Abstract

Tea is popular global beverage and abundant provider of biologically active plant molecules which have been attributed to its health properties. Relationships between tea drinking and certain aspects of health have been the subject of past reviews. The present systematic review focuses on tea consumption in relation to psychological stress and the challenges of stress and anxiety on sleep health. Publications were searched up to 21^st September 2022, in the PubMed database along with references of original articles. Thirty-three publications were included in the main review-17 human trials and 16 mechanistic studies. Human trials were graded to assess quality using the Jadad scale. Overall, a growing body of evidence suggests that tea (including green and oolong) and herbal infusions, at relatively low intakes (around 1 to 2 cups daily), could help to facilitate sleep, alleviate psychological stress and anxiety, primarily by facilitating relaxation. Evidence for black tea, German Chamomile, Lavender, Rose, Jasmine, and Passionflower tea is emerging and looks promising. Ongoing research is needed in the form of randomised controlled trials to build on these provisional findings.

Keywords

Anxiety; Black tea; Gamma-Aminobutyric Acid (GABA); Green tea; Herbal infusions; Herbal teas; L-Theanine; Polyphenols; Sleep

Introduction

Stress has been defined as a state of homeostasis with inadequate stress (sustress) and heightened stress (distress) potentially impairing normal physiological functions and eustress (the homeostatic state between sustress and distress) being most favorable [1]. Anxiety relates to the mind and body’s anticipation of stressful, unfamiliar or dangerous situations which in extreme instances can become debilitating e.g. in the case of anxiety disorders which include: general anxiety disorders, obsessive-compulsive and related disorders and trauma-and stressor-related disorders [2]. Both stress and anxiety can affect sleep, a concept known as ‘sleep reactivity’ [3]. This is the level to which stress disturbs sleep, resulting in challenges in falling and staying asleep [3]. Increased anxiety levels have been identified as a consequence of sleep deprivation, with a meta-analysis of 18 publications (compiled of 34 experiments) confirming that sleep deprivation results in a heightened state of anxiety [4]. In the corona virus pandemic negative changes in sleep have been linked to increased stress and anxiety symptoms [5].

The term ‘sleep health’ is used infrequently compared with other terms such as ‘bone’ or ‘brain’ health [6]. Yet good sleep is central to good health [7,8]. Sleep health is a multidimensional concept with five main dimensions appearing to be most relevant (Figure 1) [6]. Given this, sleep health has been defined as “A multidimensional pattern of sleep-wakefulness, adapted to individual, social, and environmental demands, that promotes physical and mental well-being. Good sleep health is characterized by subjective satisfaction, appropriate timing, adequate duration, high sleep efficiency, and sustained alertness during waking hours” [6]. This definition was devised for adults but can be adapted to other populations such as adolescents and children [6].

Figure 1: Five Dimensions Most Relevant to Definitions and Measurements of Sleep Health.

The American Academy of Sleep Medicine and the Sleep Research Society both recommend that most adults should sleep between 7-9 hours nightly to promote health [9]. Sleep durations of 9 hours or more may be more appropriate for young adults, those with sleep debt or medical illnesses [9]. The National Sleep Foundation similarly recommends that young adults and adults should aim for 7 to 9 hours sleep [10]. A meta-analysis of 1.1 million people from the United Kingdom, Netherlands and United States concluded that 1 in 4 people had less sleep than age-specific benchmarks. Women 41-years or older had shorter sleep and poorer sleep efficiencies (the ratio between the time a person spends asleep and total time dedicated to sleep) than men of the same age. Half (51.5%) of the included teenagers reported total sleep times below the advised 8 to 10 hours a night [11]. Another assessment of 80,000 mid-life adults living in the United Kingdom found that one-third slept for around 6-7 hours a night whilst high coffee intake, social deprivation and older age were associated with shorter sleep durations (i.e. less than 6 hours nightly) [12]. Sleep duration has also been correlated with certain biological biomarkers, with levels of C-reactive protein (an inflammatory biomarker) and gamma glutamyl transferase (a liver function biomarker) found to be 14% higher in those having <6 hours compared to 7-8 hours of sleep a night [13].

