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  • Aug 23, 2014
  • Updated: 11:59am
NewsHong Kong

Health bureau raises cancer warning for stir-fried greens

PUBLISHED : Tuesday, 30 July, 2013, 12:00am
UPDATED : Wednesday, 31 July, 2013, 7:54am


  • I'll eat none: 4%
  • I'll eat less: 39%
  • I'm not worried: 56%
31 Jul 2013
  • I'll eat none
  • I'll eat less
  • I'm not worried
Total number of votes recorded: 347

Hongkongers are being urged to eat fewer stir-fried greens after a study found they account for half the local intake of a potentially cancer-causing substance.

Processed at the high temperatures created in a wok, vegetables such as zucchinis and green peppers can produce the toxic contaminant acrylamide, the Department of Health warned.

In excessive amounts, acrylamide can damage the nervous system and has been identified as a probable cause of cancer in humans, the department said.

The department's food safety officer Dr Xiao Ying said the findings on acrylamide intake "indicate a health concern", despite Hongkongers intake of the substance being lower than that of mainlanders and consumers in seven Western countries.

"The public can avoid the substance by cooking the food in a healthier way such as boiling or steaming," Xiao said.

"More acrylamide is formed when frying at a higher temperature and for a longer time, but it was not detected in non-fried items, including uncooked fruits and boiled vegetables."

The contaminant is formed during the high-temperature processing of food containing the amino acid asparagine - so named because it was first discovered in asparagus.

Dr Philip Ho Yuk-yin, the department's consultant on community medicine, said that although the amount of acrylamide required to be a risk to health had not been established internationally, people should keep their intake "as low as possible".

The findings came after an analysis of 133 common food items in the Hong Kong diet.

Stir-fried zucchini, water spinach (kangkong), green pepper, onion and garlic contained the highest levels of acrylamide, with up to 360 milligrams of acrylamide present per kilogram. Bitter melon, Chinese lettuce and watercress had the lowest, all with less than 10 milligrams.

The stir-fried greens are still healthier than snacks such as potato chips, crisp bread and crackers, which contain up to 680 milligrams in each kilogram.

From the study, the department estimated that the average Hongkonger is exposed to 0.21 milligrams of acrylamide in each kilogram of food they eat, while those who consume a higher than average amount of food may take in 0.54 milligrams.

But consumers on the mainland, the UK, Canada, Europe, the US, France, Ireland and New Zealand all have higher intakes of the substance. Mainlanders take in between 0.28 and 0.49 milligrams, the second highest intake.

Half of all daily exposure to the contaminant in Hong Kong comes from vegetables and their products while about 15 per cent comes from cereals and 4.7 per cent from snacks. Meat contributes only 2 per cent.

The study did not find an obvious association between the use of oil and the amount of acrylamide released during cooking.

"The discrepancy in exposure between the East and the West may be a result of their diet habits," Ho said. "Westerners tend to consume more potato chips and fried potatoes, which have high levels of asparagine."

Ho advised the public to eat at least three servings of vegetables a day, using moderate-heat cooking, and to avoid eating fried foods altogether.



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This article is now closed to comments

is this someone from the mainland talking about food safety?
Wasn't there a study a while ago on why Chinese women have disproportionally higher lung cancer rate, given much lower rate of smoking? The culprite was inhaling smoke from stir fry.
Try stir frying with water and oil at a moderate heat so things don't break down at high heat.
Nice! in other words, skip the Chinese way of cooking and switch to boiling the food without taste.
For centuries we stir fry our food in woks. Especially garlic is the main ingredient for almost all Chinese food. If you don't stir fry the garlic, well then stop cook Chinese. Question is then whether it is still worth to live on.
so, then crackers and cereals are as well contaminated? I thought cereals are very healthy.
This report is likely to produce quite a stir !
How much is excessive?
I would take this quite seriously. It would seem logical that the increased prevalence of all types of cancer in the last century probably has to do with the increased consumption of various carcinogenic substances from the change in dietary habits.
Reduce the intake of stirred fried vegi.
Dr Xiao Ying has zero scientific basis for his recommendation. Read about it. No link has ever been established between human consumption of acrylamide and cancer notwithstanding dozens of enormous epidemiological studies. This is just a case of the government trying to look like it's working hard protecting Hong Kong public health. This kind of PR is a whole lot cheaper than going out and building hospitals and recruiting medical staff to bring Hong Kong public health into line with that of other developed economies.
Kindly take care to ensure statements made here are accurate and not misleading.
It is inaccurate to say Dr Xiao Ying has zero scientific basis for his recommendation. Its carcinogenic effects on rodents has been clearly established, and the WHO believes further investigation on the effects on humans is necessary. There are various studies, such as this one by Health Canada, which indicate an elevated risk of certain cancers due to acrylamide consumption.
How about a retort with facts? The WHO says there is "probably" a link and says so on only one basis: that a 900x typical consumption of acrylamide causes cancer in rats. Well, almost any otherwise innocuous substance will do even worse, i.e. kill you, if you consume 900x what's normal. A recent review of 15 huge epidemiological studies revealed NO LINK. All that the WHO are doing is making a blind mathematical extrapolation. That hardly comes close to the facts established by so many massive studies. Try eating 900x normal consumption of salt and see what that does to you. Giving up salt tomorrow?




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