The guide

How alcohol causes cancer, from the first sip to broken DNA

By GyroscopeUpdated November 15, 20267 sources

Alcohol causes cancer through a chemical your own body makes from it. The liver turns alcohol into acetaldehyde, which breaks DNA, and broken DNA that gets repaired wrong is how cancers start. That’s why the National Cancer Institute lists seven cancers alcohol causes or raises, and why there’s no amount below which the risk is zero.

Most people know smoking causes cancer. Far fewer know alcohol does. It sounds like an exaggeration, because nobody you know got throat cancer from wine with dinner. But cancer risk works like a lottery with more tickets. Every drink adds a few, and you only find out years later which ones were drawn.

The chain, step by step

1. Alcohol to acetaldehyde. An enzyme called alcohol dehydrogenase, mostly in the liver, turns alcohol into acetaldehyde. NCI calls it “a toxic chemical and a probable human carcinogen.”
2. Acetaldehyde damages DNA. It sticks to DNA and proteins. In mice, researchers at Cambridge showed in 2018 that it snaps both strands of DNA in the stem cells that make blood, and that the repairs leave deletions and scrambled chromosomes behind.
3. A second enzyme cleans up. ALDH2 turns acetaldehyde into acetate, which is harmless. The faster this step, the less time acetaldehyde has to do damage.
4. More damage on the side. Breaking down alcohol makes reactive oxygen molecules that damage DNA, proteins and fats. Alcohol also gets in the way of folate, which cells need to copy DNA correctly.
5. Hormones. Alcohol raises estrogen in the blood, and high estrogen drives many breast cancers.
6. A solvent for other poisons. Alcohol helps the lining of the mouth and throat absorb harmful chemicals, like the ones in cigarette smoke. That’s why drinking and smoking together are much worse than either alone.

The seven cancers

The International Agency for Research on Cancer found “sufficient evidence” that alcohol causes cancers of the mouth, throat (pharynx), voice box (larynx), esophagus and liver. It also raises the risk of breast and colon cancer. NCI adds that there’s some evidence for melanoma and cancers of the pancreas, prostate and stomach.

The tissues alcohol touches first are the ones hit hardest. Your mouth, throat and esophagus get it straight from the glass. Your liver gets the most acetaldehyde. Your breast tissue gets the extra estrogen.

How much is too much for cancer?

There’s no line where the risk starts. NIAAA says even one drink a day can raise a woman’s risk of breast cancer by 5% to 15%. A pooled analysis of 53 studies found each 10 g a day, about two thirds of a US drink, raised breast cancer risk by about 7%. In the US Surgeon General’s 2025 figures, as given by NCI, about 17 of 100 women who drink less than once a week get an alcohol-related cancer in their lifetime. At a drink a day it’s 19, and at two it’s 22.

It isn’t only heavy drinkers. The World Health Organization’s office for Europe found that about half of the region’s alcohol-caused cancers happen in people whose drinking doesn’t count as heavy. In the US, NCI puts alcohol behind about 5% of all cancer cases in 2019, nearly 100,000, and about 25,000 cancer deaths.

The red face is a warning

About 36% of East Asians (Japanese, Chinese and Koreans) flush red when they drink, mostly because of a variant in the ALDH2 gene that slows step 3. Acetaldehyde builds up, and the face goes red. People with one copy who drink anyway have a much higher risk of esophageal cancer. In case-control studies the odds were 3.7 to 18 times higher than for people who cleared it normally, even at the same amount of alcohol. NCI says the extra risk doesn’t show up in carriers who don’t drink. Why do I get red when I drink? has more, and a 23andMe or Ancestry file can show whether you carry it.

Does quitting lower the risk?

Yes. NCI says stopping is linked to lower risks of mouth and esophageal cancers, and possibly throat, breast and colon cancers. It can take years for the risk to fall back toward a never-drinker’s, but NCI says it’s “never too late to stop drinking and reduce the risks.” Ways to stop or cut back has the practical side, and cancer, with and without and breast cancer, with and without have the numbers.