How does alcohol cause cancer?

Researchers have hypothesized multiple ways in which alcohol may increase the risk of cancer (23), including:

metabolizing (breaking down) ethanol in alcoholic drinks to acetaldehyde, which is a toxic chemical and a probable human carcinogen; acetaldehyde can damage both DNA and proteins
generating reactive oxygen species (chemically reactive molecules that contain oxygen), which can damage DNA, proteins, and lipids (fats) in the body through a process called oxidation
impairing the body's ability to break down and absorb a variety of nutrients that may be associated with decreased cancer risk, including vitamin A; nutrients in the vitamin B complex, such as folate; vitamin C; vitamin D; vitamin E; and carotenoids
making it easier for the mouth and throat to absorb harmful chemicals, such as those from cigarette smoke, that can lead to cancer
increasing blood levels of estrogen, which at high levels can cause breast cancer
negatively influencing one-carbon metabolism and folate absorption, leading to DNA damage (24)