The ramifications of sleep loss are far reaching [9,14]. Sleeping for less than 7 hours nightly has been linked to increased risk of developing diabetes, weight gain, obesity, heart disease, hypertension, stroke, depression, impaired immune function, impeded performance, increased errors, exacerbated risk of accidents and all-cause mortality [9]. Sleep loss can impair cognitive and task performance, attention and memory, heighten fatigue, and impede decision-making [15,16]. Sleep disturbances and depression share an intricate and bidirectional relationship [17]. Moreover, a recent meta-analysis of 65 trials consisting of 72 interventions and a sample size of 8608 adults identified a dose response relationship between greater improvements in sleep quality in relation to better mental health [18]. An umbrella review also found that a 1-hour daily reduction in sleep duration (per 24-hours) was associated with an 3 to 11% increased risk of all-cause mortality and risk of stroke, coronary heart disease, type two diabetes mellitus and osteoporosis [19]. Poor sleep can also affect the regulation of hormones (those influencing metabolism and hunger) involved in appetite and weight regulation thus predisposing an individual towards obesity [20]. Habitual sleeping patterns <7 hours nightly have been further linked to increased respiratory tract infection susceptibility [21,22].

The natural cycle of life revolves around: 1) awakening, 2) eating and drinking, 3) surviving and 4) returning to sleep [23]. Focusing on drinking habits, it should be recognised that amongst adults tea drinking patterns in relation to the frequency, form and amount of tea can vary [24]. European data from the EPIC (European Prospective Investigation into Cancer and Nutrition) study has shown that patterns of tea intake range from 14 g/Day (0.1 cups) in Navarra (Spain) and were up to 788 g/day (around 4.3 cups) in the UK population and similar patterns were also observed by men [25].

Herbal infusions are increasingly being recognised as being a therapeutic vehicle delivering benefits in certain aspects of clinical and preventative health [26]. There are around 3 billion people who enjoy drinking tea and infusions globally with this seen as an inexpensive complementary alternative medicine [27]. It has been previously reported that tea and herbal infusions are a valuable source of flavonoids and other polyphenols and that ingestion (around 1 to 3 cups daily) could potentially benefit certain aspects of health [28]. In particular, L-theanine, an amino acid naturally found in green and black tea (Camellia sinensis) is thought to help attenuate the negative effects of psychological stress and anxiety on health [29]. The present systematic review focuses on tea (including green and oolong tea) and herbal in fusions and how their ingestion could specifically impact on stress, anxiety, and dimensions of sleep health.

Materials and Methods

Search strategy & study selection

The National Library of Medicine, National Center for Biotechnology Information PubMed.gov data base was used to filter, screen, and identify relevant publications. In Phase 1publications were restricted to: (1) articles with an English abstract (2) Randomized Controlled Trials (RCTs) (3) clinical trials and (4) publications using tea infusions only.

In Phase 1 the search terms ‘tea and sleep*’, ‘tea and anxiety’ and ‘tea and psychological stress’ were applied. The asterisk (*) was applied to capture studies using extensions of the word ‘sleep’ such as sleeping. No time restrictions were applied. The term ‘psychological stress’ was used as studies relating to ‘oxidative stress’ were deemed irrelevant. Observational studies were excluded from the present review as causeand-effect relationships are more difficult to decipher from these studies [22]. A PICO model formed the basis of the search strategy [30]. The Population (P) was defined as young people and adults which included older adults and pregnant/postpartum mothers. The Intervention (I) that was considered was tea and herbal infusions. The Comparison (C) was a defined control or placebo group, and the Outcomes of interest (O) were sleep, anxiety and psychological stress.

