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David Bradley ISSUE #45
April - May 2005

Oil's Not Well

Speaking at the 96th annual meeting of the American Oil Chemists Society in Salt Lake City, Utah, on May 4, A. Saari Csallany and PhD candidate Christine Seppanen explained that when highly unsaturated vegetable oils, such as corn, soybean, and sunflower oil are heated at frying temperatures (185 Celsius) for even just half an hour, HNE forms. The amount produced is proportional to the cooking time and accumulates with a second and subsequent heating. Csallany and her colleagues also found three other toxic compounds related to HNE (4-hydroxyhexenal, 4-HHE, 4-hydroxyoctenal, 4-HOE, and hepta-2,4-dienal, 2,4-HDE) in heated soybean oil.

Cooking with highly unsaturated oils and especially re-using oils can lead to high levels of a toxic compound hydroxy-trans-2-nonenal (HNE) in the food. The compound is readily absorbed by the body and is well-known for its harmful effects on proteins, DNA, and other biomolecules.

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(Structure and mol file by David Bradley)

"HNE is a well-known, highly toxic compound that is easily absorbed from the diet," said Csallany. "The toxicity arises because the compound is highly reactive with proteins, DNA, and other biomolecules because of the presence of an alpha-beta-hydroxy group. HNE is formed from the oxidation of linoleic acid, and other researchers have linked it with several diseases, including atherosclerosis, stroke, Parkinson's, Alzheimer's, Huntington's, and liver disease." She told Reactive Reports that intermittent heating of these oils leads to an accumulation of the toxic compounds. Cafes and restaurant and users of home fryers are often loathe to discard many liters of oil, she explained, so often re-use the same oil day in day out. "The effect on HNE levels is just as if the oil were being heated continuously," she told us, and that could lead to long-term health problems.

Refried vegetable oils such as sunflower and soybean oils are ??
Refried vegetable oils such as sunflower and soybean oils are not a healthy option




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Unsaturated fats and oils containing high levels of linoleic acid, a polyunsaturated fatty acid, have been regarded as specifically beneficial to the cardiovascular system in contrast to saturated fats. However, Csallany's work, which follows in the wake of research into the presence of the putative carcinogen acrylamide in fried carbohydrates, offers more evidence of the detrimental effects of fried foods in the diet.

Csallany and her colleagues are now planning research to determine how long polyunsaturated oil must be heated at lower temperatures in order to form HNE and related compounds. In the meantime, their results suggest that re-using unsaturated oil for frying is not the healthiest option.

http://data.che.umn.edu/expertise/FacultyBio.asp?FacID=45

http://www.aocs.org/news/amnews.asp

http://www.sciscoop.com/story/2004/4/8/8644/15794 - acrylamide