[MOL] Wok cooking may be harmful for lung cancer [02358] Medicine On Line


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[MOL] Wok cooking may be harmful for lung cancer



Cooking with a wok may contribute to lung cancer risk, depending on the
cooking conditions and the type of oil used. That is the finding of
researchers at the National Cancer Institute, the Shanghai Cancer Institute
in China, and the Research Triangle Institute. Shields et al. note that
Chinese women have one of the highest incidences of lung cancer in the
world, but that tobacco smoking does not appear to be responsible. Previous
epidemiologic studies have implicated indoor air pollutants, including
volatile compounds in the vapors from cooking woks. 

Shields et al. tested various oils and fatty acids, heating them to
temperatures ranging from 240 deg-C to 280 deg-C (typical of cooking
temperatures in Shanghai), collecting condensates from the boiling, smoking
oil, and analyzing the condensates for composition and mutagenicity.
Included in the testing were unrefined Chinese rapeseed oil, canola oil (a
refined form of North American rapeseed oil), peanut oil, sesame oil, and
soybean oil. Also tested were linolenic, linoleic, and erucic fatty acids.
Mutagenicity tests employed Salmonella typhimurium test strains. 

Chinese rapeseed oil tended to produce the highest emissions of the
potentially carcinogenic or mutagenic compounds 1,3-butadiene, benzene,
acrolein, and formaldehyde, while peanut oil tended to produce the lowest
emissions. Quantities of 1,3-butadiene were about 22 times as high from
Chinese rapeseed oil as from peanut oil, and quantities of benzene were
about 12 times as high. Of the individual fatty acids, linolenic acid
produced the greatest emissions of 1,3- butadiene, benzene, and acrolein. 

Emissions from Chinese rapeseed oil were mutagenic, and those from soybean
oil were weakly mutagenic. Emissions from peanut oil, sesame oil, lard, and
canola oil were not mutagenic under the test conditions. Mutagenicity was
attributed mainly to linolenic acid in the various samples, this compound
being the fatty acid with the greatest number of double bonds (unsaturated
carbons). Although canola oil has concentrations of linolenic acid similar
to those in unrefined Chinese rapeseed oil, other components of canola oil
are believed to inhibit formation of hazardous compounds. Lowering the
cooking temperature or adding an antioxidant such as butylated
hydroxyanisole to various samples before heating decreased toxic emissions
during cooking. 

The researchers concluded that exposure to wok fumes may be a controllable
risk factor for lung cancer. For the United States population, further
research is needed to determine the actual risk. Exposure to toxic
emissions, however, can be reduced by lowering cooking temperatures
(although this may result in undesirable odors in Chinese food), adding
antioxidants to or refining cooking oils, and increasing ventilation during
wok cooking. (Shields PG et al. J Natl Cancer Inst. 1995; 87: 836-841.) 

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