In discussing bad fats, the media tends to focus on excessive saturated fat in the diet while trans fats often slip by unnoticed. However, research shows that these fats can have a similar, if not worse, effect than saturated fat; and when it comes to heart disease, even very small amounts have a big impact.
In nature, most parts of a fat (fatty acids) are cis-fatty acids – this simply refers to the bent nature of their chemical structure. However, when fats are changed from a liquid such as an oil to a solid, for example margarine (via a process called hydrogenation, which is also used to prolong shelf life and protect against rancidity), some of the fatty acids are altered from a cis-fatty acid shape to a trans-fatty acid shape.
Trans fats are rare in nature; their straighter make-up makes them less pliable and our bodies don’t handle them very well. Trans fats alter blood cholesterol in the same way that saturated fat does. Several Australian and international health agencies, including the NHMRC and the National Heart Foundation, have concluded that trans fats should be regarded as equivalent to saturated fats when it comes to preventing coronary heart disease.
In nature, trans fats can be found in rumen, in other words cows and sheep; hence there are small amounts in the fat-containing products from these animals (milk and cheese) and in their flesh. However, it seems that the naturally occurring versions don’t bring with them the same problems. The trans fats that we need to be concerned about are those made through food processing. Such trans fats are in deep-fried food (due to the temperature applied to the fat or oil), margarine and processed foods made with margarine or shortening (such as cakes, donuts, buns, foods with pastry etc). Other foods that notoriously contain trans fats include processed meats such as salami, and any food that contains partially hydrogenated vegetable oils as an ingredient, such as some crackers and biscuits.
Foods that list partially hydrogenated oils among their first three ingredients usually contain substantial amounts of trans fats as well as saturated fat. According to recent labelling laws, manufacturers are required to include the amount of trans fats (if any) present in foods where they have made a nutritional claim in relation to cholesterol or fatty acids.
Trans fats act in a similar way to saturated fat in the body: they increase the bad cholesterol (known as LDL cholesterol or low-density lipoprotein) and also increase the risk of heart disease such as atherosclerosis. But trans fats go one step further than saturated fat – they also lower the good fat (HDL). HDLs mop up fat in the body for excretion, so it’s a double whammy. Therefore, while saturated fat in excess can pose a health problem, in controlled amounts it is essential for life. However, trans fats, to the best of our knowledge, perform no health function; instead they have the potential to do significant damage.
Trans fats may also increase the risk of type 2 diabetes as well as allergies in children, although this latter risk is still not clear. Indeed, the mechanisms by which trans fats may increase susceptibility to allergies appear different to the role of saturated fat in diabetes.
Unfortunately, on average the amount of trans fats we are eating has increased in recent years. This may be due to a number of factors: food manufacturers are using more partially hydrogenated vegetable oils and we are eating more takeaways and fast foods. Therefore, one really good way to avoid trans fats is to eat whole, unprocessed food. Yes, I know this is easy to say, and I am no purist; after all, we live in the real world. So what else can we do?
Does it sound like you are being denied all the tasty food? That’s what fat does: it makes food tasty and feel good in our mouths – but at what cost?
In Australia and New Zealand, many healthcare professionals and academics espouse the virtues of margarines whereas in other countries such as Canada and some parts of Europe, health agencies warn people off such ‘foods’. Yes, there are some differences in the production methods down under. Nonetheless, it can’t be denied that margarine and similar foods made from otherwise healthful oils undergo extensive processing, loss of nutritional compounds and addition of other compounds. Surely the real thing is best?
Where is the logic in making a new food such as margarine, which would not be in our diets if it weren’t for technology, to help lower cholesterol from a naturally occurring oil which, if eaten originally, ultimately could provide protective health benefits? You might like to look at the Mediterranean diet (in the Food Pyramid tip sheet) and see just how healthy oils can be. Personally, I think this logic may be one of the causes of our increasing waistlines. I agree with Choice (the Australian Consumer Watchdog) who recommends that we eat as few trans fats as possible.
Sometimes, health authorities brush aside the risk from trans fat on the grounds that we eat a lot less of it than saturated fat. However, the US National Academy of Sciences’ Institute of Medicine has suggested that the only safe level of trans fat is zero, and that we should eat as little as possible consistent with a healthy, balanced diet.
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Levels of just 2% of trans fats (of our total energy intake) appear to significantly affect health. Some European countries have banned foods with more than 2% of trans fat in the total fat content while other countries have introduced strict labelling laws where any level of trans fats must be indicated.
Sadly, in Australia and New Zealand manufacturers are not required to note the presence of trans fats in their products unless they make a claim about cholesterol or fatty acids. No claim, no information!
So let’s consider some of the great research Choice has conducted on fatty foods; it might just change the way you think about having that donut with your coffee -
In 2005, CHOICE tested 55 foods including deep-fried fast foods, takeaways, biscuits, cakes and more. The results looked at total fat, saturated fat and those dreaded trans fats. Seventeen of the tested foods would be banned in some countries due to the presence of 2% or more trans fats (of their total fat content. Interestingly, when CHOICE retested 17 of the original products in 2009 two of them had made significant reductions, and four had almost eliminated trans fats altogether. This is a good sign that industry is capable of reducing trans fats if they choose.
Of the 32 foods that were analysed in 2009, the following list shows those that contained more than* 4% trans fats *(as a percentage of total fat), listed from highest to lowest (according to Choice).
Donuts make a strong appearance on the list above as CHOICE chose to test donuts from 12 different outlets. Five of the twelve samples showed trans fats levels below 2% – again showing that manufacturers can reduce trans fats in products if they choose.
Switching to margarines and cooking oils that are low in trans fats does not appear to affect the cost, quality or availability of foods. Until Australian regulations change to ensure all manufacturers disclose trans fat levels on food labels, and legislation is created to place a maximum cap on the level of trans fats used in restaurants and fast-food outlets, we must continue to rely on industry to respond to the market demand to lower trans fats in their foods. Whether or not they are capable of this is yet to be seen, and in the meantime it may be worth following some of the simple guides above when choosing your next snack.
I hope you have enjoyed this foray into trans fats. Remember to eat a wide variety of healthy whole foods, enjoy your food rather than count or labour over it, and stay active!
This information has been provided by Leanne Cooper from Sneakys baby and child nutrition. Leanne is a qualified nutritionist and mother of two very active boys.
This article was last reviewed May 2010
This article was written by Leanne Cooper, nutritionist and director of Cadence Health and Nutrition Courses and Sneakys Baby and Child Nutrition