Your Genes and Asian Flush


Welcome to the Genetics Society blog, where I (Leina, hi!) will be posting a little article twice a month. I’ll be giving you the latest deets in the world of genetics, and we’ll learn about current and past research topics impacting our everyday life. In keeping with the freshers theme, for the first post I have chosen some research that might interest the curious partygoers. 

If you have anything to ask about genetics, biology or general life, the Gensoc committee is here to help. Catch us at the Freshers Fair!

Your Genes and ‘Asian Flush’

You may have wondered why you or your Asian friends quickly begin to glow red after only sipping at a glass of wine. It is actually a symptom of alcohol intolerance, and the cause a genetic mutation causing a deficiency in the isoenzymes responsible for metabolising alcohol. 

Alcohol is metabolised in two steps:

  1.  alcohol (ethanol) ->  acetaldehyde
  2.  acetaldehyde -> acetic acid (vinegar)

The acetaldehyde dehydrogenase enzyme group (ALDH) is responsible for step 2. The flush is caused specifically by a deficiency in the ALDH2 isoenzyme. Genetic polymorphism occurs at the locus for ALDH2, meaning the alleles can take different forms. The mutated ALDH2 variant exhibits little to no catalytic activity, so the acetaldehyde (toxic) is not converted quickly enough into vinegar (non-toxic) and it builds up in the blood and tissues. This causes cell damage and the nausea of alcohol intolerance. The release of histamines caused by the build-up results in the rosy cheeks.

The common name ‘Asian Flush’ stems from the disproportionate amount of Asian people who inherit the recessive ALDH2 mutation. 47-85% of Oriental Asians get the glow, compared to 3-29% of Caucasians. Its prominence in Asia has been linked to the emergence of cultivated rice in Ancient China up to 10,000 years ago. This may be because farmers quickly realised the rice could be fermented to make alcohol and the body noped out – a mutation emerged as a protective measure against the toxic liquid. It’s interesting that the environmental factors of diet and lifestyle change can impact a * seemingly * random part of the genome.

Well, what about your genes and alcohol metabolism (AKA how drunk, how fast)? 

This is determined by the rate of the first step that converts alcohol into the toxic acetaldehyde. Unsurprisingly, it does depend mostly on genetics (49%), so if your parents are lightweights, maybe take it easy. 12% rests on prior drinking experience – the more you drink the more ‘tolerant’ your body gets. Less than 10% of the factors contributing to alcohol metabolism is based on your age, weight, body fat content and lung volume. 

So, the beaming red face is dependent on a single mutated gene for one enzyme. It’s almost purely contained within Asia as cultivated rice became a staple food source. This mutation has little relation to alcohol ‘tolerance’, although this also depends mostly on your genetics. Maybe get drinking to optimise that 12%. Or don’t – it’s cheaper to be a lightweight. Enjoy your freshers and re-freshers!

Find some further reading here!

Here’s an article that tackles the question of what the link is between cultivated rice alcohol metabolism

Racial Differences in Alcohol Sensitivity

Polymorphism of ethanol-metabolism genes and alcoholism: correlation of allelic variations with the pharmacokinetic and pharmacodynamic consequences

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