Single or Double Asian Glow: why some people suffer worse than others from Alcohol Flush Reaction.
Do some people get Alcohol Flush Reaction worse than others? The short answer is yes. The Alcohol Flush Reaction story is more complicated than just having it or not having it. To understand why, we need to first look at the genetics that cause it.
Those who experience Alcohol Flush Reaction, also known as Asian Glow, have a gene mutation that leaves them unable to break down the toxin called acetaldehyde. However, some people have it worse than others and can have 2 mutations instead of just 1. About 10% of those with ALDH2 Deficiency will have Double ALDH2 Deficiency, which means 'Double Asian Glow'.
Single ALDH2 Deficiency
For (almost) every gene, whether it encodes the color of your eyes, your height, or your ALDH2 enzyme, you have 2 copies. 1 copy comes from your mother, and 1 from your father. It only takes 1 mutated ALDH2 gene from either parent for a person to have ALDH2 Deficiency and experience Alcohol Flush Reaction. This is why the ALDH2 mutation is called a “dominant” gene. In this case, your body makes some mutated enzyme, and some healthy enzyme.
Those with 1 mutated gene and 1 healthy gene are called heterozygous.
However, in the liver, the ALDH2 enzyme works by grouping together in groups of 4 with other ALDH2 enzymes, and together the group is only as good as the weakest link. This is why people with a single ALDH2 mutation and still produce some healthy enzyme, have ALDH2 Deficiency and cannot properly break down acetaldehyde. An estimated 90% of people with ALDH2 Deficiency have only a single mutation.
Since there is a chance that one of these groups of 4 will be made up of only healthy enzyme, those with the single ALDH2 mutation will still have some ability to break down acetaldehyde.
Double ALDH2 Deficiency
An estimated 10% of people with ALDH2 Deficiency have 2 mutated genes or Double Asian Glow. This is called homozygous. Those who have 2 mutated ALDH2 genes produce no healthy enzyme, and all mutated enzyme, and have almost no ability to break down acetaldehyde. These individuals have a severe reaction to alcohol, and can experience all the intense symptoms of Alcohol Flush Reaction after only a few sips of alcohol! Without a genetics test, this subjective experience is the only way to tell if you may have a single or double mutation.
Many people with 2 mutated ALDH2 genes do not drink alcohol at all for this reason. It’s even more important that those with 2 mutated genes avoid sources of acetaldehyde like air pollution, cigarette smoke, certain foods and beverages, and alcohol. This is because acetaldehyde is a carcinogen that causes damage to the liver, and those with ALDH2 Deficiency are significantly more likely to get certain types of cancers, like gastric and esophageal cancer, and liver diseases.
How Do I Know If I Have a Single or Double ALDH2 Deficiency?
Since the ALDH2 gene is passed from parents to children, if both of your parents experience Alcohol Flush Reaction (and have ALDH2 Deficiency), it is possible for you to be homozygous for the ALDH2 mutation (or have 2 mutated ALDH2 genes). If your reaction to alcohol is extremely severe, this may also be an indication.
For those with a double ALDH2 Deficiency or Double Asian Glow, it’s important to note that since the ALDH2 gene is passed from parents to children, and it only takes one mutated copy of the ALDH2 gene to have ALDH2 Deficiency, all of the children of those with 2 mutated ALDH2 genes will have ALDH2 Deficiency.
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