From the moment you take a sip, drinking starts to influence your biology. Here’s an inside look.
By Dana G. Smith, Illustrations by Montse Galbany – in the NYT
Dry January has come and gone, but Americans’ relationship with drinking is undergoing a more lasting change. According to one recent poll, just 54 percent of U.S. adults said they consume alcohol, the smallest percentage in nearly 90 years of data collection. That may be because more people are taking alcohol’s negative health consequences seriously.
Drinking alcohol can have profound effects on the brain and body. In the moment, some of those effects can be pleasurable. But in the long term, especially when it’s consumed in large quantities, alcohol can cause serious health harms.
Here’s an inside look at what alcohol does to the body, both while you’re drinking and over time.
In the Brain
Alcohol has a rapid effect in the brain, causing people to feel more relaxed and sociable. That buzzed feeling stems from alcohol’s interactions with several important neurochemicals.
Drinking temporarily increases levels of the neurotransmitter dopamine, which is partly why people feel good when they have a few drinks. It’s also a primary reason why alcohol can be addictive for some.
Alcohol also changes the activity of two neurotransmitters, called glutamate and GABA, that act like the gas and the brakes in the brain. By increasing the effects of GABA (the brakes) and decreasing the effects of glutamate (the gas), alcohol suppresses brain activity.
When brain activity, especially in the frontal cortex, is inhibited, your actions become disinhibited. That’s why you don’t have as much self-control when you drink and may say or do things you wouldn’t otherwise (like that karaoke solo).
It also causes you to have less control over your motor skills, which is why it’s so dangerous to drink and drive. If a person consumes very high levels of alcohol, brain activity can be suppressed to the point of unconsciousness.
Over the long term, alcohol use is associated with changes in brain structure. Some studies have found that middle-aged and older adults who average even one drink a day tend to have slightly less brain volume than people who don’t drink. And the more alcohol someone consumes, the more the brain shrinks. Experts don’t know exactly why that is, but one theory is that alcohol alters the brain’s immune system, ramping up inflammation, which can damage neurons.
In the Mouth and Neck
The tissues that are most at risk from drinking tend to be the ones that come into direct contact with alcohol, including in the mouth and neck.
Alcohol is primarily metabolized in the liver, but the process also occurs in the digestive tract. As soon as alcohol passes through the mouth, it starts to be broken down.
Microbes in the mouth begin to convert alcohol into a compound called acetaldehyde, which then hangs around in the saliva.
Acetaldehyde is nasty stuff. It causes oxidative stress in the cells, which can result in inflammation and tissue damage.
It’s also a carcinogen that can modify DNA, potentially leading to cancer-causing mutations.
Drinking alcohol increases the risk of four types of cancer in the mouth and upper digestive tract: oral, pharyngeal (throat), laryngeal (voice box) and esophageal. The mouth, throat and esophagus are particularly vulnerable since those tissues have some of the greatest exposure to acetaldehyde. According to one analysis, the risk of mouth and throat cancers increases by 13 percent and the risk of esophageal cancer by 26 percent with just one drink per day. For people who have five or more drinks a day, the risk of all three cancers is roughly four times higher.
In the Heart and Chest
A few decades ago, scientists thought alcohol might benefit heart health. But that perspective has changed among some experts in recent years as more research has come to light.Alcohol affects the cardiovascular system in a number of ways, some better understood than others.
While you’re drinking, alcohol causes blood vessels to dilate, bringing blood to the surface of the skin. That’s why people can look flushed and feel warm when they have a cocktail. Dilation is also thought to be one reason heart rate slightly increases and blood pressure slightly decreases, both temporarily, as you imbibe.
Regular alcohol use is associated with higher blood pressure and an increased risk of hypertension. One reason for this could be alcohol’s damaging effect on the cells that line the blood vessels.
Alcohol can also disrupt the heart’s electrical system. Research shows that heavy drinking can cause atrial fibrillation, and some studies suggest that the risk goes up slightly starting at one drink per day. People with atrial fibrillation are more likely to have an arrhythmia event on days that they drink.
