200 mg of Zen by Allergy Research Group

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Anxiety. Although there has been interest in using oral GABA for anxiety, there is insufficient reliable information about the clinical effects of GABA for this condition.
• Athletic performance. Although there has been interest in using sublingual GABA for athletic performance, there is insufficient reliable information about the clinical effects of GABA for this purpose.
• Attention deficit-hyperactivity disorder (ADHD). Although there has been interest in using oral GABA for ADHD, there is insufficient reliable information about the clinical effects of GABA for this condition.
• Cerebral palsy. It is unclear if oral GABA is beneficial for cerebral palsy in children. Details: Preliminary clinical research in children with cerebral palsy shows that taking a specific product containing GABA (Gammalon) one to four tablets daily (depending on age) for 2 months, in addition to standard therapy for cerebral palsy, improves mental development, learning, vocabulary, physical function, motor strength and activity, and motor hyperactivity in a greater percentage of children when compared with standard therapy alone (19362). These findings are limited by poor study design.
• Chronic bronchitis. It is unclear if oral GABA is beneficial for chronic bronchitis. Details: Preliminary clinical research in adults with chronic bronchitis shows that taking a specific GABA product (Aminalon) 1.5-3 grams daily for 18-20 days, along with conventional treatment for acute exacerbations of bronchitis, increases the duration of subsequent remission by about 3 months when compared with conventional treatment alone (19361).
• Cushing syndrome. It is unclear if oral GABA is beneficial for Cushing syndrome. Details: Preliminary clinical research shows that taking a specific GABA product (Aminalon) 1-3 grams daily for one month decreases plasma levels of adrenocorticotropic hormone (ACTH) 60 minutes after administration, as well as cortisol and ACTH levels up to 2 days after GABA discontinuation, when compared with baseline (19363). The validity of these findings is limited by the lack of a comparator group.
• Depression. Although there has been interest in using oral GABA for depression, there is insufficient reliable information about the clinical effects of GABA for this condition.
• Epilepsy. It is unclear if oral GABA is beneficial for epilepsy. Details: Preliminary clinical research shows that taking a combination of GABA 2.5-3 grams and phosphatidylserine 500 mg daily for 3-8 months reduces seizure frequency when compared with placebo in patients with absence seizures, but not in those with focal aware or focal impaired awareness seizures (19364). Other preliminary clinical research suggests that taking GABA 3 grams with phosphatidylserine 600-1200 mg daily for 2 days does not affect the seizure photosensitivity range in people with photoconvulsive responses (5113).
• Hypertension. Preliminary clinical research suggests that oral GABA may modestly reduce blood pressure in patients with mild or borderline hypertension. Details: Preliminary clinical research in adults with hypertension shows that drinking 100 mL of fermented milk containing GABA 10-12 mg daily at breakfast for 12 weeks reduces systolic and diastolic blood pressure by about 17 mmHg and 7 mmHg, respectively, when compared with baseline. Compared with patients treated with a placebo milk, these reductions were significant. However, it is unclear if the placebo milk also differed from the fermented milk in other ways (19367). Other preliminary clinical research in patients with borderline hypertension shows that taking a chlorella supplement containing GABA 20 mg twice daily for 12 weeks reduces systolic blood pressure when compared with placebo (19368). However, these findings are limited by poor study design.
• Insomnia. It is unclear if oral GABA is beneficial for insomnia. Details: Two small clinical studies in adults with insomnia show that taking fermented rice germ extract, standardized to provide GABA 75 mg or 300 mg, one hour before bedtime for 4 weeks modestly decreases sleep latency when compared with placebo, but does not improve sleep efficacy or reduce episodes of waking after sleep onset (110134,110135). As these doses were evaluated in separate studies, no direct comparison between GABA 75 mg and 300 mg has been conducted.
• Meningitis. It is unclear if oral GABA is beneficial for meningitis. Details: Preliminary clinical research in children aged 7 months to 16 years with meningitis shows that taking a specific GABA product (Aminalon) 0.5-1.5 grams daily, starting within 2-4 weeks of illness and continuing for one month thereafter, decreases the incidence of residual disease manifestations and prevents the development of cerebrospinal syndrome when compared with control (19369). However, this study was conducted prior to the development of current treatment guidelines for meningitis; it is unclear if GABA is beneficial when used in conjunction with current standard care.
• Menopausal symptoms. Although there has been interest in using oral GABA for menopausal symptoms, there is insufficient reliable information about the clinical effects of GABA for this purpose.
• Motion sickness. It is unclear if oral GABA is beneficial for motion sickness. Details: Preliminary clinical research shows that taking a specific GABA product (Aminalon) 0.5 grams as a single dose 40-50 minutes before induced motion sickness or three times daily for 4 days significantly delays onset of motion sickness when compared with placebo. GABA also decreases the occurrence of motion sickness symptoms including chills, cold sweats, and pallor when compared with placebo (19370).
• Obesity. Although there has been interest in using oral and sublingual GABA for weight loss, there is insufficient reliable information about the clinical effects of GABA for this purpose.
• Pain (acute). Although there has been interest in using oral and sublingual GABA for acute pain, there is insufficient reliable information about the clinical effects of GABA for this purpose.
• Post-traumatic stress disorder (PTSD). Although there has been interest in using oral GABA for PTSD, there is insufficient reliable information about the clinical effects of GABA for this condition.
• Premenstrual syndrome (PMS). Although there has been interest in using oral GABA for PMS, there is insufficient reliable information about the clinical effects of GABA for this condition.
• Psychological well-being. Although there has been interest in using oral and sublingual GABA to improve well-being, there is insufficient reliable information about the clinical effects of GABA for this purpose.
• Stress. It is unclear if oral GABA is beneficial for stress. Details: Preliminary clinical research shows that taking a single dose of GABA 100-200 mg by mouth 10-70 minutes prior to completing a mentally stressful task does not appear to reduce subjective measure of stress when compared with placebo (90568). However, it does attenuate alpha wave reduction and reduces beta wave upsurge on the EEG during testing when compared with placebo (19373,90568). More evidence is needed to rate GABA for these uses.

