Where are trans fats found?
Trans fats are present in a wide range of foods: according to one estimate, 40 percent of products in the typical US supermarket contain trans fat, and the UK is not far behind.
This is because the hydrogenated vegetable fats which provide most dietary trans fat are a mainstay of the food industry - a cheap bulking agent perfect for padding out expensive processed products, with a long shelf life and a luxurious 'mouth feel'.
They are to be found, for example, in margarine, vegetable shortening, ice-cream, puddings & pudding mixes, ready-made pies, cakes & cake mixes, biscuits, pizza, potato chips, fritters, doughnuts, gravy & sauce mixes, artificial creamers, confectionery and other processed foods, including many foods marketed at children, including some sugary breakfast cereals.
They are also commonly found in restaurant food, especially - but not only - in fast food. You can also make your own trans fat (in small amounts) by repeatedly re-heating cooking oil.
Some trans fats occur naturally in ruminants' stomachs and are thus found in meat and dairy produce. However the quantities are small, and in any event these natural trans fats do not appear to be harmful to human health - as are the man-made trans fats found in hydrogenated vegetable oils.
So when you're out shopping, always inspect the list of ingredients before you buy any product, looking in particular for :
- hydrogenated vegetable oil
- partially hydrogenated vegetable oil
- vegetable shortening
If any of these are listed, leave the product on the shelf. According to the The U.S. Food and Drug Administration's website,
"Consumers can know if a food contains trans fat by looking at the ingredient list on the food label. If the ingredient list includes the words "shortening," "partially hydrogenated vegetable oil" or "hydrogenated vegetable oil," the food contains trans fat. Because ingredients are listed in descending order of predominance, smaller amounts are present when the ingredient is close to the end of the list."
Click below for more information on trans fats in...
- Cakes & biscuits
- Fast food and restaurants
- Canola / rapeseed oil
- Your frying pan
- Meat & dairy produce.
Cakes and biscuits
Trans fats are ubiquitous in ready-made cakes, sweet biscuits and cake / cookie mixes, indeed a substantial majority of products contain them, including those branded as Mr Kipling, Lyons, Cadbury, Fox's, McVities, Border Biscuits, Wagon Wheels ...
Many confectionery products contain trans fats. Hydrogenated vegetable oils are found, for example, in many 'bars', including Mars, Twix, Milky Way, Tracker, Snickers, Picnic, Double Decker, Time Out and Fuse. They are also added to chocolate, in place of far more expensive (and healthy) cocoa butter. Common offenders include 'Belgian' milk chocolates (various makes). They also occur in 'cream' and 'praline' fillings for chocolates. And in Rolos and Peanut M&Ms.
HVOs are also used widely in 'cereal bars' of various (though not all) makes - contradicting the healthy, fit, dynamic image that manufacturers seek to associate with them.
Fast food & restaurants
Trans fats are also present in many prepared foods bought in fast food outlets. For example, you can expect to find trans fat in frying oil, whether in your favourite burger bar, or your local fish & chip shop. Trans fat may also be present in ice cream, shakes, pies, crackers and other fast food products.
A surveys of high end restaurants in Canada also found trans fats to be widely present in batters, pastries and other dishes. The same is probably the case in the UK. To be safe, Ask your waiter / waitress whether or not the restaurant uses hydrogenated or partially hydrogenated vegetable oils in its cooking.
Canola / rapeseed oil
One little-known source of trans fat is canola / rapeseed oil. The trans fat occurs as a result of processing, which takes place at high temperature. The raw seed begins with a high level of beneficial omega-3 oils, however these tend to oxidise during processing producing off, rancid odours. During deodorisation, some of the omega-3 fatty acids are converted to trans.
The proportion converted to trans is highly variable - in general, UK oils have low levels of trans, however Researchers at the University of Florida at Gainesville, found that liquid canola / rapeseed oils sold in the USA contained as much as 4.6 percent trans fat. Currently this trans fat content is not usually listed on labels and consumers have no way of knowing it is present.
Thanks to generous subsidies to EU growers, this is now one of the cheapest and most widespread vegetable oils. In general, if an oil is made from anything other than canola / rapeseed, this will be stated on the label. If an oil is simply described as "vegetable oil" - it is likely to be made from canola / rapeseed. If you want to be certain of the trans content of your brand of vegetable oil, you will have to write to the manufacturer and ask.
Canola is also a popular choice for hydrogenation - further raising the trans fat levels:
"... canola oil hydrogenates beautifully, better than corn oil or soybean oil, because modern hydrogenation methods hydrogenate omega-3 fatty acids preferentially and canola oil is very high in omega-3s. Higher levels of trans mean longer shelf life for processed foods, a crisper texture in cookies and crackers - and more dangers of chronic disease for the consumer."
Sally Fallon and Mary G. Enig, PhD, in The Great Con-ola.
Trans fat in your frying pan
If you fry a lot of your food, you may also be making your own trans fat: ordinary vegetable oil converts to trans fat at high temperature. However the rate of conversion is low in a domestic context. As Robert M. Reeves, president of the Institute of Shortening & Edible Oils wrote to the Washington Post (August 30, 2003; Page A27):
"High heat can cause the formation of minuscule amounts of trans fatty acids over extended lengths of time. But temperatures for traditional frying (300 to 350 degrees F) and relatively short cooking times (5 to 10 minutes) would have a negligible effect on the formation of trans fat in cooking oil. For example, a recent study conducted to determine the levels of trans fat isomers formed by heat found that in canola [rapeseed] oil heated to 500 degrees F for 30 minutes, trans fat levels were increased by only 1 percent. Traditional frying at lower temperatures for shorter lengths of time would produce significantly fewer trans fats."
To see the full letter, click here.
However if you re-use the same oil many times over, for example in a deep fryer, the trans fat content will rise over time - and particularly if you are using canola / rapeseed oil, high in omega-3 fatty acids. You should therefore remember to change your frying oil often.
Meat & dairy produce
See our page on the trans fats that occur naturally in meat and dairy produce here.