Dr Malcom Kendrick: Does Diet have a Role to Play in Heart Disease?
Dr Malcolm Kendrick graduated from Aberdeen medical school in 1981, and has been a GP for over 25 years, working with the European Society of Cardiology for some of this time. His scepticism of the evidence behind heart disease risk prompted him to author ‘The Great Cholesterol Con’. This talk was given at the Public Health Collaboration conference 2017 in Manchester.
To start, Dr Kendrick outlines the progression of atherosclerosis, which is a build-up of plaque in the blood vessel walls, weakening them and restricting blood flow to greater degrees over multiple decades. Eventually, the plaque can rupture, forming a clot and preventing blood flow to various organs such as the heart and brain, resulting in a myocardial infarction (heart attack) or stroke, respectively. It is worth noting that ‘heart disease’ and ‘cardiovascular disease’ are often used interchangeably, though cardiovascular disease also includes stroke.
The current mainstream thinking has generated a model of cardiovascular disease, with many risk factors at play, most of which are out of our control (e.g. genetics). Other risk factors include smoking, high blood pressure and dyslipidaemia (abnormal cholesterol and triglycerides). The consensus model puts type 2 diabetes and high saturated fat intake as the causes of dyslipidaemia, whilst placing salt intake as a major cause of high blood pressure. Thus, mainstream advice is to reduce saturated fat intake, reduce salt intake, stop smoking and do more exercise. There are also a number of drug interventions to lower cholesterol, blood pressure and blood sugar. Dr Kendrick disagrees with demonising saturated fat and salt, and offers the alternative explanation that sugar has more involvement.
The idea that saturated fat is correlated with heart disease deaths was popularised by an American scientist named Ancel Keys between the 1960s and 1980s. This supposed relationship is called the diet-heart hypothesis, and it has never been proven. In fact, the evidence on which the hypothesis stands is very questionable indeed, as Dr Kendrick explains. Ancel Keys published a plethora of anti-fat studies in his time, but as Dr Kendrick points out, one very important study, the Minnesota Coronary Experiment, was purposely not published because it disagreed with Keys’ opinion. This study showed that although reducing saturated fat intake lowered cholesterol, it also increased death rate. It is this kind of misconduct and bias that has led to inaccuracies in current medical advice. Even today, evidence that contradicts low fat advice is often ignored. Dr Kendrick gives a few interesting examples of this.
Dr Kendrick accepts that overeating carbohydrates will make you obese and diabetic, and that these conditions will contribute to heart disease in their own right. However, the falling rates of heart disease, despite increased carbohydrate consumption, over the last 40 years imply that diet is not the only factor at play.
There are hundreds if not thousands of risk factors for heart disease, and Dr Kendrick notes that, in his opinion, they all have a root mechanism in common, upon which he has constructed his model. In general, he says, things that increase the risk of cardiovascular disease cause damage to the endothelium (blood vessel lining), clotting and reduced endothelial recovery. Diabetes fits into this category. On the other hand, things that protect the endothelium or reduce clotting, such as vitamin C and magnesium, also reduce cardiovascular disease risk. Dr Kendrick also explains how statins, interestingly, exert any beneficial effects via action on the blood vessels themselves and not via cholesterol.