Many coffee and tea drinkers try to ignore the ping-pong game of good for you/bad for you news about caffeine. If you want (or need) your morning joe or afternoon Earl Grey, you’re going to have it. Right?
But here’s a reason to tune back in: The good news side recently won a major point.
An observational study published online by the Journal of the American Medical Association in February suggested that people who consumed two to three cups of coffee per day or one to two cups of tea (or about 300 milligrams of caffeine) had an 18% lower risk of developing dementia compared with peers who drank little to no coffee or tea—or drank decaf.
At the personal level, this is only a small reduction in risk, but at scale—given that dementia affects about 55 million people worldwide—those few daily cups may be helping millions of us keep our brains sharp.
Prior Evidence
Research suggesting coffee and tea offer some protection against dementia—and other age-related issues such as heart problems and Parkinson’s disease—has been mounting for two decades. But this latest study, which crunched data collected from 131,821 people between 1980 and 2023 for two major studies—the Nurses’ Health Study and the Health Professionals Follow-up Study—is significant for a few reasons.
First, the effects were clearer. “Prior evidence on coffee, tea and cognitive health has been mixed, so one thing that stood out to us was the consistency and robustness of the findings across the dementia continuum,” said Yuxi Liu, a study author and research fellow in the Department of Medicine at Brigham and Women’s Hospital in Boston, in an email to Wine Spectator.
Second, the study was larger and more vigorous than most previous research. “We were able to update diet every two to four years and follow participants for more than four decades, which is critical for [tracking]slowly developing cognitive changes,” said Liu, who’s also a postdoctoral fellow at the Harvard T.H. Chan School of Public Health. “We also adjusted for a wide range of lifestyle and clinical factors … including education, neighborhood socioeconomic status, smoking, alcohol intake, physical activity, diet quality, medical history, and medication use.”
Third, this is the first study to suggest an ideal daily dosage for maximum protection against dementia—two to three cups of coffee or one to two cups of tea,. Higher intakes showed no greater benefit, but no negative effects, either.
People at Genetic Risk Also Benefited
Importantly, coffee and tea drinkers who carried the APOE4 gene, which increases the risk for Alzheimer’s disease, also showed a lower rate of dementia. This suggests that “even people with elevated genetic risk may still benefit from healthy lifestyle patterns,” said Liu. Further, among people without dementia, the daily coffee and tea drinkers were slightly sharper cognitively than those who took in little or no caffeine. In tests, they performed as if they were about seven months younger.
The benefits were strongest in younger subjects, below age 75. This supports the idea that processes that cause dementia begin early in life, and the study authors believe lifelong coffee and tea drinkers may enjoy more protection than those who started brewing later.
It’s Probably the Caffeine
Researchers don’t yet understand what may be delivering the benefits. Coffee and tea contain many compounds that could protect brain health, such as polyphenols and antioxidants. But caffeine is the likely hero. “Caffeine is the leading candidate based on our data,” said Liu, who drinks tea daily. It may protect the brain by reducing inflammation, lowering diabetes risk and affecting proteins related to Alzheimer’s disease, among other actions.
But don’t assume that caffeine from other sources will offer similar benefits. The study adjusted for caffeine intake from sources such as soda and chocolate, Liu said, and only coffee or tea drinkers showed the reduced dementia risk.
The Observational Research Clause
While this study strongly suggests drinking coffee or tea daily lowers the risk of dementia, it doesn’t prove it. All observational studies, which analyze data taken over years in the past, can reveal only possible correlations—they can’t identify a true cause and effect. But if you already drink it daily, this study provides more comfort that, at minimum, it’s doing your brain no harm. Yes, exercising, eating well, sleeping well, maintaining social ties, managing high blood pressure and many other well-known measures will do far more to keep you mentally sharp. But none are as steamy and delicious.
“I used to think that intentionally weaning off coffee was healthier,” said cardiologist David Kao, the Jacqueline Marie Schauble Leaffer Endowed Chair in Women’s Heart Disease at the University of Colorado School of Medicine, who’s led research showing coffee drinkers have a lower risk of heart failure. “Now, I just don’t worry about it, and I enjoy drinking coffee every day.”
Ron Geraci is a coffee- and wine-loving writer who splits his time between San Diego and Salerno, Italy.
