Dementia is the second leading cause of death over 70 and Alzheimer’s disease (AD), the leading cause of dementia, progresses gradually through mild cognitive impairment (MCI).
Green tea has previously been reported to have some positive effects on mental health such as reduction of anxiety thanks largely to its high amounts of tea theanine, polyphenols and fat-soluble nutrients. Matcha green tea is believed to contain even higher amounts of these beneficial compounds due to the special harvesting and processing.
The aim of the current study was to investigate the effects of Matcha green tea extract on cognitive memory function and impulsivity in clinically normal elderly people. The research team, from Japan, conducted a randomised, double-blind, placebo-controlled 12 week trial using a psychometric test battery, and they investigated the difference in effect by gender.
The results suggest that daily supplementation of Matcha green tea powder may have a beneficial effect against cognitive decline in elderly women, but not men.
The report concludes: "Though we could not know for sure which is the most fundamental bioactive compound in Matcha green tea powder that enhances cognition, hydrophobic compounds such as vitamin K may be considered a possible candidate. We shall investigate the independent activities of each compound and underlying mechanisms in future studies."
This is the first report to investigate the effects of daily Matcha green tea powder supplementation on cognitive and memory functions and impulsivity in clinically normal elderly individuals.
Of the 54 subjects, there were 15 men and 39 women, and the age was between 60 to 84 (Average: 73.6). Participants first underwent a cognitive psychological function test at the beginning of the trial, followed by a second cognitive psychological function test after 12 weeks of green tea extract consumption.
Each subject received a green tea powder drink serving as 15g powder containing 1.5 g Matcha new green tea powder (Yabukita) with non-dairy creamer and low calorie sweetener, or placebo black tea flavoured powder, twice a day for 12 weeks.
All participants completed the Brief-type Self-administered Diet History Questionnaire (BDHQ) combined with a short Food Frequency Questionnaire (FFQ) for total polyphenol intake.
All participants underwent a Cognitive and Memory Function Test, an Assessment of Impulsivity and an Assessment of Dietary Habits.
Improvement in cognitive function was seen in female subjects, shown in the difference in Montreal Cognitive Assessment (MoCA) score changes from the start-up to follow-up between groups (p = 0.0103; +1.95 in the active group and +0.15 in the placebo). Especially in the language domain of the MoCA score, a noteworthy gain was seen in female subjects.
The data showed no improvement in male participants. This female-specific result is consistent with previous studies showing that large-dose supplementation of decaffeinated green tea extract enhances working memory capacity of healthy elderly women.
The report states: "Based on these findings, we concluded that the cognitive protective effect of matcha powder was detected by MoCA, which is a more sensitive cognitive function test, only in elderly women, who have greater resilience to age related cognitive decline, especially in the language domain, which is a cognitive function showing large gender differences.
"However, in this study, the number of male subjects was much smaller than that of female subjects, and only 15 male subjects were used in the analysis in total. This may be the reason why no positive effect of matcha was observed on the cognitive function of male subjects. Further studies with appropriate sample sizes of male subjects would help to understand the gender-specific effect of matcha on cognitive function of elderly people."
The authors note limitations to the study being the small sample size and concern about language translation in the impulsivity assessment test.
The anti-inflammatory and strong antioxidant properties of epigallocatechin gallate (EGCG), one of the most abundant catechins inside green tea extract, are widely known, and it is also suggested that it ameliorates cognitive defects. L-theanine, the main amino acid in tea, is also said to ease the symptoms of cognitive impairment and assisted in the hippocampal long-term potentiation of Alzheimer’s disease in mice.
Its role in anxiety and stress relief and improving sleep quality is commonly known, and it has been suggested to possess the ability to prevent stress-induced brain atrophy by modifying early stress responses. Caffeine, which is abundant in tea, strengthens the effect of theanine on the enhancement of neurophysiological performance, such as attention. As for fat-soluble nutrients, the role of vitamin K and lutein has been well noted.
Vitamin K, while it is more commonly known for its important role in blood coagulation, also acts as an essential nutrient in the central nervous system (CNS). Previous evidence has also shown that higher serum phylloquinone status in elderly people has been associated with better performance in verbal episodic memory, and higher dietary intake of vitamin K was also linked with less severe subjective memory complaints among older adults.
On the other hand, being a kind of carotenoid, lutein comprises not only the ability to reduce the risk of some chronic health disorders, but is also believed to aid in cognitive function, and is associated with word recall ability among older adults.
Gender difference in the clinical phenotype and progression of AD have been documented previously. According to statistical analysis, women in the age range of 65–75 may have a higher increased risk of AD than men. Mechanisms that underlie the gender difference may be associated with physiological changes that accompany oestrogen loss and menopause.
On the other hand, it was reported that elderly women have a greater resilience to age-related cognitive decline compared with their male counterparts. Besides, older women are known to have better reasoning and verbal abilities than older men and to perform better on verbal memory tests.
Hisatsune. T., et al
"Effects of Matcha Green Tea Powder on Cognitive Functions of Community-Dwelling Elderly Individuals"