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POSSIBLY EFFECTIVE

• Cognitive function. Oral L-theanine may improve some aspects of cognitive function. It is unclear if using L-theanine in conjunction with caffeine can enhance the effects of either ingredient. Details: A single dose of L-theanine 100 mg seems to improve vigilant attention, reducing error rates in cognitive tests when compared with placebo (91747). However, taking L-theanine (Suntheanine, Taiyo Kagaku) 200 mg daily for 4 weeks does not improve verbal fluency, memory, motor speed, or executive function in an adult population, although it may moderately improve verbal fluency in a subgroup of people with lower cognitive function at baseline (101986). When L-theanine is combined with caffeine, a meta-analysis and multiple individual clinical studies show that the combination improves alertness, as well as accuracy during a test that requires switching attention between different tasks, but does not improve reaction time (38116,91750,96335,96336). Some research also shows that L-theanine plus caffeine improves cognitive performance and reduces task-induced fatigue when compared with baseline and placebo. However, it is unclear if this is due to the individual ingredients or the combination (38116,96335,96336). Some research suggests that the combination is no better than either individual ingredient alone (91747,96335,96336).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. It is unclear if oral L-theanine, taken continuously or as a single dose, improves cognition in older adults. Details: A small clinical study in healthy, Japanese adults aged 50-69 years shows that taking a specific product (Suntheanine; Taiyo International.) containing L-theanine 101 mg daily after breakfast for 12 weeks does not improve mini-mental state exam (MMSE) scores when compared with placebo. However, a single-dose analysis from this study shows that administration of L-theanine 101 mg may improve the quality of working memory and reaction times during a cognitive function test when compared with placebo (108553). Patients were permitted to consume polyphenol-rich beverages during the study period; however, consumption was not documented, limiting the validity of this finding.
• Alzheimer disease. Although there is interest in using oral theanine for Alzheimer disease, there is insufficient reliable information about the clinical effects of theanine for this condition.
• Anxiety. It is unclear if oral L-theanine is beneficial in patients with anxiety. Results of clinical research are conflicting. Details: A preliminary clinical study shows that taking a single dose of a specific L-theanine product (Suntheanine, Taiyo Kagaku) 200 mg does not reduce experimentally-induced anticipatory anxiety when compared with placebo (12188). However, another preliminary clinical study in healthy adults with stress-related anxiety shows that taking L-theanine 200 mg daily for 4 weeks reduces anxiety scale scores and sleep disturbance when compared with placebo (101986).
• Attention. It is unclear if oral theanine improves attention. Details: A small clinical study in healthy males shows that taking a single dose of L-theanine 200 mg improves selective attention similar to a single dose of caffeine 160 mg (96337). However, other small clinical studies in adults show that taking L-theanine 100-400 mg does not improve most measures of attention, especially sustained attention or attention in executive control tasks, but doses of 100-200 mg may improve performance in simple attentional tasks when compared with placebo (96338,111396). Some of these studies suggest that taking L-theanine with caffeine appears to provide more benefit than either individual ingredient alone (96337,96338).
• Attention deficit-hyperactivity disorder (ADHD). Oral L-theanine seems to improve some aspects of ADHD, including cognition and sleep. Details: Some preliminary clinical research in children with ADHD shows that taking a one-time dose of L-theanine 2.5 mg/kg increases cognition scores, but does not improve results on sustained attention or inhibitory control tests, when compared with placebo. Taking L-theanine with caffeine 2 mg/kg also increases cognition scores and improves performance on a sustained attention test, but does not improve inhibitory control, when compared with placebo (104141). Other preliminary clinical research in males aged 8-12 years with ADHD shows that taking a specific L-theanine product (Suntheanine, Taiyo Kagaku) 200 mg orally twice daily for 6 weeks increases the percent of time spent in restful sleep by about 5% and decreases the number of bouts of nocturnal activity by about 6 when compared with placebo (91744).
