Trans fats are bad news for heart health but what should we do about them? Should we give them top billing in the new Dietary Guidelines, demand trans fats be declared in nutrition information panels on food labels, or regulate them in some other way? Hang on … haven’t we already dealt with trans fats?
All fats in our diet are made of substances called fatty acids. Although there are hundreds of them, fatty acids can be grouped into three broad classes – saturated, monounsaturated and polyunsaturated. By far the majority of mono- and polyunsaturated fatty acids have a characteristic ‘bent’ shape, which the scientists call cis. However, a small proportion of unsaturated fatty acids are ‘straight’ and this trans shape gives them different physical properties, more like saturated fats. Fats with a high proportion of trans fats (or saturated fats) tend to be solid, not liquid like oils rich in cis fatty acids.
Where do trans fats come from?
There are two sources of trans fats in the human diet – animals and factories. Until relatively recently an industrial process called partial hydrogenation was commonly employed to ‘harden’ vegetable oils. This involved converting some of the unsaturated fats in vegetable oils to saturated and trans fats, turning the oil from liquid to solid. These hardened fats were used in the baking industry where solid fats similar to butter were required and could also be blended with liquid vegetable oils to make soft margarines.
Trans fats are also formed in the gut of ruminant animals such as cattle, sheep and goats. Unsaturated fats in an animal’s feed undergo partial hydrogenation in the rumen, increasing the proportion of saturated and trans fats – basically the same process that occurs in a factory. As a result about 3-5% of the fatty acids in the meat and milk of these animals are trans fats. Butter and the fat on a rump steak are solid at room temperature because of the high proportion of saturated plus trans fats they contain.
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‘Natural’ versus ‘artificial’ trans fats
Trans fats in meat and dairy foods are sometimes referred to as ‘natural’ trans fats to distinguish them from the ‘artificial’ trans fats made in a factory. This is just a public relations exercise. The majority of the trans fats found in hardened fats are also found in meat fat and dairy fat. So-called ‘natural’ and ‘artificial’ trans fats are basically different combinations of the same substances. And they have the same effect on the human body.
Are trans fats bad for health?
Early studies of the health effects of trans fats found they had a neutral effect on the total level of cholesterol in the blood, similar to olive oil. No worries there. But in 1990 some Dutch researchers took another look at trans fats and discovered their unique double negative effect on heart health: trans fats raise the level of bad LDL-cholesterol in the blood and lower the good HDL-cholesterol. Both effects would be expected to increase the risk for coronary heart disease. Many studies have now confirmed these findings and it is clear that both ‘artificial’ and ‘natural’ trans fats have similar adverse effects on cholesterol. Large population studies have found that trans fats are indeed associated with increased risk for heart disease.
Do Australians eat a lot of trans fats?
Intake of trans fats in Australia is low. In a recent study by the food regulator, FSANZ, the average trans fats intake was about half of one percent of daily calories, which is half the upper limit recommended by the World Health Organization. Nearly three-quarters of the trans fats in the Australian diet now come from so-called ‘natural’ trans fats, primarily from dairy products. ‘Artificial’ trans fats now comprise just one-eighth of one percent of daily calories – a tiny figure.
Trans fats intake has never been particularly high in Australia, partly because much of our commercial frying has traditionally relied on meat fat (low in trans fats) or palm oil (no trans fats). This is in contrast to the United States where partially hydrogenated soybean oil was widely used for commercial frying and consequently intake of trans fats was two or three times that in Australia. Nevertheless, the intake of trans fats by Australians in the early 1990s was 2.0-2.5% of daily calories – four to five times what it is now. So what happened in the meantime?
Two waves of trans fat reduction
Australia’s leading nutrition authorities including the NHMRC and the Heart Foundation were quickly onto the new trans fats developments, making recommendations in expert reviews. In 1996, the Heart Foundation introduced changes to the margarine criteria for its Tick food approval program and the industry quickly responded, minimising the trans fats content of the majority of leading brands of table spreads by late 1997.
In the early 2000s another wave of trans fats reduction commenced as many food manufacturers began combing through their product portfolios weeding out the trans fats. Quick service restaurants, a major donut chain and a leading supermarket chain all played their part. During this phase of trans fats reduction the Commonwealth Government was actively involved and deserves credit. Public health nutrition relies on inter-sectoral collaboration – nutritionists, policy makers and industry working together – and on this occasion it happened and it worked.
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Should trans fats be further regulated?
I recently wrote an article on this topic which is now available online as an ‘early view’ paper ahead of publication in the journal Nutrition and Dietetics. My answer was no based on the facts summarised above. As the job of lowering trans fats intake is already done what would be the purpose of further regulation? The amount of trans fats in our diet is less than that in the Danish diet which is often held up as an example of what regulation can achieve. Advocates of regulation do not appear to be aware that by far the majority of the large fall in the trans fats content of the Danish diet occurred before anti-trans regulations were introduced.
