New Perspectives on Sleep Regulation by Tea: Harmonizing Pathological Sleep and Energy Balance under Stress

Uncovering the effects and mechanisms of tea and its components on depression, anxiety, and sleep disorders: A comprehensive review

Depression, anxiety and sleep disorders are prevalent psychiatric conditions worldwide, significantly impacting the physical and mental well-being of individuals. The treatment of these conditions poses various challenges, including limited efficacy and potential side effects. Tea, a globally recognized healthful beverage, contains a variety of active compounds. Studies have shown that consuming tea or ingesting its certain active ingredients have a beneficial impact on the mental health issues mentioned above. While the effects of tea on physical health are well-documented, there remains a gap in our systematic understanding of its impact on mental health. This article offers a thorough overview of animal, clinical, and epidemiological studies examining tea and its components in the treatment of depression, anxiety, and sleep disorders, and summarizes the associated molecular mechanisms. The active ingredients in tea, including L-theanine, γ-aminobutyric acid (GABA), arginine, catechins, theaflavins, caffeine, theacrine, and several volatile compounds, may help improve depression, anxiety, and sleep disorders. The underlying molecular mechanisms involve the regulation of neurotransmitters, including monoamines, GABA, and brain-derived neurotrophic factor (BDNF), as well as the suppression of oxidative stress and inflammation. Additionally, these ingredients may influence the microbiota-gut-brain (MGB) axis and the hypothalamic-pituitary-adrenal (HPA) axis. This review provides valuable insights into the effects and mechanisms by which tea and its components regulate depression, anxiety, and sleep disorders, laying the groundwork for further research into relevant mechanisms and the development of tea-based mental health products.

Associations between tea-drinking habits and health-related quality of life in Chinese adults: a mediation analysis based on sleep quality

BACKGROUND

The aim of this study was to explore the association between tea-drinking habits and health-related quality of life (HRQoL) in Chinese adults and the mediating effect of sleep quality in this association.

METHODS

Data were derived from the 2020 Survey of Social Factors for Chronic Disease Prevention and Control among adults in Lishui District, Nanjing, Jiangsu Province, China. Tea-drinking habits were measured by participants' self-report. The HRQoL was measured using the 12-item Short Form Health Survey. Multiple linear regression modelling and mediating effects modelling were used for analyses.

RESULTS

Habitual tea drinking, frequent tea drinking (drinking tea 6-7 days per week), tea concentration and <10 g of tea per day were strongly associated with an increase in HRQoL among Chinese adults (all p<0.05). The association between tea-drinking habits and HRQoL among Chinese adults was more pronounced in the male population and in those ≥45 y of age (all p<0.05). Tea drinking habits may improve HRQoL in Chinese adults by enhancing sleep quality (all p<0.05).

CONCLUSIONS

Maintaining the habit of habitual tea drinking (6-7 days per week), in small amounts (<10 g tea per day) was conducive to improving HRQoL of Chinese adults by improving sleep quality.

L-Theanine Prolongs the Lifespan by Activating Multiple Molecular Pathways in Ultraviolet C-Exposed Caenorhabditis elegans

L-theanine, a unique non-protein amino acid, is an important bioactive component of green tea. Previous studies have shown that L-theanine has many potent health benefits, such as anti-anxiety effects, regulation of the immune response, relaxing neural tension, and reducing oxidative damage. However, little is known concerning whether L-theanine can improve the clearance of mitochondrial DNA (mtDNA) damage in organisms. Here, we reported that L-theanine treatment increased ATP production and improved mitochondrial morphology to extend the lifespan of UVC-exposed nematodes. Mechanistic investigations showed that L-theanine treatment enhanced the removal of mtDNA damage and extended lifespan by activating autophagy, mitophagy, mitochondrial dynamics, and mitochondrial unfolded protein response (UPRmt) in UVC-exposed nematodes. In addition, L-theanine treatment also upregulated the expression of genes related to mitochondrial energy metabolism in UVC-exposed nematodes. Our study provides a theoretical basis for the possibility that tea drinking may prevent mitochondrial-related diseases.

Does frequent tea consumption provide any benefit to cognitive function in older adults? Evidence from a national survey from China in 2018

Objectives

This present study aims to investigate the effect of tea consumption on cognitive function and examine possible psychosocial mechanisms in older adults.

Participants and methods

The data of this study came from the 2018 wave of the Chinese Longitudinal Healthy Longevity Survey(CLHLS), and a total of 11,910 valid samples were included. We used ordinary least squares (OLS) to explore whether frequent tea consumption had significant effect on the cognitive function of older people. The problem of endogeneity was addressed by using a propensity score matching (PSM). Then we further explored the psychosocial mechanisms of the effect using a stepwise regression approach.

Results

Frequent tea consumption produced a positive effect on Mini-Mental State Examination (MMSE) score (coefficient = 0.340, p < 0.01), and PSM showed similar results. Specifically, the positive effect of green tea (coefficient 0.409, p < 0.01) was significantly greater than the other teas (coefficient 0.261, p < 0.1). Moreover, frequent tea drinkers were 59.7, 74.8, and 81.8% less likely to have severe, moderate and mild cognitive impairment respectively, compared to infrequent tea drinkers (p < 0.01). Levels of depression and sleep quality had partial mediation effect for frequent tea consumption on cognitive function, accounting for 27.6 and 3.5% of the total effect, respectively.

Conclusion

Frequent tea consumption was found to have beneficial effects on cognitive function, especially in older people with green tea intake. Sleep quality and levels of depression partially mediated the association between frequent tea consumption and cognitive function among Chinese older adults.