Trans-fatty acids in the diet: a coronary risk factor?

Dietary trans-FA, mostly derived from partially hydrogenated fats and dairy products, have been suspected of increasing the risk of coronary heart disease (CHD). Recent research in this field has focused on the effects of trans-FA on plasma lipids, and on the epidemiological link between dietary trans-FA and CHD. Trans-FA have consistently been shown to elevate LDL-cholesterol and apolipoprotein B to a similar extent as C12-C16 saturated fatty acids. In addition, trans-FA may reduce HDL-cholesterol, particularly at intakes above 10-20 g/day. Data on the metabolic effects of trans-FA at the lower levels of intake seen in most European countries (below 5 g/day) is still lacking. Two large epidemiological studies from the US found a significant, positive correlation between the dietary intake of trans-FA estimated from food frequency questionnaires and CHD risk. Studies based on the trans-FA content of adipose tissue have provided inconsistent results. The recent EURAMIC study did not find a correlation between adipose tissue trans-FA and CHD in most European countries. However, even this study does not rule out the presence of such a relationship in some northern European regions. These regional differences could for example be due to different sources of trans-FA (hydrogenated vegetable vs. marine oils). However, the significance of the source and composition of trans-FA for their atherogeneity, as well as the mechanisms involved, remain speculative.