Fats and atheroma: a retrial

The controversy over medical endorsement of dietary measures to reduce cholesterol intake has been reconsidered. The results of several published reports that apparently do not confirm the association between diet, cholesterol concentrations, and ischaemic heart disease (IHD) were found to be largely inapplicable to the argument. Results of primary prevention trials, however, suggested that lowering the cholesterol concentration had a beneficial effect in reducing morbidity from IHD. The "average Western diet" is particularly associated with accelerated or premature atherosclerotic disease, yet the saturated fatty acid component of the diet may be only one of several factors relevant to IHD. Such diets are usually high in refined carbohydrate and total energy intake. Disordered nutrition generally, and other environmental and constitutional factors seem to be important in the aetiology of IHD. A prudent diet, incorporating decreased intake of fats, simple sugars, and refined carbohydrate, with polyunsaturated fats comprising less than 25% of total energy intake, may be the best method of reducing the incidence of IHD and other diseases of overnutrition.

Fats and atheroma: an inquest

All well-controlled trials of cholesterol-reducing diets and drugs have failed to reduce coronary (CHD) mortality and morbidity. Nevertheless, commercial, professional, and even government-sponsored propaganda continues. Experimentally some vegetable oils and hardened fats can be more damaging to arteries than butter. There are other hazards to heart muscle from vegetable oils. Israelis consume a high polyunsaturated fat diet equal to that recommended for prevention of CHD in USA but their CHD incidence is very high. Urban Bedouins are also affected. The primary clofibrate prevention trial underlines unacceptable risks which could apply also to diets. Official medical endorsement of these cholesterol reducing measures should be withdrawn.

Carcinogenesis induced by 7,12-dimethylbenz[a]anthracene in c3H-A vyfB mice: influence of different dietary fats

The effect of a diet containing either sunflower-seed oil (polyunsaturated fat diet) or tallow (saturated fat diet) on 7,12-dimethylbenz[a]anthracene (DMBA)-induced carcinogenesis in C3H-A vyfB mice was examined. After receiving either diet for 28 days, some of the mice were given an intragastric dose of 5 mg DMBA. To identify the stage of carcinogenesis that might be influenced by dietary fat, the diets of half of the mice were then interchanged so that those previously fed the saturated fat diet were fed the polyunsaturated fat diet and vice versa. The cumulative incidence of tumor-bearing mice was significantly greater among the females fed the polyunsaturated fat diet compared to those fed the saturated fat diet. This enhancement of carcinogenesis was observed only when the mice were fed the polyunsaturated fat diet after DMBA administration. Similar trends were observed in the male mice, but these mice developed fewer tumors and none of the differences between the tumor incidences were statistically significant. The most common sites for tumors in the male mice were the liver, lungs, and skin, whereas those for tumors in the females were the mammary glands and ovaries. The differences in tumor incidence suggest that carcinogenesis was enhanced by the polyunsaturated fat diet during the promotion stage of carcinogenesis.

The nutritional epidemiology of cardiovascular disease

A basic review of the extensive literature focusing on the major risk factors of atherosclerotic coronary heart disease and stroke, i.e., elevation of blood lipids related to diet, blood pressure elevation, and genetic factors using the traditional epidemiological model of interaction between host, agent, and environment, has strongly supported the concept that diet and particularly saturated fat and/or cholesterol are significant contributors to the elevation of blood lipids, especially cholesterol, and contribute importantly to the premature development and mortality of atherosclerotic coronary heart disease. Certainly genetics exert an important impact on this process. To date it remains unclear whether or not major changes in the dietary pattern of huge population groups can be practically effected. The minor dietary modifications so far studied in the average atherosclerosis-prone population cannot be anticipated to make a major dent in the epidemic proportions of atherosclerotic coronary heart disease. It is quite clear that prospective preventive medicine must be implemented at a very early age in the pediatric age group, in which atherosclerosis is now recognized by many as the number one pediatric problem. Tremendous biochemical advances have provided new insights in knowledge regarding the transport of blood lipids, particularly cholesterol, and the regulatory mechanisms at the cellular level for cholesterol under normal circumstances and in the genetic influenced hyperlipidemias (TABLE 4). A bright future lies ahead for the reduction of the epidemic of atherosclerosis which could be greatly enhanced by a greater personal responsibility for health care and a much more careful and prudent diet selection and exercise managment.

Effect of dietary polyunsaturated fat on the growth of a transplantable adenocarcinoma in C3HAvyfB mice

Weaning male and female C3HAvyfB mice were fed a low-fat (4.5%) diet until they were 60-70 days of age when they were fed high-fat (18.6%) diets containing either sunflower-seed oil (polyunsaturated fat diet) or tallow (saturated fat diet). After receiving either of the high-fat diets for 4 weeks, each mouse received an inoculum of approximately 1,700 single cells from a transplantable mammary adenocarcinoma. The cumulative incidence of tumor-bearing mice was significantly greater among both males and females fed the polyunsaturated fat diet than among males and females fed the saturated fat diet. The mean times elapsed before palpable tumors developed were less when mice were fed the polyunsaturated fat diet than when mice were fed the saturated fat diet, but these differences were not statistically significant. The cumulative incidence of tumor-bearing mice was also significantly greater among females than males. The results supported the suggestion from previous work in this laboratory that the polyunsaturated fat diet exerts its effect on the promotional stage of carcinogenesis rather than on the initial event of neoplastic transformation.

Do polyunsaturated fats predispose to malignant melonoma?

The consumption of polyunsaturated fats of patients with malignant melanoma and of a control group of patients with benign naevi has been compared in order to determine whether polyunsaturated fats predispose to the development of malignant melanoma. Patients with malignant melanoma had not consumed excessive quantities of polyunsaturated fats. Thus, there was no evidence to indicate that ingestion of polyunsaturated fats is associated with an increase in incidence of melanoma.

Effect of dietary fats on the incidence of 7,12-dimethylbenz(a)-anthracene-induced tumors in rats

Female rats have been fed high fat diets containing either polyunsaturated or saturated fat. After being fed either of the diets for 4 weeks, some of the animals received an intragastric dose of 7,12-dimethylbenz(a)anthracene (DMBA). At this point, the diets of half of the animals were interchanged so that animals previously fed the polyunsaturated fat diet were fed the saturated fat diet and vice versa. The cumulative incidence of tumor-bearing rats among DMBA-dosed rats was greater when the polyunsaturated fat diet was fed. The mean induction time of tumors decreased and the proportion of tumor-bearing rats which developed malignant tumors increased when the polyunsaturated fat diet was fed. This promotional effect of the polyunsaturated fat diet was exerted only when the diet was fed after DMBA administration.

The limitations of statistical correlations in pathology

Many hypotheses as to the causes of disease, for example some of those for coronary heart disease, depend on statistical correlations. It is well known that correlations do not prove a cause-and-effect relationship, yet it is often tempting to ignore this axiom.