I’m often asked by clients about trans fat (also called trans fatty acids), what they are, and what are the risks.
They are saturated fats, while trans and cis just refer to the configuration of hydrogen molecules in the fat. Fat starts off as cis, which means the hydrogen atoms are all on the same side of the saturated bonds. When cis fatty acids are heated, more of the hydrogen atoms change configuration to become on opposite sides. These are then called trans fatty acids.
Why does this matter?
There is now lots of evidence that trans fatty acids increase risk of cardiovascular disease and even cancer. So it is best to reduce your intake as much as possible.
What types of foods are trans fat found in?
Each time a fat is re-heated, the composition changes from cis to trans. This means that when you reheat a ready meal, the fat changes into trans fats. This is one of the reasons why it is better for your health to eat whole foods as much as possible.
Trans fatty acids are also found in baked goods such as donuts, cakes biscuits and margarine which contain hydrolysed oil.
There is no legal requirement to list trans fat on food labels, which is why most people are unaware that they are eating them.
You might find my article on which oil to cook with interesting.