Alcohol dehydrogenase (ADH) is an important enzyme responsible for the first stage of alcohol breakdown in the body. It makes the metabolism of ethanol possible – a process in which consumed alcohol is converted into less toxic compounds. How ADH works, as well as subsequent enzymes such as aldehyde dehydrogenase (ALDH2), determines how quickly the body handles alcohol and what effects its presence in the blood causes.
What is alcohol dehydrogenase (ADH)?
The enzyme alcohol dehydrogenase (ADH) is found mainly in the liver, but can also be found in the kidneys, stomach lining, and brain. It is present in organisms of many species, but in humans it occurs in several variants that differ in activity and distribution in tissues. The main task of ADH is the detoxification of ethyl alcohol, which enters the body through the digestive tract. This enzyme converts ethanol into a more harmful but short-lived compound – acetaldehyde. It is then metabolized by other enzymes, including aldehyde dehydrogenase (ALDH2), so that it can leave the body in a safe form.Metabolism of ethyl alcohol – how does ADH work?
Alcohol dehydrogenase plays a central role in ethanol metabolism because it initiates the detoxification process. Without ADH activity, the body would not be able to effectively break down alcohol, which would lead to its accumulation in the blood and prolonged toxic effects. The efficiency of ADH determines how quickly alcohol is eliminated from the body, how intense the intoxication symptoms will be, and whether side effects such as headache or nausea will occur. After consumption and absorption from the digestive tract into the bloodstream, ethanol reaches the liver, where ADH converts it into acetaldehyde – a compound significantly more toxic than ethanol itself. It is responsible for all the unpleasant ailments and complications associated with alcohol consumption. The acetaldehyde formed at this stage is quickly metabolized further by aldehyde dehydrogenase (ALDH2).What affects ADH activity?
The activity of alcohol dehydrogenase is not the same in all people – it is influenced by many factors:- Genetics: There are different variants of genes encoding ADH that can significantly change the rate of ethanol metabolism. Some people can convert alcohol faster (which may increase the toxicity of acetaldehyde) or slower (which leads to slower alcohol elimination from the body).
- Sex: Women typically have lower ADH activity in the stomach lining, which means more alcohol enters the blood in unchanged form. This is one of the reasons why women feel the effects of alcohol faster than men at the same dose.
- Diet and nutritional status: Deficiency of certain nutrients can affect enzyme function, including ADH. Additionally, consuming alcohol on an empty stomach increases its absorption and burdens the mechanisms responsible for metabolism.
Aldehyde dehydrogenase (ALDH2) – the next stage of alcohol metabolism
After alcohol dehydrogenase converts ethanol into acetaldehyde, another enzyme comes into action – aldehyde dehydrogenase (ALDH2). It is responsible for the detoxification of acetaldehyde, converting it into acetic acid, which can then be broken down into carbon dioxide and water. Thanks to this reaction, the harmful and highly reactive aldehyde does not remain in the body for long, which limits its toxic effects. Disruptions in ALDH2 function are the main cause of alcohol intolerance. People with an inactive form of the enzyme (e.g., ALDH2*2 variant) are unable to effectively break down acetaldehyde, resulting in an immediate, unpleasant body reaction to alcohol. Although such a reaction may discourage consumption and thus protect against addiction, it is also associated with an increased risk of toxic organ damage with frequent alcohol consumption.Consequences of ALDH2 deficiency – aldehyde poisoning and adverse reactions
Deficiency or reduced activity of ALDH2 (particularly common in people of East Asian descent) leads to acetaldehyde accumulation in the body. Even a small amount of consumed alcohol can then cause severe side effects: facial flushing, headache, nausea, rapid heartbeat, and shortness of breath. Chronic exposure to elevated acetaldehyde concentrations also increases the risk of liver damage, inflammation of the stomach lining, and tumor development, especially in the esophageal area.Dehydrogenases and the risk of alcohol addiction
The activity of enzymes involved in ethyl alcohol metabolism (primarily alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH2)) has a direct impact on the risk of developing alcohol addiction. People whose ADH works very quickly and ALDH2 slowly or not at all are exposed to the accumulation of toxic acetaldehyde, which results in a strong body reaction even after a small dose of alcohol. Such intolerance often reduces the risk of addiction. On the other hand, people with the opposite profile – slower ADH activity and functioning ALDH2 – may not experience intense consequences of alcohol consumption, which promotes more frequent and riskier drinking. The absence of negative symptoms after alcohol can mask its toxic effects, increasing the risk of addiction and long-term health damage.Ethanol metabolism and liver and other organ damage
Impaired ethanol metabolism caused by disturbances in ADH and ALDH2 function increases the toxic burden on the body. Excessive acetaldehyde concentrations lead to inflammation, liver cell necrosis, and the gradual development of alcoholic fatty liver, alcoholic hepatitis, and eventually liver cirrhosis. Toxins produced during alcohol breakdown can also damage other organs, including the pancreas, heart, and brain. Additionally, chronic acetaldehyde exposure can have mutagenic and carcinogenic effects, especially in the esophageal and oral cavity areas.How does alcohol dehydrogenase affect alcohol metabolism?
Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH2) perform important functions in the detoxification process of ethyl alcohol. ADH begins the breakdown of ethanol, converting it into toxic acetaldehyde. Then ALDH2 neutralizes this compound, converting it into harmless acetic acid. The efficiency of both enzymes determines how the body handles alcohol: whether it quickly neutralizes it or toxic metabolites accumulate. Well-functioning dehydrogenases protect cells from damage, limit oxidative stress, and reduce the risk of chronic complications.:::cta Need help fighting addiction? Our specialists are ready to help. Call or schedule an online appointment. Call: 880 808 880 | Schedule appointment :::
