Sustained Focus by Nature's Way

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. It is unclear if oral spearmint extract is beneficial for age-related cognitive decline. Details: A small clinical study in older adults with age-related cognitive decline shows that taking a specific spearmint extract 900 mg daily for 90 days modestly improves quality of working memory, as well as time to sleep, overall mood, and feelings of vigor, when compared with placebo. However, no improvements were seen in attention, overall quality of memory, speed of memory, quality of sleep, or feelings of anxiety, depression, or confusion. Additionally, taking 600 mg daily does not seem to provide benefit (98523).
• Cognitive function. Small clinical studies suggest that oral spearmint extract or spearmint-flavored gum may not improve most measures of cognitive function. Details: One small clinical study in healthy young adults shows that taking a proprietary spearmint extract (Neumentix Phenolic Complex K110-42, Kemin Foods, LC.) 900 mg daily for 90 days modestly improves attention, but not working memory, executive function, speed, reasoning, or other measures of cognitive function, when compared with placebo (101713). Other small clinical studies in healthy adults shows that chewing spearmint-flavored gum during memory testing does not improve memory or attention when compared with chewing unflavored gum (75725,75754).
• Flatulence. Although there has been interest in using oral spearmint for flatulence, there is insufficient reliable information about the clinical effects of spearmint for this purpose.
• Hirsutism. Small clinical studies suggest that drinking spearmint tea may modestly reduce testosterone levels in patients with hirsutism; any effects on hair growth are unclear. Details: A small clinical study in patients with hirsutism associated with polycystic ovary syndrome (PCOS) shows that drinking spearmint tea twice daily for one month can reduce the subjective severity of hirsutism when compared to pretreatment; however, it does not seem to reduce the amount or location of hair based on objective assessment when compared with placebo tea (68500). Any effect of spearmint tea in patients with hirsutism is believed to be related to its antiandrogenic properties. Two small clinical studies in patients with idiopathic hirsutism or hirsutism associated with PCOS show that drinking spearmint tea twice daily for 5-30 days can decrease free testosterone levels and increase levels of luteinizing hormone, estradiol, and follicle-stimulating hormone when compared to baseline (68451,68500).
• Irritable bowel syndrome (IBS). Oral spearmint has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with IBS shows that using 30 drops of a combination product containing lemon balm, spearmint, and coriander (Carmint) three times daily after meals for 8 weeks along with conventional therapy with loperamide or psyllium reduces abdominal pain and discomfort by approximately 81% when compared with conventional therapy alone (19535). It is unclear if these findings are due to spearmint, other ingredients, or the combination.
• Osteoarthritis. It is unclear if drinking spearmint tea is beneficial in patients with knee osteoarthritis. Details: A small clinical study in patients with knee osteoarthritis shows that drinking 2 cups of spearmint tea daily for 16 weeks reduces pain and stiffness when compared to baseline (94923). The validity of these findings is limited by a lack of control group.
• Postoperative nausea and vomiting (PONV). Aromatherapy with spearmint oil has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One clinical study in patients reporting nausea after surgery shows that inhaling vapors from a mixture of spearmint, peppermint, ginger, and cardamom essential oils reduces symptoms of postoperative nausea in approximately 15% more patients when compared with inhaling ginger essential oils alone, and in about 43% more patients when compared with inhaling saline (89888). It is unclear if these findings are due to spearmint oil, other ingredients, or the combination. More evidence is needed to rate spearmint 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 in amounts commonly found in foods. Spearmint and spearmint oil have Generally Recognized as Safe (GRAS) status in the US (4912).

POSSIBLY SAFE ...when used orally or topically for medicinal reasons (11,12). Spearmint extract up to 900 mg daily has been used safely for up to 90 days (94925,101713,101714). Spearmint tea has been consumed safely twice daily for up to 16 weeks (68500,94923).

PREGNANCY: LIKELY SAFE
when used in the amounts commonly found in foods (4912).

PREGNANCY: POSSIBLY UNSAFE
when used orally during pregnancy in excessive amounts. Animal research suggests that spearmint tea may cause uterine damage (68448). Avoid using in amounts greater than those typically found in foods during pregnancy.

LACTATION: LIKELY SAFE
when used in the amounts commonly found in foods (4912). There is insufficient reliable information available about the safety of spearmint during lactation. Avoid using in amounts greater than those typically found in foods.

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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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CNS DEPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, spearmint might alter the sedative effects of CNS depressants.  Details Animal research suggests that (-)-carvone, a major constituent of spearmint, has sedative effects (39800,75758). However, in humans, chewing spearmint-flavored gum induced arousal effects (75699).

HEPATOTOXIC DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, high doses of spearmint might increase the risk of liver damage when taken with hepatotoxic drugs.  Details Animal research suggests that drinking spearmint tea for 30 days can increase markers of liver damage, including aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and cause liver degeneration and necrosis, in a dose-dependent manner (12731). This effect has not been reported in humans.

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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, spearmint is well tolerated.
Most Common Adverse Effects:
Topically: Allergic contact dermatitis or cheilitis in sensitive individuals.

Cardiovascular ...Orally, taking spearmint extract 600 mg daily has been associated with one report of tachycardia in one clinical trial. However, it is not certain that this adverse event was caused by spearmint extract (94925).

Dermatologic ...Orally, drinking 2 cups of spearmint tea with normal amounts of rosmarinic acid has been associated with one report of itchy skin in clinical research (94923).

Gastrointestinal ...Orally, taking spearmint extract 600 mg daily has been associated with dyspepsia in one clinical trial (94925). Taking a higher dose of 900 mg daily has been associated with diarrhea and belching (94925). Drinking 2 cups of spearmint tea with normal amounts of rosmarinic acid has been associated with one report of dry mouth in clinical research. Drinking 2 cups of spearmint tea containing high amounts of rosmarinic acid has been associated with three reports of constipation and one report of loose bowel movements (94923). Taking 1 mL of spearmint oil equivalent to 500 mg of spearmint has been associated with reports of regurgitation in clinical research (75700).

Immunologic ...Topically, spearmint oil and leaves have caused allergic dermatitis (75711,75731,75737). Allergic contact cheilitis has also occurred from spearmint oil in toothpaste or chewing gum (31403,31528,75706,75739,75777,75790). Spearmint oil inhalation has also caused allergic dermatitis (56955). Orally, spearmint leaves have caused allergy-associated swelling of the soft palate. A specific 50 KDa protein in the spearmint was found to be the responsible allergen (94922). In some cases, spearmint allergy was associated with oral lichen planus of the tongue, lips, palate, buccal mucosa, and gingivae. Observational studies suggest that exposure to spearmint is associated with exacerbation of oral lichen planus as confirmed by patch testing (94924,112844).

Neurologic/CNS ...Orally, drinking 2 cups of spearmint tea containing high amounts of rosmarinic acid has been associated with two reports of headache in clinical research (94923).

Psychiatric ...Orally, taking spearmint extract 600 mg daily has been associated with one report of anxiety in one clinical trial. However, it is not certain that this adverse event was caused by spearmint extract (94925).

Other ...Orally, taking spearmint extract 600 mg daily has been associated with one report of increased appetite and weight gain in one clinical trial. However, it is not certain that these adverse events were caused by spearmint extract (94925).

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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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