Fats and atheroma: an inquest

Atherosclerosis pathogenesis from the perspective of microvascular dysfunction

The article discusses different points of view on atherosclerosis development. The facts confirming the lipid hypothesis are presented. Attention is drawn to the possible participation of vasa vasorum in the development of atherosclerosis.

A network analysis of the propagation of evidence regarding the effectiveness of fat-controlled diets in the secondary prevention of coronary heart disease (CHD): Selective citation in reviews

OBJECTIVE

To examine how the first randomised controlled trials (RCTs) evaluating the efficacy of cholesterol-lowering diets in the secondary prevention of coronary heart disease were interpreted in reviews of the literature prior to the National Institutes of Health consensus conference in 1984.

DESIGN

Claim-specific citation network analysis was used to study the network of citations between reviews and RCTs over a defined period (1969-1984). RCTs were identified and classified according to whether their conclusions supported or opposed the use of dietary fat modification/restriction in the secondary prevention of coronary heart disease. Each review published in this period that cited any of the RCTs was classified as supportive, neutral, or unsupportive to the use of dietary fat modification based on a quotation analysis of its evaluation of the findings of these RCTs. Citation bias and underutilisation were detected by applying a comparative density measure, in-degree centrality, and out-degree in a series of sub-graph analyses.

RESULTS

In total, 66 unique publications were identified (four RCTs-one supportive, three unsupportive; 62 reviews-28 supportive, 17 neutral, 17 unsupportive). On average, supportive reviews underutilised the available RCTs to a greater degree than other reviews. Amongst the supportive group, citation bias was common-23 (82%) reviews cited only the one RCT that was supportive.

CONCLUSION

Most reviews that disseminated a supportive evaluation of the results of RCTs in the context of secondary prevention cited only data that supported this position.

History of the cholesterol controversy in Britain

The lipid hypothesis, the concept that cholesterol plays a causal role in atherosclerosis and cardiovascular disease, has been the subject of a controversy which started in the 1950s, peaked in the 1970s and 80s and then subsided in the 1990s. It was finally resolved by the positive outcome of the Scandinavian Simvastatin Survival Study, the first of 14 prevention trials using statins which showed that lowering cholesterol reduced both cardiovascular events and total mortality. This commentary focuses primarily on the events and people involved in the cholesterol controversy in Britain. The foremost critics of the lipid hypothesis are now deceased but unfortunately for many of the patients with hypercholesterolaemia and coronary heart disease it took the best part of 50 years to disprove the sceptics. This brief account relates why it took so long.

Thematic review series: The Pathogenesis of Atherosclerosis. An interpretive history of the cholesterol controversy: part II:the early evidence linking hypercholesterolemia to coronary disease in humans

The first in this series of historical reviews dealt with the pioneering animal model work of Anitschkow, implicating blood cholesterol in the pathogenesis of atherosclerosis, and the pivotally important work of Gofman, providing evidence that lipoprotein-bound cholesterol was a major factor in the human disease. This second installment reviews the early lines of evidence linking hypercholesterolemia in humans to the progression of atherosclerosis and the risk of coronary heart disease. The argument is made that by 1970, the evidence was already strong enough to justify intervention to lower blood cholesterol levels if all the available lines of evidence had been taken into account. Yet, it would be almost two decades before lowering blood cholesterol levels became a national public health goal. Some of the reasons the "cholesterol controversy" continued in the face of powerful evidence supporting intervention are discussed.

Thematic review series: the pathogenesis of atherosclerosis. An interpretive history of the cholesterol controversy: part I

This is the first of a series of reviews of the controversy that swirled around the "lipid hypothesis" of atherosclerosis for so many years. Today, in the era of the statins, there is no longer any doubt about the value of decreasing blood cholesterol levels. In fact, "the lower the better" is the position of many clinicians. However, getting to this point has been a long uphill battle marked by heated debate and sometimes violent disagreement. The history of this controversy is worth telling for its own sake and because remembering it may help us avoid similar mistakes in the future. The history of this controversy is worth telling for its own sake and because remembering it may help us avoid similar mistakes in the future.

Diet and risk of coronary heart disease and type 2 diabetes

A high intake of saturated fat is an important risk factor for coronary heart disease (CHD) and type 2 diabetes. However the declining rates of CHD in many affluent societies and the steady increase in type 2 diabetes worldwide suggest that these important causes of serious morbidity and premature mortality have differing risk or protective factors worldwide. Changed macronutrient composition, reduced cigarette smoking, and improved treatment of risk factors and acute cardiac events might explain the reduction in risk of CHD, whereas the increasing rates of obesity are probably the most important explanation for the increase in diabetes. Coronary risk factors associated with diabetes could outweigh improvements in conventional cardiovascular risk factors such that the decline in CHD could be stopped or reversed unless rates of obesity can be reduced. Reduced intake of saturated fatty acids and other lifestyle interventions aimed at lowering rates of obesity are the changes most likely to reduce the epidemic numbers of people with type 2 diabetes and CHD.

