Omega-3 and omega-6 are essential fatty acids. Our body is not able to produce these and hence why we need these from our diet. In the Western diet, we are over consuming on omega-6 fatty acids and under consuming on omega-3 fatty acids.
Omega-6 fatty acids are pro-inflammatory whereas omega-3 fatty acids are anti-inflammatory. Inflammation is an important part of our immune system's response to infections and injuries. It signals the immune system to heal and repair damaged tissues as well as defend against foreign invaders like viruses and bacteria. Omega-3 fatty acids help control the inflammation through its anti-inflammatory properties. Problem arises when we have too much inflammation in our body. This is why having the right balance between omega-6 and omega-3 fatty acids is important.
Foods high in omega-6 fatty acids include highly processed foods, oils, most meats, eggs, nuts, whole grains, etc.
Key here is to reduce processed foods, oils, and meats to reduce omega-6 fatty acids from your diet while incorporating more foods that are higher in omega-3 fatty acids. Omega-3 fatty acids come in different forms: short-chain ALA and long chain EPA and DHA. ALA can be converted by our body into EPA and DHA.
Foods high in ALA omega-3 fatty acids include flaxseed, chia seeds, hemp hearts, walnuts, pumpkin seeds, beans, etc.
EPA and DHA are often found in fish and fish oil. However, it is important to note that fish do not make omega-3 fatty acids. They get the EPA and DHA form of omega-3 fatty acids from microalgae. Just like other important nutrients, omega-3 fatty acids are originally made by plants and in this case microalgae, flaxseed, chia seeds, hemp hearts, walnuts, etc.
It was believed the amount we convert from ALA to EPA/DHA to be quite low. However, research is now suggesting people eating exclusively plant-based adapt and hence get better at this conversion than those who get their EPA/DHA from animal-based foods like fish.
The recommended RDA for ALA is 1.6g/day which one can easily get by consuming two tablespoons of ground flaxseed daily.
If you are unsure on if you're consuming enough omega-3 or would prefer to get DHA/EPA form of omega-3, you can supplement with DHA/EPA algae oil. It cuts out the middle man (fish) and gets you the long chain omega-3 from the source (microalgae). Look for a supplement with at least EPA (60-130mg) & DHA (120-250mg).
Reference:
Welch AA, Shakya-Shrestha S, Lentjes MA, Wareham NJ, Khaw KT. Dietary intake and status of n-3 polyunsaturated fatty acids in a population of fish-eating and non-fish-eating meat-eaters, vegetarians, and vegans and the product-precursor ratio [corrected] of α-linolenic acid to long-chain n-3 polyunsaturated fatty acids: results from the EPIC-Norfolk cohort. Am J Clin Nutr. 2010 Nov;92(5):1040-51.