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Highly toxic
compound found in fried foods |
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
From
the Huntingdon's Disease Lighthouse newsletter:
Although Huntington's Disease is mentioned in the press
release below, I can find no research which reports that
HNE is elevated in the brains of HD patients. There is
research showing that elevation of this neurotoxin
occurs in the brain tissue of Alzheimer's patients and
HIV patients experiencing progressive dementia, however.
HNE even appears to associated with the formation of
neurofibrillary tangles in Alzheimer's.
There
would certainly appear to be a connection with HD. We
know that lipid peroxidation results from free
radical-mediated injury to brain. Free radical damage
and the resulting oxidative stress in neurons occurs in
Huntington's Disease and lipid peroxidation is also
found. 4-Hydroxy-trans-2-nonenal (HNE) is a product of
lipid peroxidation.
Given the
findings in the press release below, it would seem best
to avoid fried food in restaurants where the vegetable
oil would be used for a considerable period of time. At
home use other ways of cooking or if you want to use
vegetable oil to crisp the food, use it at the end of
the cooking process. This seems like good advice for all
of us since we are all aging and good advice for people
with Huntington's Disease in particular since their
neurons are particularly vulnerable to oxidative stress.
--Marsha L. Miller, Ph.D.
29 May 2005
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