L-Theanine Supplements Review
Find the Best L-Theanine
Supplement. Find Out If L-Theanine Helps for Stress and Which Products Are
Best.
Medically reviewed and
edited by Tod Cooperman, M.D. 
Last Updated
: 05/12/2020 | Initially Posted:
08/08/2015
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Table of Contents
Summary
·
What is L-theanine? Often just called theanine, L-theanine,
is a water-soluble amino acid found in black and green tea. (See What It Is).
·
What are the health benefits of L-theanine? Some small clinical
studies (funded by manufacturers of L-theanine) have found L-theanine may
reduce stress, anxiety and blood pressure in stressful situations, but not all
studies have found a benefit (See What It Does).
·
How much L-theanine should I take? L-theanine is
typically taken at a dose of 200 mg to 400 mg per day (See Dosage).
·
L-theanine safety and side effects: At these doses, it
appears to be generally safe, but there are possible interactions with blood
pressure medications and benzodiazepines (see Concerns and Cautions).
·
Best value for L-theanine: ConsumerLab.com did not find problems
with the quality of selected L-theanine products sold in the U.S., but did find
large differences in the cost to obtain L-theanine. The least expensive,
Approved product cost 22 cents to obtain 200 mg of L-theanine while the cost
was often 60 cents for other products (See What CL Found).
What It Is:
L-theanine
is a water-soluble amino acid found primarily in black and green tea, and
certain mushrooms. The L-theanine in supplements, however, is generally
synthetic, produced from food grade L-glutamine and ethylamine, but may also be
an enzymatically-processed extract of tea leaves. It is thought to have both antioxidant
and relaxant effects, possibly through influence on excitatory chemicals in the
body, such as noradrenaline, and chemical messengers in the brain, such as GABA
and serotonin.
What It Does:
There is mixed evidence as to whether L-theanine reduces stress
and anxiety. For example, a placebo-controlled study showed that taking 50
mg of L-theanine increased alpha brain waves, which are associated with a
relaxed but alert state of mind (Nobre, Asia Pac Clin Nutr 2008).
The effect was measured 45 minutes after L-theanine was taken and continued to
increase over the 1˝ hours that brain waves were measured. One small
placebo-controlled clinical trial found that 200 mg L-theanine (Suntheanine) dissolved in water and taken after
beginning a stressful cognitive task significantly reduced self-reported
anxiety and physiological measures of stress, such as increased heart rate (Kimura, Biol Psychol 2007).
A study among middle-aged adults in Japan with mild emotional, sleep, and/or
cognitive symptoms found that a 200-mg tablet of L-theanine taken before sleep
each night for four weeks led to improvements from baseline on most
measures. However, compared to results with placebo, these
improvements were only statistically significant for three measures: time to
fall asleep, sleep efficiency and reduced sleep disturbances, and were only
significant for the later two measures because of
adverse results in the placebo group. L-theanine did not result in any
statistically significant improvement relative to placebo on cognitive function
tests (Hidese, Nutrients 2019).
Another study using the same dose and brand of L-theanine found that it did not
reduce anxiety when taken by young adults prior to a stressful task — although
neither did 1 mg of alprazolam (Xanax). Interestingly, during a non-stressful
task, treatment with the alprazolam was found to significantly increase self-reported
anxiety while L-theanine significantly decreased self-reported
anxiety (Lu, Hum Psychopharmacol
Clin Exp 2004). A small study among men and
women in Australia with generalized anxiety disorder (GAD) (many of whom also
had social phobia, panic disorder or agoraphobia), found that daily
supplementation with L-theanine for two months (450 mg daily for one month,
increased to 900 mg for the second month for those who did not respond) did
not decrease anxiety, or improve cognition or insomnia severity
compared to placebo, although those taking L-theanine reported improved
"sleep satisfaction." (Sarris, J Psychiatr Res 2019).
At higher doses, L-theanine may be helpful for people with schizophrenia.
In an independent study of people diagnosed with schizophrenia or schizoaffective
disorder taking antipsychotic medication, 400 mg of L-theanine taken daily for
8 weeks significantly reduced measures of anxiety and other symptoms, compared
to placebo (Ritsner, J Clin Psychiatry 2011).
L-theanine has been suggested as a treatment in ADHD (attention deficit
hyperactivity disorder), although the evidence of benefit is very limited. In a
10-week study of 93 boys (average age 9) diagnosed with ADHD, some
of whom were also taking stimulant medication such as methylphenidate
(Ritalin), 200 mg of L-theanine in the morning and again in the afternoon
(total daily intake of 400 mg) was found to significantly improve sleep
quality compared to placebo, although it did not reduce the amount of
time it took to fall asleep. This study did not measure effects on daytime
hyperactivity, attention, or cognitive function (Lyon, Altern Med Rev 2011).
All of the studies (other than the study by Ritsner) used a branded version of
L-theanine called Suntheanine from
Taiyo International, Japan, which typically funded the studies. (Suntheanine is the form of L-theanine found in
most of the products in this Review, as shown in the second column of the Results table below).
L-Theanine may lessen blood pressure increases associated with
caffeine use. One study found that healthy adults who consumed a drink
containing 200 mg of L-theanine (provided by Unilever plc, UK) in addition to
taking a capsule containing 250 mg of caffeine had less of an increase in blood
pressure than those who consumed only caffeine. It did not, however, reduce
other effects of the caffeine, such as alertness or jitteriness (Rogers, Psychopharmacology 2008).
Although some laboratory and animal studies suggest L-theanine may have
anti-tumor properties, there is a lack of human studies for this use.
