You Need To Stay Away From This Oil. It Releases Dangerous Chemicals. The thing is vegetable oils releases harmful chemicals that can trigger the onset of cancer and other life-threatening conditions in the long run. According to the team of researchers, some of the most dangerous substances include aldehydes, chemicals linked to cancer, dementia, and heart issues. Professor Martin Drootveld claims that the amount of toxic aldehydes in fish & chips fried in vegetable oil is 200 times higher than the allowed limit. On the other hand, butter, olive oil, and even lard were found to release far less aldehydes compared to vegetable oils.