- Japanese researchers recently evaluated the potential cognitive benefits of matcha green tea (powdered green tea) for older adults.
- Green teas contain antioxidants that can provide health benefits and even prevent some diseases.
- The researchers who conducted the current study wanted to see whether this range of benefits can extend to cognitive benefits.
- While the scientists learned that matcha green tea may help with social cognition and sleep, they did not find a connection between matcha and other cognitive improvements.
Millions of people in the United States live with dementia, and according to the Alzheimer’s Association, this number is only set to grow unless researchers make significant advances in the diagnosis and treatment of this memory-affecting condition.
As dementia cases continue to climb, scientists continue to research ways people can improve their cognitive health.
Researchers in Japan recently turned to matcha green tea to find out whether its properties can provide cognitive benefits.
The study did not quite yield the results the researchers expected since participants who took matcha did not make improvements in memory and other broader cognitive functions. However, older adults with mild cognitive decline who took matcha did show improvement in social cognition and sleep.
The study findings appear in PLOS ONE.
Matcha green tea is high in vitamins and minerals, including vitamins C and E, magnesium, and potassium. Matcha also has bioactive compounds, such as theanine and catechins.
Theanine is an amino acid in different foods and beverages that can help relax the mind. Catechins are polyphenols and can suppress inflammation in the body and prevent cell damage.
The researchers who conducted the current study examined how matcha impacts cognitive functioning by recruiting 99 participants and observing them for 12 months. The participants were aged 60 to 85.
Of the participants, 64 reported subjective cognitive decline, and 35 reported mild cognitive impairment. Participants were randomly assigned to the matcha or placebo group using a computer-generated system, ensuring a balance based on age (74 and older, or younger than 74), and apolipoprotein E (APOE) genotype, which is indicative of dementia risk.
The matcha group took 2 grams of green tea via a capsule daily while the placebo group took a capsule with corn starch.
This method aimed to evenly distribute these characteristics between the groups to minimize differences in dementia risk, especially because the 10-year Alzheimer’s disease risk is higher in people over 74 than those who are younger.
According to the researchers, the matcha capsules contained the following properties:
- 170.8 milligrams (mg) of catechins
- 48.1 mg of theanine
- 66.2 mg of caffeine per daily serving.
The researchers administered cognitive assessments at the beginning, end, and 6 months after the study intervention, including the Montreal Cognitive Assessment-Japanese version (MoCA-J) and Alzheimer’s Disease Cooperative Study Activity of Daily Living (ADCS-MCI-ADL).
They also tested the participants’ neuropsychological status, memory, executive functioning, attention, social acuity, and sleep quality.
Additionally, the researchers conducted neuroimaging at the baseline and end of the study to check the participants’ gray and white matter levels in their brains.
The scientists monitored the participants regularly throughout the 12 months. After the baseline visit, they saw the participants every 3 months until the end of the study intervention to assess their cognitive functioning levels.
The researchers noted having a high adherence rate in both the placebo and test groups. They said the participants in the test group had a higher blood level of theanine, which did not occur in the placebo group.
While the scientists expected the participants in the test group to show improvement in broader cognitive functioning by the end of the study, the test group did not show improvement compared to the placebo group.
Even when considering the neuroimaging, the participants taking matcha did not show improvements.
While the test group did not experience significant benefits where memory or executive functioning was concerned, the scientists did note improvements in sleep and social acuity in the test group.
The results showed that the matcha group had significantly improved social acuity in the neurocognitive domain scores and showed a trend toward improved sleep quality after 12 months, although other cognitive functions did not show significant changes compared to the placebo group.
Getting a good night’s sleep is important especially for older adults to stay physically and mentally healthy. The scientists think the theanine in matcha contributed to improved sleep quality.
Since poor sleep is connected with increasing the risk of developing dementia and can negatively impact memory, the study results may be beneficial for people concerned about their sleep quality.
The researchers found the improvements in social acuity scores in the test group promising. Participants in this group showed improvements in recognizing facial expressions and understanding word meanings.
Not only is poor social communication an early indicator of dementia, but the social difficulties caused by dementia can be especially stressful. The improvement in social acuity needs to be further explored so providers can determine whether matcha is something to focus on in a clinical setting.
Ralph Waldo, MD, an integrative medicine practitioner with HolistiqMD based in Indiana, spoke with Medical News Today about the study. Waldo was not involved in the research.
“As a physician focused on root cause medicine, I have found matcha green tea intriguing for supporting cognitive health,” said Waldo. “The high theanine content is likely key for the sleep benefits seen in this study. Theanine reduces anxiety and stress, allowing for deeper sleep — essential for memory and focus, especially as we age.”
Waldo also discussed how the catechins in matcha green tea may have improved the test group’s social acuity.
“The catechins in matcha may protect social cognition specifically by decreasing inflammation in the brain and stimulating new neural connections,” he explained. “Matcha appears to target specific cognitive domains, as broader cognitive tests showed no change.”
Waldo did note, however that more studies are needed to explore exactly how matcha benefits people.
“More sensitive neuropsychological testing and biomarker analyses are needed to confirm matcha’s precise effects before recommending it as an intervention for mild cognitive impairment,” he emphasized.
Clifford Segil, DO, a neurologist at Providence Saint John’s Health Center in Santa Monica, CA, also spoke with MNT about the study. Segil was also not involved in the research.
Segil noted that while matcha might not have a future as a standalone dietary intervention for dementia, he is curious to learn more about how matcha impacts sleep.
“This study noted matcha improved sleep quality, and I would be interested to focus on the time of day matcha green tea drinks were consumed, as I would be concerned if they were imbibed in the late afternoon or early evening its effect on sleep may be very different than if it was consumed in the morning,” said Segil.
“Theanine has not been shown to be a sleep aid, and my hypothesis would be that if this activating compound was taken early in the day, there could be rebound sleep at night like having coffee in the morning helps people wake up, be busy, and then sleep well at night.”
— Clifford Segil, DO
He said people should continue to enjoy matcha drinks but focus on the effects it may have on mood.
“Matcha green tea should be enjoyed but should not be consumed with any expectations that its health benefits include the prevention of dementia in the preclinical stages,” Segil noted.