Phase 1 followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and 2020 Checklist [15]. Publications using tea capsules, tablets, supplements, multiplecomponent teas, multi-interventions e.g., tea and supplements, extracts, or oils were excluded. Reference lists were also searched for further relevant publications. ED and TB identified and screened the articles which were compared against the inclusion/exclusion criteria. Any disagreements were to be outlined to JE to make a decision, no disputes were apparent.

Similar terms were applied in Phase 2. No time restrictions were applied. The filter was restricted to only include results from animal studies using the category ‘other animals’ to identify mechanistic studies. After reviewing and identifying relevant publications, suitable trials had data extrapolated including: Study (author, year, location), subjects, study design, tea intervention (type), tea intervention (dosage), the sleep dimensions studied, main findings and Jadad quality score. The algorithm used to select studies is displayed in Figure 2.

Figure 2: PRISMA Algorithm used to Identify Trials.

To determine quality scores for each human trial, the Jadad criterion was applied with scores of 1–5 being allocated (5 indicated that trials were of a higher quality) [16]. This included analyzing whether randomization, methods of randomization, blinding, methods of blinding and reporting of withdrawal and dropout were appropriate and described adequately in the studies identified [16].

Results

For Phase 1, 65 results were obtained and 28 RCTs and clinical trials identified for screening. A further 11 publications were identified from reference lists. Subsequently, 39 publications were screened and 22 excluded due to these being off topic or irrelevant (n=12), using interventions that were not a tea infusion (n=6), applying multiinterventions (n=2) or being a pilot or feasibility study (n=2) leaving 17 publications which were included in the review. The algorithm of qualifying publications is shown in figure 2.

In Phase 2 the search yielded 139 publications after restricting the search to ‘other animals’. Of these 43 were deemed relevant for further screening. A further 10 publications were identified from reference lists. After excluding studies that were irrelevant, did not use tea infusion/components, were review papers or not a mechanistic study 16 publications were identified for the main review.

Human trials

Psychological stress and anxiety: Seven key human trials were identified investigating links between tea ingestion and markers of psychological stress and anxiety which affect sleep and sleep patterns (Table 1). Of these two focused on green tea [31,32] whilst others studied the role (s) of lavender tea [33], rose tea [34] or black/instant tea aroma forms [35-37]. The studies showed that the various tea forms help to lower markers of stress and anxiety and aid relaxation. For example, amongst elderly adults’ lavender tea ingestion (twice daily) resulted in lower anxiety and depression levels in the tea compared with the control group [33]. Similarly, for rose tea, 2 tea cups ingested daily, each approximately 300 mL resulted in lower perceived levels of anxiety and improved psycho physiological well being [34].

Table 1: Phase 1: Tea Infusions, Psychological Stress, Anxiety and Sleep Health: Evidence from Human Trials.
Key: DB, Double-Blind; LCGT, Low-Caffeine Green Tea; LTW-Long-Term Caffeine Withdrawal; ONW-Overnight Caffeine Withdrawal; PC-Placebo Controlled; sAAm: Salivary Α-Amylase Activity; SGT-Standard Green Tea. Slow wave sleep is also known as N3 sleep or delta sleep.

For green tea, amongst a population of younger adults (mean age 23 years) 500 mL matcha green tea (around 2 cups) was associated with significantly lower anxiety levels determined using the statetrait anxiety inventory [31]. Yoto, et al. (2014) found that salivary chromogranin A levels increased after mental stress load tasks and green tea ingestion inhibited this [32]. Samant, et al. (2016) found that tea consumption appeared to induce a state of calmness particularly that sweetened with nutritive sweetener [36]. Similarly, earlier work by Steptoe and colleagues (2007) showed that 6-weeks of tea consumption could aid stress recovery [37]. Other research work showed that the inhalation of black tea could reduce stress following mental arithmetic tasks (sometimes referred to as math’s anxiety) [35]. These findings suggest that tea (in an array of forms) may attenuate feelings of anxiety and stress. Replications of such studies are now needed.

