Four surprising and evidence-based health benefits of drinking coffee

By Anahad O’Connor

Most people drink coffee for a bit of buzz and a boost in their energy levels.

But coffee has wide-ranging effects on your health. Coffee is, arguably, the world’s most scientifically scrutinized beverage. Researchers have collectively carried out thousands of studies looking at its effects on lifespan, to cardiovascular health, blood sugar levels, weight loss, cancer risk and more.

Coffee contains more than 1,000 chemical compounds, many of which are active in the body, such as magnesium, potassium, niacin and other B vitamins.

For a while, scientists suspected that drinking coffee was hazardous to your health. In 1991, the World Health Organization listed coffee as “possibly” carcinogenic because of studies linking it to bladder cancer. Other studies suggested that drinking coffee might also increase the risk of lung cancer.

Then scientists realized that, in some cases, they had mistaken correlation for causation. People who smoke also tend to drink a lot of coffee — and in many of the early studies, a large percentage of the coffee drinkers were also smokers. Once studies took this into account, the link between coffee and lung and bladder cancers essentially disappeared.

In the decades since, hundreds of studies have painted coffee in a different light, showing that it may be protective against some major diseases, including several cancers. As scientists began to take a closer look at the compounds in coffee, they discovered that a number of them have anti-inflammatory and anti-cancer properties.

One large meta-analysis that reviewed decades of research on 67 health outcomes concluded that for most adults, drinking coffee on a daily basis was “more likely to benefit health than harm” it. On average, the analysis found, people who drink several cups of coffee a day are nearly 20 percent less likely to die early compared with people who drink little or no coffee.

We reviewed the data and interviewed experts to find out which of the health benefits of coffee consumption are backed by the strongest evidence. Here’s what we found.

A boost for liver health
After decades of research on coffee and its health benefits, one of the most consistent findings is that drinking coffee is good for your liver, said Rob van Dam, a professor at the Milken Institute School of Public Health at George Washington University.

Many studies have found that coffee drinkers have lower rates of liver cancer, nonalcoholic fatty liver disease, liver cirrhosis and other forms of liver disease. Coffee consumption is also associated with lower liver enzyme levels, which is typically an indication that your liver is healthy and not stressed.

Van Dam, who researches nutrition sciences, said that coffee’s protective effects on the liver have been demonstrated in large observational studies, experimental studies, animal research and clinical trials. One study published in 2021, for example, followed nearly a half million adults for roughly 11 years and found that coffee drinkers had a 21 percent lower risk of developing chronic liver disease and a 49 percent lower likelihood of dying from chronic liver disease compared with people who did not drink coffee.

The effects were seen in people who drank coffee of all types, including espresso, instant coffee and decaffeinated coffee. The reduction in risk was associated with an intake of as little as one cup of coffee daily, but people who consumed between three and four cups per day saw the greatest benefits.

The reason coffee appears to protect the liver is not entirely clear. “It’s a bit complicated because coffee has thousands of plant compounds,” van Dam said. One component in particular, chlorogenic acid, improves how effectively the liver responds to insulin, while other compounds in coffee may protect the liver by reducing inflammation.

A lower risk of Type 2 diabetes
Coffee’s ability to improve insulin sensitivity may also explain why researchers have found that coffee drinkers are less prone to developing Type 2 diabetes. Many large studies have found that people who drink three to four cups of coffee daily have about a 25 percent lower risk of the disease compared with people who drink little or no coffee. In fact, your likelihood of developing diabetes decreases about 6 percent for each cup of coffee you consume daily (up to about six cups).

This effect has been found in dozens of studies involving more than a million participants across Europe, North America and Asia. It has been found in men and women, in young and old people, in smokers and nonsmokers, and in people with and without obesity.

Researchers have also shown that the risk rises and falls with changes in coffee consumption. In studies that tracked thousands of men and women over two decades, scientists found that when coffee drinkers increased their coffee intake by an extra cup or two a day, their risk of Type 2 diabetes fell 11 percent. But when people decreased their coffee intake by roughly the same amount, their likelihood of developing diabetes rose by 17 percent. Scientists did not see the same effect when they looked at changes in tea consumption.

Coffee is a rich source of polyphenols — compounds in fruits, vegetables, whole grains and other plants that are known to confer health benefits. Studies have found that these polyphenols, including chlorogenic acid, improve insulin sensitivity and blood sugar control. They also help protect the beta cells of the pancreas, which produce insulin and play a critical role in the development of Type 2 diabetes, said Hubert Kolb, a visiting scientist at the West German Center of Diabetes and Health in Düsseldorf who studies coffee’s health effects.

A lower risk of Parkinson’s disease
One of the most surprising and consistent findings about coffee consumption is that it lowers your risk of developing Parkinson’s disease. Scientists think this is in large part due to the caffeine in coffee.

In a large meta-analysis of data from two dozen studies involving more than a million people, scientists found that people who drank up to three cups of coffee daily were 28 percent less likely to develop Parkinson’s disease compared to people who drank little or no coffee. Meanwhile, people who drank up to two cups of tea daily had a 26 percent lower likelihood of developing Parkinson’s.

“Initially people were skeptical,” van Dam said. “But this has been seen again and again in study after study, that people drinking a lot of caffeine — both from coffee and tea — have a lower risk of Parkinson’s disease.”

In Parkinson’s disease, dopamine-releasing neurons in the brain progressively degenerate and die, which causes tremors, muscle stiffness and other motor symptoms. But caffeine may help prevent the destruction of these dopaminergic neurons, which could explain why coffee and tea drinkers have a lower likelihood of developing the disease.

More physical activity
Exercising on a daily basis is one of the best things you can do for your health. And one way to get more exercise is to drink coffee.

In a rigorous study published in the New England Journal of Medicine in 2023, scientists recruited 100 healthy men and women and equipped them with Fitbits, heart monitors and other devices that measured health metrics. Participants were tracked for two weeks and instructed to drink caffeinated coffee on some days and to abstain from coffee on other days.

The scientists found that on the days when people drank coffee — typically consuming about one to three cups — they got 1,000 more steps in. That’s equivalent to walking about a half mile. That’s a significant increase in physical activity, which could be one reason drinking coffee is generally linked to better health, said Gregory M. Marcus, an author of the study and a professor of medicine in the division of cardiology at the University of California at San Francisco.

“Taking a thousand more steps per day has a meaningful effect on multiple health outcomes,” he added.

In fact, taking an additional 1,000 steps per day is associated with a 6 to 15 percent reduction in mortality — “effect sizes that are remarkably similar to the magnitude of mortality benefit observed among coffee drinkers,” Marcus and his colleagues wrote in their study.
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Credit: Washington Post