Here the author addresses claims that transfats lurk at even medium heat:
6. Go ahead and turn up the heat. Because of its high polyphenolic content, extra-virgin is more stable than many other oils. The widely held belief that disaster lurks at temperatures above 250 degrees Fahrenheit is simply wrong. Extra-virgin remains stable up to about 410 degrees or a bit higher, depending on the extent of filtration (less filtered means lower temperatures). So deep-frying—best at 350 to 360 degrees—is more than acceptable. Use olive oil in baking too: Cakes gain a moist, rich texture when it’s swapped in for butter, as in the recipe for gluten-free blueberry muffins above.