Natural trans fats not as bad as industrial-produced: study

"The TRANSFACT study is the first to directly compare the effects of food products containing trans-fatty acids (TFAs) from industrially produced and those containing TFAs from natural sources on CVD risk markers," wrote lead author Jean-Michel Chardigny in the American Journal of Clinical Nutrition.

Though trace amounts of trans fats are found naturally, in dairy and meats, the vast majority are formed during the partial hydrogenation of vegetable oil (PHVO) that converts the oil into semi-solids for a variety of food applications.

Trans-fatty acids (TFAs) are attractive for the food industry due to their extended shelf life and flavour stability, and have displaced natural solid fats and liquid oils in many areas of food processing.

But scientific reports that trans fatty acids raise serum levels of LDL-cholesterol, reduce levels of HDL-cholesterol, can promote inflammation can cause endothelial dysfunction, and influence other risk factors for cardiovascular diseases (CVD), has led to a well-publicised bans in New York City restaurants, and other cities, like Boston and Chicago, considering similar measures.

But according to the results of the TRANSFACT study - a randomised, double-blind, controlled cross-over study - natural and industrially-produced fatty acids do not behave the same.

"The TRANSFACT study shows that TFAs from industrially produced and natural sources have different effects on CVD risk factors.

The HDL cholesterol-lowering property of TFAs seems to be specific to that from industrial sources," wrote the authors from the French National Institute for Agricultural Research (INRA), the Nestlé Research Center (NRC), and the French Dairy Council (CNIEL).

Moreover, the differences between the TFA sources were most pronounced in women than men, they added.

Study details Forty healthy subjects (24 women, average age 27.6, average BMI 22.0 kg per sq. m) were randomly assigned to consume food items containing 11 to 12 grams per day of TFAs from industrially-produced sources or natural sources for three weeks.

A one week washout period followed before they crossed over to receive food containing TFAs from the other source.

At the end of the study, Chardigny and co-workers report that consuming the TFAs from natural sources led to significant increases in HDL cholesterol levels in women but not men, compared to industrially-produced TFAs.

Moreover, increases in LDL-cholesterol levels were recorded in women, but not men, after consuming natural TFAs.

"This study shows that TFAs from industrially produced and from natural sources have different effects on CVD risk factors in women," wrote the researchers.

"The HDL cholesterol-lowering property of TFAs seems to be specific to industrial sources," they added.

The reasons why different results were observed in women and men was not known, they said, and mechanistic studies should attempt to elucidate the reasons.

Missing the point?

In a corresponding editorial in the same journal, Walter Willett from Harvard School of Public Health and Dariush Mozaffarian from Brigham and Women's Hospital and Harvard Medical School noted that "a control arm replacing TFA with non-hydrogenated fats would have made the study more informative."

They also note that the study participants consumed the natural TFAs in quantities far exceeding that normally consumed in the diet, and stated that, while a comparison between the sources is "an interesting scientific question", the most pressing issue was the elimination of the use of partially hydrogenated vegetable oils from foods.

"Beyond the details of food labelling, the broader public health issue is the identification of ways in which to reduce the intake of industrial TFA, ideally by replacing them with cis unsaturated fatty acids," wrote Willett and Mozaffarian.

"When food manufacturers and restaurants do not voluntarily remove industrial TFA, both the Danish government and the New York City Department of Public Health have shown that, with a reasonable allowance of time to make the transition, legislation to limit the use of partially hydrogenated vegetables oils in foods is feasible and effective.

"To its credit, the food industry appears to be generally taking advantage of the costs and effort of reformulation to make an overall healthier product and to avoid replacing one problem with another."

Voices grow louder Dr. Joop Kleibeuker of the European Dairy Association (EDA) recently told FoodNavigator.com's sister site, DairReporter.com, that there was as yet no peer reviewed studies to suggest that these naturally occurring TFAs had similar negative impacts on health.

He added to the contrary, that various findings from recent intervention and epidemiological studies found that that there appeared to be no negative health affects of naturally occurring TFAs present in dairy goods, and do not need to be labelled on products.

"We are very confident there is a real difference between the impacts of consuming naturally occurring and industrially produced TFAs," he stated.

"The EDA will now look to start discussions with the European parliament at national level on the conclusions of the [TFA Policy Conference, held by the EDA]."

However, Willett and Mozaffarian appear to disagree, and state that not including all sources of TFAs on labels would create "regulatory complexity especially for prepared dishes with mixed animal and vegetable constituents, because of the lack of simple methods to distinguish analytically among ruminant and industrial TFA."

"Although the possibility remains that subtle differences are present between the metabolic effects of industrial and ruminant TFA at the rather small amounts actually consumed, at present there is no compelling evidence to exclude natural TFA from the total TFA on food labels," wrote the Harvard scientists.

Source: American Journal of Clinical Nutrition Volume 87, Number 3, Mach 2008, Pages 558-566 "Do Trans Fatty Acid from Industrially-Produced Sources and from Natural Sources Have the Same effect on Cardiovascular Diseases Risk Factors in Healthy Subjects?

Results of the trans Fatty Acids Collaboration (TRANSFACT) Study" Authors: J.-M. Chardigny, F. Destaillats, C. Malpuech-Brugere, J. Moulin, D. E. Bauman, A. L. Lock, D. M. Barbano, R. P. Mensink, J.-B. Bezelgues, P. Chaumont, N. Combe, I. Cristiani, F. Joffre, J. B. German, F. Dionisi, Y. Boirie and J.-L. Sebedio Editorial: American Journal of Clinical Nutrition March 2008, Volume 87, Number 3, Pages 515-516 "Ruminant or industrial sources of trans fatty acids: public health issue or food label skirmish?"

Authors: W. Willett and D. Mozaffarian