Little evidence that high intake increases the risk

Increasing the amount of polyunsaturated fat in people's diets has been widely advocated as a means of reducing their risk of heart disease. Compared with carbohydrates, dietary polyunsaturated fat reduces low density lipoprotein cholesterol and raises high density lipoprotein cholesterol concentrations,1 and in several intervention trials people taking diets that were high in polyunsaturated fat and low in saturated fat had significantly lower rates of coronary heart disease.2 3 In the United States the average intake of polyunsaturated fat as a proportion of total energy intake has increased from about 3% in the 1950s to 6% today. This increase, which is due to both increased consumption of vegetable fats and reduced hydrogenation of vegetable oils, may have contributed to the massive decline in the prevalence of coronary heart disease in the United States over the past 30 years. Further increases in consumption, to up to 10% of total energy intake, have been recommended.4 But the question still remains: are such high levels of polyunsaturated fat in the diet safe?

The main concern is that diets …