The trial, which also measured the effects of matcha green tea on cognitive functions, reported no significant improvements post-supplementation.
Findings of the study were recently published in Plos One.
A total of 99 Japanese seniors aged 60 to 85 years old took part in the 12-month trial.
These seniors have either subjective cognitive decline, meaning self-reported confusion or memory problems that have worsened in the past 12 months, or mild cognitive impairment, which is the early stage of memory loss or cognitive ability loss.
During the study, they were randomised to take nine capsules of placebo or matcha green tea. The nine capsules were equivalent to two grams of matcha green tea powder.
Two grams of matcha green tea was given for the intervention group as this is the amount consumed in the traditional Japanese tea ceremony Tea Otemae.
Each daily serve of matcha contains 170.8 mg of catechin, 48.1 mg of theanine, and 66.2 mg of caffeine. These are components which have been shown in existing studies to support sleep and cognitive function.
There are also a variety of catechins present in the matcha green tea given.
This includes 105.3 mg of EGCG, 1.5 mg of gallocatechin gallate, 20.3 mg of epicatechin gallate, 0.1 mg of catechin gallate, 33.1 mg of epigallocatechin, 1.6 mg of gallocatechin, 8.1 mg of epicatechin, and 0.8 mg of catechin.
Japanese beverage company ITO EN provided the trial materials.
The seniors’ sleep quality was assessed using the Pittsburg Sleep Quality Index (PSQI) scores, with lower score indicating better sleep quality.
Changes in their cognitive function were also assessed the questionnaires Montreal Cognitive Assessment-Japanese version (MoCA-J) and Alzheimer’s Disease Cooperative Study Activity of Daily Living (ADCS-MCI-ADL).
Findings showed that matcha consumption has improved sleep quality by the end of the trial, based on the lower PSQI scores in the intervention group.
The PSQI scores between the two groups differed by 0.86. However, the difference was not statistically significant.
Still, the researchers said that the difference showed that matcha consumption showed “a trend towards improved sleep.”
“The PSQI total score indicated a trend toward improved sleep with matcha consumption. Despite the presence of caffeine, which disrupts sleep, matcha demonstrated a sleep-enhancing effect.
“This beneficial effect is attributed to theanine, a constituent of matcha…As the change in the total score in the matcha group compared with that in the placebo group showed a decreasing trend (P = 0.073), theanine was suggested to improve sleep quality,” said the researchers.
In this case, the intervention group has indeed seen a significant increase in theanine levels due to their matcha consumption, and this was not observed in the placebo group.
Citing a 2019 study, the researchers added that consuming 200mg of theanine per day for four weeks has shown to significantly reduce PSQI score – indicating improvements in sleep quality.
In the present study, the intervention group’s daily intake of matcha green tea consists of 48.1 mg of theanine.
Significant improvements in social acuity
The study also reported significant improvements in a subset of cognitive function – in this case, social acuity – in the intervention group.
Social acuity refers to the ability and inclination to perceive the psychological state of others, such as identifying certain facial expressions, and act accordingly.
It is also an area examined to assess vital signs of the central nervous system (CNS).
“In the present study, a significant enhancement in social cognition was observed following matcha consumption. Social cognition is related to the perception of emotions, one of the tests of CNS vital signs, and the incidence of false responses was reduced by matcha consumption,” said the researchers.
False responses, in this case, refer to inaccurate responses to facial expressions and words descriptions administered during the test.
“A decrease in false response scores suggests that participants were more proficient in recognising facial expressions and descriptions following 12-month matcha consumption,” said the researchers, adding that the examination of social acuity could be a suitable test for early stages of cognitive decline.
However, no significant improvements were seen in other subsets of cognitive function, such as executive function and visuospatial function.
The researchers explained that this could be due to the types of tests used for this study, namely Montreal Cognitive Assessment and Alzheimer’s Disease Cooperative Study Activity of Daily Living scores.
“Matcha intervention had no effect on the primary outcomes…possibly due to their (the tests’) sensitivity to slight declines in cognitive function.
“These tests are typically used during clinical diagnoses of cognitive impairment rather than for evaluating early-stage cognitive decline in the disease,” said the researchers.
They concluded that the consumption of matcha could enhance certain cognitive functions, such as facial expression recognition and attention, as well as improving sleep quality.
These, they said, were beneficial for maintaining cognitive function in older adults.
“Matcha consumption may be considered as a lifestyle improvement strategy for dementia prevention,” they concluded.
Source: Plos One
Effect of matcha green tea on cognitive functions and sleep quality in older adults with cognitive decline: A randomized controlled study over 12 months
https://doi.org/10.1371/journal.pone.0309287
Authors: Kazuhiko Uchida et al
