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.

喝酒就脸红的人遇到的问题可能不仅仅只是尴尬而已，根据研究人员的报告，脸色发红可能意味着患上致命的喉癌的风险在增加。

喝酒脸红，一般会伴随着恶心还有心跳加速的症状，而这些主要是因为天生缺乏一种叫ALDH2的酶。而超过三分之一的东亚血统的人喝酒都会脸红，包括日本人、中国人还有韩国人。只要半瓶啤酒就可以引起这样的反应。

缺乏ALDH2酶会造成酒精在体内循环不顺畅的问题，最终导致一种叫乙醛的有毒物质在体内堆积。有两套基因的人会有这种令人不快的反应，所以他们一般喝不了太多酒。而这种厌恶的情绪能够避免他们增加患上癌症的风险。

不过只有一套基因的人却会能接受乙醛，最终变成一个严重的饮酒人。

“我们现在要做的就是试着提高医生还有他们的ALDH2缺乏病人的风险意识，”Philip J. Brooks博士说，他是国家酗酒和酒精中毒研究机构的研究院，也是星期一在PLoS医学日报上发表的报道的作者。“这个风险是极大的。”

由于吸烟造成的恶性肿瘤，也叫鳞状上皮细胞食道癌是可以通过手术手段治疗的，不过成功率很低。甚至适度的饮酒都可能增加患上食道癌的风险，而在酗酒的人中这种风险更是显著。缺乏ALDH2患者如果每天喝两瓶啤酒，比那些不缺乏这种酶的人患上食道癌的风险要高上6到10倍。

少喝酒能显著的减少亚洲成年人患上这种癌症的可能。研究人员计算了一下适度或者大量饮酒且缺乏ALDH2的日本男人每周少喝16瓶酒的情况，发现这一组人中患上食道鳞状上皮细胞癌的风险减少了53%。

有一种传闻，说年轻人将脸红当成是持续喝酒时，化妆品抵触抗组胺剂(译者注：用以治疗过敏反应)的反应。忽略这些症状继续喝酒很可能增加患上食道癌的风险，研究人员称。

为了确定风险程度，医生可以问病人两个简单的问题。首先，你喝完一瓶酒后会不会脸红？第二个问题是，在你开始喝酒后的一到年两年里，你是不是一喝酒就脸红？

第二问题是为了确认病人是不是有接受这种反应的可能。

Brooks博士说这两个问题让医生很容易就确认人是不是缺乏ALDH2。还有另外一种测试方法，就是在皮肤上帖一个用酒精浸湿后的贴布。如果在10到15分钟后皮肤开始发红，说明这个人很可能缺乏ALDH2。