"Vegetable oil" can refer to a variety of plant-based oils, including canola oil, sunflower oil, peanut oil, and olive oil. Products sold as "vegetable oil", however, are typically just soybean oil, or a blend of soybean oil and other vegetable oils.1
Vegetable oils have varying smoke points (i.e. the temperature at which they literally start to smoke—and, worse, degrade). Thus, different vegetable oils are best suited for different purposes in the kitchen. For example, refined canola oil can be heated up to about 400 °F (204 °C), while flax seed oil can only be heated to about 225 °F (107 °C).2
|Fat||Smoke Point in °F|
|Refined Avocado Oil||520|
|Refined Safflower Oil||510|
|Refined Grape Seed Oil||485|
|Refined Olive Oil||465|
|Refined Corn Oil||450|
|Refined Peanut Oil||450|
|Refined Soybean Oil||450|
|Refined Sunflower Oil||440|
|Refined Canola Oil||400|
|Virgin Avocado Oil||375-400|
|Unrefined Sesame Oil||350|
|Virgin Coconut Oil||350|
|Extra-Virgin Olive Oil||325-375|
|Refined Flax Seed Oil||225|
Note: the values above vary depending on if and how the fat/oil has been refined.
Vegetable oils also contain different amounts of fats—saturated, monounsaturated, and polyunsaturated (which include the famous omega-6 and omega-3 fatty acids). The different fat compositions of cooking oils means they also have different impacts on our health.
Olive oil, canola oil, and other oils low in saturated fat have been promoted as the healthiest cooking fats for many years. Recent studies have suggested, however, that saturated fats may not be quite as detrimental to our health as previously thought. 3 Moreover, recent studies have even suggested that vegetable oils low in saturated fat, but much higher in omega-6 fatty acids than omega-3 fatty acids may actually increase the risk of heart disease. In light of these findings, it might be advisable to avoid corn, safflower, and sunflower oils.4
All that said, it seems like a reasonably healthy approach to use a mixture of cooking fats high in saturated fat (e.g. butter and coconut oil) and cooking oils that are both low in saturated fat and high in omega-3 fatty acids (e.g. flax, canola, and olive oils). Note: according to the Non-GMO Project, about 90% of the canola oil in the United States is made from genetically modified rapeseed, so if this issue is important to you be sure to buy certified organic or certified GMO-free canola oil.5
The nutrition DNA of vegetable oil. For example, you can see that 1 tablespoon vegetable oil covers 72% of your daily need of Saturated Fat and 22% of the recommended Fat intake. Hover over the bars to see which nutrient is covered.