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(article, Laura Troyer)

Hot pan, cold oil. It’s a long-debated piece of advice that some cooks swear by and others scoff at. Both camps agree, though, that cooking with oil requires heat. 

But how hot? And which oils? 

Nina Planck wants people to reconsider the oils they use for cooking. In her book Real Food, Planck cites literature that says heat damages unsaturated fatty acids — in other words, the fats found in high quantities in many plant oils — and makes those fats unhealthy. 

“That’s why it was bad news for health when fast-food restaurants stopped using saturated beef fat and palm oil,” Planck writes, “and started frying foods in rancid polyunsaturated oils.” Oils high in polyunsaturated fatty acids include liquid vegetable oils, like corn oil and soybean oil.

Sally Fallon likewise takes issue with polyunsaturated oils in her book Nourishing Traditions. Fallon believes polyunsaturated oils can cause disease because they “tend to become oxidized or rancid when subjected to heat, oxygen, and moisture as in cooking and processing,” and thus contain body-damaging free radicals.

Mehmet Oz, a doctor and frequent guest on “The Oprah Winfrey Show,” has advised Oprah viewers to avoid heating oil to a temperature at which it emits smoke. "If you take a healthy fat and you fry it — if it reaches its smoking point — then you actually are oxidizing it," Oz told Oprah’s viewers. "When you oxidize it, you actually damage the fats, so you lose a lot of the benefit."

But Harold McGee, in On Food and Cooking, calls the vegetable oils Planck and Fallon eschew more stable at high temperatures because of their initial low content of free fatty acids. And the American Heart Association lists vegetable oils as appropriate for “sautéing, stir-frying, and deep-frying” on its website.

Simmered down to the basics? Don’t heat oil past its smoke point; burned oil makes food taste acrid anyways. Don’t reuse frying oil over a long period of time. And consume any fat in moderation.