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This
is a contribution from a member of THINCS, 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 |