The structure of the carbon chain of trans fatty acids (TFAs) is similar to that of the saturated fatty acids (SFA) molecules, which takes effect in higher melting points. There are two major sources of TFAs, those that come from ruminant animals and those that are produced during technological process. Results of numerous studies show that the intake of either saturated or TFAs raises blood levels of LDL cholesterol. This fraction of cholesterol is a risk factor of heart diseases. In addition to raising “bad” cholesterol, TFAs reduce blood levels of HDL cholesterol which protects against heart diseases. In contrast to hydrogenated TFAs, those originating from ruminants are healthy components of diet. Although a negative influence of TFAs on health has been scientifically proven, the UE has not yet adopted any regulations concerning reduction of TFAs levels in food (except Denmark) or labelling TFAs content. Nevertheless, on the basis of many experiments, a conspicuous decrease of TFA level in foods is observed. Food and nutritional organisations recommend that the intake of TFAs by all population groups should be kept as low as possible, which is about 1% of energy intake or less.