February 07, 2020
Asian Flush (Alcohol Flush Reaction): Symptoms, Causes & Treatments
What is Asian Flush?
For most people when they drink alcohol, it can make them feel more confident and comfortable. But for some people, drinking makes them feel physically uncomfortable because thanks to their DNA, alcohol makes their skin turn red. It's called alcohol flush reaction, or Asian flush, and is a condition in which a person develops flushes, redness or blotches throughout their entire body or on specific areas after consuming alcohol. Luckily, not all Asians suffer from this unfortunate condition as the best studies estimate that it affects about 36 percent of Northeast Asians (Chinese, Japanese and Koreans).
The Cause of Asian Flush
Alcohol flush happens when the blood vessels under the surface of the skin dilate. This is part of an immune response where the body is detecting a threat. The threat isn't the alcohol itself but a substance that's produced when alcohol is broken down. When normal people drink ethanol, the chemical name for booze, the liver gets rid of it using two main enzymes, alcohol dehydrogenase (ADH), which metabolizes ethanol into acetaldehyde, a highly toxic substance and aldehyde dehydrogenase (ALDH2), which turns acetaldehyde into acetate. Acetate is similar to vinegar and easy for the body to eliminate. It's that second enzyme, ALDH2, that really screws things up for people with Asian flush.
If you look inside the DNA of sufferers of Asian flush, you'll find that the gene providing the instructions for the ALDH2 enzyme was tweaked at some point in their history. And that gene mutation produces an inactive ALDH2 enzyme so when they drink, their bodies accumulate acetaldehyde at a level about 6X higher than normal people. If acetaldehyde sounds familiar, that's because it's similar to formaldehyde. It's extremely toxic. That's why it triggers the immune response and the red face is really the least of it.
What Are the Symptoms of Asian Flush?
People tend to assume that a red face equals inebriation, but that's a myth. But the real signs and symptoms of Asian flush due to acetaldehyde build up - can include:
- Redness in the face and upper body (flushing)
- Red, itchy skin bumps (hives)
- Nausea and vomiting
- A warm, tingly sensation
- Racing heartbeat
- Difficulty breathing
- Red Eyes
- A feeling of pressure in the upper body
Health Risks of Asian Flush
Besides the on the surface symptoms of Asian flush, which may seem embarrassing and slightly irritating at most, there are more serious consequences to this condition.
Acetaldehyde is a known carcinogen and can cause esophageal cancer for everyone but especially for people with Asian flush. To make the problem worse, people can actually develop a tolerance to Asian flush that allows them to drink pretty heavily. So if you have Asian flush, be careful, your body is freaking out for a reason.
Why Are Asians Disproportionately Affected by ALDH2 Deficiency?
Why Are Asians Disproportionately Affected by ALDH2 Deficiency?
Ever wonder why your face turns red after one drink? Well you can thank the Chinese farmers if you’re of Asian descent! Researchers have discovered that the "Asian Flush" mutation cropped up just as rice was first being domesticated, and it served as protection for early farmers against the negative effects of drinking too much.
When you consume alcohol, one liver enzyme, alcohol dehydrogenases (ADHs) converts it into a toxic byproduct called acetaldehyde; another enzyme further breaks it down from acetaldehyde to acetic acid. Surprisingly, 50% of Asians and 5% of Europeans have mutations in these enzymes that can increase the rate of alcohol metabolism up to 100-fold. This leads to a rapid buildup of acetaldehyde, which causes capillaries in the face and body to dilate—ultimately creating redness in the face. Other unpleasant side effects of this mutation can include nausea and headaches. In 2008, a team led by geneticist Kenneth Kidd of Yale University found that one of these mutations--known as ADH1B*47His--may have been favored by natural selection in many East Asian populations.
A team led by Bing Su, a geneticist at the Kunming Institute of Zoology in China, set out to find the source of this selection. The researchers searched for the ADH1B*47His mutation in 2275 people across China representing 38 ethnic groups. They found that it was highly prevalent, up to 99%, in ethnic groups from southeast China; a bit less prevalent, 60% to 70%, in western China; and relatively uncommon, 14%, among Tibetans. Moreover, the team found a strong geographical correlation between regions with a high prevalence of the mutation and archaeological sites in China where rice had been domesticated thousands of years ago.
When Su and his colleagues calculated the age of the mutation, it came out at between 7000 and 10,000 years ago. That corresponds roughly to the earliest known evidence for rice farming, the team reports online this week in BMC Evolutionary Biology. "The [mutation] rose to extremely high frequency in a relatively short time, implying that the selective force was quite strong," Su says.
As for what the selective pressure was, the team concludes that the mutation was favored because it protected early farmers from the potentially fatal harms of drinking too much. The researchers cite two additional pieces of evidence for this hypothesis. First, recent archaeological evidence suggests that Chinese farmers concocted an alcoholic brew of rice, honey, and grape or hawthorn as early as 9000 years ago. Second, the drug disulfiram, which causes acetaldehyde to accumulate in the body, discourages alcoholics from drinking by causing nausea, vomiting, and other severe alcohol flush reaction symptoms.
"This study is the latest in a growing body of research showing just how important human culture has been as a transformational force in human evolution," says Darren Curnoe, an anthropologist at the University of New South Wales in Sydney, Australia. Indeed, the rise of farming has been linked to evolutionary changes in genes for other enzymes, such as amylase, which breaks down starch, and lactase, which breaks down lactose in milk.
Other researchers are not entirely convinced. Kidd says that the hypothesis is "quite reasonable" but that it's still speculation at this point. He also questions whether the team has determined the age of the mutation correctly, because the estimates range over at least 3000 years. And Dorian Fuller, an archaeologist at University College London, argues that the team may be wrong to pin the mutation's origins solely on rice cultivation. The archaeological sites the researchers chose, he says, included settlements where rice had just begun to be farmed and those where rice farming was in full flower. Fuller adds that if the team had restricted its analysis to those later sites where rice had become a predominant crop, beginning about 8000 years ago, then alcoholic beverages could also have been made from grapes--and rice might not be solely responsible for the Asian Flush.
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