Why, exactly, is alcohol so bad for you?

The tide has largely turned against alcohol. Drinking, at least in moderation, was once seen as a harmless—or even healthy—indulgence that could strengthen your heart and even lengthen your

lifespan. But in many scientific circles, consuming virtually any amount of alcohol is now seen as toxic. On Jan. 3, outgoing Surgeon General Vivek Murthy released an advisory warning that

alcohol consumption raises the risk of at least seven types of cancer. Shortly afterward, a second federal report warned that people who consume more than nine drinks per week have a one in

100 chance of dying from their habit, due to alcohol’s links to a range of health problems. Increasingly, reports like these conclude there is no safe level of drinking. Even moderate

consumption—no more than one alcoholic beverage per day for women, and no more than two per day for men—comes with dangers, and the situation snowballs the more a person sips. But alcohol is

an ancient and natural beverage, made by fermenting grains, fruits, or vegetables—all of which are part of a balanced diet in their original forms. So what’s so bad about booze, exactly? 

IT CREATES A TOXIC BYPRODUCT After you drink any kind of booze—vodka, wine, sake, you name it—enzymes in your body get to work metabolizing the alcohol (chemically known as ethanol) in your

system. Most of this process happens in the liver. Ethanol breaks down into a byproduct called acetaldehyde, and that’s where the trouble begins, says Dr. Eden Bernstein, an assistant

professor and internal-medicine physician at the University of Colorado School of Medicine. “If I were to point to one thing that alcohol does that’s harmful to the body,” Bernstein says,

“it would relate to the production of acetaldehyde.” Acetaldehyde is “very toxic to a lot of different tissues,” says Dr. Sarah Wakeman, senior medical director for substance-use disorder at

Mass General Brigham. It can damage body parts that are directly involved in alcohol metabolism, such as the liver, pancreas, and brain, as well as DNA itself. Exposure to acetaldehyde can

result in DNA damage and mutations that lead to cancer, Bernstein explains. Plenty of factors influence how damaging acetaldehyde is to the body, Wakeman says. The most obvious is the amount

of alcohol consumed; a heavy drinker will be exposed to more acetaldehyde than a light drinker, leading to more damage. But even two people who drink the same amount may be affected

differently, depending on their genes and other risk factors.  After ethanol becomes acetaldehyde, it continues breaking down into non-toxic byproducts. But some people’s enzymes work more

slowly than others, which leaves them exposed to acetaldehyde and its toxic effects longer, Wakeman says. Damage can also compound if someone has multiple risky habits, like drinking heavily

and smoking cigarettes, she adds. ALCOHOL CREATES INFLAMMATION Drinking alcohol also leads to inflammation in the body. This, too, happens when booze is metabolized. The process creates

what’s known as oxidative stress, or an imbalance between different types of molecules that results in inflammation. Alcohol also disrupts the colonies of microbes that live in your mouth,

intestines, and gut, Bernstein explains, which can lead to overgrowth of “bad” bacteria. Booze can also damage intestinal cells, allowing pathogens that are normally confined to the GI tract

to travel throughout the bloodstream. These effects can result in inflammation-causing immune responses. READ MORE: _9 Things You Should Do for Your Brain Health Every Day, According to

Neurologists_ “Inflammation can really be an enemy,” Wakeman says. “It can lead to tissue changes over time that can increase the risk for cancer” and other health problems, such as liver

scarring known as cirrhosis. Among very heavy drinkers, alcohol metabolism and the resulting inflammation may even contribute to serious brain damage, possibly including shrinkage of the

brain or alcohol-induced dementia, Wakeman says. DRINKING MAY AFFECT HORMONES Drinking-related cancers are typically seen in parts of the body that alcohol directly touches: the mouth,

throat, stomach, and so on. But there’s also a “unique relationship around breast cancer risk and alcohol use,” Wakeman says. READ MORE: _Some Early Forms of Breast Cancer May Not Need

Treatment_ Drinking alcohol seems to change the way the body metabolizes estrogen, leading to higher levels of the hormone. This may translate to an increased risk of estrogen-related breast

cancers. Researchers are still learning about exactly how alcohol affects hormones, according to the recent Surgeon General report. ALCOHOL AND INJURY In addition to the complex domino

effect that alcohol sets off inside the body, intoxication has “direct effects on health through people falling and crashing cars and getting in all kinds of other accidents,” says William

Kerr, scientific director of the Alcohol Research Group at the Public Health Institute in California. More than 30% of alcohol-related deaths recorded in the U.S. from 2020 to 2021 were due

to acute issues including accidents and injuries. WHAT ABOUT THOSE HEART BENEFITS? For a long time, researchers thought moderate drinking—that nightly glass of red wine—improved heart

health, and some studies continue to suggest that. In contrast to other recent reports on alcohol, a December 2024 report by the National Academies of Sciences, Engineering, and Medicine

concluded with “moderate certainty” that moderate drinking is associated with a lower risk of dying from any cause, including cardiovascular disease, compared to never drinking. (It also

found, however, that moderate drinking likely raises the risk of some cancers.) But many researchers now believe that design flaws in older studies falsely inflated the cardiovascular

benefits of drinking. In some studies that correct for those flaws, booze’s apparent health benefits disappear. “Contrary to popular opinion, alcohol is not good for the heart,” the World

Heart Foundation wrote in a 2022 policy brief. Drinking in excess is, in fact, linked to high blood pressure, abnormal heart rhythms, and sometimes even heart failure, according to American

Heart Association researchers. READ MORE: _How Stress Affects Your Heart Health_ Scientists are still learning about the true relationship between drinking and heart health, Wakeman says.

But given all of the other known risks, it’s safe to say that “drinking is not a health-promoting activity,” Wakeman says. “No one should fool themselves into thinking that they are starting

to drink for their health.” Does that mean everyone should quit drinking immediately? Not necessarily. Like other potential health hazards—such as spending time in the sun or eating

not-so-nutritious foods—moderate or light drinking can fit into an otherwise healthy lifestyle, Wakeman says. “It’s not this binary, all or nothing” issue, she says. Ultimately, people must

make their own decisions based on their personal risk factors and tolerances, ideally with the help of a trusted health professional.