Virgin olive oil is the superior choice when it comes to vegetable oil, according to European researchers. Not only is it high in heart-healthy monounsaturated fat, but also it is the only vegetable oil that's rich in antioxidants called polyphenols, which may help prevent cancer, heart disease and neurodegenerative diseases.
All other vegetable oils are heavily refined, and during this process the polyphenols are lost. Even regular olive oil (the non-virgin variety) has a lower polyphenol content because it is processed more.
Men in the study who used virgin olive oil for three weeks had higher levels of good HDL cholesterol and a decline in markers of dangerous oxidative stress. Another reason why I always recommend avoiding vegetable oils (except for extra virgin olive oil), is that they are full of omega-6 fats and will only worsen your omega-6 to omega-3 ratio. Extra virgin olive oil is clearly a healthy oil, great for salad dressings and other non-heated purposes, but you should be aware that it's not the best oil to cook with.
Annals of Internal Medicine September 5, 2006
Yahoo News September 6, 2006