Sleep health: A growing number of human trials have investigated the role of tea and herbal infusions in relation to the various dimensions of sleep health. Ten human trials were identified and synthesized in the present review (Table 1). Of these, two focused on oolong tea [38,39], two reported on green tea, including standard and low-caffeine green tea [40,41], two studied regular or black tea [42,43] and the others investigated Chamomile (German) tea [44], lavender tea [45], passionflower tea [46] or a combination of three different herbal teas [47].

Several different methodologies were adopted to evaluate dimensions of sleep health. This included the use of Electroencephalograph (EEG) in two trials [40,41], polysomnography [39], an actiwatch [38], validated sleep quality questionnaires or scales [43-45,47] and sleep diaries [46]. One study investigated the effects of decaffeinated or regular tea ingestion on participants that were sleep deprived [42]. Regarding study quality, the 10 human trials identified were of average or good quality, rating 3 or more on the Jadad quality index (Table 2), though it should be noted that methods of randomization and blinding were not always reported. It can, however, be difficult to ‘blind’ beverage trials, so most studies used regular drinking habits as a control or disseminated beverages in containers where the drink was not visible e.g., using covered metal containers.

Study (Author, Year, Reference Number)	Tea Intervention (type)	Main findings
Forouzanfar, et al. [63]	Green tea	Green tea and its EGCG appeared to prevent memory impairments during 6 h of total sleep deprivation.
Zhang, et al. [53]	L-theanine and Neumentix mixture	The L-THE/PSE mixture regulated sleep disorders by the GABA receptor and neurotransmitter systems.
Zhang, et al. [65]	Jasmine tea	Jasmine tea could attenuate mild stress/depression in rats via the brain- gut-microbiome axis.
Chaves, et al. [66]	Chamomile tea	4-O-methyl-glucuronoxylan in chamomile tea may contribute to the calming effects obtained by chamomile tea ingestion.
Yang, et al. [54]	Tea polyphenols	Increased TNFα in tea polyphenols ameliorated memory impairment caused by sleep deprivation
Kim, et al. [56]	GABA/l-theanine mixture	The mixture had a positive synergistic effect on sleep duration & quality. Increased GABA receptor & GluN1 expression was attributed to the neuromodulatory properties affecting sleep behaviour.
Unno, et al. [31]	Matcha green tea	High levels of theanine and arginine in matcha exhibited a high stress-reducing effect. This outcome was only possible when the molar ratio of caffeine and epigallocatechin gallate to theanine and arginine was less than two.
Ikram, et al. [59]	Green tea	The beneficial effects of green tea and coping with stressful conditions/stimuli are related to altered 5-Hydroxy tryptamine metabolism.
Unno, et al. [61]	Green tea	Drinking green tea resulted in anti-stress effects, where theanine, EGCG and Arg appear to induce effects.
Ferlemi, et al. [74]	Rosemary tea	Rosemary tea administration exerts anxiolytic and antidepressant effects on mice potentially by inhibiting liver cholinesterase activity.
Zhao, et al. [57]	GABA black tea	GABA black tea improved the sleeping quality (sleep time and sleep rate) of mice.
Mirza, et al. [61]	Green tea	Beneficial effects of green tea drinking may be due to alterations in serotonin and/or dopamine metabolism.
Burckhardt, et al. [55]	Green tea catechin polyphenols	Green tea–derived polyphenols reduced the neural susceptibility to intermittent hypoxia during sleep in rodents.
Adachi, et al. [62]	Epigallocatechin gallate	EGCG had sedative and hypnotic effects in the brain, partially through GABA receptors.
Vignes, et al. [64]	Epigallocatechin gallate	EGCG may induce anxiolytic activity which could result from an interaction with GABA(A) receptors.
Hossain, et al. [58]	Oolong tea	Fragrant compounds may be absorbed by the brain potentiating the GABA receptor response having a tranquillizing effect on the brain.

