How Alcohol Affects Your Risk of Lung Cancer

Many people have wondered if drinking alcohol increases the risk of lung cancer, as it's now thought that alcohol is associated with roughly 3.5 percent of cancers in the United States. Overall, studies have been mixed, but it's likely that risk varies depending on sex, smoking status, and more. Among never smokers, a large study showed a protective effect of light to moderate alcohol intake, though not all studies agree. For those who have been diagnosed with lung cancer, heavy drinking may increase the risk of complications as well as mortality.

Alcohol is now classified been classified as a carcinogen (cancer-causing agent) by the U.S. Department Of Health and Human Services, and is classified as a Group 1 carcinogen by the International Agency for Research on Cancer.

Unlike some carcinogens such as tobacco smoke, however, alcohol is thought to work primarily as a "promoter" of cancer growth in a cancer that is already present, rather than as an "initiator" of cancer (a toxin that causes the original DNA damage (mutations) that eventually gives rise to a cancer).

Before discussing the research on alcohol and lung cancer, it's helpful to define a "serving"of alcohol since terminology can vary.

A "serving" of alcohol is defined as 14 grams of alcohol. This translates to:

• 12 ounces of beer
• 8 ounces malt liquor
• 5 ounces of wine
• 1.5 ounces of 80-proof (40 percent) alcohol

Alcohol intake may also be separated into:

• No alcohol
• Light intake
• Moderate intake
• Heavy intake
• Very heavy intake

Alcohol intake has now been established as a risk factor in a number of different cancers, though the amount of alcohol and risk varies considerably.

A 2018 study looked at the risk of cancer related to alcohol intake overall. If was found that alcohol consumption followed a "J" shaped curve when plotted against lifetime risk of cancer and death; light to moderate consumption (described as 1 to 3 drinks per week) was associated with a lower death rate than either abstaining completely, or drinking more than 2 drinks per day. As would be expected, heavy consumption increased the risk of death substantially.

While this was true for cancer overall, the results may not pertain to breast cancer, as the link between alcohol and breast cancer suggests that even one serving of alcohol can increase risk slightly.

Studying alcohol and lung cancer risk has been a challenge. Since alcohol intake is often connected with smoking. That said, studies in never smokers as well as controlled studies in people who have smoked are beginning to create a bigger picture.

A large 2017 study looked specifically at the risk of lung cancer related to alcohol consumption in over 2500 never smokers with lung cancer and over 9000 never smokers without lung cancer. For those who equate lung cancer with smoking, lung cancer in never smokers is not uncommon, and is actually increasing in the United States.

In the study, alcohol consumption was inversely associated with lung cancer, meaning that people who drank more alcohol had a lower risk and vise versa. The inverse relationship was seen for wine and liquor, but not for beer. People who drank lightly or moderately had a 20% lower risk of developing lung cancer than those who drank less than 20 grams of alcohol per day. (Of note is that this study did not take into account the dangers of heavy alcohol intake.)

The association was seen for lung cancer overall, lung adenocarcinoma, and squamous cell carcinoma of the lungs, but not for small cell lung cancer.

As with many issues, not all studies agree. A 2018 European study looking at never smokers yielded different results. In this study, alcohol intake was associated with an increased risk of lung cancer in never smoking women, but no increase in men. In women, the highest risk was with wine consumption.

A separate issues involves the impact of alcohol intake in people who are already living with lung cancer.

A 2018 study found that veterans who had an "unhealthy intake of alcohol (describes as two or more drinks per day) had an increased risk of postoperative complications following lung cancer surgery.

An association between alcohol intake and lung cancer risk begs the question "why." What is the mechanism behind a connection? It appears there may be more than one pathway.

With breast cancer, it's thought that alcohol may increase estrogen. In addition alcohol intake produces acetaldehyde that accumulates in breast tissue.

With liver cancer, alcohol can directly cause inflammation to the tissues. It can also lead to cirrhosis, which in turn raises liver cancer risk.

With lung cancer and some others, it may be related to oxidative stress induced by consumption. Alcohol consumption may also alter DNA methylation in cells. DNA methylation does not affect the structure of DNA (DNA mutations underlie the development of cancer), but can affect how genes are "expressed" or read.

There may also be reasons why alcohol intake (at least mild or moderate) would be associated with a reduced risk of lung cancer. A number of studies have found that flavonoids, such as those found in apples, are associated with a lower risk of lung cancer. Wine is also a source of flavonoids as well as other phytochemicals.

There is also some research that has found wine drinkers have a healthier diet, and there's some evidence that diet can lower lung cancer risk.

In general, light to moderate drinking of wine or liquor does not appear to increase, and may actually be associated with a lower risk of lung cancer. That said, alcohol takes it's toll. Alcohol intake has been associated with other cancers and diseases, not to speak of the damage to relationships, interference with jobs, and more. The association of light alcohol intake (at least in never smokers) with a lower lung cancer risk (but not in all studies) should not be read as an an "all clear," but only as a potential green light for those who already enjoy a glass of wine in moderation, are able to drink responsibly, understand the association of even light drinking with breast cancer, and are worried about their risk of lung cancer.