A good explanation of why some oils are good and some oils are bad

I was recently asked to defend my position on what fats I've deemed good and bad. I had to admit that I had done the research and that I used to know, but that I couldn't remember the specifics. Now I remember:

http://www.askdrsears.com/html/4/t043800.asp

"Oils are liquid fats. Most commercial oils come from plant sources, such as nuts and seeds. Oils are an important part of a balanced diet because, besides being a rich source of energy, they provide essential fatty acids which are the building blocks for cell membranes, especially cells in growing brains. Oils help the body absorb certain vitamins, such as A, D, E, and K, and contribute to healthier skin. And oils carry and intensify flavors in food and give it a pleasurable feel in the mouth.

Most oils come from the seeds of plants, which are crushed and pressed to remove the oil. Heat can damage oils and alter the fatty acids, creating harmful substances, so the best oils are produced with minimal heat. This is called cold pressing. However, when you see the term "cold-pressed" on a label, don't assume that the oil in the bottle was not heated during manufacturing. "Cold-pressed" is a little fib that appeals to consumers who are savvy enough to equate heating with damage to oils. The problem is that the term has no chemical, legal, or technological definition, and it means something different to a manufacturer than it does to the consumer. To a manufacturer, cold-pressed simply means that no external heat was applied during the pressing of the oil, yet the press itself, which comes in contact with the oil, may become quite hot anyway and damage the oil. A more informative label would state the temperature at which the oil was processed, which ideally should be below 110 degrees. The words "omegaflow process" on a label means that the oil has been protected from reaching high temperatures during processing.

Most of the oils you'll find in the supermarket have not only been extracted with heat or solvents, but have also been refined with potentially toxic substances. These processes improve shelf life and make oil cheap to produce, but they take the product further away from its natural state and leave chemical residues behind. If the label does not boast that the oil is "unrefined," you can assume that it has been through some kind of chemical process that makes it worse for your health."