Polyunsaturated fats come from plant oils, nuts, seeds, and fatty fish. The two main groups are omega-3 fatty acids (from fish oil, flaxseed, and chia seeds) and omega-6 fatty acids (from soybean and sunflower oils).
Getting enough polyunsaturated fat, especially omega-3s, helps the body maintain normal cholesterol and triglyceride levels. These fats build cell membranes and support brain function.
Most people get them from food, but fish oil supplements supply EPA and DHA, while flaxseed oil provides ALA. The right dose depends on the specific fatty acid.
High-dose omega-3 supplements can thin the blood and may interact with blood-thinning medicines. Very large intakes might suppress parts of the immune system in certain people.