If you’re reading this with a cup of coffee or tea in hand, you might want to keep sipping—a large new study published in JAMA has found that drinking two to three cups of caffeinated coffee or one to cups of caffeinated tea a day may reduce the risk of dementia and slow cognitive decline. Here’s what to know.
Given the popularity of coffee and tea, the researchers wanted to explore whether drinking these beverages long-term might be linked to brain health, said study author Yu Zhang, MBBS, a research assistant at the Channing Division of Network Medicine at Brigham and Women’s Hospital.
Previous evidence linking coffee and tea to cognitive health has been inconclusive, and most studies haven’t differentiated between caffeinated and decaffeinated coffee.
With this in mind, Zhang and his colleagues turned to data gathered from 131,821 participants involved in two research programs, the Nurses’ Health Study and the Health Professionals Follow-Up Study. For the last 43 years, participants have provided information on their dietary habits and have received tests assessing cognitive function and potential dementia and cognitive decline.
By comparing participants’ coffee intake to their rates of dementia development, the researchers identified a link. Men and women who drank the most caffeinated coffee had an 18% lower risk of dementia compared to people who consumed little to no caffeine. To a lesser extent, they also experienced improvements in subjective cognitive decline and performed better on overall cognition tests.
Two to three cups per day appeared to be a sweet spot, with this amount producing the most pronounced cognitive differences.
Caffeinated tea drinkers experienced similar effects at one to two cups per day, with about a 15% less dementia risk. Going above this amount did not show additional benefit.
According to Zhang, the length and size of the study make it an important benchmark in the research on coffee, tea, and dementia. “A lot of earlier studies were shorter, or they measured diet just once,” he said. “What’s different here is we had repeated diet data and up to 43 years of follow-up, which is really valuable for dementia research.”
Nikhil Palekar, MD, director of the Center of Excellence for Alzheimer’s Disease at Stony Brook Medicine, agreed that the study’s multiple-decade length adds to its credibility, and noted that the link found between cognition and caffeine specifically, rather than other substances in coffee, is a valuable new addition. “It was surprising to see the findings that drinking decaffeinated coffee was not associated with lowering dementia risk,” he told Health.
There are a couple of ways caffeine may boost brain health. According to neurologist and lifestyle medicine physician Lynette Gogol, DO, DipABLM, caffeine works by blocking adenosine receptors in the brain that are involved in inflammation and communication between nerve cells. “In laboratory and animal studies of Alzheimer’s disease, blocking these receptors has been linked to reduced amyloid buildup and improved memory performance,” she said. Amyloid is a protein found in the brains of Alzheimer’s patients.
Additionally, Palekar said caffeine is associated with improved vascular health, which can reduce the risk for vascular dementia. “It can also increase insulin sensitivity, which can help prevent metabolic risk factors such as obesity, diabetes, and elevated cholesterol—all risk factors for dementia.”
The new study is promising for caffeinated coffee and tea drinkers. But take note: its results are observational, not causal. In other words, it can’t definitively prove coffee or tea directly lowers dementia risk. Though the researchers adjusted for many lifestyle and health factors, unmeasured differences between people could still play a role in cognitive outcomes.
The study also didn’t distinguish between the different types of tea consumed or how coffee was prepared, Gogol pointed out. “These differences can affect caffeine and antioxidant content, which may influence potential health effects,” she said.
It’s important to note that for some people, caffeinated drinks could also cause unpleasant side effects. Palekar stressed the importance of discussing your caffeine intake with your healthcare provider if you have health concerns like anxiety, dehydration, insomnia, or rapid or irregular heartbeat.
That said, established caffeinated coffee and tea drinkers can confidently maintain a one- to three-cups-per-day habit. “In short, if you enjoy coffee or tea and tolerate caffeine, moderate intake may complement a brain-healthy lifestyle,” Gogol said.
