necrosis, irrespective of the source of erucic acid (rapeseed oil or nasturtium oil). Increasing the linoleic: linolenic acid ratio of the high erucic oils to that of soybean oil failed to reduce necrosis, but the absence of linolenic acid from a high erucic acid oil blend resulted in a markedly reduced lesion incidence-severity rating, comparable to those obtained for low erucic acid rapessed oil and soybean oil which were similar. Lowest lesion incidence was obtained with safflower oil and hydrogenated coconut oil. We have postulated that linolenic acid plays a role in the etiology of cardiac necrosis observed when rats are fed diets containing low erucic acid rapeseed oils.     

Dietary polyunsaturated fat in relation to mammary carcinogenesis in rats

High fat diets promote the development of mammary tumors induced in rats by 7,12-dimethylbenz(a)anthracene (DMBA), and polyunsaturated fats are more effective than saturated fats. This difference is related to the linoleic acid content of polyunsaturated vegetable oils, but the amount of linolealte required for maximum tumor promotion appears to be higher than indicated by earlier experiments. Comparison of the effects of a polyunsaturated vegetable oil (corn oil) containing linoleate with a fish oilo (menhaden oil) containing polyunsaturated fatty acids derived from linolenic acid showed that higher dietary mammary tumors, while corresponding levels of menhaden oil had an inhibitory effect. This is further evidence that promotion of mammary tumorigenesis by polyunsaturated vegetable oils may be mediated by prostaglandins or other biologically active eicosanoids derived from n−6 fatty acids.     

Nutritional evaluation of some heated oils

Summary Soybean oil, cottonseed oil, and lard were heatedin vacuo for either 70 and/or 100 min. at 610°F. and were fed to male and female rats at a level of 15% in the diet over a complete life span. Nutritional indices such as growth, including food efficiency and digestibility of the fats, reproduction and lactation, longevity, and tissue cholesterol and total lipid were measured. No evidence of impaired nutrition or harmfulness was observed in any group except in those fed the more highly polymerized soybean oil, where a decrease in iodine value of 10% and a 100% increase in viscosity was associated with a slight depression in growth and an interference with reproductive performance in the female animal. This interference with the reproductive process was alleviated by supplementation with α-tocopherol. There was no evidence of increased tumor incidence in the groups ingesting the heated oils. Digestibility of the heated soybean and cottonseed oils was only slightly reduced. Presented at the fall meeting, American Oil Chemists' Society, Chicago, Ill., October 21, 1958. Contribution No. 467.     

Biliary and fecal steroid excretion in rats fed partially hydrogenated soybean oil

Male Wistar rats were fed cholesterol-free or cholesterol-enriched diets containing partially hydrogenated soybean oil with different levels of trans-fatty acids or unhydrogenated soybean oil at the 10% level. The linoleic acid content of hydrogenated fat diets was adjusted to 3.6% of the total energy. Hydrogenated fat diets contained 29% and 41% trans-acids, mainly as t-18:1. Trans-fats exerted no untoward effects on growth parameters, but increased liver weight. Dietary hydrogenated fats influenced neither the concentration nor composition of biliary steroids, irrespective of the presence or absence of cholesterol in the diet. In rats fed a cholesterol-free diet, daily fecal output of neutral and acidic steroids was enhanced by hydrogenated fats and the magnitude of augmentation was proportional to the dietary level of trans-fatty acids. The increased fecal steroid excretion corresponded to an increase in total excreta. Hydrogenated fats also tended to enhance bile acid excretion when feeding a cholesterol-enriched diet. The results suggest that dietary trans-fatty acids, in relation to cis-polyunsaturated fatty acids, provoke demonstrable change in steroid homeodynamics.     

Influence of sources of dietary oils on the life span of stroke-prone spontaneously hypertensive rats

