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Green tea (Camellia sinensis) contains a number of bioactive substances that are responsible for its health-promoting effects. Two of the most important active ingredients are: L-Theanine – a unique amino acid – and Epigallocatechin gallate (EGCG) – the most prominent polyphenol in green tea. L-theanine is primarily known for its calming effects on mind and psyche, while EGCG is a potent antioxidant and Anti-inflammatories This applies, as there are diverse signaling pathways modulated in cells.[3]. Both substances have been extensively studied in high-quality trials, sometimes individually, sometimes in combination – often in the form of green tea extracts. In this article, we examine the current state of research, focusing on... clinical trials in humans regarding L-theanine and EGCG. We will discuss possible therapeutic applications one and explain why the Combination of both active ingredients – as is also present in the product presented – could be useful.
L-Theanine – a natural relaxation aid from tea
L-Theanine L-theanine is a non-proteinogenic amino acid found almost exclusively in tea leaves. Although chemically related to the stimulating amino acid glutamate, L-theanine has no stimulating effect, rather On the contrary, it promotes relaxation and mental balance.. Studies suggest that L-theanine increases the concentration of the calming neurotransmitter in the brain. GABA increased and the effect of Glutamate (of an important excitatory neurotransmitter) dampens[4]. This mechanism could explain why tea consumption – despite its caffeine content – is often perceived as “relaxing alertness” is perceived. Many people today use L-theanine as a dietary supplement to reduce stress or improve concentration and sleep without feeling tired.
Research findings: Stress reduction, anxiety relief and sleep quality
A growing number of clinical trials confirms the anxiety-relieving and stress-reducing Effects of L-theanine. In a review article, researchers found that daily doses of 200–400 mg L-Theanine (over several weeks) are safe and measurable anxiety-relieving effects demonstrate – both in acute stress situations and in chronic stress[5]. Participants in such studies report inner peace and less tension when taking L-theanine compared to placebo.These subjective impressions are consistent with physiological measurements: In experiments, L-theanine was able to reduce stress-related increases in pulse and blood pressure and decrease the release of stress hormones.[5].
Also for the Sleep Positive effects appear to emerge. A recent systematic review (Bulman) et al., (2021) analyzed 18 clinical trials with a total of 897 participants who took between 50 mg and 1000 mg of L-theanine daily. Result: In several studies, L-theanine subjectively improved sleep quality.[6]. In particular The time it took to fall asleep was reduced. and the subjects felt less tired during the day (lower Daytime fatigue or daytime dysfunction in standardized questionnaires)[6]. This sleep-promoting effect has frequently been observed in combination with other substances – many of the included studies used combination preparations. Overall, the evidence suggests that L-theanine may make a mild, natural contribution to better sleep, particularly in individuals with mild sleep disturbances or high levels of daily stress.
Effects on cognitive functions and mood
One particularly interesting application of L-theanine is the cognitive performance. Because L-theanine has a relaxing effect without sedating, it can alleviate a condition “relaxed vigilance” Promotes well-being – ideal for learning, working, or meditating. In fact, some studies show that L-theanine Attention and concentration can provide support.A meta-analysis of five randomized, placebo-controlled trials (148 healthy adults) specifically investigated the effect of L-theanine on various cognitive tests.[7]. The results were partly contradictory: In higher doses improved L-theanine in these studies significant performance on complex attention tests – z.B. in tasks where subjects had to react quickly to visual stimuli or process a lot of information simultaneously[8]. In simpler reaction tests (z.B. (simple reaction time to a single stimulus) however showed no difference to placebo[8]. The authors conclude that L-theanine may only specific cognitive domains positively influenced – namely those who deal with Attention control and multisensory processing have to do[8]. However, it seems to offer no advantage for the simplest tasks or general psychomotor speed.
Therapeutic use and safety of L-theanine
Therapists appreciate that L-theanine... relatively quickly works (within ~30–60 minutes after ingestion)[14]) and thereby does not make you tired – unlike many traditional tranquilizers. Initial studies in patients with clinical anxiety disorders or depression also suggest potential benefits as adjuvant (supporting) measure towards[5]. Even in schizophrenia research, L-theanine has been given on a trial basis as an adjunct therapy to alleviate patients' anxiety and sleep problems – with a preliminary positive trend, but this still requires further confirmation.[15].
One major advantage: L-Theanine is considered very safe. The evaluated studies showed that Hardly any side effects The frequency of adverse events was virtually identical to that of placebo. Even higher doses (400–500 mg daily) were well tolerated over several weeks.[16].
