A new study published in JAMA examines data from more than 130,000 individuals followed for up to 43 years.
Participants continuously reported their diet and health, providing a strong foundation for analysis.
Coffee and tea
Researchers note that coffee and tea contain compounds such as caffeine and polyphenols.
These may have a positive effect on the brain, including reducing inflammation and protecting cells.
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Previous studies have shown mixed results, but they have often been smaller in scale or had shorter follow-up periods, making this study more reliable.
How much coffee or tea should you drink?
During the study, just over 11,000 participants developed dementia.
Individuals with a moderate intake of coffee or tea performed better in tests of memory and cognitive function.
The effect was observed in both individuals with high and low genetic risk, suggesting that the findings are broadly applicable.
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A daily intake of around 2 to 3 cups of coffee or 1 to 2 cups of tea was associated with approximately an 18 percent lower risk of dementia compared with those who rarely consumed these beverages.
Decaffeinated coffee did not show the same association.
Sources: Science Daily, and JAMA.
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