Table 2: Phase 2: Tea Infusions, Psychological Stress, Anxiety and Sleep Health: Evidence from Mechanistic Studies.
Key: Arg, arginine; EGCG (-)-Epigallocatechin gallate; GABA, gamma (γ)-aminobutyric acid; L-THE, L-theanine; PSE-Neumentix proprietary spearmint extract; TNF-tumour necrosis factor.

Overall, the identified studies concluded that drinking tea and herbal infusions had beneficial or neutral effects on dimensions of sleep [38-41,43,44,46,47]. Focusing on oolong tea, research with nonobese males demonstrated that oolong tea (two 350 mL/day servings) increased fat oxidation by around 20% without impacting on sleep [39]. A trial conducted with children diagnosed with autism spectrum conditions showed that GABA delivery (in the form of oolong tea) could benefit anxiety levels and sensorimotor abilities, thus relaxing children which could aid sleep. [38].

Two studies undertaken by the same research team focused on green tea [40,41]. A double-blind crossover study with a sample of middleaged adults (51.3 ± 6.7 years) found that sleep quality (included light sleep, slow wave sleep and onset of sleep) determined using EEG was improved and higher amongst participants ingesting larger amounts of low-caffeine green tea (≈300 ml daily eluted with water) [40]. Another study with older participants (89.3 ± 4.2 years) ingesting five cups of standard or low-caffeine green tea daily showed that low-caffeine green tea could aid sleep quality (included light sleep, slow-wave sleep, sleep onset and total sleep time), potentially by modifying stress as levels of Salivary α-amylase activity (sAA) were reduced and lower sAA correlated with higher sleep quality [41].

A further two studies focused on regular black tea [42,43]. Rogers, et al. (2005) studied the effects of caffeine consumption in sleeprestricted participants [42]. Subjects who were moderate to moderate– high caffeine consumers were provided with: 1) decaffeinated tea and/or coffee for 3 weeks or 2) regular tea and/or coffee for 3 weeks and after overnight caffeine abstinence were evaluated for mood and cognitive performance [42]. It was concluded that cognitive performance was adversely impacted by acute caffeine withdrawal aligning with the ‘withdrawal reversal hypothesis’ [42]. No conclusions were drawn that related specifically to tea [42]. Hindmarch, et al. asked 30 healthy participants to drink either: 1) 1 or 2 cups of tea (37.5 mg or 75 mg caffeine), 2) coffee (75 mg or 150 mg caffeine), or water [43]. Researchers found that day-long tea consumption produced alerting effects similar to coffee but were not as likely to disrupt sleep, measured using the Leeds Sleep Evaluation questionnaire daily and a wrist actigraph [43].

Other publications focused on infusions which included German Chamomile [44], Lavender [45] and Passionflower tea [46]. Two of these conducted research with mothers after they had given birth [44,45]. Chang & Chen (2016) recruited 80 postnatal mothers and allocated 40 of these to drink one cup of German Chamomile tea daily for two weeks [44]. Compared with the control group, the Chamomile group had fewer symptoms related to sleep inefficiency [44]. Authors concluded that Chamomile tea could be a useful aid for sleep quality problems [44]. Using a similar sample population Chen & Chen (2015) similarly found that Lavender tea (aromatic inhalation and consumption) resulted in significantly less fatigue and improved child bonding when one cup was drank daily for 2 week [45]. An Australian study providing young adults (18 to 35 years) with one cup of Passionflower tea daily found that sleep quality was better rated over the 7-day consumption period [46]. Other research using a combination of three different herbal teas in an infusion (Astragali Radix, Angelicaegigantis Radix, and Zizyphi Fructus) showed that when this was consumed twice daily for 4 weeks sleep quality, determined using the Pittsburgh Sleep Quality Index significantly improved [47].

Mechanistic research

Specific components found in tea, including the amino acid L-theanine are thought to aid sleep quality and induce relaxing effects [48]. L-theanine is thought to modulate aspects of human brain function including increasing alpha frequency band activity, and relaxing the mind [49]. Some research has shown that L-theanine can counteract and partially reverse reductions in slow-wave sleep induced by caffeine [50]. Gamma (γ)-aminobutyric acid (GABA) and glutamate neurons located within the brain reticular core regulate cortical activity and behaviour across wake-sleep states [51,52].

