Polyunsaturated fat is more unstable than other fats and more likely to go rancid at room temperature.
Foods high in polyunsaturated fat include corn oil, safflower and sunflower oil, nuts, seeds and some fish.
Foods containing polyunsaturated fat are best eaten cold or lightly cooked.
The polyunsaturated group of fats contains the important omega-3 fatty acids. A regular intake of omega-3 fat is vital for health. Good sources of omega-3 fatty acids include linseed oil (flaxseed), and oily fish such as mackarel, salmon and herring.
Ideally aim for a diet containing about 25 percent calories from fat, divided as follows: polyunsaturated fat (10 percent), monounsaturated (10 percent) saturated/trans fats (no more than 5 percent).
For more information about all aspects of fat in our diet, see Dietary Fat