Trans fats, which occur naturally in small amounts in dairy products and meat, are also formed artificially when manufacturers hydrogenate fat or oil, primarily to extend the shelf life of their products.
But research suggests that they 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.
As a result, the food industry is gradually slicing out their use as more consumers look for alternative products and under new FDA rules, in the US food manufacturers will have to label any TFA content from January 2006. Europe has yet to impose such regulations, but pressure is building from consumer-led organisations to eliminate these fats.
"We believe the government, urgently, needs to set targets to slice artificial trans fats from foods," a spokesperson for Which? magazine, that carried out the study on 30 food products, said to FoodNavigator.com.
The group has written to the Department of Health and the Food Standards Agency in a bid to bring about change.
Asked if the FSA had plans to push for labelling of trans fats, a spokesperson for the government agency told FoodNavigator.com that this would be 'discussed at an EU level'.
"We are focusing on salt at the moment. We are also working with industry to reduce saturated fats, we believe they pose a greater public health risk than trans fats. But trans fats are bad for you and people should consume less,"said the FSA representative.
Current UK recommendations for trans fats are 4.4g per day for women, the same amount detected by Which? in a KFC meal. A McDonalds McNuggets and regular fries meal contains 3g, while 2.5g came in for Saxby's short pastry, the same as for Tesco's gluten-free toffee fudge shortbread.
Of the 30 products tested, a Sainsbury's treacle tart bought from the bakery counter, a McVitie's Penguin biscuit and Morrisons pork pie were bottom of the table with 0.2g of trans fat per portion.
But the food industry is starting to tackle the issue. "The government's latest national diet and nutrition survey (NDNS) shows how the consumption of trans fats has fallen from 2.1 per cent of total energy in 1985 to 1.2 per cent energy in 2000," the UK's Food and Drink Federation commented in response to the Which? study.
Nestlé, the leading food company in the world, recently announced that its priority was to reduce the addition of TFAs in food products: "We are looking to reduce the content by the end of the year," the Swiss firm told FoodNavigator.com, confirming that new formulations are 'in the pipeline'.
Nestlé joins a raft of food makers - North American for the most part - that have already cut the trans-fat content. Kraft foods said it had launched a trans-fat-free version of its iconic Oreo biscuit. Frito-Lay, a division of PepsiCo, removed the TFAs from its snack product Doritos last year and soup giant Campbells announced in February that its Goldfish crackers, sold through the company's Pepperidge Farm unit, would become trans fat-free.
In Europe Which? pointed out that McVities have removed trans fatty acids from biscuit dough, but they are still present in cream fillings. UK retailer Sainsbury's has already switched to low trans-fat pastry (although 1.8g found in its puff pastry minced beef pie), and while KFC branches run directly by KFC use oil that contains trans fats, the franchised shops use non-hydrogenated vegetable oil.
Replacing the role of a partially hydrogenated fat in terms of aerating, emulsifying, lubricating and providing textural, structural and flavour characteristics is a challenge for food developers.
Increasing numbers of ingredients suppliers are rolling out replacements for the TFAs to meet the market demand. Earlier this year, Danish ingredients firm Danisco claimed its emulsifier/oil blends fitted the bill.
"These emulsifier blends with mixtures of non-hydrogenated oil offer the same properties as a partially hydrogenated shortening in most systems," said Jim Doucet, technical manager, emulsifiers at Danisco.
Dutch nutritional oils and fats firm Loders Croklaan said it was looking to target market opportunities in the trans-fat free market through its palm oil based ingredients, and is currently constructing a major new production plant in Rotterdam, The Netherlands.
US oil giant ADM has pushed out the NovaLipid portfolio that includes naturally stable oils, tropical oils, blended oils, and enzyme inter-esterified shortenings and margarines to provide alternatives in various food applications.
As the race continues for trans fat alternatives, last week US firm Dow AgroSciences said its Natreon canola oil, crushed from the high yield Nexera seed, is a 'naturally stable alternative to partially hydrogenated oils'.
And this week, soybean giant Bunge, in alliance with DuPont, launched Nutrium low lin soybean oil, sourced from the pioneer seed variety (93M20), in turn developed by DuPont subsidiary Pioneer Hi-Bred International. The firms claim the new soybean variety features oil with a low linolenic acid profile of less than 3 per cent and offers 'better natural stability and increased shelf life and eliminates the need for partial hydrogenation.'