Sally Fallon is concerned about the high consumption of unhealthy oils in our society. She cautions people to steer clear of highly processed oils and the packaged foods that also contain them. It's not possible to really know just what type of oil has been added to the processed foods we buy.
Cold-pressed oils are usually the least processed of the oils. They'll do best in dark bottles, protecting the oil from sunlight. In order to avoid the free radicals released by vegetable oils that have been heated to too high a temperature, check out oils with a higher smoke point like non-hydrogenated coconut, or olive oil.
"High-temperature processing causes the weak carbon bonds of unsaturated fatty acids, especially triple unsaturated linolenic acid, to break apart, thereby creating dangerous free radicals. In addition, antioxidants, such as fat-soluble vitamin E, which protect the body from the ravages of free radicals, are neutralized or destroyed by high temperatures and pressures. BHT and BHA, both suspected of causing cancer and brain damage, are often added to these oils to replace vitamin E and other natural preservatives destroyed by heat."
http://inpraiseoffat.com/2010/02/28/its-time-for-an-oil-change