Downing cup after cup of coffee might keep the body energized and alert, but it could be having a dangerous effect on the brain.
Drinking more than six cups of coffee a day was associated with a 53% increased risk of dementia and a smaller brain volume, Australian researchers have found.
The data strongly suggests high coffee consumption can adversely affect brain health, said Elina Hypponen, study co-author and director of the Australian Centre for Precision Health at the University of South Australia Cancer Research Institute.
“As with most things in life, moderation is the key. Very high coffee intakes are unlikely to be good for you,” Hypponen told TODAY.
The findings are based on the coffee drinking habits of more than 398,000 adults taking part in a long-term British study — including more than 17,000 who had undergone a brain MRI. The participants were recruited between 2006 and 2010, and followed until 2018.
People who reported drinking the most coffee, defined as more than six cups a day, had “notable increases” in the odds of dementia — 53% higher compared to people who drank one to two cups daily, even after adjusting for lifestyle and other factors.
There were no differences in estimates found among men and women, or among different age groups, the authors wrote. And the more coffee people drank, the more brain shrinkage their brain scans showed.
That correlation between coffee consumption and brain volumes was an especially interesting part of this study, said Dr. Amy Guzik, a neurologist at Wake Forest Baptist Health in Winston-Salem, North Carolina, and a member of the American Neurological Association.
Everyone experiences some decreases in brain volume with aging, but higher amounts of brain volume loss or atrophy can be associated with dementia, Guzik noted. The study doesn’t show a cause and effect, but higher amounts of coffee are potentially worrisome, she added.
“We all know that coffee affects the brain. We feel it with increased concentration or attention when we have a cup of coffee or tea, and that's not concerning to me, but too much of anything is probably not good,” Guzik said.
“This study reinforces that perhaps very high levels of caffeine intake — over six cups of coffee a day — would be concerning and would be a reason to be talking to your doctor if you're having memory trouble.”
In the study, the evidence for an association between high coffee consumption and stroke was less strong, Hypponen said. Indeed, doctors typically don't think of caffeine as a stroke risk factor, Guzik said. The study also didn’t find any troublesome associations with tea drinking.
Previous research has found caffeine has positive actions on the brain: It can increase alertness, help concentration, improve mood and limit depression, doctors have noted in the journal Practical Neurology.
People who drink regular, moderate amounts of coffee are also less likely to die from diabetes, heart disease and other illnesses.
But many of the apparent benefits of coffee may simply reflect the fact that people who are not well tend to drink less coffee, Hypponen noted.
The new study didn’t allow researchers to quantify how much caffeine is too much, but the findings translate to keeping daily caffeine intakes at 300 milligrams or lower, Hypponen said. The U.S. Food and Drug Administration advises limiting it to 400 milligrams a day for healthy adults, which works out to about four 8-ounce cups of coffee. Keep in mind one venti cup at Starbucks contains two-and-a-half times that amount of coffee — 20 ounces.
One to two standard cups might be enough to give people that pick-me-up in the morning without causing problems, Guzik noted.
Simply drinking some water every time you have a cup of coffee could also help because coffee-related dehydration may have a harmful effect on the brain, Hypponen added.
Kristin Kirkpatrick, the lead dietitian at Cleveland Clinic Wellness & Preventive Medicine, often recommends her patients enjoy two to four cups of coffee a day — if they so desire, don’t experience anxiety or shakiness afterwards and aren’t found to be slow metabolizers.
She also recommends starting with whole beans and grinding them — because studies show there may be more benefits this way — and keeping sugar and creamers in check.
“Coffee is an abundant source of bioactive compounds that have been found to benefit health in multiple ways,” Kirkpatrick said.
“But these benefits can be seen in smaller amounts and studies like this are a great reminder that excess, even in foods that are found to be healthy, may not always benefit health.”