The cardiovascular health of the nation - should we be advocating a low-carbohydrate, high-fat diet?

A spate of articles in the lay press have advocated a low-carbohydrate high-fat diet for cardiovascular health, questioning 'What's cholesterol got to do with it?' and whether cholesterol-lowering drugs, particularly statins, are doing more harm than good. It is correct that excessive carbohydrate intake, particularly refined carbohydrates found in sugary drinks and energy snacks, is behind the global 'diabesity' epidemic of overweight, obesity and type 2 diabetes mellitus (T2DM). However, it is wrong to conclude that high carbohydrate intake is the major cause of atherosclerosis, the leading cause of cardiovascular disease (CVD). If a high-carbohydrate diet increases the risk for obesity and T2DM, and if diabetes is a risk factor for atherosclerosis, one cannot conclude that a high-carbohydrate diet is the cause of atherosclerosis. Atherosclerosis, particularly coronary artery disease (CAD), is not a disease of carbohydrate metabolism and there is no evidence to support the measurement of carbohydrate or insulin resistance to identify atherosclerosis risk. 1 There is also little evidence that low-carbohydrate diets prevent atherosclerosis. Marathon runners who 'carbo-load' – consume large quantities of refined and complex carbohydrates before major events – are exquisitely sensitive to insulin, as they have a low percentage body fat and are in top physical condition. If insulin resistance was the cause of atherosclerosis, patients with familial hypercholesterolaemia (FH) – who, if untreated, develop severe atherosclerosis and often die prematurely from CVD (particularly CAD) in their 40s or 50s – would have marked insulin resistance, which they do not. 2 In addition, small dense low-density lipoprotein cholesterol (LDL-C) particles, typical of the metabolic syndrome or T2DM, are thought to be more atherogenic. However, subjects with FH tend to have large LDL-C particles and are at much greater risk for atherosclerosis. 3 Although there are several major risk factors for atherosclerosis, such as hypertension, diabetes and cigarette smoking, elevated LDL-C is the driving force. Hunter-gatherer populations still following an indigenous lifestyle show little or no evidence of atherosclerosis, even in individuals living into their 70s or 80s. 4 In populations of low serum cholesterol levels, such as the rural Chinese, CAD prevalence is also low, even in the presence of other CAD risk factors. Persons with genetically lifelong low LDL-C levels – resulting from hypobetalipoproteinaemia or loss-of-function mutations in the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene – have a markedly reduced risk (80-90%) of developing CAD, despite a similar prevalence of other CVD risk …