Modern fat technology: what is the potential for heart health?

Saturated and trans-fatty acids raise total cholesterol and LDL-cholesterol and are known to increase the risk of CHD, while dietary unsaturated fatty acids play important roles in maintaining cardiovascular health. Replacing saturated fats with unsaturated fats in the diet often involves many complex dietary changes. Modifying the composition of foods high in saturated fat, particularly those foods that are consumed daily, can help individuals to meet the nutritional targets for reducing the risk of CHD. In the 1960s the Dutch medical community approached Unilever about the technical feasibility of producing margarine with a high-PUFA and low-saturated fatty acid composition. Margarine is an emulsion of water in liquid oil that is stabilised by a network of fat crystals. In-depth expertise of fat crystallisation processes allowed Unilever scientists to use a minimum of solid fat (saturated fatty acids) to structure a maximum level of PUFA-rich liquid oil, thus developing the first blood-cholesterol-lowering product, Becel. Over the years the composition of this spread has been modified to reflect new scientific findings and recommendations. The present paper will briefly review the developments in fat technology that have made these improvements possible. Unilever produces spreads that are low in total fat and saturated fat, virtually free of trans-fatty acids and with levels of n-3 and n-6 PUFA that are in line with the latest dietary recommendations for the prevention of CHD. Individuals with the metabolic syndrome have a 2-4-fold increased risk of developing CHD; therefore, these spreads could make a contribution to CHD prevention in this group. In addition, for individuals with the metabolic syndrome the spreads could be further modified to address their unique dyslipidaemia, i.e. elevated blood triacylglycerols and low HDL-cholesterol. Research conducted in the LIPGENE study and other dietary intervention studies will deliver the scientific evidence to justify further modifications in the composition of spreads that are healthy for the heart disease risk factors associated with the metabolic syndrome.

Functional food science and the cardiovascular system.

Cardiovascular disease has a multifactorial aetiology, as is illustrated by the existence of numerous risk indicators, many of which can be influenced by dietary means. It should be recalled, however, that only after a cause-and-effect relationship has been established between the disease and a given risk indicator (called a risk factor in that case), can modifying this factor be expected to affect disease morbidity and mortality. In this paper, effects of diet on cardiovascular risk are reviewed, with special emphasis on modification of the plasma lipoprotein profile and of hypertension. In addition, dietary influences on arterial thrombotic processes, immunological interactions, insulin resistance and hyperhomocysteinaemia are discussed. Dietary lipids are able to affect lipoprotein metabolism in a significant way, thereby modifying the risk of cardiovascular disease. However, more research is required concerning the possible interactions between the various dietary fatty acids, and between fatty acids and dietary cholesterol. In addition, more studies are needed with respect to the possible importance of the postprandial state. Although in the aetiology of hypertension the genetic component is definitely stronger than environmental factors, some benefit in terms of the development and coronary complications of atherosclerosis in hypertensive patients can be expected from fatty acids such as alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid. This particularly holds for those subjects where the hypertensive mechanism involves the formation of thromboxane A2 and/or alpha 1-adrenergic activities. However, large-scale trials are required to test this contention. Certain aspects of blood platelet function, blood coagulability, and fibrinolytic activity are associated with cardiovascular risk, but causality has been insufficiently proven. Nonetheless, well-designed intervention studies should be initiated to further evaluate such promising dietary components as the various n-3 and n-6 fatty acids and their combination, antioxidants, fibre, etc. for their effect on processes participating in arterial thrombus formation. Long-chain polyenes of the n-3 family and antioxidants can modify the activity of immunocompetent cells, but we are at an early stage of examining the role of immune function on the development of atherosclerotic plaques. Actually, there is little, if any, evidence that dietary modulation of immune system responses of cells participating in atherogenesis exerts beneficial effects. Although it seems feasible to modulate insulin sensitivity and subsequent cardiovascular risk factors by decreasing the total amount of dietary fat and increasing the proportion of polyunsaturated fatty acids, additional studies on the efficacy of specific fatty acids, dietary fibre, and low-energy diets, as well as on the mechanisms involved are required to understand the real function of these dietary components. Finally, dietary supplements containing folate and vitamins B6 and/or B12 should be tested for their potential to reduce cardiovascular risk by lowering the plasma level of homocysteine.

Health aspects of fish and n-3 polyunsaturated fatty acids from plant and marine origin.

An expert workshop reviewed the health effects of n-3 polyunsaturated fatty acids (PUFA), and came to the following conclusions. 1. Consumption of fish may reduce the risk of coronary heart disease (CHD). People at risk for CHD are therefore advised to eat fish once a week. The n-3 PUFA in fish are probably the active agents. People who do not eat fish should consider obtaining 200 mg of very long chain n-3 PUFA daily from other sources. 2. Marine n-3 PUFA somewhat alleviate the symptoms of rheumatoid arthritis. 3. There is incomplete but growing evidence that consumption of the plant n-3 PUFA, alpha-linolenic acid, reduces the risk of CHD. An intake of 2 g/d or 1% of energy of alpha-linolenic acid appears prudent. 4. The ratio of total n-3 over n-6 PUFA (linoleic acid) is not useful for characterising foods or diets because plant and marine n-3 PUFA show different effects, and because a decrease in n-6 PUFA intake does not produce the same effects as an increase in n-3 PUFA intake. Separate recommendations for alpha-linolenic acid, marine n-3 PUFA and linoleic acid are preferred.

