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East Asians lack alcohol enzyme

24th March 2009

Many people of East Asian descent are deficient in an enzyme called ALDH2, which processes alcohol.


This results in a biochemical process different from that of people who have the enzyme, and they are certain to experience increased heart rates, facial flushing, and nausea whenever they drink alcohol.

But something else is happening in the body of the 8% of the people on the planet who lack the enzyme which researchers say greatly increase the probability they will contract oesophageal cancer.

Kenneth Warren, NIAAA Acting Director, said that it is very important for clinicians who treat patients of East Asian descent to be aware of the risk of oesophageal cancer from alcohol consumption, if they exhibit the alcohol flushing response.

All people who lack the ALDH2 enzyme metabolise alcohol into an indigestible carcinogen.

However, people with only one copy of the gene that codes for the deficiency are likely not to notice.

Philip Brooks of NIAAA's Laboratory of Neurogenetics, notes that a medic can determine whether or not a patient has the enzyme by asking about their previous experiences with alcohol.

He said that cancer of the oesophagus is particularly deadly, with five-year survival rates ranging from 12-31% throughout the world, and at least 540 million people at risk.

When the enzyme, known as ALDH2, is absent in a person, alcohol is metabolised into acetaldehyde, a dangerous chemical capable of causing damage to cellular DNA as well as other cancerous effects.

Because ALDH2 is responsible for metabolising acetaldehyde into its nontoxic counterpart, acetate, East Asians whose genetics give them an inactive version of the enzyme accumulate acetaldehyde in their bodies whenever they drink.

People with a tolerance for alcohol, despite the occurrence of the gene, are at a higher risk for people whose tolerance is low, because they tend to keep drinking even when the presence of acetaldehyde in their bodies is already quite high.

Akira Yokoyama, co-author of the finding, has worked with his colleagues in Japan to show that people are most at risk if they lack the enzyme yet tolerate the carcinogenic products of alcohol metabolisation.

Such people are up to 1000% more likely to develop esophageal cancer on average, and up to 9000% more likely if they tend to have 33 or more drinks per week.

Researchers say that informing ALDH2-deficient people about these cancer rates is an important task which should be done while they are still young, and especially before they reach college.


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Wednesday 15th April 2009 @ 15:24

I don't want to appear flippant, but isn't some flushing, increased heart rate and nausea what happens to all who drink alcohol? Or have I just misunderstood its effect on me all this time?

Jonathan Pham

Tuesday 5th January 2010 @ 19:38

I find this discovery qutie amusing actually because I am Vietnamese and live in Ireland and all my friends when out drinking always thought I was allergic or something but now ive got a reason why my eyes go bright red and my face turns reddish when I drink lol

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