In order to clarify the role of trans fatty acids (TFA or “trans fats”) in human health, the European Commission asked the European Food Safety Authority (EFSA) for a scientific opinion. The EFSA report was published in August 2004 (1).

What are trans fats?

Unsaturated fatty acids are fatty acid molecules containing at least one double bond. They can be classified as cis (bent form) or trans (straight form) according to the structure of the double bonds within the molecule. Most unsaturated fats in the diet exist in the cis form whilst a small proportion can be found in the trans form. TFA originate in foods from three main sources:

• bacterial transformation of unsaturated fatty acids in the rumen of ruminant animals such as cows and sheep (passing to the fat, meat and ruminant’s milk);
• industrial hydrogenation or hardening of oils for use in fat spreads, and baking fats;
• heating and frying of oils at high temperatures.

Thus TFA are present in beef, lamb and mutton fat and products derived from their meat and milk, in some fat spreads and bakery products, such as crackers, pies, cakes and biscuits, and fried foods.

Current intakes

Across the EU intakes of TFA vary widely. In 1995/6 estimated average intakes of TFA were between 1.2-6.7g/day in men and 1.7-4.1g/day in women with the lowest intakes of TFA being recorded in Mediterranean countries. However more recent dietary surveys indicate that intakes of TFA in many EU countries have continued to fall with the increased popularity of low-fat dairy products and the reformulation of fat spreads and shortenings to reduce TFA content.

Heart disease

Evidence from many human studies indicates that TFA, like saturated fatty acids, raise LDL (or bad) cholesterol levels in the blood thereby increasing the risk of coronary heart disease (CHD).

But unlike saturates, TFA also lead to a fall in HDL (or good) cholesterol and raise blood triglyceride levels, both of which are associated with an increased risk of CHD. Furthermore, consumption of diets containing TFA results in increased concentration of fasting triacylglycerol (TAG), which, in epidemiological studies, is positively associated with the risk for cardiovascular disease. So, at equivalent levels (per gram), TFA may increase the risk of CHD more than saturates. However TFA intakes in Europe are about 10 times lower than those of saturated fats and Professor Albert Flynn, Chair of the EFSA scientific panel, said ‘… given current intake levels of TFA, their potential to significantly increase cardiovascular risk is much lower than that of saturates, which are currently consumed in excess of dietary requirements in many European countries’.

Other health risks

With regard to other health issues, the EFSA panel concluded that human studies revealed no consistent evidence of any effect of TFA on blood pressure or insulin sensitivity associated with diabetes. Epidemiological evidence for a possible relationship of TFA intake with cancer, type 2 diabetes, or allergy is weak and inconsistent. No causal link has been established for the suggested adverse effects of TFA on foetal and infant development although further research is needed in this area.

Animal versus Industrial TFA

Although animal fats and industrially hardened fats contain similar types of TFA, the quantities of each type clearly differ between them. In most human intervention studies carried out so far, TFA from hydrogenated vegetable oils have been used. For this reason EFSA concludes that it is currently not possible to tell if there are different health effects of TFA according to source. Also, there is currently no method of analysis applicable to a wide range of foods capable of distinguishing TFA found in foods like dairy products and beef fat from those formed during the preparation of hydrogenated oils.

Keep them low

The EFSA review highlights that TFA increase the risk of heart disease and for this reason the intake of TFA from all sources should be kept low. The removal or reduction of trans fats from many food products should continue and they should be replaced with cis-unsaturated fats rather than saturated fats where possible.

Reference

• European Food Safety Authority (2004) Opinion of the Scientific Panel on Dietetic Products, Nutrition and Allergies on Trans fatty acids in foods and the effect on human health of the consumption of trans fatty acids. www.efsa.eu.int

FOOD TODAY 12/2004