In recent studies, the life span of stroke-prone spontaneously hypertensive (SHRSP) rats was altered by a variety of dietary fats. It was relatively shorter in rats fed canola oil as the sole source of fat. The present study was performed to find out whether the fatty acid profile and the high content of sulfur compounds in canola oil could modulate the life span of SHRSP rats. SHRSP rats (47 d old, n=23/group) were matched by body weight and systolic blood pressure and fed semipurified diets containing 10% canola oil, high-palmitic canola oil, low-sulfur canola oil, soybean oil, high-oleic safflower oil, a fat blend that mimicked the fatty acid composition of canola oil, or a fat blend high in saturated fatty acids. A 1% sodium chloride solution was used as drinking water to induce hypertension. After consuming the diets for 37 d, five rats from each dietary group were killed for collection of blood and tissue samples for biochemical analysis. The 18 remaining animals from each group were used for determining their life span. The mean survival time of SHRSP rats fed canola oil (87.4±4.0 d) was not significantly different (P>0.05) from those fed low-sulfur canola oil (89.7±8.5 d), suggesting that content of sulfur in canola oil has no effect on the life span of SHRSP rats. The SHRSP rats fed the noncanola oil-based diets lived longer (mean survival time difference was 6–13 d, P<0.05) than those fed canola and low-sulfur canola oils. No marked differences in the survival times were observed among the noncanola oil-based groups. The fatty acid composition of the dietary oils and of red blood cells and liver of SHRSP rats killed after 37 d of treatment showed no relationship with the survival times. These results suggest that the fatty acid profile of vegetable oils plays no important role on the life span of SHRSP rat. However, phytosterols in the dietary oils and in liver and brain were inversely correlated with the mean survival times, indicating that the differential effects of vegetable oils might be ascribed, at least partly, to their different phytosterol contents.     

Studies on Nutritional Quality of Interesterified Fat Products

The nutritional quality of the fat products with melting range 36° to 37°C having been prepared from non-traditional oils like mowrah (Madhuca latifolia), ricebran (Oryzasativa) containing sal (Shorea robusta) and cottonseed (Gossypium hirstum) mixed with sal by interesterification (randomisation) were examined with rats and compared with that of “Vanaspati”, produced by hydrogenation of mixtures of liquid oils and used exclusively as a substitute of ghee (butter fat) in India. The average food intake, body weight gain, food efficiency ratio, weight of different organs, total lipid content of serum, liver, heart and kidney were similar in all the cases. Serum triglyceride levels were quite low in case of interesterified fats fed rats though total and free cholesterol levels were not significantly different. Serum phospholipid levels were slightly higher in case of the interesterified fats fed rats. Total and free cholesterol, phospholipid and triglyceride content of liver, kidney and heart were similar for the four dietary groups of rats. Serum lipids and liver lipids contain more polyunsaturated fatty acids when rats were raised on various interesterified fats in place of hydrogenated fat product “Vanaspati”.     

Nutritive value of heated vegetable oils

Peanut, sesame and coconut oils were heated at 270C for 8 hr, in an open iron pan. These fats were fed to albino rats at 15% level in otherwise adequate diets. All rats fed heated fats showed a growth depression. Livers of rats receiving heated oil were congested and showed extensive periportal fatty infiltration. Rats on heated peanut oil showed i) reduced B-vitamin storage in the liver, ii) increased glucose and cholesterol levels in the blood and iii) a disruption in the digestion and absorption of carbohydrates.     

Applicability of the stamm reaction for rancidty

Summary The Korpaczy modification of the Stamm reaction for detecting rancidity in fats has been applied to a variety of fats and oils, including hog and beet fat, cottonseed oil, a number of other vegetable and seed oils, and a group of marine oils. This reaction has been shown to be generally inapplicable to vegetable, seed and marine oils but applicable to lard and beef fat.     

Effect of dietary palm oil and its fractions on rat plasma and high density lipoprotein lipids

Male Sprague Dawley rats were fed semipurified diets containing 20% fat for 15 weeks. The dietary fats were corn oil, soybean oil, palm oil, palm olein and palm stearin. No differences in the body and organ weights of rats fed the various diets were evident. Plasma cholesterol levels of rats fed soybean oil were significantly lower than those of rats fed corn oil, palm oil, palm olein or palm stearin. Significant differences between the plasma cholesterol content of rats fed corn oil and rats fed the three palm oils were not evident. HDL cholesterol was raised in rats fed the three palm oil diets compared to the rats fed either corn oil or soybean oil. The cholesterol-phospholipid molar ratio of rat platelets was not influenced by the dietary fat type. The formation of 6-keto-PGF_1α was significantly enhanced in palm oil-fed rats compared to all other dietary treatments. Fatty acid compositional changes in the plasma cholesterol esters and plasma triglycerides were diet regulated with significant differences between rats fed the polyunsaturated corn and soybean oil compared to the three palm oils.     

Magnesium silicate treatment of dietary heated fats: Effects on rat liver enzyme activity

In an effort to reduce the deleterious nutritional effects of oxidation products generated in heated fats, a partially hydrogenated soybean oil (PHSBO) used 7 d (7-DH) for frying foodstuffs was obtained from a commercial deep-fat frying operation. The used fat was treated with magnesium silicate (T-7DH). Isocaloric diets containing 15% of either 7-DH or T-7-DH fats were prepared and fed to male weanling rats for 10 wk in a pair-feeding experiment and compared to control rats fed nonheated PHSBO (NH). Animals fed the 7-DH diet showed higher liver enzyme cytochrome b₅ and P₄₅₀ activity than the T-7DH diet compared to the NH group, suggesting a positive effect of the treatment. These results suggested the presence of lower amounts of harmful compounds in the diet containing the heated used oil which had been treated with the active adsorbent.     

