People whose faces turn red when they drink alcohol may be facing more than embarrassment. The flushing may indicate an increased risk for a deadly throat cancer, researchers report.

The flushing response, which may be accompanied by nausea and a rapid heartbeat, is caused mainly by an inherited deficiency in an enzyme called ALDH2, a trait shared by more than a third of people of East Asian ancestry — Japanese, Chinese or Koreans. As little as half a bottle of beer can trigger the reaction.

The deficiency results in problems in metabolizing alcohol, leading to an accumulation in the body of a toxin called acetaldehyde. People with two copies of the gene responsible have such unpleasant reactions that they are unable to consume large amounts of alcohol. This aversion actually protects them against the increased risk for cancer.

But those with only one copy can develop a tolerance to acetaldehyde and become heavy drinkers.

“What we’re trying to do here is raise awareness of this risk factor among doctors and their ALDH2-deficient patients," said Dr. Philip J. Brooks, an investigator with the National Institute on Alcohol Abuse and Alcoholism, and an author of the report published on Monday in the journal PLoS Medicine. “It’s a pretty serious risk."

The malignancy, called squamous cell esophageal cancer, is also caused by smoking and can be treated with surgery, but survival rates are very low. Even moderate drinking increases the risk, but it rises sharply with heavier consumption. An ALDH2-deficient person who has two beers a day has six to 10 times the risk of developing esophageal cancer as a person not deficient in the enzyme.

Reducing drinking can significantly reduce the incidence of this cancer among Asian adults. The researchers calculate that if moderate- or heavy-drinking ALDH2-deficient Japanese men reduced their consumption to under 16 drinks a week, 53 percent of esophageal squamous cell cancers in that group could be prevented.

There is some anecdotal evidence that young people treat the flushing as a cosmetic response to be countered with antihistamines while continuing to drink. Ignoring the symptom and continuing to drink is likely to increase the incidence of esophageal cancer, researchers said.

To determine risk, doctors can ask their patients two simple questions. First, do you flush after drinking a glass of beer? Second, in the first one or two years after you began drinking, did you flush after having a beer?

The second question covers the possibility that a person has become tolerant to the effect.

Dr. Brooks said that the two questions give doctors an easy way to find out if the patient is ALDH2-deficient. There is also a patch test in which an ethanol-soaked pad is applied to the skin. If it causes reddening after 10 or 15 minutes, there is a high likelihood that the person is ALDH2-deficient.

喝酒就臉紅的人遇到的問題可能不僅僅只是尷尬而已，根據研究人員的報告，臉色發紅可能意味著患上致命的喉癌的風險在增加。

喝酒臉紅，一般會伴隨著惡心還有心跳加速的癥狀，而這些主要是因為天生缺乏一種叫ALDH2的酶。而超過三分之一的東亞血統的人喝酒都會臉紅，包括日本人、中國人還有韓國人。只要半瓶啤酒就可以引起這樣的反應。

缺乏ALDH2酶會造成酒精在體內循環不順暢的問題，最終導致一種叫乙醛的有毒物質在體內堆積。有兩套基因的人會有這種令人不快的反應，所以他們一般喝不了太多酒。而這種厭惡的情緒能夠避免他們增加患上癌癥的風險。

不過只有一套基因的人卻會能接受乙醛，最終變成一個嚴重的飲酒人。

“我們現在要做的就是試著提高醫生還有他們的ALDH2缺乏病人的風險意識，”Philip J. Brooks博士說，他是國家酗酒和酒精中毒研究機構的研究院，也是星期一在PLoS醫學日報上發表的報道的作者。“這個風險是極大的。”

由于吸煙造成的惡性腫瘤，也叫鱗狀上皮細胞食道癌是可以通過手術手段治療的，不過成功率很低。甚至適度的飲酒都可能增加患上食道癌的風險，而在酗酒的人中這種風險更是顯著。缺乏ALDH2患者如果每天喝兩瓶啤酒，比那些不缺乏這種酶的人患上食道癌的風險要高上6到10倍。

少喝酒能顯著的減少亞洲成年人患上這種癌癥的可能。研究人員計算了一下適度或者大量飲酒且缺乏ALDH2的日本男人每周少喝16瓶酒的情況，發現這一組人中患上食道鱗狀上皮細胞癌的風險減少了53%。

有一種傳聞，說年輕人將臉紅當成是持續喝酒時，化妝品抵觸抗組胺劑(譯者注：用以治療過敏反應)的反應。忽略這些癥狀繼續喝酒很可能增加患上食道癌的風險，研究人員稱。

為了確定風險程度，醫生可以問病人兩個簡單的問題。首先，你喝完一瓶酒后會不會臉紅？第二個問題是，在你開始喝酒后的一到年兩年里，你是不是一喝酒就臉紅？

第二問題是為了確認病人是不是有接受這種反應的可能。

Brooks博士說這兩個問題讓醫生很容易就確認人是不是缺乏ALDH2。還有另外一種測試方法，就是在皮膚上帖一個用酒精浸濕后的貼布。如果在10到15分鐘后皮膚開始發紅，說明這個人很可能缺乏ALDH2。