Redox (oxidation/reduction) reactions involve the losing or gaining of an electron, respectively, by a molecule. oxidation is losing (OIL) and reduction is gaining (RIG) - mnemonic OIL RIG. reduction is gaining as it refers to the "reduction" of the overall charge of the molecule - e.g., gaining an electron is the gaining of one negatively charged particle, e.g., the complete charge of the molecule decreases by 1 arbitrary charge unit. (electrons charge -1, protons charge +1, neutrons are neutral, etc. if more interested, go take a chemistry class and then a biology class - both will help you understand nutritional information.) Oxidation makes molecules lose an electron because that is the definition of what oxidation is. so if you see anything about PUFAs being oxidized, it means that that poly-unsaturated fatty acid chain has lost an electron due to overheating or chemical intervention. This means that the PUFA is POSITIVELY CHARGED compared to its previous state after having lost an electron. (electrons are -1, so losing an electron means you lose one overall -1 charge, so you are +1 compared to what you previously were. not +1 overall, necessarily, but +1 compared to before the oxidative reaction.) that is the DEFINITION of oxidation - ergo, oxidation makes molecules lose electrons because that's what oxidation is.
2) a fatty acid chain, such as in a PUFA, in a +1 charged state compared to its natural state, is liable to "steal" electrons from other molecules - including your DNA or protein structures. this is to say - the PUFA *gains* an electron (RIG - reduction is gaining!) or becomes reduced by stealing an electron from another intracellular molecule like DNA or a structural protein. since reduction is GAINING an electron, this means that the donor molecule is LOSING and electron, and what is losing? (oxidation is losing! OIL RIG!) this means that the donor molecule is OXIDIZED. ergo, DNA or another donor molecule has lost an electron, become positively charged compared to its previous state, and is liable to bind to things electromagnetically that it would not have otherwise.
Gadsie, working up from this concept can be tough. Analogizing from molecular theory to biological reality is always going to be theoretical and not 100% accurate, so don't be too overly terrified of so-called "oxidizing foods!" and too bent on "antioxidant sources!" because it is by necessity an oversimplification. People do PhDs on this stuff and it still doesn't get more straightforward than what I've outlined above - it only gets more complex and specifically circumstantial. Having said that, this model does seem to hold for PUFAs and oxidative stress. And... go, jimhensen! If you need more explanation, feel free to PM me; I used to teach high school chem/bio before I left to do more postgrad so I've got a few resources up my sleeve I can link you to if you need. However, as I stated in the first paragraph - the best thing you can do to understand the above shizzle is to take chemistry, take biology, and do your best to absorb *specifically* the molecular principles from each. It is seriously, seriously worth it.