Sixteen key mechanistic studies were found investigating links between tea and sleep (Table 2). Zhang, et al. (2021) reports that L-theanine can modulate sleep, potentially by acting on neurotransmitter systems including the brain GABA [53]. Two studies focused on the role (s) of polyphenols [54,55]. Yang and colleagues (2020) concluded that tea polyphenols (active compounds in green tea) reduced tumour necrosis factor alpha (TNF-α) by down regulating TNF-α Converting Enzyme (TACE) level which could potentially ameliorate memory impairment caused by sleep deprivation [54]. Burckhardt and authors (2008) showed that green tea catechin polyphenols reduced oxidative stress which could be linked to sleepdisordered breathing [55].

Two publications focused on the role (s) of GABA [56,57]. The study undertaken by Kim, et al. (2015) demonstrated that the GABA/ L-theanine had positive and synergistic effects on sleep quality and duration [56]. Zhao and researchers (2015) found that GABA black tea improved murine sleeping [57]. One other study focused on oolong tea [58]. It was found that the fragrant compounds present in this tea, once inhaled, improved sleeping duration potentially by inducing a sedating effect [58].

Four studies investigated green tea [31,59-61]. Unno, et al. (2018) studied match a green tea finding that theanine and arginine present in this appeared to induce a stress-lowering effect [31]. An earlier study by the same research team also found similar effects with green tea [60]. Ikram, et al. (2017) concluded that altered 5-hydroxytryptamine metabolism could be one mechanism behind green teas ability to facilitate coping with stressful situations [59]. Mizra, et al. (2013) further concluded that benefits of green tea drinking could be attributed to alterations in serotonin and dopamine metabolism [61]. Regarding epigallocatechin-3-gallate (EGCG-a compound abundantly found in green tea), Adachi, et al. (2006) observed that EGCG induced hypnotic and sedative effects on the brain, potentially by modifying GABA receptors [62]. Other work showed that EGCG, could attenuate memory impairments during 6-h of total sleep deprivation [63]. Similarly, Vignes. et al. (2006) reported that EGCG may induce anxiolytic activity which can be due to interactions with GABA receptors [64].

Other research has studied the role (s) of other tea forms including Jasmine (green tea scented with jasmine flowers) and Chamomile tea [65,66]. Jasmine tea has been proposed to lower stress levels, potentially via the actions of the brain-gut microbiome axis which could potentially also aid sleep [65]. Chaves, et al. (2020) found that chamomile tea had calming effects with this appearing to be induced by 4-0-methyl-glucuronoxylan (a hemicellulosic plant cell wall) present in chamomile tea [66]. These mechanisms also have scope to facilitate sleep. Ongoing research is now needed.

Discussion

Tea and herbal infusions could be beneficial in certain areas of preventative health [26]. Polyphenols are chief active compounds present in teas and include catechins epigallocatechin-3-gallate, epigallocatechin, epicatechin-3-gallate, epicatechin amongst others [67]. Oolong tea (semi-aerated/fermented), a traditional Chinese tea also provides polyphenols including epigallocatechine-3-gallate, higher molecular weight flavonoids, polysaccharides and alkaloids [68,69]. Mechanistic studies show that Gamma (γ)-aminobutyric acid, present in black and oolong tea may exert effects that prolong sleep time [53,57,58]. In Chamomile tea (Matricaria recutita L.) its flower components provide phenols including the flavonoids apigenin, glucosides, patuletin, quercetin and luteolin possessing some antioxidant and antimicrobial properties [70]. Passiflora incarnata (Passion flower tea) is often used in traditional herbal medicine for insomnia in Europe, and in North American has been suggested as a sedative tea [71,72]. The plant has a complex Phytochemistry with only a portion of the pharmacologically active compounds believed to have been identified [71].

