Green Tea May Boost Cognition and Cut Dementia Risk
Recent studies support benefits of drinking green tea, including cardiovascular health and reducing blood sugar
Jean-Christophe Gabler swapped his morning coffee for green tea more than 20 years ago and hasn't looked back since. "I made the transition from coffee because I needed something that could wake me up without leaving me jumpy," says the 53-year-old Santa Monica, California, resident. "I felt the difference immediately. Rather than a spike and crash, I felt more sustained energy."
Decades of research suggest that besides providing jitter-free energy, green tea may impart various health benefits from supporting cardiovascular health to reducing blood sugar.
"It's not only a beverage; it's a small ceremony for me. It energizes me, supports digestion and keeps me grounded every day," Gabler says. "I continue to drink it because I feel its benefits immediately and even after many years."
A recent study from Japan suggests it may also help prevent dementia — even in those who start drinking it later in life.
"Taking care of your brain health through managing blood pressure, cholesterol and sugar — plus staying physically and mentally active, eating well and not smoking — can help reduce the risk of developing more of these lesions in the cerebral white matter."
For the study, published in Nature Portfolio Journal Science of Food, researchers surveyed 8,766 older, community-dwelling Japanese adults about their coffee and tea consumption, excluding those with signs of cognitive impairment. Researchers also performed MRIs to measure the volume of participants' brains and check for white matter lesions. Previous research has linked lower brain volume to an increased risk of Alzheimer's disease and white matter lesions to an increased risk of dementia.
White matter lesions are small areas of damage to the brain's "wiring," says Amy Sanders, M.D., a dementia neurologist with Sunday Health based in Wethersfield, Connecticut. She explains that the brain resembles a complex electrical system, with "processing centers" (gray matter, where neurons live) connected by "wiring" (white matter) that facilitates communication between neurons.
White Matter Lesions
"White matter lesions interrupt the communication pathways between different brain regions," Sanders says. "Think of it like damage to the internet cables connecting computers in a complex network: even if each computer (e.g., neuron) works fine individually, the network loses its functional integrity and begins to become dysfunctional. The signals no longer get through as they should."
After adjusting for confounding factors, such as diabetes, hypertension, depression and the presence of APOE e4 allele (a genetic variation that raises dementia risk), researchers found people who routinely drank three or more 200 ml cups of green tea per day had 3% fewer lesions than those who drank one. Meanwhile, participants who had seven or more cups daily had 6% fewer lesions, on average, than those who drank one. These results didn't hold true for people with the APOE e4 allele or depression.
The researchers didn't find any correlation between tea drinking and brain volume or between coffee and brain health. And they didn't evaluate the impact of black tea, as not enough participants consumed it. Other research, however, suggests coffee and black tea — also rich in antioxidants —benefit the brain and body in other ways.
Lesions can occur for several reasons, including small blood vessel problems, inflammation or swelling in the brain, or having multiple small strokes, Sanders says.
"High blood pressure, diabetes or smoking damage over time are powerful causes of white matter lesions," she adds.
She says that normal aging also contributes, noting that virtually everyone eventually develops some lesions.
Sanders says that you may not notice any symptoms when lesions are mild. However, as they become more widespread, they may contribute to slow thinking, attention and concentration difficulties, balance and coordination problems, memory loss and mood changes. Extensive white matter lesions can significantly impair cognitive function, often leading to dementia, she continues.
"The good news is that taking care of your brain health through managing blood pressure, cholesterol and sugar — plus staying physically and mentally active, eating well and not smoking — can help reduce the risk of developing more of these lesions in the cerebral white matter," she says.
Bolstering Brain Health
Many factors — including age, head injuries and genetics — can raise a person's likelihood of developing serious memory issues, and the 2025 study doesn't prove cause and effect. However, the study authors wrote that the findings suggest a daily green tea habit may help bolster brain health and, potentially, reduce dementia risk. This conclusion aligns with previous research including a 2022 review and analysis supporting green tea's cognitive benefits and potential role in dementia prevention.
"Green tea may improve cognitive function in older adults in multiple and diverse ways," Sanders says.
"Green tea may improve cognitive function in older adults in multiple and diverse ways."
Study authors wrote that one reason is that green tea may reduce blood pressure. Hypertension, they wrote, is "the most important risk factor for white matter lesions." That may also help explain why coffee didn't elicit the same effect, they wrote, since coffee and its higher caffeine content can raise blood pressure.
Additionally, researchers said, green tea may boost brain health due to its anti-inflammatory and antioxidant properties. Green tea is rich in catechins, which are antioxidants that help counteract harmful free radicals, says Therese Huston, Ph.D., a Seattle-based cognitive scientist.
"Think of your body like a high-performing automobile. As you're burning fuel, your body produces energy to help you think and move, but it also produces unstable molecules called free radicals," Huston says. "Consider free radicals your body's exhaust fumes. If too many free radicals build up in your brain and body, they begin to damage cells, including brain cells, and that's called oxidative stress…Green tea basically neutralizes these free radicals before they can do brain damage."
Studies have found that older adults who consume more green tea tend to have better memory and focus than those who drink less, and it's believed that antioxidants are responsible.
Previous studies have found that older adults who consume more green tea tend to have better memory and focus than those who drink less, and it's believed that antioxidants are responsible, Huston says.
EGCG and other catechins can also help reduce harmful inflammation in the brain, promote the development of new neurons and support the brain's ability to enhance communication between existing neurons, she continues. Moreover, EGCG seems to help prevent the formation of amyloid beta peptides, which are central to Alzheimer's disease development, she says.
"The compounds in green tea also help keep blood vessels healthy and flexible, ensuring your brain gets enough oxygen and nutrients," she continues. "Better blood flow means better brain function."
Plus, the polyphenols, which are the antioxidant, anti-inflammatory plant compounds in green tea may help the brain synthesize important chemical messengers like serotonin, dopamine and norepinephrine, which are vital for various purposes, including sleep, mood, memory and cognition, she says.
"Finally, green tea contains L-theanine, an amino acid that supports sleep, reduces anxiety and stress, and boosts mental clarity, prompting a state of relaxed alertness that enhances focus and attention," she adds.
As the study authors noted, drinking three or more cups of green tea daily appears to have the best benefits on brain health. Still, you can have too much of a good thing, so moderation is key. According to the Cleveland Clinic, most people can safely enjoy up to eight cups daily or 2 to 4 teaspoons of matcha.
"The key is regular, moderate consumption over time rather than occasional use," Sanders says.
Importantly, green tea supplements – capsules that can be exponentially more potent than the beverage – may cause side effects such as constipation, abdominal discomfort, constipation and increased blood pressure, according to the National Center for Complementary and Integrative Health. It's also crucial to talk to your doctor before taking green tea as a beverage or pill, as it may interfere with certain medications.
Additionally, bear in mind that no substance can counteract the effects of a healthy (or not-so-healthy) lifestyle, says Kathleen Moore, dietitian nutritionist at The Ohio State University Wexner Medical Center in Columbus.
Eating a balanced, nutrient-rich diet, getting regular exercise, reducing stress, prioritizing sleep and getting routine medical checkups are essential for cognitive and overall health.
Moore also recommends choosing freshly brewed, loose-leaf green tea instead of bottled, canned, powdered, or sweetened. Antioxidant potency diminishes with time and processing, and sugar and artificial sweeteners may counteract tea's anti-inflammatory benefits, she explains.
