Un effet «neuroprotecteur» : trois tasses de café ou de thé par jour pourraient réduire le risque de démence, selon une étude de Harvard
To reach this conclusion, researchers analyzed data from 131,000 healthcare professionals in the United States over 43 years.
A comforting beverage for some, an essential fuel for others, and even a true addiction for some: coffee occupies a special place in our daily lives. Regularly scrutinized by science, caffeine is the subject of studies with sometimes contradictory conclusions. The latest, conducted by Harvard University and published in the journal JAMA, suggests an encouraging result: drinking three cups of coffee or tea a day could reduce the risk of dementia by approximately 20%.
After 43 years of follow-up, this American study suggests that caffeine may have a neuroprotective effect. According to the researchers, a daily consumption of about three cups would constitute an optimal amount. Caffeine may slow the degeneration of brain cells by reducing inflammation and limiting the accumulation of toxic proteins associated with dementia. Drinking two to three cups of coffee per day would reduce the risk of dementia by 18%, while one to two cups of tea would be associated with a 16% decrease.
To reach these conclusions, researchers analyzed data from 131,000 healthcare professionals in the United States. Every two to four years, participants completed questionnaires detailing their diet, particularly their consumption of caffeinated beverages, and underwent cognitive tests. At the end of this follow-up period, 11,033 cases of dementia were identified.
“A piece of the puzzle” in prevention
Dr. Daniel Wang, assistant professor at Harvard Medical School and lead author of the study, believes that encouraging moderate coffee and tea consumption "may be a piece of the puzzle" in preventing dementia. "In looking for possible prevention tools, we thought something as widespread as coffee might be a promising dietary intervention," he explained in the Times.
Yu Zhang, another author of the study, points out that dementia represents "one of the world's most significant and complex public health problems." In the absence of truly effective treatments, identifying modifiable lifestyle factors becomes crucial. "Coffee and tea are widely consumed around the world. Even modest associations could have significant population-wide implications," he emphasizes. However, the researchers clarify that further increasing consumption would provide "no additional benefit."
Results to be interpreted with caution
It is important to emphasize, however, that this study remains observational: it highlights an association, without establishing a direct cause-and-effect relationship. "While our results are encouraging, it is important to remember that the magnitude of the effect remains modest and that there are many other ways to protect cognitive function as we age," Dr. Wang emphasizes.
The scientific literature on coffee is abundant. Besides its possible role in the prevention of dementia, some studies attribute beneficial effects on aging, cardiovascular health, thanks in particular to its polyphenols, as well as on certain pathologies such as digestive cancers, type 2 diabetes or Parkinson's disease.
Other studies, however, highlight some of its adverse effects, such as sleep disturbances, tachycardia, anxiety, and caffeine addiction. Faced with this sometimes conflicting data, health authorities advocate caution. The European Food Safety Authority (EFSA) recommends that a healthy adult not exceed an average of 400 mg of caffeine per day, the equivalent of four to five cups of coffee.
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