Although trace amounts of trans fats are found naturally, in dairy and meats, the vast majority are formed during the manufacture of processed foods.
They are created during the process of partial hydrogenation, when liquid vegetable oils are converted into margarine and shortening: essentially to extend shelf life and flavour stability, as well as contributing to a harder texture.
But mounting evidence suggests the TFAs raise LDL (bad) cholesterol levels, causing the arteries to become more rigid and clogged. An increase in LDL cholesterol levels can lead to heart disease, the number one global killer.
The latest study by Chung-Jyi Tsai and colleagues from the University of Kentucky, US examined the consumption of trans fatty acids in relation to the risk of gallstone disease in a cohort of 45 912 men.
The researchers hypothesised that trans fatty acids may cause a change in lipid profile, associated with gallstone formation.
TFA consumption was tracked using a food frequency questionnaire and newly diagnosed gallstone disease, by radiology or cholecystectomy, was ascertained every two years.
"Our results suggest that a higher intake of trans-fatty acids modestly increases risk of gallstone disease. This adds to the concern that partial hydrogenation of vegetable oils to form shortening and margarine can lead to adverse health effects," conclude the researchers in the May 9 issue of the Archives of Internal Medicine.
Food makers are encouraged by consumer groups and national governments to hunt for alternatives to TFAs: and new regulations are propelling them to do so.
In the US from 1 January 2006 food manufacturers will have to list trans fat on the nutrition label of all food products. Europe has yet to impose similar labelling rules although, in 2003 Denmark became the first country in the world to introduce restrictions.
Oils and fats are now forbidden on the Danish market if they contain trans fatty acids exceeding 2 per cent, a move that effectively bans partially hydrogenated oils.
There are further signs that certain national governments in Europe could soon push the Commission for trans fat label proposals. In a recent report from France's food watchdog AFSSA, for example, the agency recommended slashing trans fat levels in a wide range of bakery products, including biscuits and cakes. The report suggests that trans fatty acids should not exceed 1 g/100 g of the product as consumed.
Identifying a growing market, leading ingredients firms have already launched a raft of oils to target 'trans free' formulation demands.
In February Germany's Bayer CropScience announced an agreement with private agro firm Cargill to bring a high oleic rapeseed oil, that will not require hydrogenation, to market by 2007.
They join Dow AgroSciences, Bunge, ADM and DuPont that have all launched their various brands of zero or low trans oil, in the battle for market share as food makers undergo the investment in new technologies and new oil ingredients.