EGCG – green health substance for metabolism and cell protection
Epigallocatechin gallate (EGCG) EGCG is the most abundant of the green tea polyphenols and is considered one of the main carriers of the tea's health-promoting properties. Chemically, EGCG belongs to the family of... Catechins, a subgroup of plants Flavonoids. EGCG is found in high-quality green tea. up to 1/3 of the dry mass the leaves[17] – an impressive proportion that illustrates why this molecule receives so much attention. As an antioxidant EGCG can neutralize harmful free radicals and thus oxidative damage It reduces the effects on cells and tissues. Furthermore, EGCG modulates various signaling pathways in our cells: effects on inflammatory mediators, cell metabolism, and even gene regulatory mechanisms have been described.[3]. In the laboratory, EGCG could be z.B. influence the cell cycle of tumor cells, downregulate inflammatory factors such as NF-κB, and inhibit enzymes that viruses need to enter cells.[17][18]. These versatile biological effects This suggests the broad therapeutic potential of green tea catechin.
Current research: Metabolism, weight management and cardiovascular health
EGCG has been particularly intensively researched in the area of Metabolism and weight management. Green tea extracts have been touted for years as a natural aid for weight loss – but what does the evidence say? In fact, several meta-analyses have shown that EGCG-containing supplements have a small but significant effect on body weight. could have.A review study found that preparations containing green tea catechins (usually in combination with some caffeine) led on average to a additional Weight loss of approximately 1–1.5 kg compared to placebo, this resulted in results lasting several weeks to months[19]. A more recent systematic review with meta-analysis (2020) specifically examined the effect of green tea extract on body composition, metabolic hormones and oxidative stress markers in 59 studies.[20][21]. The results underscore the benefits: Green tea or EGCG supplementation led to significant decreases in body weight, body mass index (BMI) and body fat percentage. compared to no supplementation[22]. While the absolute changes were moderate, they were consistent across many studies. Interestingly, the meta-analysis also showed improved oxidative stress parameters:
The value of the harmful lipid oxidation marker MDA (Malondialdehyde) in the blood decreased significantly, while the total antioxidant capacity (TAC) of the blood increased[22]. At the same time, the level of the hormone increased. adiponectin[22] – a fat-tissue-produced hormone known for its anti-inflammatory and insulin-sensitive properties. These effects show that EGCG not only affects weight, but also holistic affects metabolism and the reduction of oxidative stress.
Besides weight, EGCG also has effects on classic Cardiovascular risk factors shown.A meta-analysis of 55 randomized clinical trials (published in 2023) investigated green tea extract regarding its effects on blood lipids, blood pressure, blood sugar, and inflammatory markers.[23]. The results are impressive: Total cholesterol and LDL cholesterolcholesterol (“bad cholesterol”) decreased significantly with green tea supplementation compared to placebo (on average ~−7.6 mg/dL TC and −5.8 mg/dL LDL)[23]. At the same time HDL cholesterol increased (Good) cholesterol increases slightly (+1.8 mg/dL)[24].
Favorable effects were also found in blood sugar levels: Fasting blood glucose decreased slightly (−1.7 mg/dL) and even the long-term blood sugar (HbA1c) decreased statistically significantly by an average of 0.15 percentage points[23]. These changes may seem small at first glance, but – especially in combination – they can have a significant impact. cardiometabolic risk noticeably affecting blood pressure. A slight effect on blood pressure was also observed: in particular the diastolic blood pressure On average, blood pressure was ~0.8 mmHg lower with green tea extract.[25]. The authors emphasize that these results support previous observational studies in which regular tea consumption was associated with lower rates of heart attack and stroke.[28][29].
Other health benefits: brain, neuroprotection and immune system
Besides metabolism and cardiovascular system, the following are increasingly coming into focus: Effects of EGCG on the brain into the research focus. Since EGCG, as a molecule, can cross the blood-brain barrier, scientists are investigating whether it can counteract neurodegenerative processes or improve cognitive functions.In epidemiological studies Evidence was found that people with high tea consumption are less likely to develop dementia in old age or remain mentally fit for longer.[30]. Catechins like EGCG could, thanks to their antioxidant and anti-inflammatory properties Protect nerve cells from damage and reduce deposits (such as β-amyloid in Alzheimer's disease).[31][32]. Clinical studies in this area are still in their early stages, but are already delivering interesting initial results:
For example, a placebo-controlled study from Japan reported that daily consumption of matcha green tea powder (corresponds to approximately 2g of powder daily, rich in EGCG) and Theanine) over 12 weeks mental state and working memory performance improved in older adults with mild cognitive impairment[33]. The participants also slept better and scored better on mood tests, suggesting an overall benefit.