The present systematic review shows that a growing number of human trials, including RCTs and mechanistic studies have investigated tea and herbal infusions in relation to dimensions of psychological stress, anxiety, and sleep. As aforementioned good sleep is central to health and wellbeing [7,8]. From the human trials identified, eight (total sample size n=192) concluded that the ingestion of tea infusions improved aspects of sleep [38-41,44-47]. The quality of most studies was ‘average’, as identified using the Jadad scale. There is scope to undertake future studies controlling rigorously for blinding and clearly reporting randomisation methods.

In terms of study populations one study was conducted with children with autism spectrum conditions, suggesting that oolong tea could have relaxing benefits [38]. Two studies were carried out with adult mothers who had recently given birth who were experiencing broken sleep [44,45]. One trial administered oolong tea to obese males, implying benefits for fat oxidation without affecting sleeping patterns [39]. Another recruited the ‘very old’ (mean age 89.3 years) finding that green tea consumption lowered salivary α-amylase activity (a marker of stress) and improved sleep parameters [41]. These findings indicate that tea infusions may potentially benefit sleep health. It would now be useful to build on this research.

Regarding frequency of tea consumption, some studies showed sleep improvements at relatively low levels of ingestion (one to two cups daily) [39,44-47]. Provisional findings suggest that tea infusion consumption could form a promising part of sleep management strategies. Of the herbal infusions, German Chamomile, Lavender, Rose, Jasmine, and Passion flower appear to be most promising as sleep health aids. In research using Lavender tea with sleep-deprived mothers, it was the consumption alongside the ‘inhalation’ of the aroma that was associated with less fatigue [45]. A separate survey of 1,000 adults in the UK (aged 18 to 60 years) reviewed by the Tea Advisory Panel has shown that when drinking tea, 57% of felt relaxed, one in two felt calm and 34% felt ready for their next task [73]. Similarly, 4 in 10 (42%) reported that regular tea drinking helped with stress and anxiety, 23% found that it helped with low mood and 22% reported increased mental alertness [74]. Taken together, these findings suggest that it is the psychological and ‘calming’ effects of tea that could help to aid relaxation.

Conclusions and Future Prospects

In conclusion, good sleep is a central part of good health. Alongside focusing on other aspects of health, the importance of lowering psychological stress, anxiety and promoting good sleep health should additionally be communicated to all. The present review demonstrates that evidence for German Chamomile, Lavender, Rose, Jasmine, and Passionflower tea looks promising. The ingestion of green, oolong and black tea, and the inhalation of their aromas could also potentially help to aid sleep, possibly due to relaxing effects. Tea and herbal infusions can be easily integrated within habitual diets and lifestyles and could be a viable means of aiding relaxation and sleep. Research also can inform consumer choice for particular end points e.g., tea drinking provides similar mental alertness versus coffee consumption but with no impacts on sleep. It should be considered, however, that variability in samples, small sample sizes and use of different sleep measures in studies means that ongoing research is needed to further verify effects.

Funding

The time spent writing this publication was funding provided by the Tea Advisory Panel (www. teaadvisorypanel.com) which is supported by an unrestricted educational grant from the UK TEA & INFUSIONS ASSOCIATION (UKTIA), the trade association for the UK tea industry. UKTIA plays no role in producing the outputs of the panel. Independent panel members include nutritionists, biochemists, dietitians, dentists, and doctors.

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Article Type: REVIEW ARTICLE

Citation: Derbyshire E, Bond T, Ellis J (2023) Tea and Herbal Infusions, Psychological Stress, Anxiety & Sleep Health: A Systematic Review of Human Trials & Mechanistic Studies. Nutr Food Technol Open Access 9(1): dx.doi.org/10.16966/2470-6086.182

Copyright: © 2023 Derbyshire E, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Received date: 01 Dec, 2022

Accepted date: 11 Jan, 2023

Published date: 06 Feb, 2023