Polyunsaturated fats are considered essential because the body cannot produce them. It's vital for the functioning of our bodies to eat these—but in the right balance.
Most people eat way more omega-6s than omega-3s. The average American diet contains 15 times more omega-6s than omega-3s. A better ratio is 2 to 4 omega-6s to 1 omega-3.
Omega-3s reduce inflammation, which helps lower the risk of heart disease, cancer, and arthritis. They are also important for brain function and memory, and during pregnancy, help brain, vision, and nerve development (because fish are also high in mercury, a better source during pregnancy is a supplement).
Foods high in omega-3 include fatty fish (salmon, halibut, herring, trout, tuna, etc.), marine algae, omega-3-enriched eggs, and meat and dairy from grass-fed animals.
Plant sources include flaxseeds and oils, chia seeds and hemp seeds. Plant sources are not absorbed by the body as well as animal and fish sources, so unless you’re vegan, your best bet is omega-3s from fish and grass-fed dairy and meats.
Although omega-6 fats are essential and have health benefits, they're inflammatory in high doses, so too much is very unhealthy. Too much inflammation can contribute to heart disease, diabetes, arthritis, asthma, and digestive problems.
The majority of omega-6 (aka linoleic acid) in our diets comes from vegetable oils and processed foods that contain these vegetable oils.
The oils highest in omega-6 are sunflower, corn, soy, peanut, and cottonseed. Cold-pressed versions of these oils are less inflammatory but still have excess omega-6 fats.