Plate Nº 59 · recorded November 13, 2026
Health & Medicine ResearchReported finding
Two to Three Cups of Coffee a Day Linked to Lowest Dementia Risk
A JAMA study tracking 131,821 U.S. health professionals found the lowest dementia risk at two to three cups of coffee daily, with no added benefit beyond about 300 mg of caffeine.
By Nathan Brooks3 min read593 words
In brief
- A JAMA study of 131,821 U.S. health professionals linked two to three cups of coffee daily to the lowest dementia risk.
- During up to 43 years of follow-up, 11,033 participants developed dementia.
- Total caffeine showed the strongest association around 300 mg per day, with no clear added benefit beyond it.
- Adults 75 or younger in the highest caffeine quartile had a 35% lower relative dementia rate than the lowest quartile.
- Decaffeinated coffee did not show the same association with lower dementia risk.
Two to three cups of caffeinated coffee a day marked the point where dementia risk looked lowest in a study of 131,821 U.S. health professionals, with follow-up stretching up to 43 years. Drink more than that, and the researchers found little evidence of any additional advantage.
The study, published in JAMA, drew on two long-running cohorts of nurses and other health professionals. Over the follow-up period, 11,033 participants developed dementia. The lowest estimated risk showed up around two to three cups of caffeinated coffee or one to two cups of tea daily, compared with people who skipped the respective drink altogether.
That plateau matters. A finding about moderate intake can easily be misread as a reason to drink more, but the data show where the association was strongest across the study population — not what's best for any individual.
What did the caffeine analysis show?
When researchers looked at total caffeine instead of cups, the pattern repeated. The strongest association appeared around 300 milligrams a day — roughly the caffeine in two to three eight-ounce cups of brewed coffee — with little evidence of extra benefit beyond that level.
A separate comparison sharpened the picture. Among participants aged 75 or younger, those in the highest quarter of caffeine intake had a 35% lower relative rate of dementia than those in the lowest quarter. The association was smaller in older adults. And that 35% figure applies only to that subgroup comparison — not to everyone drinking a particular number of cups.
How was the data collected?
Participants reported what they drank through repeated diet questionnaires over the decades. That gave researchers a better read on long-term habits than a single question at the start would have — though it still depended on how accurately people recalled their own intake.
The study defined a cup as eight fluid ounces. Even so, actual caffeine content varied widely, because bean type, brewing method and serving size all change the dose. Two people reporting the same number of cups could be consuming quite different amounts of caffeine.
The study also measured usual consumption across everyday routines. That means it can't say whether morning coffee behaves differently in the body than an afternoon cup.
Why didn't decaf show the same link?
Decaffeinated coffee did not show the same relationship with lower dementia risk. Caffeine itself could play a role — but there's a catch. People who choose decaf may differ from other coffee drinkers in ways that also affect their health, so the decaf result doesn't settle the question.
Does coffee actually prevent dementia?
No — and the researchers are careful not to claim it does. Because they observed habits over time rather than running a controlled experiment, the study cannot establish that caffeine caused the difference in dementia risk.
What the findings do offer is direction. The moderate-intake pattern gives future studies a range to investigate, without turning two to three cups into a prescription for preventing dementia.
The work comes from researchers at Mass General Brigham and the Harvard T.H. Chan School of Public Health. It sits alongside related nutrition research on whether the MIND diet may slow brain aging, and on how Mediterranean-style eating patterns relate to Alzheimer's risk.
For now, the takeaway is modest: among more than 131,000 health professionals tracked for up to four decades, moderate coffee and tea drinking lined up with the lowest dementia rates. Whether caffeine deserves the credit — and whether the finding applies to you — remains an open question.
via knowridge.com (Source)
More from Nathan Brooks
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Market editor covering companies, deals and strategy in general science news at SciBeat.
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