Absorption in rats of rapeseed, soybean, and sunflower oils before and following moderate heating

Rapeseed, soybean, and sunflower oil were heated for 15 min in a 5-mm oil layer in a pan at 180°C. The fatty acid composition was almost unaffected by heating, while the polymer content rose slightly and the tocopherol content decreased, except in soybean oil. The absorption of oils before and after heating was investigated in lymph-cannulated rats. Oils were administered as emulsions through a gastrostomy tube and lymph was collected during the next 24 h. The highest accumulated lymphatic transport of total fatty acids was observed after administration of rapeseed oil, and the lowest after heated sunflower oil. The accumulated transport was similar for all unheated oils. The transport of fatty acids was significantly lower in rats receiving heated oil compared to those receiving the corresponding unheated oil. Small increases in polymers may have contributed to the decreased lymphatic transport of oil following heating, although this probably does not fully explain the effect. The absorption of sunflower oil was more affected by heating than the absorption of soybean or rapeseed oil. Furthermore, the largest decrease in total activity of tocopherols following heating was observed in sunflower oil. Overall, these results demonstrate that the absorption of vegetable oils is affected by moderate heating.     

Increased plasma triglyceride secretion in EFA-deficient rats fed diets with or without saturated fat

Metabolic responses to essential fatty acid-deficiency in rats include an increased rate of triglyceride secretion into the plasma, a large reduction in the HDL₁ plasma lipoprotein concentration, and increased concentrations of liver triacylglycerols and cholesteryl esters. Because of differences in the types of EFA-deficient diets used, it is not clear whether these responses were solely due to the absence of EFA from the diet or whether saturated fat, or differences in acyl group chain length in this fat, might be responsible. Therefore, we fed rats diets differing only in amounts and kinds of fat, and measured triacylglycerol secretion rates and liver concentrations of triacylglycerols and cholesteryl esters, for comparison with our earlier measurements of plasma high density lipoprotein subpopulations in rats fed exactly the same diets. The purified diets contained either no fat, 5% by weight hydrogenated coconut oil, 5% hydrogenated cottonseed oil, or each of these three diets supplemented with 1% safflower oil, or 5% corn oil. We also fed some rats a nonpurified stock diet for comparison with literature reports. The present results indicate that the metabolic responses to essential fatty acid deficiency described above are definitely due to essential fatty acid-deficiency and not to the presence or chain length of acyl groups in saturated fat in the diet. Presented in part at the May 1984 meeting of the American Oil Chemists' Society in Dallas, Texas.     

Influence of dietary fat and protein on serum cholesterol of cholesterol-fed chicks

Summary Cottonseed oil, partially hydrogenated cottonseed oil and corn oil, were fed at 4% and 10% of the diets with two levels of protein, 19% and 25%, and with 0.5% cholesterol to cockerels 21 days of age for a period of 38 days. Blood samples were obtained at 0, 14, 24, and 38 daysvia heart puncture. The data indicate that the serum cholesterol value, irrespective of the level or type of fat, was significantly lower in those groups of birds which were fed the higher level of protein. Excluding the combination of 19% protein and 10% cottonseed oil, the degree of saturation did not have any apparent effect upon serum cholesterol because the mean differences among the oils and between the fat levels were not statistically significant.     

Effects of dietary heated fats on rat liver enzyme activity

The objective of this study was to evaluate the effects of dietary heated fats from a commercial deep-fat frying operation on rat liver enzyme activity. The fats, partially hydrogenated soybean oil (PHSBO) used for four days and for 7 days (7-DH) for frying foodstuffs in a commercial restaurant, were fed to rats in either free access to food or by pair-feeding graded doses. All diets were isocaloric and contained 15 g/100 g of diet. Experiments were conducted with control rats fed nonheated (NH) PHSBO diet. Animals fed 7-DH diet in each set of experiments had larger amounts of cytochromes P₄₅₀ and b₅ and greater activity of NADPH-cytochrome P₄₅₀ reductase when compared to controls. The activities of carnitine palmitoyltransferase-I and isocitrate dehydrogenase were significantly lower in rats fed test diets in comparison to controls. A significantly depressed activity of glucose 6-phosphate dehydrogenase was also noticed for these animals when compared to those fed NH. In addition, liver and microsomal protein concentrations were significantly greater in rats fed the used oils in comparison to controls, and liver glycogen was significantly lower.