But the vast majority of trans fats are artificially produced, and are only used because they're cheap and extend the shelf life of processed food.
Trans fats are produced when vegetable oils are treated with hydrogen gas to make them semi-solid at room temperature, so they won't melt easily in high temperatures and will have a longer shelf and "fry" life.
These semi-solid oils, known as partially hydrogenated vegetable oils, are totally artificial and have no nutritional value. They're completely unnecessary, too, because there are alternatives manufacturers can use.
They are found in cooking oils used in some deep-fried fast foods such as chicken nuggets, deep-fried fish and chips, as well as in some processed foods like pastries, margarine, biscuits, donuts, sausage rolls, croissants, muffins, frozen pizzas, and sandwich spreads that are made with margarine or shortening.
A 2003 Food and Drug Administration (FDA) panel concluded that they are more harmful than saturated fats. A 2006 study, published in the New England Journal of Medicine, concluded that reducing the amount of trans fatty acids in food by 2 per cent could avert 19 per cent of heart attacks a year.
It found that people who consume trans fats in everyday foods such as croissants, biscuits and fast food could increase their chance of developing coronary heart disease by more than 20 per cent. Another large study concluded they increase the risk of heart disease more than any other micronutrient in the food supply.
The World Health Organisation (WHO) wants them eliminated from the food supply, while the Centre for Science in the Public Interest claims that getting rid of trans fats would be "the easiest, fastest, cheapest way to reduce heart disease and save thousands of lives".
Now the powerful American FDA has declared that there is no safe level of consumption of trans fats, and is taking steps to remove them from the American food supply. "Current intake remains a significant public health concern," FDA commissioner Margaret Hamburg said. "And there is no safe level of it."
The FDA says its move, if finalised, could prevent 20,000 heart attacks a year, and 7000 deaths.
Other countries have regulated to reduce the amount of trans fat in food, or to require mandatory labelling, so consumers can avoid consuming them, if they wish.
But our Government has done nothing to restrict the trans fat content of our food, and has refused repeated calls for them to be declared on a label, so they remain hidden in our food.
It has taken a nonchalant, hands-off approach, declaring that trans fats constitute only 0.6 per cent of our daily energy intake, and blandly reassuring consumers not to worry about them because they're only found in small amounts in the food supply.
Yet a 2006 survey by Food Standards Australia New Zealand found that up to 15 per cent of New Zealanders are eating too many foods that contain trans fats, like deep fried fish and pastry. It also found that 18 per cent of food had more than 2 per cent of trans fat in it - a shockingly high amount for a substance that is not considered safe in food. The consumer organisation Choice also measured 50 foods in 2005 and found many had unacceptably high levels of trans fats.
Despite these findings, the only action our Government has taken so far is to urge the food industry to reduce the amount of trans fats in food. Manufacturers are only required to declare them on a label if they make a "nutrition claim" on food.
Thousands of New Zealanders die every year from coronary heart disease, so the Government's refusal to take a simple step that could reduce heart disease and save lives is mystifying. You would hope that if organisations like the FDA or the WHO say removing them could reduce our rates of heart disease, it would act immediately, instead of sitting on its hands.
Sue Kedgley is a former Green MP and current Wellington regional councillor.