• Cancer. Although there is interest in using oral theanine for cancer, there is insufficient reliable information about the clinical effects of theanine for this condition.
• Chemotherapy-induced diarrhea. Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with colon cancer shows that taking L-cystine 700 mg and L-theanine 280 mg (Ajinomoto Co. Inc.) orally once daily, starting one week before chemotherapy with TS-1 (Taiho Pharmaceutical) and continuing for 28 days, increases the rate of therapy completion by 49%, reduces the incidence of diarrhea by 37%, reduces appetite loss by 33%, and improves the reported tolerability of chemotherapy when compared with chemotherapy alone (96334). However, this combination does not appear to be beneficial in patients with gastric cancer, or in those with colorectal cancer receiving 4 courses of capecitabine-based adjuvant chemotherapy. (96334,101985).
• Cognitive impairment. Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One very small clinical study in adults with mild cognitive impairment shows that taking a product containing L-theanine 120 mg and green tea extract 720 mg (LGNC-07, LG Household & Health Care, Ltd) orally twice daily after meals for 16 weeks modestly improves memory and attention when compared with baseline. However, taking this product does not appear to improve memory and attention when patients with self-reported memory problems, but without mild cognitive impairment, are also considered (96339).
• Depression. It is unclear if oral L-theanine is beneficial in patients with depression. Details: A small clinical study shows that taking a specific L-theanine product (Suntheanine, Taiyo Kagaku Co. Ltd.) 250 mg orally at bedtime for 8 weeks reduces symptoms and improves sleep quality when compared to baseline in individuals with mild major depressive disorder (MDD) (96331). The validity of these findings is limited by the lack of a comparator group.
• Erythema. Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in healthy females with self-perceived skin sensitivity shows that taking a specific supplement containing L-theanine, ashwagandha, and saffron (InnerCalm, Arbonne) daily for 8 weeks reduces facial pigmentation when compared to baseline (111399). The validity of this finding is limited by a lack of a placebo group. It is unclear if these effects are due to L-theanine, other ingredients, or the combination.
• Generalized anxiety disorder (GAD). It is unclear if oral L-theanine is beneficial for reducing anxiety in people with GAD. Details: One small clinical study in adults with GAD shows that taking L-theanine 225 mg twice daily for 4 weeks, then 450 mg twice daily for 4 weeks, in conjunction with prescribed antidepressants, does not reduce anxiety scores when compared with antidepressants and placebo (104976).
• Hypertension. Although there is interest in using oral theanine for hypertension, there is insufficient reliable information about the clinical effects of theanine for this condition.
• Influenza. Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking a combination of green tea catechins (THEA-FLAN 90S, Ito-en Co.) 378 mg, standardized to contain epigallocatechin gallate 270 mg and L-theanine (Suntheanine, Taiyo Kagaku) 210 mg daily for 5 months reduces the risk of developing clinically diagnosed influenza when compared with placebo. However, the combination does not seem to prevent laboratory-confirmed influenza infection (54021).
• Insomnia. Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in adults with insomnia or disturbed sleep patterns shows that a specific product (RLX2; LiveLife Biosciences AG) containing L-theanine 50 mg and a specific casein peptide, alpha-s1-casein tryptic hydrolysate, 150 mg, taken one hour before bedtime for 4 weeks, increases sleep duration by 45 minutes and improves habitual sleep efficiency and daytime dysfunction when compared with baseline. However, it does not affect blood pressure, heart rate, or cortisol levels (108556). Another very small clinical study in healthy adults shows that taking a combination product containing tryptophan, glycine, magnesium, tart cherry powder, and L-theanine 2 hours before bedtime decreases sleep onset latency and increases total sleep duration, leading to better sleep efficiency and reduced morning sleepiness, when compared with placebo (111184). Another combination product containing L-theanine, ashwagandha, and saffron (InnerCalm, Arbonne), taken daily for 8 weeks, seems to improve sleep quality when compared to baseline (111399). However, the validity of this finding is limited by a lack of a control group. It is unclear if the effects described above are due to L-theanine, other ingredients, or the combination.
