This is a contribution from a member of THINCS,
The International Network of Cholesterol Skeptics

Uffe Ravnskov. Report from the First International Symposium on Trans Fatty Acids And Health in Rungsted Kyst, Denmark. 


The background to the meeting was that Denmark as the first country in the world has introduced a new regulation that the level of industrially-produced trans fatty acids (TFA) in human food must not exceed 2 % of the total fat content. (Note that the rules do not apply to naturally occurring content of TFA in animal fats.) The regulation was based on scientific reports from the Danish Nutrition Council. According to former head of the Council Arne Astrup their interest in the issue was initiated by a paper by Willet and his group from the Channing Laboratories at Harvard (Lancet 1993;341:581-5) and by further studies suggesting that industrially-produced TFA also might introduce other health hazards. The issue raised much furore and concern in the Danish media, and although the final report from the council was heavily criticised by the European margarine industry and by scientists from the other Scandinavian countries the disappearance of TFA from the food in Denmark has been most successful and was performed in good co-operation with the margarine industry. Broad investigations of the content of industrially produced TFA in Danish food have been carried out after the legislation and have shown that practically no food contains more than the stipulated maximum.


Beneath follows a short review of the most important papers presented at the symposium. The full Abstract Book is freely available on the web. The Danish Nutrition Council has also published a booklet “The influence of trans fatty acids on health - fourth edition” with much useful information.


Several speakers reported about the degree of trans fatty acid consumption in various countries. According to Margaret Craig-Schmidt from Aubum University, USA there was a variation between less than1 g/person/day in the Asian/Pacific countries to 10-20 g/person/day in subpopulations of some Western countries, more in northern European countries than in the Mediterranean. These figures were from estimates of the content of the diet, not from food disappearance data, but they included ruminant TFA.


Steen Stender and coworkers from various institutions in Copenhagen had asked family and friends to collect various food items from countries all over the worlds when travelling and had analysed its content of fatty acids. Foods were obtained in 12 European countries, in North America, Russia and in Tonga. In addition French fries and chicken nuggets were bought at two international fast food chains in each of the European countries. They found foods with TFA above 15 % of total fat in all countries. In 50 % of the foods more than 2 % of the fat was industrially produced TFA. Some items, especially microwave oven popcorn, contained more than 10 gram per 100 gram product; nuggets 0.1-8 gram, biscuits 3.3-10.4 gram (note that this is not percent of fat, but percent of total product). Foods with an extremely high content were found in Eastern Europe. However, Karsten Nielsen, development and application manager at Aarhus United, a large Danish manufacturer of vegetable fats and oils, told that the application of fats and oils without trans fatty acids was increasing all over the world. Contrary to expectations this has been done without adverse economical effects for the consumers.


According to Julie J. Moss from the FDA, a final rule requiring the declaration of the amount of TFA present in foods on the nutrition label has been issued and should be implemented by January 1, 2006 in the US. Although, as reported by Walter Willett in his final appearance, the US Institute of Medicine has concluded that TFA intake should be as low as possible, and that the US Dietary Guidelines Committee has concluded that intake should be below 1% of energy, attempts to place a maximum limit of TFA had been unsuccessful. However, some of the American food producers are now competing by producing food items with lower and lower amounts of TFA. Less positive was that in the future FDA would like to place limits also on the amount of saturated fat on the food labels.


In his first talk Willett mentioned that countries with a high intake of trans fatty acids tend to have higher rates of CHD. Positive associations have been found in several large cohort studies. In the Nurses’ Health Study they found 80 % increase in risk for a 2% energy increment in TFA intake. This increase was much higher than expected by the effects of TFA on cholesterol judged from epidemiological studies, and he suggested that adverse effects on inflammatory markers and other risk factors could explain it. According to Willett TFA can account for as much as 30-40% of CHD in countries with a high intake.


Alberto Ascherio from Willett´s group, and also Martijn B. Katan from Wageningen University, The Netherlands commented further on this apparent paradox and suggested that the TFA have effects on other lipid fractions, LDL particle size, and postprandial lipids, but also may influence inflammatory markers and insulin resistance. (I commented their speculations by mentioning that meta-analyses of the dietary trials have found no effect on total or heart mortality after lipid lowering by change of fatty acid intakes only. It is therefore highly unlikely that the effect of TFA goes via cholesterol or other lipid fractions; but must be due entirely to other mechanisms.)


Dariush Mozaffarian, also from Harvard, suggested that TFA are proinflammatory. He pointed out that systemic inflammation may be involved in the pathogenesis of atherosclerosis , acute coronary syndromes, sudden death, insulin resistance, dyslipidemia, and heart failure. The mechanisms are not well-established and he suggested that further research should concentrate on potential isomer-specific effects.


Jorge Salmeron reported about the association between fatty acid intakes and the risk of type 2 diabetes from a 14 year follow-up of the Nurses’ Health Study. No associations were found with total intake of fat, or with intakes of saturated or monounsaturated FA, but intake of PUFA was associated with a significantly lower risk, and intake of TFA with a significantly higher risk.