The association of increasing dietary concentrations of fish oil with hepatotoxic effects and a higher degree of aorta atherosclerosis in the ad lib.-fed rabbit.

The long-term effects of consumption of marine long-chain n-3 polyunsaturated fatty acids (PUFA) on atherosclerosis in the rabbit were examined. Female Dutch rabbits were fed purified diets, containing 40 energy% total fat, for a period of 2.5 years. To study the dose response relationship between fish oil intake and atherosclerosis, four diets were formulated with fish oil levels being 0, 1, 10 and 20 energy%. A fifth and sixth group were fed an alpha-linolenic acid-(C18:3, n-3) and linoleic acid-(C18:2, n-6) rich diet, respectively. Every 6 weeks, blood samples were taken for determination of clinical chemical parameters, triacylglycerol and total cholesterol levels. Feeding 10 and 20 energy% fish oil containing diets, resulted in an increase of liver enzymes (AST, ALT and ALP). Histological evaluation of the liver also revealed adverse effects of fish oil containing diets. Triacylglycerol blood levels were similar in all groups, and remained constant throughout the study. Total cholesterol levels in blood was significantly lower in the animals fed a linoleic acid-rich diet, as compared with the other five groups. An n-3 long-chain PUFA concentration dependent increase in aorta plaque surface area was observed in the fish oil groups. A significant positive relationship was found between the group mean score for severity of liver pathology and the aorta plaque surface area. These results indicate that the long-chain n-3 polyunsaturated fatty acids in fish oil may be hepatotoxic to the herbivorous rabbit, which may interfere with the outcome of atherosclerosis studies. This finding necessitates the exclusion of liver pathology in experimental studies on atherosclerosis in animal models.

Effect of the amount of dietary fat on the development of mammary tumors in BALB/c-MTV mice.

The relationship between dietary fat consumption and the incidence of breast cancer, if any, needs to be quantified so that dietary guidelines can be issued for the prevention of breast cancer. Frequently, only two widely different dietary fat levels, often differing in essential fatty acid content, have been compared in animal models. Moreover, the latent period in common animal models for breast cancer is very short and does not reflect the relatively long latent periods in human breast cancer. We describe a study with BALB/c-MTV mice, a strain with a high average tumor incidence and a latent period of over 60 weeks on average. The mice were fed diets with fat levels ranging from 10% to 40% of energy, in which fat was isocalorically substituted for carbohydrates. The level of linoleic acid in these diets was kept constant at 6.5% of energy. Both the mean tumor incidence and latent periods of the groups fed diets with 10-16% of energy as fat were not significantly different from each other. There were also no differences between these parameters in the groups fed 22-40% of energy as fat. However, the mean incidence and latent period of the groups fed 22% or more of energy as fat was significantly higher than that of the groups fed less fat. We conclude that above about 22% of energy, fat does not influence the incidence and latent period of mammary tumors in BALB/c-MTV mice.

Evaluation of vitamin E requirement and food palatability in rabbits fed a purified diet with a high fish oil content.

The vitamin E requirement of rabbits fed a semi-synthetic diet containing high amounts of fish oil was studied. Three groups of 5 rabbits were fed fish oil diets containing, respectively, 50, 100 and 500 mg/kg vitamin E. Moreover diet palatability was evaluated by using different levels of grass meal: 0.5, 1 and 2%, respectively. Incorporation of 1% grass meal in the diet was sufficient to achieve acceptance of the fish oil diet. Increased vitamin E intake resulted in a dose-related rise in vitamin E levels in serum, blood platelets, liver and adipose tissue. The higher vitamin E intake was reflected by a twofold increase of vitamin E in serum, platelets and adipose tissue, and a tenfold increase in the liver. The adipose tissue revealed histopathological changes of yellow fat disease, mainly in the low-dose vitamin E group. In the liver microgranulomas of lipofuscin-laden macrophages were seen. Vitamin E was found to decrease but not to prevent the formation of these lesions. The results indicate that protection of marine oils against in vivo oxidation is problematic in the rabbit. It is questionable whether in this animal vitamin E is an adequate biological anti-oxidant for very long chain n-3 fatty acids.

Evaluation of jojoba oil as a low-energy fat. 1. A 4-week feeding study in rats.

