Reheating Vegetable Oil Releases Toxin: Study
(HealthDayNews, 5/6/05)

Christine Seppanen and Saari Csallany of the University of Minnesota report that there are high levels of the toxin, 4-hydroxy-trans-2-nonenal (HNE), in vegetable-based cooking oils that are heated for extended periods of time or reheated. Once in the body, HNE reacts with various amino groups (proteins, DNA, RNA) and disrupts cellular processes, potentially contributing to such serious illnesses as heart disease, neurological disorders and cancer. The investigators report that polyunsaturated oils that are high in linoleic acid—including canola, corn, soybean and sunflower oil—are particularly unstable and, therefore, tend to form this dangerous chemical; whereas, oils that are higher in saturated and monounsaturated fats—like peanut oil and olive oil—are more stable when heated. These findings suggest that it may be prudent to avoid fried foods, especially in restaurants and, if you do fry, choose a more stable oil and do not reuse it.

(American Oil Chemists Society annual meeting, Salt Lake City, May 2005)