Also worth mentioning is the Cancer prevention and immune system potential of EGCG. In cell culture and animal models, EGCG was able to inhibit the growth of various tumor cells – therefore, it was investigated whether high doses of green tea extract could prevent or delay certain types of cancer in humans. Meta-analyses on cancer prevention are inconsistent so far; some observational studies suggest z.B. suggests a reduced risk of prostate cancer in tea drinkers [35].
In a study with 25 men (with pre-prostate cancer), the daily intake of 800 mg EGCG to the fact that the PSA level (prostate-specific antigen, a tumor marker) significantly slower increase or even decreased compared to the control group[36]. This suggests that EGCG could slow the progression of early prostate changes.Research is also being conducted on other types of tumors – for example, on alleviating side effects: One study found that a topical EGCG solution reduced the Radiation therapy-induced skin inflammation in breast cancer patients, it was able to significantly reduce the risk.[37]. Such findings are promising, but further large studies are needed before EGCG can be definitively recommended in oncology.
Also relevant is the antiviral and immunomodulatory effect of EGCG: Especially during the pandemic, it became known that green tea components can inhibit viruses. Laboratory experiments show, for example, that EGCG binds to virus surfaces and blocks the penetration of influenza or coronaviruses into cells.[38][18]: In a randomized, placebo-controlled study of nurses, the Incidence of influenza infections significant when subjects took capsules daily for 5 months with 378 mg green tea catechins (of which ~270 mg EGCG) + 210 mg L-theanine revenue[39]. The flu infection rate in the treated group was only 4.1% compared to 13.1% in the placebo group.[39] – a drastic decrease of approximately 70%. This result suggests that EGCG and theanine together can strengthen the immune system and protect against colds/flu.
Tolerance and dosage of EGCG
Most clinical studies report that green tea extracts containing EGCG at typical dosages are effective. well tolerated are. Occasionally mild symptoms occur. Gastrointestinal problems Nausea, stomach ache – often occurs when the supplements are taken on an empty stomach. Such effects can be minimized by taking the supplement with a meal. Important to know: In very high doses (typically >800 (mg EGCG per day, which is far above what is in 1-2 cups of tea) some adverse effects have been observed.According to consumer information, a chronic high dose by EGCG z.B. Gastrointestinal irritation and effects on blood clotting cause[40]. Overall, however, the The health benefits of EGCG clearly outweigh the potential risks., as a comprehensive review in 2025 summarizes[2].
Synergies: Why the combination of L-theanine and EGCG makes sense
After considering the individual substances, the question arises: Why combine both active ingredients? – The answer lies partly in the nature of green tea itself and partly in the complementary effects of L-theanine and EGCG:
- Natural example: Green tea A cup of green tea contains L-theanine and EGCG. always together It contains [various ingredients]. Millennia of cultural experience with tea suggest that this blend unfolds optimal effects when combined. Modern research confirms that the tea's components... complement each other and support each other in their effect[17][18]. Catechins (EGCG) provide antioxidant cell protection and metabolic benefits, while theanine provides the relaxing component – together they create a holistic Effect on body and mind.
- Complementary effects: As shown, L-theanine primarily targets the nervous system ab – it promotes relaxation, stress reduction, and focused calm in the brain. EGCG, on the other hand, primarily affects the Metabolic functional circuit and that immune system It reduces oxidative damage, improves blood values, and supports the immune system. In combination, the two cover a broad spectrum: from mental to physical health. For example, someone under stress benefits mentally from theanine (a calmer mood) and simultaneously physically from EGCG (z.B. lower stress-related cholesterol increase (see above).
- Synergy effects proven: Initial studies point to real Synergy effects That is to say, the combination is more effective than the individual components on their own.A striking example is the one mentioned above. Prevention study on colds/flu, in the EGCG + Theanine together offered significant protection against infections[39]. EGCG likely mobilizes the immune system (antiviral properties), while theanine indirectly strengthens the immune system through stress reduction and improved sleep quality – both together result in a greater protective effect.Similarly, in-vitro-Experiments on nerve cells indicate that EGCG and theanine together Neuroprotective effect: In an Alzheimer's model with brain cells, the combination protected the neurons from β-amyloid damage significantly better than either substance alone.[31][32]. In this experiment, EGCG suppressed amyloid-induced inflammation and promoted cell metabolism, while theanine simultaneously activated neuronal regeneration processes.[31][32]. The researchers conclude that EGCG and L-theanine synergistically promote the repair and regeneration of nerve cells. and thus potentially slow the progression of neurodegenerative diseases[32].
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