Coffee & Alzheimer’s Disease: What’s the Verdict?

According to legend, Kaldi, an Ethiopian goat herder who lived more than 1000  years ago, noticed something curious about his goats: If they ate the berries from one type of plant, they wouldn’t sleep at night. He told a local monastery about this discovery and started brewing a drink from the beans inside the berries — what we know now as coffee. News of this elixir spread around the world. 

Today, the average American drinks more than three cups of coffee every day, researchers have been curious as to whether this caffeinated drink had any effect on our brain health. 

Every month there’s an article in the news connecting coffee to cognition. The caffeine and chlorogenic acid show beneficial properties across animal models as well as cells grown in Petri dish, but in humans, the data is less simple to interpret.Sometimes the studies featured in these articles indicate that coffee staves off dementia, but other studies suggest negative effects. Why does the research seem to yield conflicting results — and how much coffee should you be drinking?

Does coffee affect brain health?

Maybe! Plenty of recent studies suggest a relationship between coffee consumption and brain health. Earlier this year, an observational study of 398,646 participants linked high levels of coffee consumption with a smaller overall brain volume. 

In that study, the risk of dementia was highest in individuals drinking more than six cups, and in support of moderation, it was found to be lowest among those drinking one to two cups. However, this observational study was not able to collect complete dietary information for all participants. Unhealthy diets are also linked to dementia, so food consumption alongside coffee intake could skew the results.

A 2018 study pooled several large studies together, forming an impressive sample of 328,885 people. Results from this study did not find any notable association at all between the risk of developing Alzheimer’s and coffee consumption.  

A 2024 study pooled together 33 studies, totaling 389 505 participants, to test whether drinking more coffee or tea affected Alzheimer’s risk. People who drank coffee or tea were less likely to develop the disease, with the effects maxing out at two and a half cups of coffee and one cup a day of tea.

The final verdict on brain health and coffee

For new Alzheimer’s treatments, scientists run randomized, blinded trials. This is impossible to do for coffee drinkers because most Americans drink coffee every day. Instead, many of these studies look at large populations to see whether people who drink a certain amount of coffee are more likely to develop Alzheimer’s than non-drinkers. These studies can’t provide a clear verdict because many variables are not measured: Are people taking their coffee with cream or milk? Are they drinking an espresso or a latte? How strong do they enjoy their brew? 

To make matters even more intricate, recent research also suggests that certain genetic traits are linked to coffee metabolism and drinking more coffee; it may be difficult to separate out this genetic factor when considering the impact of coffee consumption on the brain.

Ultimately these studies provide scientists with a few clues; none have definitively shown that drinking a certain amount of coffee will affect brain health. So, what have we learned? Firstly, that articles proclaiming some clear, definitive link between a daily habit like coffee and your dementia risk are likely oversimplifying the issue; and secondly, that if you are looking to improve your brain health, turn your attention from your caffeine habit to better known lifestyle opportunities: like a healthy diet, exercise, and good sleep to name a few.

In summary, from the research: Drinking coffee generally doesn’t hurt (unless there’s tons of sugar in the brew) — but it isn’t clear it will help that much either. 

UPDATE, National Coffee Day 27 September 2024, 00:01 ET: This January 2022 article was updated with new research and perspective to better inform our readers.