Trans fats and the draft Australian Dietary Guidelines
It was surprising to see trans fats introduced into the top line messages of the draft Australian Dietary Guidelines. Firstly, there was no systematic literature review on trans fats so there was no evidence base on which to base a new guideline (there was no review of saturated fats either). Also, there was only passing reference to trans fats in the text of the Guidelines, which basically said trans fats intake is very low in Australia. And there is the issue of practicality. How could the general public implement the advice as the amount of trans fats in most food products is not currently required to be included in nutrition information panels? Why elevate this issue now when in public health terms it’s already done and dusted?
Best dietary advice?
In Australia, the best advice to lower intake of trans fats is to choose lean meats and low fat dairy products, which also lowers intakes of saturated fats. Other than that, don’t worry.
Just some comments on the trans fat issue.
I see the whole issue as problematic on several accounts.
Firstly – there seems to be very little dispute – that we should be minimising trans fat intake. Therefore – should it go into the guidelines?
The public sees the guideline – searches google – comes across a crank internet site stating margarine is full of trans fat and is close to plastic, and changes to butter (with end result being they increase rather than decrease their own consumption).
On the other hand – does having the guideline – provide some further incentive for industry to lower trans fat use. You only need to go onto a website for a manufacturer of baking industry oils to see that significant amounts of trans fat are in use in Australia. Does the ANZFA review account for individuals who may eat a lot of bakery products (eg. I have worked on a building site where some people eat meat pies or other high fat products from a bakery every day)? With no food label – these people will be unaware of their trans fat intake. Given this potential – I’m not sure that the issue is done and dusted.
I have also seen a generic brand cooking chocolate with 13% trans fat identified. Does the lack of regulation mean that in the future, trans fats could find their way back into the food supply?
Hi Paul. As long as people eat meat and dairy products we will always have trans fats in our diet. I guess the point is, at what level do we say trans fat intake is acceptable. The WHO recommendation is less that 1% of energy. Our intake is half that, so we have already minimised our trans fat intake. Should we really focus in on the one-eight of 1% of energy coming from ‘artificial’ trans fats? Saturated fat intake is 25 times higher than trans fat intake – shouldn’t that be our priority now?
Believe me, the food industry does not need any incentive to lower trans fat use. They have been doing it for the last 17 years and very successfully. I was working on it in 1995!
The issue is often raised that an individual may choose to eat a lot of pies, chocolate, etc containing trans fats and their intake may be higher than desirable. That a problem for the individual but it’s not a public health problem. If mean population intake of trans fats is very low the public health players have done their job. Regards, Bill
Thanks for this nice summary Bill. I think the trans fat controversy is yet another example of the Australian food supply being tarred with the same brush as the US food supply when our food is different. I also think it is a pity that the triumph of inter-sectoral collaboration to achieve such low levels of trans fats is a good story that hasn’t been told (or celebrated) and its good you’ve made a start. I would add to your final comments about best dietary advice the importance of limiting ‘sometimes foods’ such as commercially produced pastries which are one of the few remaining sources of trans fats (because partially hydrogenated oils are cheap and provide good texture and keeping qualities). Of course such foods are high in saturated fats and nutritionally poor choices as well. The next phase of reducing trans fats further is for a trans-free baking shortening to be developed that is functional and economical. It’s only a matter of time.
Hi Nicole. Ah, inter-sectoral collaboration – so much potential, so little of it realised. Why is so much effort in public health nutrition invested in fighting with those we should be collaborating with? Regards, Bill
Hi Bill,
Thank you for your post on trans fats. It’s great to know our current intakes of industrial produced trans fats are low with limited supply in the foods we eat. You might also be aware of WHO’s recent review of trans fats (http://www.who.int/nutrition/topics/trans_fatty_acids/en/index.html) presenting the evidence on the impact of industrial produced trans fats and ‘natural’ trans fats, (or the more correct term, ruminant trans fats) on health. The review notes the intake of ruminant trans fats in most societies is low and concludes the current evidence does not support an adverse effect of these fats on the risk of cardiovascular disease. It’s also worth noting the evidence statements in the NHMRC draft Dietary Guidelines (http://www.eatforhealth.gov.au/page/public-consultation) demonstrate the consumption of dairy foods, such as milk, cheese and yogurt, is associated with reduced risk of chronic diseases including CVD, stroke, hypertension and type 2 diabetes.
Kind regards,
Dr Roxanne Portolesi, Nutrition Science Manager, Dairy Australia
Hello Roxanne
In my article I said that ruminant and industrial trans fats were basically different combinations of the same substances. For example, there are about ten 18:1 trans isomers in industrial trans fats and all ten also appear in dairy fat. They are the same chemicals and have exactly the same effect on the human body.
