By Susan M. Gapstur, PhD, MPH
Do you enjoy an occasional, or even a daily, glass of wine, beer, or other drink that contains alcohol? Many adults do. Indeed, 37% of adults in the U.S. report drinking low to moderate amounts, which is, on average, up to 1 drink per day if you are a woman, and 2 drinks per day if you are a man. Another 28% of adults drink more each day, which is considered heavy drinking. A drink of alcohol is generally defined as 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of 80-proof distilled spirits.
Modest Benefit but Many Risks Associated with Alcohol Drinking
While low to moderate alcohol consumption is linked to a reduced risk of heart disease, drinking too much alcohol can increase risk of high blood pressure, heart failure, sudden death and stroke. Overall, alcohol consumption is one of the top 10 contributors to sickness and death from injuries, motor vehicle crashes, homicides and suicides, sexual assaults, sexually transmitted infections from unsafe sex, falls, birth defects, depression, disorders of the gastrointestinal tract, and sleep disorders.
Additionally, there is a lot of evidence that drinking alcohol increases the risk of several cancers. In 2007, a working group of experts convened by the World Health Organization's International Agency for Research on Cancer (IARC) reviewed the scientific evidence on alcohol and cancer risk for 27 different anatomic sites. They found sufficient evidence that alcohol drinking is a cause of cancers of the mouth, pharynx, larynx, esophagus, liver, colon, rectum, and female breast. And for cancers of the mouth, larynx, and esophagus, when people drink and use tobacco, the risks are combined to be greater than either tobacco use or alcohol use alone!
Importantly, it is also now well recognized that drinking even low amounts of alcohol can increase the risk of breast cancer, the most commonly diagnosed cancer among women in the U.S. and worldwide. Compared to non-drinkers, there is a 10% to 12% higher risk of female breast cancer associated with each drink per day.
The IARC working group also noted that the scientific evidence is limited for several other cancer sites and more research is needed. One cancer for which there has been considerable interest is pancreatic cancer, the fourth most common cause of cancer death among men and women in the U.S. While heavy alcohol consumption causes acute and chronic pancreatitis, it has never been linked definitively to pancreatic cancer. The lack of convincing evidence is in part due to the fact that many individual studies have been too small to tease apart the effects of alcohol from the risk due to cigarette smoking, a well-established risk factor for pancreatic cancer.
To help address this issue, epidemiologists at the American Cancer Society used data collected from the Cancer Prevention Study II (CPS-II), a large cohort of more than 1.2 million U.S. men and women who were followed for cancer death from 1982 through 2008. During that follow-up time, nearly 7,000 study participants died of pancreatic cancer. The large size of the cohort allowed investigators to examine the risk of pancreatic cancer for heavy drinkers and break out whether or not they were smokers.
In those who never smoked, there was a 36% higher risk of pancreatic cancer death among men and women who drank 3 or more alcoholic drinks a day, compared to never drinkers. However, among in those who ever smoked, there was a 16% higher risk associated with drinking 3 or more drinks per day. (The reason that the association between drinking alcohol and pancreatic cancer risk is not as strong in those who ever smoked is because they already have higher rates of pancreatic cancer, so the difference between drinkers and non-drinkers in this category is not as strong.) Regardless, these findings strongly suggest that heavy alcohol drinking is a risk factor for pancreatic cancer.
How does alcohol cause cancer?
We don't completely understand how alcohol causes cancer. Particularly for cancers of the head, neck, and esophagus, and perhaps other cancers such as liver cancer, one reason involves acetaldehyde, a toxic chemical that the body makes when it breaks down alcohol. Acetaldehyde can directly affect normal cells by damaging DNA, which can lead to cancer. For other cancers such as colorectal (colon and/or rectal) cancer, alcohol might adversely affect the metabolism of different nutrients that might play a role in reducing cancer risk. For breast cancer, drinking alcohol can increase circulating estrogens or other hormones in the blood, and hormones play a key role in the development of many breast cancers.
Are the effects of wine, beer, and liquor different?
Most people want to know if drinking wine is better than drinking beer or hard liquor. The research shows that it does not matter what type of alcohol you drink, and that the risk of these cancers is elevated for all alcoholic beverage types.
How to reduce your risk from alcohol
Based on the information and research available to date, a recent study noted that approximately 3% (19,500) of all cancer deaths in U.S. each year can be blamed on alcohol consumption, and about 1/3 of alcohol-related deaths are among those who drink up to about 1.5 drinks per day.
Some people could reduce their risk of cancer by having less alcohol. According to the American Cancer Society's guidelines for cancer prevention, people who drink alcohol should have no more than 2 drinks per day for men and 1 drink a day for women. The recommended limit is lower for women because of their generally smaller body size and slower metabolism of alcohol. (This is the average per day and doesn't justify drinking more drinks on fewer days of the week).
People who are at particularly high risk for cancer should talk to their doctor about not drinking alcohol or limiting the amount they drink to help reduce their risk.
For more information about alcohol and cancer, visit this page.
Dr. Gapstur is vice president of epidemiology for the American Cancer Society.