For most cooking, I use organic extra-virgin olive oil, but when I want a neutral tasting oil, I use canola oil in moderation. Canola oil is extracted from rapeseed, a plant related to mustard in the cabbage family.
Although it is predominantly a monounsaturated fat, canola oil is a distant runner-up to olive oil in terms of its health benefits. We know that when olive oil is used as a primary fat, people have significantly lower rates of both heart disease and cancer than those that don’t rely on it as much. We don’t have comparable epidemiological data for canola oil. I recommend choosing organic, expeller-pressed brands of canola oil over the lower-cost products sold in supermarkets because these less expensive oils often have been extracted with chemical solvents or high-speed presses that generate heat. Both these methods alter the oil’s chemistry in undesirable ways. In addition, canola oil producers use a lot of pesticides on their crops, and I suspect that residues find their way into the finished product, so be sure to check labels to make sure the oil you’re considering is organic. If you can’t find organic, expeller-pressed canola oil in the natural food sections of your local supermarkets, look for it in health food stores. Alternatively, you can order it online.
You ask about using grapeseed oil as an alternative to canola oil. Grapeseed oil is a byproduct of grape seeds pressed in the process of winemaking. It has a neutral taste, and it has the advantage of a higher smoke point. Buy only organic expeller-pressed grapeseed oil, and once a bottle is opened, keep it in the refrigerator. You can use grapeseed oil for sautéing but not for deep-frying, which you shouldn’t be doing anyway. Frying puts excessive fat into dishes and also exposes you to the health risks of chemically altered fats. Stir-frying is perfectly acceptable if you use reasonable amounts of high quality oils and keep them below the temperatures at which they smoke.
Whatever type of oil you use, be sure to store it away from light and heat and don’t buy more than you can use in a month or two.
Andrew Weil, M.D.