New research indicates that enjoying a daily cup of tea or coffee could be associated with a reduced risk of dementia and slightly better cognitive performance. A comprehensive analysis of health records from more than 130,000 individuals over four decades has uncovered a potential link between these popular beverages and brain health.
Key Findings on Caffeine and Cognitive Decline
The study, published in the Journal of the American Medical Association, found that people who routinely consumed two to three cups of caffeinated coffee or one to two cups of caffeinated tea each day had a 15-20% lower risk of developing dementia compared to those who avoided these drinks. Additionally, caffeinated coffee drinkers reported marginally less cognitive decline than those who opted for decaffeinated versions and performed better on certain objective tests of brain function.
Understanding the Research Limitations
While the findings suggest a positive correlation, the research cannot definitively prove that tea and coffee consumption directly causes improved brain health. Lead author Yu Zhang, a nutritional epidemiology researcher at Harvard University, emphasised that the study alone does not establish causality. Factors such as lifestyle choices or sleep patterns could influence the results; for instance, individuals who avoid caffeine to improve sleep quality might already be at a higher risk for cognitive issues.
Zhang noted, "Our study alone can’t prove causality, but to our knowledge, it is the best evidence to date looking at coffee and tea intake and cognitive health, and it is consistent with plausible biology." The research analysed data from two major US public health studies, the Nurses' Health Study and the Health Professionals Follow-up Study, tracking participants for up to 43 years.
Potential Biological Mechanisms
Coffee and tea contain caffeine and polyphenols, compounds that may offer protective effects against brain ageing. These substances could improve vascular health, reduce inflammation, and combat oxidative stress—a process where free radicals damage cells. Caffeine has also been linked to lower rates of type 2 diabetes, a known risk factor for dementia, suggesting potential metabolic benefits.
Overall, the study reported that men and women who drank the most caffeinated coffee had an 18% lower dementia risk compared to those with little or no intake, with similar results observed for tea. The benefits appeared to plateau at the recommended daily amounts, and no significant link was found between decaffeinated coffee and dementia risk.
Expert Insights and Future Directions
Naveed Sattar, a professor of cardiometabolic medicine at the University of Glasgow, highlighted the complexity of caffeine's effects on the brain. While antioxidants in tea and coffee may be beneficial, and caffeine can enhance motivation for activities like work and exercise, it can also raise blood pressure in some individuals—a significant driver of dementia. Sattar remarked, "Caffeine does a multitude of things, some which may be beneficial, some which may be harmful, and the net effect can never be estimated until you do a randomised trial."
Further research is needed to confirm whether these drinks actively protect the brain. Gold-standard randomised trials over decades are impractical, but studies could explore biological changes linked to brain function through scans or other tests. Researchers estimate that about half of dementia cases worldwide could be prevented or delayed by addressing factors like obesity, smoking, and high blood pressure.
Practical Advice for Brain Health
Zhang advised against viewing tea or coffee as a "magic shield" against dementia. Instead, he stressed the importance of a holistic approach to brain health, including regular exercise, a balanced diet, and good sleep. "I’d say maintaining a healthy lifestyle, getting regular exercise, having a balanced diet and getting good sleep are all important to get better brain health," he told the Guardian.
This study adds to growing evidence on lifestyle factors that may influence cognitive decline, encouraging further investigation into the role of dietary habits in dementia prevention.