• Postoperative recovery. Oral theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study of adults with esophageal cancer undergoing esophagectomy shows that taking theanine 280 mg and cystine 700 mg daily, staring 4 days before surgery and continued for 13 days after surgery, does not improve measures of physical activity but does improve exercise tolerance and some measures of quality of life when compared with placebo (111400). It is unclear if these findings are due to theanine, cystine, or the combination.
• Schizophrenia. It is unclear if oral L-theanine is beneficial in patients with schizophrenia; the available evidence is limited and conflicting. Details: One preliminary clinical study in adults with schizophrenia or schizoaffective disorder shows that taking L-theanine (Biosynergy) 200 mg orally twice daily for 8 weeks along with antipsychotic medications improves positive symptoms, anxiety, and general psychopathology symptoms, such as poor impulse control and disorientation, when compared with placebo. However, theanine does not improve general disease severity, negative symptoms, depression, cognitive function, extrapyramidal side effects, or quality of life (96341). Another small clinical study shows that taking L-theanine 400 mg (Suntheanine, BioSynergy Health Alternatives) with pregnenolone 50 mg daily for 8 weeks, in addition to antipsychotic medications, improves negative symptoms, general psychopathology symptoms, and anxiety when compared with placebo in patients with schizophrenia or schizoaffective disorder. However, there were no improvements in positive schizophrenia symptoms or extrapyramidal side effects (97923). The inconsistency of results might be due to the small study sizes and the subjectivity of the outcomes measured.
• Stress. It is unclear if oral L-theanine is beneficial in patients with stress. Details: One very small clinical study shows that taking L-theanine 200 mg prior to a stress-inducing exam reduces tension-anxiety and may prevent blood pressure increases caused by psychological stress when compared with placebo (91746). Other preliminary clinical research in pharmacy students shows that taking theanine 200 mg twice daily for one week prior, and then for the first 10 days of a pharmacy practice period, decreases subjective stress scores when compared with placebo (91745). Another small clinical study in healthy young adults shows that drinking a beverage containing L-theanine 200 mg alone or combined with L-arginine 50 mg after a psychological stressor reduces stress, as measured by salivary alpha-amylase activity, when compared with placebo. The combination of L-arginine and L-theanine did not differ from L-theanine alone, suggesting that the combination does not act synergistically to reduce markers of stress (110393). However, not all research has been positive. A small clinical study shows that taking a specific L-theanine product (Suntheanine, Taiyo Kagaku) 200 mg induces subjective feelings of tranquility in relaxed people, but not those with experimentally-induced anticipatory anxiety, when compared with placebo (12188). Also, a small, clinical crossover study in healthy, moderately stressed adults shows that taking a single dose of a specific product (Alphawave; Ethical Naturals) containing L-theanine 200 mg prior to a stress-inducing exam does not improve anxiety at any time point when compared with placebo (108554). Due to the single-dose nature of this study, the effects of continued administration of this product are unclear. L-theanine has also been evaluated in combination with other ingredients. A small clinical study in adults with stress shows that taking a specific combination product (Mg-Teadiola, Sanofi-Aventis Group), containing green tea extract 125 mg (providing 50 mg L-theanine), magnesium 150 mg, vitamin B6 0.2 mg, vitamin B9 0.1 mg, vitamin B12 1.25 mcg, and rhodiola 222 mg, orally once daily for 28 days modestly improves stress and anxiety scores when compared with placebo. Improvements in stress scores, but not anxiety scores, appear to persist at 28 days after treatment completion (108672). It is unclear if any effects are due to L-theanine, other ingredients, or the combination.
• Tourette syndrome. It is unclear if oral L-theanine is beneficial in children with Tourette syndrome. Details: A small, nonblinded clinical study in children aged 4-17 years with untreated Tourette syndrome or with chronic tic disorder and associated symptoms of anxiety shows that taking a liquid nutritional supplement providing L-theanine 200 mg and vitamin B6 2.8 mg daily for 2 months improves scores on the Yale Global Tic Severity Scale, but does not reduce anxiety, when compared with patients receiving psychoeducation (108555). This study may have been inadequately powered to detect a difference between groups. More evidence is needed to rate theanine for these uses.