Copper and ischemic heart disease

Absolute or relative deficiency of copper is hypothesized to be of prime importance in the etiology of ischemic heart disease. According to recent estimates, only 25% of the diets in the United States contain the 2 mg of copper thought to be required daily by adults. Some of these diets have ratios of zinc to copper greater than those that have produced hypercholesteremia in animals. There are many epidemiologic associations between the ratio of zinc to copper and dietary characteristics, organ analyses, clinical status, and environmental features that relate the metabolism of these elements to the anatomy, chemistry, pathology, pharmacology, and physiology of ischemic heart disease. Animals deficient in copper or exposed to a high dietary ratio of zinc to copper, which can produce a relative copper deficiency, are hypercholesteremic and hyperuricemic, and have glucose intolerance and abnormalities of the electrocardiogram. Their hearts and arteries have abnormal connective tissue, lipid deposits, and inflammatory changes; they die suddenly, often with ruptured hearts. Hypercholesteremia and glucose intolerance have been found in men depleted of copper and in children with Menkes' disease, an inability to absorb copper.

Dietary advice and heart disease: a nursing dilemma?

This paper reviews the debate concerning the relationship between dietary fats and heart disease. The paper also addresses the questions "should nurses persuade patients with heart disease to follow a low-fat, low-cholesterol diet?", "If so, will patients be less liable to a heart attack?" and "are such recommendations based on valid scientific evidence?". The author examines the recent evidence which is critical of such dietary regimens, and claims that much of the dietary advice given by nurses to these patients is biased, misleading and scientifically unfounded.

Contribution of the risk factor concept to patient care in coronary heart disease

This article deals with the question of whether or not the risk factor concept, a principal aspect of preventive cardiology, has contributed to patient care in coronary heart disease. The risk factors considered are plasma cholesterol, high blood pressure, smoking, diabetes and marked obesity. With the exception of plasma cholesterol and diabetes, all of these factors enhance myocardial oxygen consumption and thus, in the presence of coronary insufficiency, promote myocardial ischemia. Their modification is therefore good general medical practice, even if not related to coronary atherosclerosis. Diabetes needs adequate medical treatment in patients both with and without coronary atherosclerosis. Because of the occasional occurrence of spontaneous regression of coronary atherosclerosis and the morphologic and functional complexity of coronary artery pathology, it has never been and probably never will be demonstrated that lowering plasma cholesterol levels by diet or other means will cause regression of coronary atherosclerosis. It follows that modification or treatment of risk factors is implemented for good medical reasons but does not demonstrably or predictably affect coronary artery disease. It is concluded that the contribution of the risk factor concept to patient care in coronary heart disease has been, and still is, trivial.

A randomised, double-blind, cross-over study into the effect of sequential mestranol and norethisterone on climacteric symptoms and biochemical parameters

A randomised, double-blind, cross-over study into the effect of graded sequential mestranol and norethisterone on climacteric symptoms was performed. The study group consisted of 23 post-menopausal women who had previously undergone hysterectomy. Active therapy resulted in a significant reduction in hot flushes and night sweats. There was a slight improvement in insomnia, lack of energy and confidence but the other symptoms were not significantly altered. A small placebo effect was noted but this was only significant 1 mth after active treatment had been discontinued in the group of women receiving placebo second. Active treatment also resulted in a significant reduction in serum sodium, calcium, albumin, alkaline phosphatase and cholesterol, and increase in serum triglycerides, but no alteration in the other biochemical parameters, weight or blood pressure.

Performance of low-pressure cuffs. An experimental evaluation

A study was carried out in vitro to determine the minimum intracuff pressure needed to produce no-leak ventilation and prevent aspiration in Portex Profile and Searle Medical Sensiv endotracheal tubes. The mean pressures required to produced no-leak ventilation were 4.16 and 1.06 kPa respectively and the mean pressures at which aspiration occurred were 2.93 and 0.54 kPa respectively. The implications of these findings are discussed and recommendations are made regarding cuff specifications.

Non-surgical management of peripheral vascular disease: a review

Although the outlook for a pronounced improvement in the ischaemic limb that cannot be surgically treated remains bleak, cessation of smoking, encouragement of exercise, and the withdrawal of vasoconstricting agents may give some symptomatic relief. There is little evidence that vasodilators or antiplatelet agents have much to offer.

