Fried foods may please the palate, but cooking them in the wrong medium, such as sunflower oil, can present a health risk. Researchers from the University of the Basque Country, in North Spain, have discovered that organic aldehyde compounds become toxic when heated. These chemicals, previously linked with some types of cancer and neurodegenerative diseases such as Alzheimer’s and Parkinson’s, are generated by the degradation of fatty acids in sunflower and other oils high in polyunsaturated fats, and some remain in food after frying. Oils with higher concentrations of monounsaturated fats, such as olive, peanut or coconut, are less worrisome if frying is the only cooking option.