Why do people with East Asian heritage get flushed after drinking alcohol?

December 28, 2017 by Terry Mulhern, The Conversation
Facial flushing in a 22-year-old before (left) and after (right) drinking alcohol. Credit: Brooks PJ, Enoch M-A, Goldman D, Li T-K, Yokoyama A - Brooks PJ, Enoch M-A, Goldman D, Li T-K, Yokoyama A 2009. The Alcohol Flushing Response: An Unrecognized Risk Factor for Esophageal Cancer from Alcohol Consumption. PLoS Med, CC BY

If your face goes red when drinking alcohol, you're not alone. More than one in three people with East Asian heritage (Chinese, Japanese and Korean) experience facial flushing when drinking beer, wine or spirits.

In Asian populations, it is due to an inherited deficiency in one of the enzymes involved in the breakdown of : . This type of reaction is very rare, but not unknown, in other ethnic groups.

But there is more to this deficiency than just an embarrassing reddening of the face. There are positive and negative health implications. And it provided a lightbulb moment, helping us understand how a common treatment for alcoholism works.

How you digest alcohol

Alcohol is broken down in your liver in two steps. In the first step, the enzyme alcohol dehydrogenase converts alcohol into a rather nasty chemical called acetaldehyde. A build up of this toxic chemical is one of the reasons you feel sick when hungover.

Then a second enzyme, aldehyde dehydrogenase, converts the acetaldehyde into acetic acid (the harmless acidic component of vinegar).

Aldehyde dehydrogenase deficiency is common among Chinese, Korean and Japanese people. Some inherit two copies of the defective gene for this enzyme; one from each parent. Their liver makes a faulty version of the enzyme.

Others inherit the from just one parent and they produce both normal and faulty enzyme. However, this partial deficiency results in only 1% of full enzyme activity, rather than the 50% you might expect. This is because the faulty version is less stable and multiple copies of the need to work together as a unit.

If you inherit full or partial deficiency in aldehyde dehydrogenase, you will experience prolonged high levels of acetaldehyde very soon after – and all the unpleasant sensations that go with that. Think of it as an instant hangover: nausea, sweating, headache, racing heart, dizziness, along with facial flushing.

What does it mean?

The good news is that because of aldehyde dehydrogenase deficiency, alcoholism and alcohol-related cancers are much less prevalent in East Asian populations. This is because people feel so bad after alcohol, they tend to drink very little, if at all.

Now for the bad news. If you do have aldehyde dehydrogenase deficiency, but still drink, you are at a higher risk of alcohol-related cancers, such as cancer of the oesophagus (the tube between your mouth and your stomach).

The risk is highest for those with partial deficiency. This is because their low residual allows them to develop some tolerance to the unpleasant effects of drinking, but they are still exposed to high levels of acetaldehyde.

It may come as a surprise that anyone with aldehyde dehydrogenase deficiency would drink. But the reasons why we like alcohol are complex. Some of it is metabolic, some is brain chemistry and some is social.

Certain people feel more intense pleasure than others when drinking alcohol and this can contribute to addiction.

Studies of the drinking habits of Asian-American university students have shown that social influences, such as exposure to drinking culture, peer pressure and family attitudes to alcohol can help override the unpleasant physical effects that come with aldehyde dehydrogenase deficiency.

What can you do about it?

It is regularly reported in the media and online that "antihistamines" prevent "Asian flush."

There are drugs that can reduce facial flushing, but they are not the classical antihistamines, such as you take for hay fever. Certain drugs used to treat gastric acid reflux (such as Zantac and Tagamet) have the side effect of reducing alcohol-induced facial flushing. We don't normally think of these drugs as antihistamines, but technically they are, because they block the histamine H2 receptors in the stomach, which are associated with the release of stomach acid.

The drugs we commonly call antihistamines (Zyrtec, Telfast and Claratyne) target the histamine H1 receptor and they have no effect on alcohol-induced .

H2 blockers have few side effects and are relatively safe drugs. But while they mask the symptoms, they won't reduce the toxic effects of acetaldehyde. Popping a pill and drinking to excess can lead to acetaldehyde tolerance and increase the risk of cancer.

So, if you have aldehyde dehydrogenase deficiency, it's better to avoid alcohol altogether. But if you do drink, just drink a little and let the flush happen.

It doesn't matter what form the alcohol comes in, it is metabolised the same way. But how much alcohol a drink contains and how fast you drink it will affect the concentration of acetaldehyde in your body.

How this helps treat addiction

The rareness of alcoholism in Asian populations has a surprising parallel with a treatment for this addiction.

It had long been noted that workers in rubber factories suffered similar symptoms when they drank alcohol. In the 1930s, the offending chemical, Disulfiram, was identified and by the 1950s it was marketed as the drug Antabuse. In the 1980s experts realised Antabuse blocks the activity of aldehyde dehydrogenase.

So, taking Antabuse creates temporary aldehyde dehydrogenase deficiency and one drink is enough to bring on the same unpleasant symptoms felt by those that inherit the deficiency.

But it isn't a silver bullet and doesn't work for everyone. Just as some people with inherited aldehyde dehydrogenase deficiency still drink to excess and develop alcoholism, an instant hangover is not enough to drive some people with alcohol problems away from the "demon drink."

Explore further: New study shows promise of gene therapy to treat alcoholism

Related Stories

New study shows promise of gene therapy to treat alcoholism

September 18, 2017
Researchers used gene transfer to block the expression of one of the two main enzymes that break down alcohol in the liver, leading to the accumulation in liver cells of acetaldehyde, a metabolic byproduct of ethanol. The ...

Even light drinkers should watch for fatty liver disease

May 24, 2016
People who have reduced enzyme activity to breakdown active aldehyde, i.e., those who become easily inebriated, are more likely to develop fatty liver disease even if they do not drink alcohol. This discovery was made by ...

Common class of chemicals cause cancer by breaking down DNA repair mechanisms

June 1, 2017
A common class of chemicals found everywhere from car exhausts, smoke, building materials and furniture to cosmetics and shampoos could increase cancer risk because of their ability to break down the repair mechanisms that ...

Recommended for you

A low-gluten, high-fiber diet may be healthier than gluten-free

November 16, 2018
When healthy people eat a low-gluten and fibre-rich diet compared with a high-gluten diet, they experience less intestinal discomfort including less bloating. Researchers at University of Copenhagen show that this is due ...

Youth dating violence shaped by parents' conflict-handling views, study finds

November 16, 2018
Parents who talk to their children about nonviolent ways of resolving conflict may reduce children's likelihood of physically or psychologically abusing their dating partners later—even when parents give contradictory messages ...

Why we shouldn't like coffee, but we do

November 15, 2018
Why do we like the bitter taste of coffee? Bitterness evolved as a natural warning system to protect the body from harmful substances. By evolutionary logic, we should want to spit it out.

Dietary fat is good? Dietary fat is bad? Coming to consensus

November 15, 2018
Which is better, a low-fat/high-carbohydrate diet or a high-fat/low-carbohydrate diet—or is it the type of fat that matters? In a new paper featured on the cover of Science magazine's special issue on nutrition, researchers ...

Low-carb diets cause people to burn more calories

November 14, 2018
Most people regain the weight they lose from dieting within one or two years, in part because the body adapts by slowing metabolism and burning fewer calories. A meticulous study led by Boston Children's Hospital, in partnership ...

Colder, darker climates increase alcohol consumption and liver disease

November 14, 2018
Where you live could influence how much you drink. According to new research from the University of Pittsburgh Division of Gastroenterology, people living in colder regions with less sunlight drink more alcohol than their ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.