As usual there are not simple answers and always exceptions but as a general rule all seed and nut oil with the exceptions of perillia, and flax are high in sixes.
Olive oil cold pressed virgin contains about 10% but varies upward. Processed olive oil may contain 50% n6 18:2.
There is a little chart on the Ben Best site and you can print the article out. It is a good reference source.
http://www.benbest.com/health/essfat.html
or more detailed information on a nutritional site with analyses of almost anything you can think of as to fats minerals etc
http://www.nutritiondata.com/facts-B00001-01c20jZ.html
I have included the link to cabbage for example (cabbages contain fats), but just use the search engine for what you want to look up. Note that fat content is expressed both by weight and calorie content.
Here is the one for a cup of canola. Look how much n6 18:2 linoleic is in just one cup, and half as much n3 18:3. When you are trying to balance three and sixes that presents a problem if you are not going to have to use lots of fish oil/ flax.
http://www.nutritiondata.com/facts-B00001-01c20A1.html
I think the message has to be SMALL quantities, some butter is ok, flax seed oil will help balance things, and avoid everything except olive.
This presents a huge problem as far as most processed food go -almost without exception - as the industry uses sunflower soy safflower etc which you can see are all high in six, and hence the problem. Until you become aware you have no idea how much you are consuming, and in unlikely things -olives in oil are often in sunflower - a salad labelled beans in olive oil read the label sunflower oil - add to that feta in oil, oil to roast your meat, salad dressings etc, and the amount is frightening.
It is reported in the US many people are at or over 14:1 n6 - n3, and some as high as 50;1 - and some of the higher ratios are those of us who were thinking how healthy we (me very much included) were with a cupboard full of top quality light oils from various seeds and nuts.
For optimum performance all the indications are you cannot avoid fish / fish oil. The body can make EPA DHA etc but does not from reports do it very well.
Women appear to have a higher need and convert n3 18:3 better than men to the longer chains. BUT NOTE omega three products can only be made from omega three sources - the three and six pathways do not cross over, so women as a minimum nees to ensure their bodies have adequate n3 18:3. A womans additonal need is unsurprising as the higher threes appear to be heavily wrapped up with the reporductive processes as well as all the uses common to the sexes.
The hunter gatherer analogy above is for me a valid one. It makes eating from prepared foods difficult until industry catches up. No simple solutions I'm afraid except check labels, and you will find yourself putting most things back and make your own.
Everything has fat in it bacteria, algae, cabbage, trees - it is just a question of how much and in what proportions. We are used to living on a bit of everything directly or indirectly.
The avoid comments on oils dont apply to the whole foods. It is the concentration that is the problem and our increasing use of oils which are with exceptions new to us in the last 100years - combined with a strong perception that they are very healthy for us in such quantities.
RE LOLLY COMMENT
Thanks Lolly a pleasure.
SATURATED FATS
There is an argument on saturated fats v unsaturated. Links have been found between consumers of a lot of saturated fat and poor heart/vascular health. BUT The body does need use make and store a range of saturated fats. Even phyto plankton have saturated fat as part of the balance. It stores better in the body as it is less prone to oxidisation.
SO they are not "poisons" - it is again balance and quantity - small.
On the plus side butter for example has low three and six and so does not disturb that balance. It also contains CLAs etc, and I have seen it suggested that fats help absorbtion of vit d etc.
So again I think natural, not heavily processed and serious moderation are key words.
Fat is a very highly concentrated enery source and so intake should be kept low, as well as all the other extensive functions they have in the body.
TRANS FATS
Trans fats produced by high temperatures (including in frying vats) appear to be a problem several sources suggest. There are suggestions the body simply has not seen some of these before and so has difficulty in handling them, dumping them where it can, or upsetting the digestive process. I really have not read or seen enough on the subject of trans fats and their metabolism to say if that is reflected in trials. But I have stopped using them now I understand how delicate and complex the bodies pathways are on precautionary grounds as they are generally high in n6, require significant processing, and are fats in a scenario where I am trying to control intake.
GENERALLY
Until much more money is invested in trials we will no have definative "proven" answers. I am afraid it is a bit like a mystery with clues and you have to look at the bits assess the risks and make up your own mind.
There is lots of information on the net, and a good range of books - check the indexes fro fat omega three etc. - you will soon find those who a passionate on the subject.
The subject cannot be divorced from general quality of diet but for me if asked what to do if nothing else in dietary terms it would be look at consumption of threes and sixes.
RB