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LIKELY SAFE ...when used orally in amounts commonly found in foods.

POSSIBLY SAFE ...when used orally in medicinal amounts, short-term. GABA has been used with apparent safety in doses of 75 mg to 1.5 grams daily for up to one month in small clinical studies (19361,19363,19369,110134,110135). There is insufficient reliable information available about the safety of GABA when used orally for longer than one month or when used sublingually or intravenously.

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using.

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POSSIBLY SAFE ...when used orally and appropriately, short-term. L-theanine has been used safely in clinical research in doses of up to 900 mg daily for 8 weeks (12188,36439,96331,96332,96334,96341,97923,101986,104976). There is insufficient reliable information available about the safety of L-theanine when used long-term.

CHILDREN: POSSIBLY SAFE
when used orally and appropriately, short-term. A specific L-theanine product (Suntheanine, Taiyo Kagaku) 200 mg twice daily has been used safely in males aged 8-12 years for up to 6 weeks (91744).

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using.

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ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, taking GABA with antihypertensive drugs might increase the risk of hypotension.  Details Some clinical research shows that GABA can decrease blood pressure in patients with hypertension (19367).

CNS DEPRESSANTS Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, GABA might have additive sedative effects when used in conjunction with CNS depressants. However, it is unclear if this concern is clinically relevant.  Details Endogenous GABA has well-established relaxant effects (51152) and GABA(A) receptors have an established physiological role in sleep (51143). However, the effects of GABA supplements are unclear, as it is unknown whether exogenous GABA crosses the blood-brain barrier (51120,51153,90570). Although there have been limited reports of drowsiness or tiredness with GABA supplements (5115,19364), these effects have not been widely reported in clinical studies. Additionally, intravenous GABA 0.1-1 mg/kg has been shown to induce anxiety in a dose-dependent manner (5116).

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ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.  Details Animal research shows that theanine can lower blood pressure in spontaneously hypertensive animals (7687,77354). Theoretically, concomitant use of theanine and antihypertensive drugs might potentiate the antihypertensive activity.

CNS DEPRESSANTS Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, theanine might have additive sedative effects when used in conjunction with CNS depressants. However, it is unclear if this concern is clinically relevant.  Details Theoretically, theanine may compete with glutamate and/or increase plasma gamma-aminobutyric acid (GABA) levels, which could cause CNS depression (96334). In one clinical study, some subjects taking oral theanine reported drowsiness (96331).

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General ...Orally, GABA seems to be generally well tolerated. Sublingually, no adverse effects have been reported. However, a thorough evaluation of safety outcomes has not been conducted.
Most Common Adverse Effects:
Orally: Drowsiness, gastric upset, minor throat burning, muscle weakness, and nausea.

Cardiovascular ...Intravenously, GABA can cause dose-related increases in blood pressure and pulse (5116).

Gastrointestinal ...Orally, minor throat burning has been associated with GABA in one study (5115). In another study in which GABA was administered with phosphatidylserine, one patient experienced severe gastric distress, two patients reported moderate nausea, and one reported constipation (19364). Children with cerebral palsy taking GABA experienced nausea and decreased appetite (19362).

Genitourinary ...In one study, one patient treated with oral GABA and phosphatidylserine reported transient amenorrhea (19364).

Musculoskeletal ...Orally, minor adverse effects associated with GABA included muscle weakness (5115).

Neurologic/CNS ...Orally, GABA may cause drowsiness or tiredness (5115,19364). Four children with cerebral palsy taking GABA had convulsions, and an unspecified number experienced motor restlessness. However, causality of these adverse effects was not clear, and the dose of GABA was not specified (19362). Intravenously, GABA 50 mg has been associated with a "lack of alertness" in healthy female volunteers (51159).

Psychiatric ...Intravenously, GABA 0. 1-1.0 mg/kg has been shown to induce anxiety, dysphoria, and mood disturbances in a dose-dependent manner (5116).

Other ...In one study, patients taking GABA experienced a slight warming of the body (19370).

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General ...Orally, L-theanine seems to be well tolerated.
Most Common Adverse Effects:
Orally: Drowsiness, headaches.

Neurologic/CNS ...Orally, L-theanine may cause headaches (36439). Patients have also reported drowsiness, increased duration of sleep, and increased dream activity after oral L-theanine use (96331).
A case of subtle facial tic starting within 4 days of taking L-theanine 400 mg daily has been reported for a pediatric patient. Although the tics reportedly ceased once theanine was discontinued, the child had exhibited tics in the past. Therefore, the adverse effect was not thought to be related to L-theanine (91744).

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