If you are not sure that the oil was extracted by cold press methods, and that the oil was from organic foods to start with, you run the risk of:
- Nasty pesticides in the food
- "Normal" oil extraction goes to great lengths (chemicals, heat, etc.) to squeeze every last bit of oil out. This includes the concentration of things like pesticides.
- Soybeans have goitrogen compounds in them. The "proper" way to eat soybeans for good nutrient uptake, from what I understand, is in small amounts of substances made from long fermentation periods (e.g. certain soy sauces)
- Back on that chemicals & heat to extract...nasty-for-your-body solvents, such as hexane, can be used in the extraction process...the heat can damage the oils...veggie oils aren't terribly heat-stable, no matter how many recommendations you hear to cook with them...they change forms with heat
- "Normal" extraction methods produce many free radicals in the oil
I encourage you to do your own research on this issue - don't just take my word for it.