Polyunsaturated fatty acids contain n3 and n6 fatty acids, including the essential fatty acids (EFA), as the body cannot synthesise these. The only EFA in the n-6 series is linoleic acid and in the n-3 series, is alpha-linolenic acid, the most common Omega-3 fatty acid. [2,3]
The remaining fatty acids in this category are not considered to be essential fatty acids.
The long-chain omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are found in a seafood only and can be synthesised from alpha linolenic acid (ALA), but the conversion efficiency is low. 
As per the World Health Organization guidelines, polyunsaturated fats intake goals are set to be around 6 to 10 E%. 1 to 2 E% for n-3 fatty acids and 5 to 8 E% for n-6 fatty acids, where E % is the percentage of total dietary energy (E%), or as ‘grams per day’ for adults. 
Good plant sources of omega-3 fats include vegetable oils, such as soybean, safflower, canola, soybean, and corn oil; nuts such as walnuts; seeds such as flaxseeds; and some vegetables. [1,4]
Also, replacing calories from carbohydrates with equivalent calories from monounsaturated fats can reduce mortality risk by 11% .
The n-6 fatty acids are almost completely absorbed. 
Polyunsaturated fatty acids are oxidised to carbon dioxide and water.  ]
Small amounts are lost via the sloughing of skin and other epithelial cells.