Dutch margarine manufacturers are reducing the levels of trans fatty acids in their products in the next 12 months. Levels will fall to below 5 per cent immediately, and to just 1 per cent within the next year.

They have also decided to state the trans fatty acid content on the label.

These changes will take effect in other countries too, although it is not clear what will happen in the US. Some American manufacturers are already producing trans-free spreads, but the majority view in the US food industry is that dangers of trans fatty acids have been exaggerated.

The first worries arose in 1990, when a link between trans fatty acids and higher cholesterol levels was reported. Later studies confirmed the effect on low density lipoprotein (LDL) cholesterol, but was less sure about high density lipoprotein (HDL).

Researchers also concluded that trans fatty acids could cause heart disease.

The acids are made as part of the hydrogenation process needed to harden margarine. Butter consists of saturated fatty acids, which are naturally hard (The Lancet, November 11, 1995).

Americans in particular who are more worried about trans fatty acids than their food industry can turn to margarine containing sitostanolester.

Sitostanolester is a derivative of a plant which helps to lower cholesterol levels. Researchers have discovered that, when it is added to margarine, it can help people with slightly higher cholesterol levels, especially if it used as a replacement for daily fat intake (New Eng J Med, November 16, 1995).

People who eat more polyunsaturated fatty acids, and lower amounts of the monounsaturated fatty acids, are less likely to die prematurely from cancer, a new French study has dicovered, adding to the confusion (BMJ, November 11, 1995).