Matcha green tea improves sleep and emotional perception in older adults with cognitive decline

A yearlong study of older adults with cognitive decline in Japan found that drinking matcha green tea improved participants’ emotional perception and sleep quality. Cognitive functioning and daily living abilities were not affected. The research was published in PLOS ONE.

Matcha green tea is a finely ground powder made from specially grown and processed green tea leaves. It was originally popular in Japan but is now enjoyed worldwide. Unlike regular green tea, matcha involves consuming the entire tea leaf in powdered form, which significantly increases the intake of nutrients and caffeine. Matcha cultivation is distinctive: the tea bushes are shaded for about 20 to 30 days before harvest to increase chlorophyll levels and boost the production of amino acids, giving matcha its vibrant green color and umami-rich flavor.

When preparing matcha, the powder is whisked with hot water until it forms a frothy beverage, distinguishing it from other teas that are typically steeped. This traditional preparation method is an integral part of Japanese tea ceremonies, emphasizing mindfulness and respect through its ritualistic nature. Nutritionally, matcha is rich in antioxidants, particularly catechins, which are believed to help neutralize harmful free radicals and may contribute to overall health.

Study author Kazuhiko Uchida and his colleagues set out to examine the effects of matcha capsules on cognitive functioning and sleep quality in older individuals with subjective or mild cognitive decline. Matcha capsules are a dietary supplement that contains powdered matcha green tea. These supplements provide a convenient way to consume matcha’s antioxidants and potential health benefits without preparing the traditional drink.

The study included Japanese older adults between 60 and 85 years of age. Participants were recruited from the University of Tsukuba Hospital and the Memory Clinic Toride, both in Japan. To be eligible, participants had to live with a partner who could help manage supplement intake and accompany them to appointments. They also had to have either subjective cognitive decline or mild cognitive impairment, have no serious illnesses in the past five years, and not be diagnosed with dementia or taking dementia treatments.

Subjective cognitive decline refers to when a person perceives a decline in memory or thinking skills, even if standard tests show no measurable impairment. Mild cognitive impairment involves detectable decline on cognitive tests that is greater than expected for age but not severe enough to significantly interfere with daily life. The study included 64 participants with subjective cognitive decline and 35 with mild cognitive impairment.

Participants were randomly assigned to one of two groups. One group took nine capsules of matcha daily—equivalent to 2 grams of matcha, the amount typically consumed in a traditional Japanese tea ceremony. The other group took placebo capsules that looked identical but contained cornstarch. The study was double-blind, meaning neither the participants nor the researchers interacting with them knew which participants were receiving matcha and which were receiving the placebo. This regimen continued for 12 months.

Participants completed a set of neurocognitive tests at the beginning of the study, after 12 months of capsule intake, and again six months after stopping the capsules. They also underwent positron emission tomography at the beginning and end of the 12-month intervention period. Additionally, participants completed assessments of sleep quality and daily functioning.

The results showed that matcha supplementation improved participants’ emotional perception, as measured by tests requiring the identification of facial emotions, and enhanced sleep quality. However, there were no observed improvements in other areas of cognitive functioning or in daily living abilities.

“The present study suggests regular consumption of matcha could improve emotional perception and sleep quality in older adults with mild cognitive decline. Given the widespread availability and cultural acceptance of matcha green tea, incorporating it into the daily routine may offer a simple yet effective strategy for cognitive enhancement and dementia prevention,” the study authors concluded.

The study sheds light on the effects of matcha tea on cognitive functioning of older adults. However, it should be noted that the number of study participants was relatively small and they were selected for mild levels of cognitive decline. Results on larger groups and demographically different groups might differ.

The paper, “Effect of matcha green tea on cognitive functions and sleep quality in older adults with cognitive decline: A randomized controlled study over 12 months,” was authored by Kazuhiko Uchida, Kohji Meno, Tatsumi Korenaga, Shan Liu, Hideaki Suzuki, Yoshitake Baba, Chika Tagata, Yoshiharu Araki, Shuto Tsunemi, Kenta Aso, Shun Inagaki, Sae Nakagawa, Makoto Kobayashi, Tatsuyuki Kakuma, Takashi Asada, Miho Ota, Takanobu Takihara, анд Tetsuaki Arai.