Scientists seem to be topping off the data on coffee’s health benefits.
In a fresh-brewed study involving more than 200,000 people, researchers found that drinking coffee—regular or decaf—is associated with an overall lower risk of mortality. Drinking between three and five cups a day perked up survival rates the most, lowering the risk of premature death by up to 15 percent compared to coffee abstinence, researchers reported Monday in Circulation.
Though the study reveals only a correlation—not a potential cause for the life-upper—it follows decades of studies that found specific and general health benefits of coffee drinking, particularly lower risks of cardiovascular disease, liver diseases, diabetes, and overall mortality. Plus, the study’s large size helps parse other health factors, particularly smoking, that may conceal coffee’s protective effects.
The authors, led by Frank Hu of Harvard T. H. Chan School of Public Health, concluded that the “results from this and previous studies indicate that coffee consumption can be incorporated into a healthy lifestyle.”
For the study, Hu and colleagues analyzed health records of more than 200,000 people, mined from three large clinical trials that included doctors, nurses, and other health professionals. In those trials, participants were periodically given food questionnaires and followed for up to 30 years, during which 30,000 participants died.
Combining all the data, researchers found that drinking up to five cups of coffee a day lowered the risk of all-cause mortality by 5 to 9 percent compared to drinking no coffee. Drinking more than five cups a day had no association with mortality risk, the authors found.
But, people who drink a lot of coffee also tend to be smokers, epidemiologist Hannah Gardener, of the University of Miami, told Ars. And this may have been a bitter note for previous research.
Many observational studies have found that moderate coffee consumption can lower mortality risks, but effects in heavy coffee drinkers have been a point of debate, she said. “Many studies did not have the size and power to look at this group of coffee consumers carefully.”
The new study did, however. When Hu and colleagues chucked smokers from their analysis, they found that mortality risks fell for moderate and heavy coffee drinkers. Non-smoking java-junkies that throw back more than five cups a day had a mortality risk 12 percent lower than non-drinkers. Non-smokers that partake in three to five cups a day had a 15 percent lower mortality risk than non-drinkers.
“Drinking high amounts of coffee may, in fact, not be bad and may possibly be beneficial for health similar to the consumption of moderate amounts of coffee,” Gardener said.
When Hu and colleagues examined the data more closely, they also found coffee consumption was linked to lower risks of cardiovascular disease, neurological disease, and suicide. They saw no link to total cancer mortality, however.
Dozens of studies have looked into specific health effects of coffee over the years, many of which have resulted in conflicting results—but not all, Christina Bamia, professor of epidemiology and medical statistics at the University of Athens, told Ars.
Links between coffee and diseases such as liver cancer and type 2 diabetes have been investigated in many studies, she said, “and findings are rather consistent in showing a benefit associated with coffee consumption.”
In relation to liver health, previous studies have suggested the caffeine and other unknown elements of coffee can block liver scarring, fat deposition, and cancer. In terms of diabetes, studies have found that caffeine and coffee components including chlorogenic acid, lignans, quinides, trigonelline, and magnesium could reduce insulin resistance and systematic inflammation. Because diabetes and cardiovascular disease share common disease pathways, the authors say their finding of lower risk of cardiovascular disease makes sense, as well.
But, with around 1,000 different compounds swirling in each cup of joe, specific chemicals and mechanisms that may protect health are dripping out slowly. Still, observational studies, such as this one, are useful steps forward in figuring it out, Bamia said.