However, EFSA's Scientific Panel on Dietetic Products, Nutrition and Allergies (NDA) stressed that current intake levels of TFAs were around 10 times lower than those of saturated fatty acids, whose intake in many European countries exceed dietary recommendations of 10 per cent of total energy.
Furthermore, other potential risks associated with TFAs, such as cancer, type 2 diabetes or allergies, were dismissed as unlikely by the panel, which said that current scientific evidence linking TFA intake to these ailments was "weak or inconsistent".
In carrying out its risk assessment on trans fatty acids, EFSA's NDA panel reviewed evidence concerning both TFAs naturally present in foods, such as in certain animal fats (dairy, beef, lamb and mutton fat), and those occurring as a result of manufacturing processes, for instance hydrogenation of oils (turning liquid oils into solid fats like shortening and margarine by adding hydrogen). Trans fatty acids are also formed during heating and frying of oils at high temperatures.
Dairy and beef fat typically contains around 3-6 per cent TFAs (as a percentage of total fatty acids) while levels in lamb and mutton can be somewhat higher. TFA levels in most edible fats are below 1-2 per cent. Vegetable oils and liquid margarines have a low proportion of TFAs, usually below 1 per cent.
The TFA content of bakery products (rusks, crackers, biscuits, etc.), as well as some breakfast cereals with added fat, French fries, soup powders and some sweet and snack products, may vary considerably (from below 1 per cent up to 30 per cent) depending on the type of fat used, the EFSA said.
The panel found that the intake of trans fatty acids varies between countries, with lowest intakes found in the Mediterranean countries. Mean daily intakes of TFAs for 14 different EU countries were estimated to range from 0.5-2.1 per cent of total energy intakes among men, and 0.8-1.9 per cent for women. Mean intakes of saturated fatty acids ranged from 10.5 to 18 per cent of total energy intake, with the lowest intakes in southern Europe.
Recent dietary surveys indicate that TFA intakes have in fact decreased in a number of EU countries, mainly due to the reformulation of food products (such as fat spreads) to reduce the TFA content.
Evidence from many human studies indicates that - as for saturated fatty acids - increasing dietary intake of trans fatty acids (when compared to cis-monounsaturated or cis-polyunsaturated fatty acids) raises blood levels of LDL cholesterol, thereby increasing the risk of CHD. The rise in LDL cholesterol is proportional to the amount of TFAs consumed.
These studies also show that for equivalent dietary levels, TFAs may increase the risk of coronary heart disease more than saturates, the NDA said. This is because - unlike saturates - TFAs also reduce blood levels of HDL cholesterol (or 'good' cholesterol) and increase blood levels of triglycerides. This is not currently a major cause for concern, however, because of the much lower intake levels of TFAs, but provides compelling evidence that further reductions in TFA levels should be pursued.
Concerning other health implications, human studies revealed no consistent evidence of any effect of TFAs on blood pressure or on other markers associated with risk of CHD (for instance, platelet aggregation), or on insulin sensitivity associated with diabetes. Epidemiological evidence for a possible relationship of TFA intake with cancer, type 2 diabetes, or allergy is weak or inconsistent, the panel said, and no causal link has been established for the suggested adverse effects of TFAs on foetal and infant development.
In most of the intervention studies, monounsaturated TFAs from hydrogenated vegetable oils were evaluated, but the panel said that it was not possible to determine whether there were differences in the health effects of TFAs according to the source (i.e. TFAs from ruminant fat in comparison with those found in hydrogenated vegetable oils). In addition, it said that there was no method of analysis applicable to a wide range of foods which could distinguish between TFAs which are naturally present in foods (e.g. dairy and beef fat) and those formed during the processing of hydrogenated oils.
The risk assessment conducted by the EFSA NDA Panel was based on a question raised by the European Commission.
In March 2003, the Danish Authorities adopted legislation which introduced limits on the level of trans fatty acids in oils and processed foodstuffs containing fats and oils as ingredients, with the exception of naturally occurring trans fatty acids in animal fat. According to the Danish Authorities the measure was justified on public health grounds in order to minimise the risk of cardiovascular disease. As the views of Member states differed, the European Commission decided to ask EFSA for a scientific opinion on the occurrence of trans fatty acids in the diet and its implications for human health.