CLA is an exception of course – a trans fatty acid that occurs in dairy fat but is not present in industrial trans fats. But studies show that it affects LDL-cholesterol and HDL-cholesterol similarly to other trans fats.
Epidemiology will never be able to demonstrate that ruminant trans fats are associated with increased risk for heart disease because the amount in the diet is too small. However, lack of evidence due to the limitations of the experimental tool is not evidence of a lack of effect ruminant trans fats on risk.
Personally, I am not concerned about having 0.5% of the energy in a typical diet coming from trans fats – it’s a very low level. However, if people are concerned and want to reduce their intake of trans fats further, they should be aware that about three-quarters of the typical intake is coming from dairy and meat fat, and one-quarter from industrial trans fats. Regards, Bill
Hello Bill,
I’m very interested in reading further about your assertion that all trans fats are “the same chemical and have exactly the same effect on the human body.” I’m having trouble finding such information. Are you able to recommend a reference to extrapolate on this? It’d be greatly appreciated.
I’m currently researching the benefits of vaccenic acid and conjugated linoleic acids in the human diet (both naturally occurring trans-fats as you’re aware).
Thanks for your column, an interesting read as usual.
Kind Regards, David Brownlea BPharm
Hello David. There was a supplement on trans fats in the American Journal of Clinical Nutrition in September 1995. The paper to look at is the one called ‘Physicochemical properties, intake and metabolism’ (Am J Clin Nutr 1995;62:659S-69S.)
Figure 2 shows that butter contains 10 trans isomers of 18.1 (oleic acid). The same figure shows that partially hydrogenated fats contain the same 10 trans isomers of 18.1. Not surprisingly, both the trans fats in butter (including CLA) and the trans fats in partially hydrogenated fats have adverse effects on the LDL/HDL ratio in the blood (Brouwer IA, Wanders AJ, Katan MB (2010) Effect of Animal and Industrial Trans Fatty Acids on HDL and LDL Cholesterol Levels in Humans – A Quantitative Review. PLoS ONE 5(3): e9434. doi:10.1371/journal.pone.0009434). Regards, Bill
Many thanks for the reply Bill. I’ve had a look over both of those references, but I’m not certain they clarify my question in light of your column. The trans isomer of oleic acid that you’re referring to is edilaic acid (the most commonly industrially produced trans fat- known to be harmful as you say). This is only present in negligible quantities (less than 0.1%) in products derived from bovine milk [Alonso L, Fontecha J, Lozada L, Fraga MJ, Juárez M (1999). "Fatty acid composition of caprine milk: major, branched-chain, and trans fatty acids". J. Dairy Sci. 82 (5): 878–84].
I can only find information stating that the predominant natural ruminant trans fats in dairy are VA and the CLAs, and the apparent health benefits of these, which is contary to what you are saying about the health dangers on trans fats in butter, milk etc.
If you can steer me in the right direction it’d be a great help. I’m a fan of your work and columns, but I think I’m missing something in the trans fat debate!
Kind regards, David Brownlea.
Hi David. Elaidic acid is ONE of the ten 18:1 isomers shown in that paper and it appears in both industrially generated trans fats and ruminant trans fats (meat and dairy trans). Similarly, vaccenic acid is also ONE of the ten 18:1 isomers and it also appears in both industrial and ruminant trans fats.
I disagree with your statement that elaidic acid is known to be harmful. What we know is that trans fats, comprising many isomers (including elaidic and vaccenic acid), are harmful to health. Saying that elaidic acid is bad but vaccenic acid is good requires a big leap of faith – it’s not supported by the evidence. Whether CLA really has beneficial effects IN HUMANS has yet to be demonstrated. However, we do know that CLA has adverse effects on blood lipids so any beneficial effect would need to be strong enough to overcome this. Regards, Bill
Hi there. Do you know this study:
Jakobsen,M, Overvad, K, Dyerberg, J and Heitmann, B. 2007 “Intake of ruminant trans fatty acids and risk of coronary heart disease” in International Journal of Epidemiology. Oxford University Press, Oxford. 37:1. pp173-182
Its worth looking at the studies showing that TFAs from animal sources might not increase the risk of CHD at all.
cheers
Hi Ulyssess. Trans fats from animal sources and industrial sources have the same effects on blood lipids, which is presumably how they increase the risk for heart disease.
It is difficult to determine whether one is better or worse than the other from the type of studies available. In diets, ruminant trans fats are present in small amounts whereas in some countries (e.g. USA) industrial trans fats have been present in quite large amounts. Consequently, the effect of ruminant TFAs may fail to reach statistical significance and the effect of industrial trans fats may reach significance, even if both have exactly the same effect on risk. It’s the higher exposure to industrial trans fats that’s making the difference, not any difference of effect.
The trend for both industrial and animal trans fats is in the same direction – increase in risk.
Replacing saturated and trans fats from animal sources with unsaturated fats lowers heart disease risk without having any known adverse effects. Regards, Bill