For women, regularly having one drink a day increases the odds of developing breast cancer by 10 percent, and two drinks a day raises them by 19 percent. Experts think this may partly be because alcohol increases estrogen levels in the body.
How we choose health experts to talk to. Times reporters often spend weeks interviewing doctors, researchers and other health professionals to help report an article. We seek leaders in their fields, watch out for conflicts of interest and try to get a variety of viewpoints.
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Alcohol’s relationship to heart attack and stroke is more complicated. Heavy drinking (three or more drinks per day) is associated with a higher risk of both. But when it comes to light to moderate drinking (two drinks a day or less), the research is mixed. A few studies suggest a small increased risk of heart attack and stroke starting at one drink a day, but several others report that people who drink in moderation actually have a reduced risk, compared with people who don’t drink at all.
In the Gut
Like the mouth and throat, the stomach and intestines come into direct contact with alcohol and acetaldehyde, making them particularly susceptible to damage.
Alcohol’s effects on the gut range from unpleasant to potentially deadly. When you drink, the valve that separates the stomach from the esophagus relaxes, sometimes resulting in acid reflux.
Alcohol can also cause inflammation in the lining of the stomach, which is why you might have gastrointestinal distress after a night of heavy drinking. Long term, heavy alcohol use can damage the intestinal lining, leading to gastrointestinal bleeding and “leaky gut syndrome,” where food and microbes escape the intestines and enter the bloodstream.
Tissues in the gastrointestinal tract are also prone to alcohol-related cancer. One recent study found that people who consistently averaged two or more drinks per day had a 25 percent increased risk of developing colorectal cancer compared with people who averaged less than one weekly drink.
In the Liver
The liver may be the organ most vulnerable to damage from drinking, and alcohol-related liver disease is the leading cause of death from excessive drinking. After alcohol is digested in the stomach and intestines, it enters the bloodstream and heads to the liver — the primary place alcohol is metabolized in the body.
Enzymes in the liver convert alcohol into acetaldehyde, which wreaks havoc on cells until other enzymes break it down into a more benign compound called acetate. Other organs turn acetate into water and carbon dioxide to be expelled from the body.
In response to the damage caused by acetaldehyde, fat deposits start to build up in the liver, resulting in fatty liver disease, or steatosis.
Those fat deposits can cause an inflammatory response, leading to the second stage of liver disease, steatohepatitis.
If the inflammation goes on for too long, scar tissue, called fibrosis, can develop, which could lead to liver cirrhosis and potentially liver failure.
According to one estimate, 90 percent of people who consume more than four drinks per day have fat deposits on their liver, and 30 percent of people who regularly have three or more drinks a day will develop cirrhosis. The fat deposits, inflammation and early fibrosis can be reversed but advanced liver cirrhosis is permanent.
Like in other parts of the body, heavy drinking also increases the risk of cancer in the liver, because of the DNA damage caused by acetaldehyde.
The facts are sobering, but take note: Experts say that the odds of experiencing health harms from drinking are relatively low if you average one drink a day or less.
The risks go up at eight to 14 weekly drinks, but whether those heightened risks result in an illness often depends on people’s genetics and pre-existing conditions. And if you currently drink heavily, research shows that some of the damage can be reversed if you stop or cut back.
Sources
Dr. Krishna Aragam, the director of cardiovascular genomics at the Cleveland Clinic; Veronika Fedirko, a professor of epidemiology at the University of Texas MD Anderson Cancer Center; Thomas Kash, a professor of pharmacology at the University of North Carolina at Chapel Hill; Dr. Frances Lee, an assistant professor in the division of liver diseases at the Icahn School of Medicine at Mount Sinai; Dr. Gregory Marcus, a professor of cardiology at the University of California, San Francisco; Dr. Robert Messing, a professor of neurology at the University of Texas at Austin; Anya Topiwala, a senior clinical researcher in psychiatry at the University of Oxford; and Vasilis Vasiliou, a professor of environmental health sciences at Yale University.