What is acetaldehyde? Why might it be important? Have you ever woken up after an evening of too much wine and felt like something the cat dragged in? Outside of your complicity in overindulgence, you might blame the effect on a molecule called acetaldehyde, a breakdown product of ethanol. Acetaldehyde is potent. It’s affect on muscle tissue is considered to be 30 times more toxic than ethanol. (Melton 2007)

Alcohol, tobacco smoke, foods, and/or exhaust fumes contribute to the formation of acetaldehyde. Bacteria in your mouth and GI tract break down ethanol and produce this molecule in large amounts when it has a large amount of raw material.

Ethanol is broken down into acetaldehyde by alcohol dehydrogenase. Aldehyde dehyrogenases, especially ALDH2 in the liver, converts acetaldehyde to acetic acid, the latter is used by muscles as fuel. The liver can convert almost all of the acetaldehyde up to about 7 – 10 grams of ethanol per hour. If more than 7 – 10 grams of acetaldehyde are produced, the remainder is in the body until it can be converted. That is where the problem may be.

The lingering acetaldehyde can attach itself to the amino groups of proteins and form adducts. The damage to these proteins are irreversible. Skeletal muscle tissues are particularly vulnerable. The damage to muscles is five times more common than cirrhosis of the liver. The immune system is also activated and causes inflammatory responses. Acetaldehyde has also been found to disrupt the structure and function of DNA. About half of Asians, in particular, Japanese, Chinese, Koreans, and Taiwanese, have faulty ALDH2 genes and have difficulty processing acetaldehyde. Those most vulnerable have rapid facial flushing, elevated heart rates, and dilated blood vessels. It can quickly lead to dizziness, headache, nausea, and vomiting.

Researchers are now implicating acetaldehyde as a contributing element in cancer, liver disease, and Alzheimer’s disease. Those who flush easily due to altered ALDH2 genes and are heavy drinkers have a higher incidence of upper GI tract and liver cancer and a higher rate of head and neck cancer. It may be a factor in some breast cancers as well.

Those with faulty ALDH2 genes should consider their risks when drinking excessive amounts of alchohol. The burning of tobacco creates acetaldehyde that is dissolved by saliva. Alcohol and smoking combined may increase the risk significantly. Poor oral hygiene may increase acetaldehyde production due to a increase in bacteria, such as, Streptococcus salivarius and Neisseria. Fermented foods have high levels of acetaldehydes. Coffee and ripe fruits are also high in this molecule. What else can one do. Some researchers think that probiotics may help. Ingesting Lactobacillus and Bifidobacterium inhibit acetaldehyde production.


Melton L. What’s Your Poison? New Scientist 10 February 2007; 193(2590):30-33.