Impact of trans fatty acids of ruminant origin compared with those from partially hydrogenated vegetable oils on CHD risk

There is a considerable overlap of trans fatty acid (TFA) isomers in fats of ruminant origin and partially hydrogenated vegetable oils (PHVOs), with many isomers in common. However, there is a considerable difference in the amount of individual TFAs in both sources. At present it is uncertain as to which component(s) of TFAs created by chemical hydrogenation are responsible for their negative metabolic effects. There is evidence of unfavourable effects of TFAs from hydrogenated vegetable oils on LDL and other risk factors of atherosclerosis. There is no evidence that the predominant TFA in milk, vaccenic acid, exerts these unfavourable effects. Prospective studies addressing the effect of TFA intake on coronary heart disease risk, whose estimate of TFA intake was based on dietary protocols, were mostly carried out in populations with a relatively low intake of dairy or ruminant TFAs. Nevertheless, several of them showed a significantly or non-significantly decreased risk with increasing intake of animal TFAs, or at least no increased risk. Up to now there is no human study available that investigates the effect of different TFAs under “Ceteris paribus” conditions (isoenergetic diets with otherwise identical fatty acid profile). By now the production of milk fat samples differing mainly in TFA content is feasible and would allow such controlled intervention studies.