Presenting their results this week at a conference in Washington D.C, scientists from the University of Missouri speculate that trans fat supplementation in a swine model would raise high density lipoprotein cholesterol ratio TC/HDL-C, a major factor in the progression of cardiovascular disease.
Trans fats in food processing are produced through hydrogenation, a chemical process by which hydrogen is added to unsaturated fatty acids. Hydrogenation gets rid of double bonds. In doing so, the molecular configuration of the fat molecule can change from the natural 'cis' to the 'trans' configuration.
Trans fatty acids are found in some margarines, crackers, candies, baked goods, cookies, snack foods, fried foods, salad dressings, and many processed foods. In 2003, the Food and Drug Administration (FDA) issued a regulation requiring manufacturers to list trans fatty acids, or trans fat, on the Nutrition Facts panel of foods and some dietary supplements. Food manufacturers have until 1 January 2006 to list trans fat on nutrition labels.
"Pigs that consume a diet of 2 per cent cholesterol (approximately 40 eggs) and coconut oil (approximately 90 per cent saturated fat) so that 46 per cent of their daily caloric intake is derived from fat, develop early stages of cardiovascular disease in 20 weeks. This effect is similar to that seen in 30-year old humans, " report the researchers.
The scientists were interested in developing a blood lipid profile that could lead to advanced stages of cardiovascular disease. Seven pigs (Yucatan and Ossabaw) were placed on four different diets. For 30 weeks, pigs consumed a 2 per cent cholesterol diet supplemented with coconut oil that derives 75 per cent of their kcal from fat.
For two weeks the pigs then returned to the 46 per cent high fat diet as a "wash-out" for the previous diet. After which time the pigs were placed on a 2 per cent cholesterol diet but the coconut oil was substituted with hydrogenated soybean oil, which increased the trans-fat content from 0 per cent to 48 per cent but reduced the saturated fats from 90 per cent to 20 per cent. This trans fat diet derived 75 per cent of the kcal from fat.
Finally, since previous data suggested that once a day feeding leads to a more atherogenic blood profile, the researchers investigated whether twice a day feeding would alter the lipid profile versus the standard once a day feeding using the 46 per cent kcal coconut oil based diet.
Blood was taken at the conclusion of the various diets 6hrs after a meal. Blood samples were measured for: TC, TG, HDL-C, LDL-C, VLDL and LDL1-5. The ratios TC/HDL-C and LDL-C/HDL-C were also calculated.
"The trans fat diet (T75) significantly increased total cholesterol, LDL-C, TC/HDL-C and LDL-C/HDL-C ratios in two weeks compared to the isocaloric diet with zero trans fat (C75). Further triglycerides were significantly greater six hours after the trans fat meal versus the isocaloric zero trans meal.
Increasing the fat content did not augment an atherogenic blood lipid profile. Therefore, these data suggest that a diet high in trans fat has the potential to promote the rapid development of cardiovascular disease in swine models, " conclude the researchers.
The FDA estimates that by three years after that date, trans fat labeling will have prevented from 600 to 1,200 cases of coronary heart disease and 250 to 500 deaths each year.
While there are no such labelling rules in the European Union certain national governments are pushing for change. Last year Denmark became the first country in the world to introduce restrictions on the use of industrially produced trans fatty acids. Oils and fat are now forbidden on the Danish market if they contain trans fatty acids exceeding 2 per cent.
Speaking at the time, Danish Minister for Food, Agriculture and Fisheries Mariann Fischer Boel said: "It is my hope that we will soon see EU regulation in this field. The next step should be common low EU limit values for trans fatty acids."
Far from dropping off, activity and opportunities in the European marketplace for trans fats will step up as consumer awareness grows, fired by movement in the US.
The growing list of manufacturers opting to remove trans fatty acids includes Swiss company Nestle, US fast food giant McDonalds and Frito-Lay North America, a division of PepsiCo. McDonalds said last year it would cook all French fries in oil with 48 per cent less trans fatty acids - although according to US consumer groups has since quietly reneged on its pledge - while Frito-Lay said it would cut trans fatty acids from its salty snacks, including Doritos, Tostitos and Cheetos.