Your Daily Coffee Habit May Protect Your Brain From Dementia—Here's What the Research Shows

Drinking 2 to 3 cups of caffeinated coffee or 1 to 2 cups of tea daily is associated with an 18% lower dementia risk, according to a new long-term study of nearly 132,000 healthy adults published in the Journal of the American Medical Association. The findings suggest that for people who already enjoy coffee or tea, their caffeine habit may offer meaningful brain protection as they age—though researchers emphasize this isn't a magic bullet for preventing dementia entirely.

What Did This Major Study Find?

Scientists at Mass General Brigham, Harvard T.H. Chan School of Public Health, and the Broad Institute of MIT and Harvard analyzed health data spanning from 1980 to 2023, tracking two groups of health professionals: more than 86,000 women from the Nurses' Health Study and more than 45,000 men from the Health Professionals Follow-Up Study. Over a median follow-up period of nearly 37 years, more than 11,000 participants developed dementia.

The results were striking. People who consumed the most caffeinated coffee had an 18% lower dementia risk compared with those who drank the least, while tea drinkers who consumed the most had a 14% lower risk. The protective effect was strongest in people aged 75 and younger. Importantly, decaffeinated coffee showed no such benefit, suggesting caffeine itself plays a key role.

How Much Coffee or Tea Should You Actually Drink?

The study identified an optimal range: people who drank 2 to 3 cups of caffeinated coffee or 1 to 2 cups of tea per day—roughly 300 milligrams of caffeine daily—had the lowest dementia risk compared with non-drinkers. This is important because it shows there's a "sweet spot" rather than a "more is always better" approach.

The association held true even for people at high genetic risk for dementia, including those carrying the APOE4 gene, a significant genetic risk factor for Alzheimer's disease. However, the study didn't differentiate between tea types (black, green, or white) or specify coffee preparation methods, which may influence the concentration of beneficial compounds.

Why Might Caffeine Protect Your Brain?

Researchers aren't entirely certain of the mechanism, but caffeine likely isn't working alone. Dr. Kellyann Niotis, a preventive neurologist at Weill Cornell Medicine, explained that coffee and tea contain multiple bioactive compounds beyond caffeine. "It's really a big challenge to disentangle the effects of coffee as a whole from all of the other compounds that are also in coffee—and tea," she said. These compounds include polyphenols, which have antioxidant and anti-inflammatory properties that may protect brain cells.

When manufacturers remove caffeine from coffee, they also extract some of these beneficial polyphenols, which may explain why decaf doesn't offer the same protection. The study also measured participants' cognitive function throughout the follow-up period, finding that higher intake of caffeinated coffee and tea was associated with lower rates of subjective cognitive decline and slightly better objective cognitive performance.

What Are the Study's Limitations?

While the findings are encouraging, the research has several important gaps:

• Preparation methods not specified: The study didn't account for how coffee was brewed or roasted, factors that may influence caffeine and polyphenol concentrations.
• Added ingredients not tracked: Researchers didn't measure whether participants added milk, cream, sugar, or other sweeteners to their drinks, which could counteract cognitive benefits.
• Tea types not differentiated: The study lumped all tea together without distinguishing between black, green, or white varieties, which have different compound profiles.
• Energy drinks excluded: The research didn't cover energy drinks, which in concentrated form may contain more caffeine than a cup of coffee.

Dr. Yu Zhang, the lead study author at Mass General Brigham, was careful to temper expectations: "We are not recommending that people who don't drink coffee start drinking. We are just seeing that for people who already drink coffee, the results are really reassuring". He also noted that dementia is complex and can't be prevented by dietary intervention alone.

What Else Should You Do for Brain Health?

Coffee and tea are just one piece of the cognitive health puzzle. Benjamin Katz, an associate professor at Virginia Tech who researches lifestyle factors and cognitive function, emphasized that diet is only a small component of brain health. He highlighted several evidence-based strategies that work alongside healthy beverage choices:

• Aerobic exercise: Regular physical activity has been shown to support cognitive function and brain health as you age.
• Adequate sleep: Getting enough quality sleep is essential for memory consolidation and cognitive performance.
• Cognitive engagement: Lifelong learning programs and mentally challenging activities help maintain brain plasticity and function.
• Avoiding smoking: Smoking accelerates cognitive decline and increases dementia risk.

The takeaway is practical: if you already enjoy coffee or tea, the research suggests your habit may offer real brain-protective benefits. But don't expect it to work in isolation. Combining moderate caffeine consumption with exercise, quality sleep, mental stimulation, and other healthy lifestyle choices gives your brain the best chance of staying sharp as you age.