Healthy Decisions for the Love of Health

Highly toxic compound found in foods fried in unsaturated vegetable oils  Source: Health Central: May 2005  Added Dec 30, 2005

A new study has shown that a highly toxic compound forms when unsaturated vegetable oils are heated at frying temperatures for even half an hour.

This toxin, HNE (4-hydroxy-trans-2-nonenal), has long been linked with a variety of heart and nervous system diseases.

The HNE toxin forms in particularly high amounts in polyunsaturated oils such as sunflower, canola, soybean and corn, which contain the essential fatty acid linoleic acid (LA), according to the lead researcher A. Saari Csallany.

Their latest experiment found that "intermittent heating is just as bad as continuous heating". This reinforces the danger of re-heating oils at home or in restaurants. A study she published last year in the Journal of the American Oil Chemists' Society also found that the level of absorbed HNE in French fries was equal to HNE concentrations in the oil the fries were cooked in.

Dr Csallany, a professor of food chemistry and nutritional biochemistry at the University of Minnesota, says "There's a tremendous literature in biochemistry on HNE, a library of studies going back 20 years. It's a very toxic compound."

She continues "HNE is a well known, highly toxic compound that is easily absorbed from the diet. The toxicity arises because the compound is highly reactive with proteins, nucleic acids - DNA and RNA - and other biomolecules. HNE is formed from the oxidation of linoleic acid, and reports have related it to several diseases, including atherosclerosis, stroke, Parkinson's, Alzheimer's, Huntington's and liver diseases."

Based on the findings, she recommends that people avoid foods fried in polyunsaturated vegetable oils. For her part, Csallany said she would abandon vegetable oils as a cooking staple altogether.

She also noted that not all vegetable oils are created equal. "Oils that are high in saturated fats and monounsaturated fats are the most stable when heated" she said. The HNE compound does not arise in saturated oils sourced from animal fat, or from coconut oil.

Presented on May 4, 2005 at the 96th annual meeting of the American Oil Chemists Society in the Salt Lake City Convention Center.

Source: Health Central: May 2005
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Revised: June 23, 2007