A good source of polyunsaturates?

So I've been doing the information architecture for a site about Flora (a margarine product from Unilever) and the thing has finally gone live. On the whole, it's pretty usable, makes a good effort towards being accessible (bit of work needed on colour contrast), and is actually very unusual in its web-saviness. You don't get a lot of brand sites doing semantic markup and organising things in such a way as to be both helpful and informative...

Anyways, in the process of working on the site, I started to find out about the different kinds of fats (so what the hell are polyunsaturates anyway?) and am now thoroughly confused. According to the Flora site's more about fats page (and their competitors I should add--in fact this appears to be the generally held opinion), polyunsaturates are good for you and can do no evil. The bit that confuses me (need to get an expert to respond to this one) is that a number of websites disagree.

This one states

Unsaturated oils, especially polyunsaturates, weaken the immune system's function in ways that are similar to the damage caused by radiation, hormone imbalance, cancer, aging, or viral infections.

So my guess is that this is either scare tactics or folk aren't comparing like with like. Either way, it'd be good to hear from a propper expert.