This is true primarily for all polyunsaturated acids, meaning omega 3 and omega 6 fatty acids. These occur more rarely in foods than mono-unsaturated and saturated fatty acids. In addition, the human body cannot make these fatty acids itself, so it depends on a sufficient intake of omega 3 and omega 6 acids from food. They have several important functions in the body, form part of cell membranes and contribute to preserving normal cholesterol levels, blood pressure and a normal cardiac function.