Ulf Riserus from Uppsala, Sweden, now Oxford Centre for Diabetes, UK has studied the influence of specific conjugated TFA (CLA) on insulin sensitivity. Previous studies have given divergent results, probably because individual TFA may have different effects, and these studies included mixtures only. The Uppsala group had studied three diets in obese men with the metabolic syndrome, one containing a specific CLA, trans10/cis12, one containing a mixture of CLA, and a placebo diet. Insulin sensitivity decreased, and plasma glucose, plasma insulin and HbA1C increased significantly on the t10/c12 diet, whereas no significant changes were seen after the CLA mixture. In a previous study (Am J Clin Nutr 2004;80:279-83) they had found that an 8 w intake of 3-4 g purified c9/t11 gave a significant 15% increase of  insulin sensitivity compared to placebo, but no rise in blood glucose or insulin. Riserus´ conclusion was therefore that more studies are necessary. (That the finding of increased insulin sensitivity should have clinical importance is in conflict with Salmeron´s report and also other epidemiological studies having showed no association between SFA intake and diabetes; if anything such intake may protect; see Pereira et al. JAMA 2002;287:2081–9 and Wirfalt et al. Am J Epidemiol 2001;154:1150–9.

 . Maybe the Uppsala group´s restraint comes from the fact that it is led by Bengt Vessby, the main scientific adviser for the Swedish Nutrition Council, whose members for many years have maintained that industrial and ruminant TFA are equally bad.)


It is true that food products from ruminant animals largely contain TFA of the same types as in industrially produced hydrogenated oils. However, there is a considerable difference in the amounts of the individual TFA; butter fat from cows for instance contains mainly trans vaccenic acid, whereas industrially produced trans fat consists of a large variety of different TFA. (See for instance fig. 3 in the booklet). There is also much evidence that the biological effects of each individual TFA vary considerably. Marianne Ohre Jakobsen from  the Institute of Preventive Medicine, Copenhagen reported about an 18 year cohort study of 3686 healthy individuals whose dietary intake was determined at baseline using a 7-day weighed food record. At follow-up they found no significant association between intake of ruminant TFA and the risk of CHD; if anything the risk was lower in women with a high intake.


Rozenn Lemaitre from the CV Health Research Unit, University of Washington gave the results from a case-control study of 179 patients with out-of-hospital cardiac arrest and 285 matched controls. Blood samples from the first group had been taken by paramedics and showed that higher risk of cardiac arrest was associated with higher levels of trans 18:2 (adjusted OR 3.1; CI 1.7-5.1), but not with higher levels of trans 18:1, the most abundant TFA in the diet.


Jørn Dyerberg (one of the omega-3 pioneers) and his group from Copenhagen had performed a controlled trial on three groups of healthy males comparing the effects on cardiac risk markers of industrially produced TFA, long-chained n-3 PUFA, and a control diet. HDL decreased in the TFA group and TG and blood pressure decreased in the n-3 group compared with the controls. Also, 24-hour heart rate was increased by 3 beats per min in the TFA group and decreased in the n-3 group. Calculated per 24 hour this effect was considered a substantial extra burden on the heart.


Already in 1992 Koletzko (Acta Pediatr 1992;81:302-6) reported that low birth weight was associated with a higher proportion of TFA in the blood. Sheila Innis from the Child and Family Research Institute in Vancouver reported that the mean intake of TFA in Canadian pregnant women was 1.4 % of the daily energy intake, or three times the intake of n-3 alpha linolenic acid (ALA). Human milk was found to have on average 7.1 g TFA/100 g fat and the concentration of milk and maternal plasma TFA was related to infant cord and plasma TFA. High intakes of TFA were associated with low intakes of ALA and docosahexaenoic acid, both of which were associated with lower development outcome measures of the infants.


Gerard Hornstra from Maastricht University, The Netherlands, supported the findings of harmful effects of TFA on birth outcome. Preliminary results from his group showed that birth length was negatively associated with the concentration of elaidic acid (the most common TFA) in the phospholipids of cord venous and arterial walls, and head circumference was negatively with plasma elaidic acid.


Generally the symposium was a most positive experience. It was good to learn that the negative health effects of industrially produced TFA was shared by almost all participants, an issue some of our members have tried to put forward for many years. In particular, Mary Enig, the original pioneer on this subject for which she has worked for decades and against vicious resistance, should be proud. However, none of the speakers mentioned Mary´s name or her achievements, which I commented upon at one of the sessions. Neither is she acknowledged in the Council´s booklet, but Stender promised to mention her in their next publication.


In private discussions with some of the more influential participants I also got the impression that the view on saturated fat is slowly changing; at least it is considered less unhealthy as previously, and certainly less harmful than industrially produced TFA. However, the official line is still unchanged; for instance, my comments about the unsuccessful sat-fat-lowering trials were considered “irrelevant” and further discussions on the subject were stopped.


It was also good to learn about the increasing evidence that ruminant TFA differ both quantitatively and qualitatively from industrially produced TF and also lack the harmful effects of the latter.


Finally, and as usual, good research creates more questions than answers. In particular it is obvious that the various TFA have different biological properties, some harmful, others neutral and a few may even be beneficial. There is room for much research on this subject in the future