The nutritional properties of jojoba oil (JO) were examined in a 4-wk feeding study of rats fed a diet with JO at dose levels of 2.2, 4.5 and 9%, supplemented with a conventional fat up to 18%. General health, survival and food intake were not adversely affected. Body-weight gains showed a dose-related decline, which amounted to 20% of the body weight in the high-dose group of both sexes. Clinical chemistry revealed significantly increased levels of various enzymes that were indicative of cell damage. Haematology showed a dose-related increase in white blood cells. On necropsy an apparent distension of the small intestine was found. Histopathological evaluation revealed marked intestinal changes characterized by massive vacuolization and lipid deposition in the enterocytes, accompanied by distension of the villi and an increased cell turnover of small intestinal cells. Faeces production and faeces lipid content were increased with increasing JO levels. The recovery of JO in the faeces also increased in a dose-related manner and was found to be correlated with the intestinal histopathological changes. The significant adverse clinical and histopathological effects observed in this study imply that JO cannot be considered as a promising alternative dietary fat with a low digestibility.

Evaluation of jojoba oil as a low-energy fat. 2. Intestinal transit time, stomach emptying and digestibility in short-term feeding studies in rats.

The influence of jojoba oil (JO) incorporation in the diet on stomach emptying and intestinal transit time, and the digestion and absorption of JO were investigated in short-term feeding studies in rats. The animals were fed purified diets containing 18% (w/w) fat, of which half consisted of a mixture of lard and sunflower seed oil (SF) supplemented with an equivalent amount of JO. The control animals were fed a mixture of lard and SF (18%). No treatment-related differences were observed in the rate of stomach emptying or the intestinal transit time. Comparative lipid analysis of lymph, intestinal content, intestinal mucosa and faeces indicated that most of the ingested JO was degraded and absorbed. Part of the JO was present as wax ester in the lymph. Hydrolysis of JO was much slower than that of triacylglycerols and continued in the alimentary tract beyond the small intestine due to bacterial processes. JO did not influence the absorption of the conventional fat.

Di-n-butyltindichloride uncouples oxidative phosphorylation in rat liver mitochondria.

In this study di-n-butyltindichloride (DBTC) was found to inhibit alpha-ketoacid-stimulated response of rat liver mitochondria to the addition of ADP and the uncoupler carbonyl cyanide p-trifluoromethoxyphenyl hydrazone (FCCP). The alpha-ketoglutarate oxidation was already inhibited at a level of 0.8 nmol DBTC/mg protein. When succinate was used as substrate together with rotenone, the State 3 and FCCP stimulated oxidation were not inhibited by DBTC. But from a level of 8.3 nmol DBTC/mg protein, the State 4 respiration was increased. It is concluded that in low amounts DBTC specifically blocks alpha-ketoacid dehydrogenases, but higher concentrations of this compound uncouples oxidative phosphorylation. However, this uncoupling will be masked when the NADH production from substrate oxidation is decreased by DBTC as will be in case of alpha-ketoacids.

Fish oil-induced yellow fat disease in rats. IV. Functional studies of the reticuloendothelial system.

In rats with "stage S/E" yellow fat disease an injection of colloidal carbon resulted in a marked reduction in the number of circulating platelets. The death rate of rats with experimental Listeria monocytogenes infection, the number of bacteria in their spleens and the decrease of bacteria in their spleens on the days after infection were the same in rats with yellow fat disease as in controls. The fact that the rats died during the first few days after infection also may indicate that their immunological resistance to L. monocytogenes was not altered by yellow fat disease.

Fish oil-induced yellow fat disease in rats. III. Lipolysis in affected adipose tissue.

Basal and hormone-stimulated lipolysis of adipose tissue was measured at successive stages during the development of fish oil-induced yellow fat disease in rats. Changes of lipolytic activity at an early stage of yellow fat disease were not seen. There was a significant increase of basal lipolysis and a decrease of stimulated lipolysis when many fat cells were affected (stage E). Since the increased basal lipolysis probably originates from degenerated fat cells, the mechanism of enzyme activation is not clear. The decreased stimulated lipolysis was proportional to the number of affected fat cells and resulted from membrane damage of these cells. Increased 5-nucleotidase activity, seen in affected fat cells, may be important, to this reduced stimulated lipolysis.

Fish oil-induced yellow fat disease in rats. I. Histological changes.

Yellow fat disease was induced in young rats given a vitamin E-deficient diet supplemented with 15% fish oil. The changes in adipose tissue of this oil-induced disorder were different from those of natural yellow fat disease in horse, pig and mink. In the natural disease all fat depots had the early stage of yellow fat disease with interstitial lipofuscin-laden macrophages exclusively. In the rat, however, this change was seen only in the subcutaneous fat depot. Moreover, affected adipose tissue of animals with natural disease had extensive fibrosis, but in the rat fibrosis was always absent. Rats with fish oil-induced yellow fat disease had degenerative changes in various fat depots that occurred at various times but in the horse, pig and mink fat depots were affected simultaneously. Lipofuscin accumulated in the reticuloendothelial system in rats. Accumulation in spleen and liver was dependent on vitamin E deficiency, but only the accumulation in the Kupffer cells was correlated with yellow fat disease. Lipofuscin accumulation in the mesenteric lymph node did not depend on vitamin E deficiency.