Epidemiology of coronary heart disease. Lessons from North and South Belgium

Differences in food intake, smoking and drinking habits in the North and the South of Belgium have been studied with the aid of household data gathered by the National Institute of Statistics, Brussels, 1973-74. Consumption of sugar, vegetables, fruits, crude fibre and meat was almost identical between the regions. Consumption of bread, fish and salt intake were slightly higher in the North and alcohol consumption higher in the South. The major differences were located in fat consumption. Saturated fat as a percentage of dietary energy amounted to 15·8% in the North v. 18·5% in the South; polyunsaturated fat was, respectively for the North and South, 7·9% and 5·5%. Dietary cholesterol intake was 320 mg/day in the North against 400 mg/day in the South. The difference in serum cholesterol, calculated with the Keys formula, was 11·9 mg%, a value totally consistent with the observed values.

The difference in saturated fat intake between the regions was almost entirely due to the difference of butter intake, thereby explaining why butter correlated so perfectly with mortality in different parts of Belgium. Similar correlations were found in France and Western Europe.

The mortality trends in both regions were compared with the available data on fat consumption over the last 15 years. Again a decreasing intake of saturated fat (less butter and less common (hard) margarine) was associated with a decreasing coronary, cardiovascular and total mortality in both the North and the South. The time-related decrease discussed in the second part was quantitatively similar to one obtained in the first part from geographical differences, making a spurious association extremely unlikely.

Similar dietary changes with identical results in terms of mortality have also been observed in the U.S.A. and Finland.

The effect of various regimens of hormone therapy on serum cholesterol and triglyceride concentrations in postmenopausal women

The serum cholesterol and triglyceride concentrations of 84 postmenopausal women both before and after 2, 6 and 12 months therapy with various regimens of hormone therapy were measured. There was little alteration in mean serum cholesterol concentration with cyclical oestrogens but both sequential mestranol and norethisterone and sequential oestradiol valerate and norgestrel significantly reduced the mean serum cholesterol concentration to a level similar to that found in age-matched premenopausal women. There was a small and sometimes significant rise in serum triglyceride concentration with cyclical oestrogens. Sequential mestranol and norethisterone significantly elevated serum triglyceride levels, but sequential oestradiol valerate and norgestrel significantly depressed them. The results suggest that the progestogenic agent norgestrel has an important role to play in reducing both serum cholesterol and triglyceride levels, and that the sequential preparations, by virtue of their greater cholesterol lowering effect, should perhaps be preferred to cyclical oestrogens.

Epidemiology as a guide to clinical decisions. The association between triglyceride and coronary heart disease

The hypothesis that triglyceride is a cause of coronary heart disease, although unconfirmed and never universally accepted, has nonetheless strongly influenced the practice of preventive medicine. We have examined the epidemiologic association between triglyceride and coronary heart disease to evaluate the validity of inferring that there is a causal relation between the two. Neither the evidence from published studies nor an analysis of data from the Western Collaborative Group Study provides strong support for the causal hypothesis. Information from other scientific disciplines is also meager, contrasting with the coherence of diverse evidence supporting the hypothesis that cholesterol is a cause of coronary heart disease. These arguments fall short of disproving the belief that lowering triglyceride will prevent coronary heart disease, especially since triglyceride and cholesterol are inextricably associated through mutual lipoprotein carriers. But we propose that the ethics of preventive medicine place the burden of proof on the proponents of intervention. We therefore recommend that widespread screening and treatment of healthy persons for hypertriglyceridemia be abandoned until more persuasive evidence becomes available.

New perspectives on the dietary management of diabetes

Some of the confusions and misconceptions surrounding the diabetic diet are discussed together with the reasons why there is controversy over its formation. Current understanding of the contribution which diet may make to the prevention of complications is outlined. A new approach to the dietary management of the diabetic is suggested.

Dietary fats and coronary heart disease: unfinished business

In the scientific and lay press, dietary recommendations that are aimed at prevention of coronary heart disease in the general public are appearing more and more frequently. The dietary pattern that is now most widely advocated is a low-fat, low cholesterol diet with a polyunsaturated/saturated ratio of 1. The argument for such a dietary change is supported mainly by extrapolations from epidemiological data and from animal experimentation. Reasons are given for concluding that the recommendations are unwise, impractical, and unlikely to lead to a reduced incidence of arteriosclerotic disease. Sinc complacency is equally inappropriate, a few practical questions are outlined that should be settled before the public is assured that a low-fat diet will lead to a reduced risk of coronary heart disease.