Nearly half of cancer cases in adults are caused by preventable risk factors, including alcohol

We've likely heard it before: Eating well, quitting smoking, and exercising more will help decrease your risk of cancer. But a new study is emphasizing a less-understood risk factor: alcohol.

New research from the American Cancer Society on Thursday estimates nearly half of adult cancer deaths in the U.S. could be prevented by making lifestyle changes, and doctors are painting a clearer picture of how much drinking contributes to cancer and death.

"We have no safe limit for a safe level of alcohol consumption," said Dr. Farhad Islami, the senior scientific director at the American Cancer Society who co-authored the report. "Ninety-seven thousand cancer cases every year can be attributed to alcohol consumption. That's a big number."

Researchers studied 2019 data on 30 types of cancer in Americans over 30 that were linked to lifestyle habits and other risks. They found preventable risk factors caused 40% of all cancer cases, and 44% of all cancer deaths.

Smoking was the leading risk factor, contributing to nearly 1 in 5 cancer cases and nearly one-third of all cancer deaths studied, followed by 7% of cases stemming from excess body weight. Drinking alcohol accounted for more than 5% of cancer cases in men and women. Diet, infections, and sun exposure also increased cancer risk.

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The National Cancer Institute links alcohol to eight different types of cancers, even among light and moderate drinkers, including cancer of the mouth, throat, voice box, esophagus, breast, liver, stomach, and colorectum. The NCI says all alcoholic beverages can cause cancer due to their ethanol content and the toxic chemical our bodies create when they metabolize alcohol, known as acetaldehyde.

"The toxins which are harmful can go inside our body and it can cause inflammation in our body," says Islami. "It can damage DNA and by damaging DNA that can cause cancer."

He also points out that alcohol can damage our organs, prevent our bodies from repairing damaged DNA, and increase estrogen levels, which is why there is an increased risk of breast cancer in women who drink.

U.S. dietary guidelines recommend no more than two drinks a day for men and one for women.

"If people reduce their consumption to the levels recommended by dietary guidelines, about 80% of all cancer deaths attributable to alcohol can be prevented," Islami said, citing a study from the Centers for Disease Control and Prevention.

Still, the World Health Organization classifies alcohol as a Group 1 carcinogen, the same as smoking cigarettes, and says there is no safe level of alcohol consumption.

Islami says one way to bring down the number of alcohol-related cancers is by increasing awareness of alcohol's cancer risk, considering a 2022 study found more than half of adults were unaware alcohol is a carcinogen.

Cigarette smoking was the leading risk factor contributing to cancer cases and deaths overall, at 19.3% and 28.5% respectively.