A coffee each morning can work as a quick pick-me-up. But don’t go overboard, researchers from the University of South Australia warn, as it could negatively impact your brain’s health.

One of the largest studies of its kind reports that high coffee consumption is associated with an increased risk of dementia and smaller total brain volumes. The study included data from 17,702 UK Biobank participants aged 37-73, finding that those who drank six or more cups of coffee per day had a 53% increased risk of dementia, and showed reduced volumes in their overall brains, white matter, gray matter, and their hippocampus.

Brain drain

“Coffee is among the most popular drinks in the world. Yet with global consumption being more than nine billion kilograms a year, it’s critical that we understand any potential health implications,” says Kitty Pham, lead researcher on the paper and a Ph.D. candidate at the University of South Australia (UniSA). “This is the most extensive investigation into the connections between coffee, brain volume measurements, the risks of dementia, and the risks of stroke—it’s also the largest study to consider volumetric brain imaging data and a wide range of confounding factors.

“Accounting for all possible permutations, we consistently found that higher coffee consumption was significantly associated with reduced brain volume—essentially, drinking more than six cups of coffee a day may be putting you at risk of brain diseases such as dementia and stroke.”

Although I personally know nobody who actually drinks six or more cups of coffee a day, there are certainly a few out there. As such, the findings could be quite important for public health, pointing to a source of preventable brain damage, including stroke and dementia.

Dementia affects about 50 million people worldwide, affecting an individual’s ability to think, their memory, impacting their behavior, and their ability to perform even everyday tasks. It’s a degenerative brain condition and a sizeable cause of death worldwide.

Strokes involve the disruption of blood flow to the brain, usually through blood clots or the rupturing of blood vessels, and end up starving areas of the brain of oxygen. This, in turn, leads to (usually significant) brain damage and loss of function. They’re surprisingly common, affecting one in four adults over the age of 25 worldwide.

The team explains that the exact mechanism through which excessive caffeine can impact brain health is not yet known but these results — along with previous research on the topic — make a strong argument that it does have such an effect. Still, this doesn’t mean you have to put your cup down for good. Moderation is the name of the game, the team explains.

“This research provides vital insights about heavy coffee consumption and brain health, but as with many things in life, moderation is the key,” says Professor Elina Hyppönen, senior investigator and Director of UniSA’s Australian Centre for Precision Health.

“Together with other genetic evidence and a randomized controlled trial, these data strongly suggest that high coffee consumption can adversely affect brain health. While the exact mechanisms are not known, one simple thing we can do is to keep hydrated and remember to drink a bit of water alongside that cup of coffee.

People typically consume between one and two cups of coffee per day, the team adds, which is not a very accurate measure, as cups are quite variable. Still, such low levels of intake should be fine. As long as you’re not closing in on five of six cups a day, they conclude, you should be safe.

The paper “High coffee consumption, brain volume and risk of dementia and stroke” has been published in the journal Nutritional Neuroscience.