Alcohol Genes: Alcohol Metabolism Rate

People have been imbibing beer and wine for millennia, enjoying alcohol ever since someone discovered the altered sensations from fermented fruits and grains. In fact, archeologists have discovered an Egyptian brewery dating to the time of the great pyramids.

This article examines how alcohol is metabolized and how your genes impact the rate at which it is broken down. Members will see their genotype report below, plus additional solutions in the Lifehacks section. Consider joining today 

Alcohol: Breaking it down and getting rid of it

What exactly does alcohol do in our bodies? And why do people react differently to alcohol? (yep – it’s genetic!)

First, alcohol is absorbed through the stomach into our bloodstream, making its way to our brain and liver.

In the liver, alcohol is first broken down with an enzyme called alcohol dehydrogenase, which helps to convert it into acetaldehyde.

In the second step of this elimination process, the enzyme acetaldehyde dehydrogenase helps convert the acetaldehyde into acetate. The acetate can then be easily excreted.

This is a simplified explanation, but it covers the majority of alcohol metabolism.[ref]

Genetics of alcohol metabolism:

The ADH genes code for alcohol dehydrogenase.

The ALDH gene family produces acetaldehyde dehydrogenase.

Two well-studied genetic variants have different ways of reaching the same endpoint:

~ an alcohol dehydrogenase (ADH1B) variant that speeds up the conversion to acetaldehyde, thus creating a buildup of acetaldehyde

~ an acetaldehyde dehydrogenase (ALDH2) variant that slows down the conversion from acetaldehyde to acetic acid, again creating a buildup of acetaldehyde.

In addition to the beer, wine, and other alcohol we might drink, the alcohol dehydrogenase enzyme also breaks down alcohols produced by bacterial fermentation in the intestines. (For example, some of your bug guts could be fermenting the apple you ate this morning, and the ADH genes are activated.)

Retinol (vitamin A) and bile acids are also metabolized by alcohol dehydrogenase.[ref]

Acetaldehyde: flushing, nausea, and carcinogenic (potentially cancer-causing)

So what is the big deal about too much acetaldehyde? Why does it make you feel cruddy and make you flush? Acetaldehyde increases skin temperature, making you feel hot and flushed. It also causes nausea, headache, and allergy-like histamine release. Top it off with being carcinogenic and damaging to your DNA. Moreover, it may also be causing catecholamine release in your brain, giving you feelings of euphoria. Your body wants to get rid of it as soon as possible since it is toxic, but the euphoria makes you want to drink again.[ref]

Alcohol Metabolism Genotype Report

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ADH1B – Alcohol dehydrogenase gene:

Encodes alcohol dehydrogenase, which converts alcohol to acetaldehyde. When this enzyme works more quickly, it results in higher amounts of acetaldehyde than the body can clear out.

Check your genetic data for rs1229984 (23andMe v4, v5):

  • TT: faster metabolism of alcohol to acetaldehyde[ref], causes a build-up of acetaldehyde, known as ADH1B*2 and more common in Asian populations, decreased alcohol consumption (on average)[ref]
  • CT: faster metabolism of alcohol to acetaldehyde, causing a build-up of acetaldehyde, known as ADH1B*2 and more common in Asian populations, decreased alcohol consumption
  • CC: typical, higher alcohol consumption compared to T allele[ref]

Members: Your genotype for rs1229984 is .

Studies of this genetic variant show:

  • increased risk of fatty liver disease with alcohol use[ref]
  • increased risk of restless leg syndrome[ref]
  • reduced risk of alcoholism (because people with the variant feel bad when they drink)[ref]
  • the variant is protective against gout[ref] (likely because people without the variant drink more alcohol, leading to gout…)

Check your genetic data for rs2066702 (23andMe v4 only; AncestryDNA):

  • G/G: typical
  • A/G: faster metabolism of alcohol to acetaldehyde, causing a build-up of acetaldehyde, known ad ADH1B*3 and more common in African populations [ref][ref]
  • A/A: faster metabolism of alcohol to acetaldehyde, causing a build-up of acetaldehyde, known ad ADH1B*3 and more common in African populations[ref]

Members: Your genotype for rs2066702 is .

ADH1C gene:

Check your genetic data for rs698 (AncestryDNA):

  • C/C: Increased risk of pancreatitis in alcoholics[ref]; slower conversion of alcohol to acetaldehyde[ref]
  • C/T: Increased risk of pancreatitis in alcoholics; slower conversion of alcohol to acetaldehyde
  • T/T: typical

Members: Your genotype for rs698 is .

ALDH2 – acetaldehyde gene:

Encodes the enzyme needed for the elimination of acetaldehyde through conversion to acetic acid

Check your genetic data for rs671 (23andMe v4, v5; AncestryDNA):

  • A/A: Alcohol flush reaction[ref], a much higher risk of lung cancer from smoking, decreased alcohol consumption (on average)[ref]
  • A/G: Alcohol flush reaction, decreased alcohol consumption (on average)
  • G/G: typical acetaldehyde metabolism

Members: Your genotype for rs671 is .

Studies on ALDH2 show:

  • Smokers with A/G and A/A have a much higher risk of lung cancer than those with G/G.[ref] While smoking isn’t healthy for anyone, people with the A/A genotype really, really shouldn’t smoke.
  • People with the A/G and A/A variants (alcohol flush reaction) are much less likely to be alcoholics, probably because they feel so bad when they drink.
  • Candida overgrowth also produces acetaldehyde in amounts close to those considered carcinogenic.[ref] If you carry the ALDH2 variant and slowly clear out acetaldehyde, you may be more negatively affected by Candida.

Lifehacks for Drinking Alcohol:

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Originally published June, 2018. Revised Feb. 2020

About the Author:
Debbie Moon is the founder of Genetic Lifehacks. Fascinated by the connections between genes, diet, and health, her goal is to help you understand how to apply genetics to your diet and lifestyle decisions. Debbie has a BS in engineering and also an MSc in biological sciences from Clemson University. Debbie combines an engineering mindset with a biological systems approach to help you understand how genetic differences impact your optimal health.

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