Similarly, while animal studies suggest L-theanine may enhance the effects
and/or reduce the side-effects of certain chemotherapy drugs, such as
doxorubicin and adriamycin, human studies have not
been conducted (Sugiyama, Cancer Lett 1998, Sugiyama, Cancer Lett 2004;).
Quality Concerns and
Tests Performed:
Neither
the Food and Drug Administration (FDA) nor any other federal or state agency
routinely tests supplements for quality prior to sale. In order to help consumers identify products of better quality,
ConsumerLab.com purchased and tested L-theanine supplements to determine
whether they contained the labeled amounts of L-theanine. In addition, tablets
were tested for their ability to properly break apart (disintegrate) in
solution. Products were also tested for potential contamination with lead,
cadmium, and arsenic. (See How Products Were Evaluated for
information on testing methods and passing score.)
What CL Found:
All 8 of the L-theanine supplements which ConsumerLab.com
selected for review, passed quality testing, containing their claimed amounts
L-theanine and meeting other quality criteria, including not containing
unacceptable amounts of heavy metals. However, the products differed in a
number of ways:
·
Serving size — As shown in results table below, the amount of
L-theanine in the supplements (all of which were capsules except for TwinLab's small "dot" tablets), ranged from 50 mg
to 200 mg. Based on the suggested daily servings on labels, the products would
provide 100 mg to 400 mg of L-theanine. Be sure to choose a product that has
the dose you need and be aware that labeled dosing may not be most clinically appropriate
for your condition.
·
Brand of L-theanine — More than half of the products
listed Suntheanine (Taiyo
International) as the source of L-theanine. Others simply listed L-theanine.
There do not appear to be clinically significant differences in the forms,
although Suntheanine is the most
clinically tested.
·
Lowest cost — We calculated the actual cost to obtain L-theanine from
the products. The lowest cost was 22 cents for a 200 mg veggie capsule of Swanson
Ultra Suntheanine -- a very good value
considering that the cost for the same amount of ingredient was often 60 cents
or greater from other products. If you want a lower dose pill, LifeExtension L-Theanine and Puritan's
Pride L-Theanine each provide 100 mg in a capsule costing 30 cents,
and TwinLab L-Theanine Dots provide
50 mg per small tablet, each costing 10 cents [Update (5/12/20): This TwinLab product has
been discontinued.]
Test Results by Product:
Listed
alphabetically below are the test results for 12 L-theanine supplements.
ConsumerLab.com selected 8 of these products. Four others (each indicated with
a CL flask) were tested at the request of their manufacturers/distributors
through CL's voluntary Quality Certification Program and
are included for having passed testing. Also listed is one product which is
similar to another that passed testing but is sold under a different brand
name.
Shown for each product is the labeled amount of L-theanine per unit, the daily
serving size, and the expected daily dose of L-theanine. The calculated cost to
obtain 200 mg of L-theanine is provided in the last column along with other
cost comparisons and notable features. The full list of ingredients is
available for each product by clicking on the word "Ingredients" in
the first column.
|
RESULTS OF CONSUMERLAB.COM TESTING OF
L-THEANINE SUPPLEMENTS |
||||||
|
Product Name, Amount
of L-Theanine per Unit, Serving Size, and Suggested Daily Serving on Label |
Claimed Amount of
L-Theanine Per Suggested Daily Serving on Label |
--TEST RESULTS-- |
Cost for Daily
Suggested Serving on Label |
|||
|
OVERALL RESULTS: |
Contained Listed
Amounts of L-Theanine |
Disintegrated
Properly |
||||
|
|
150 mg |
APPROVED |
|
NA |
$0.52 |
|
|
|
200 mg |
APPROVED |
|
NA |
$0.32 |
|
|
|
200 mg |
APPROVED |
|
NA |
$0.45 |
|
|
|
200 mg |
APPROVED |
|
NA |
$0.28 |
|
|
|
100 mg to 400 mg |
APPROVED |
|
NA |
$0.30-$1.20 |
|
|
|
200 mg to 400 mg |
APPROVED |
|
NA |
$0.28-$0.55 |
|
|
|
200 mg |
APPROVED |
|
NA |
$0.60 |
|
|
|
300 mg |
APPROVED |
|
NA |
$0.82 |
|
|
|
200 mg to 400 mg |
APPROVED |
|
NA |
$0.24-$0.48 |
|
|
|
200 mg |
APPROVED |
|
NA |
$0.22 |
|
|
|
200 mg to 400 mg |
APPROVED |
|
NA |
$0.58-$1.74 |
|
|
|
100 mg to 200 mg |
APPROVED |
|
|
$0.20-$0.40 |
|
|
Similar to Approved Products*: |
||||||
|
Vitamin World® L-Theanine (100 mg per capsule;
2 capsules, once daily) |
Similar to Puritan's
Pride® L-Theanine. |
$0.57 |
||||
|
|
||||||
|
Unless otherwise noted, information about the products
listed above is based on the samples purchased by ConsumerLab.com (CL) for
this Product Review. Manufacturers may change ingredients and label
information at any time, so be sure to check labels carefully when evaluating
the products you use or buy. If a product's
ingredients differ from what is listed above, it may not necessarily be of
the same quality as what was tested. |
||||||
|
Copyright ConsumerLab.com, LLC, 2015. All rights reserved.
Not to be reproduced, excerpted, or cited in any fashion without the express
written permission of ConsumerLab.com LLC. |
||||||
ConsumerTips™:
What to Consider When Buying:
ConsumerLab.com found that pill strengths and suggested serving sizes vary
widely among products. Be sure to choose a tablet strength (50, 100, 150, or
200 mg) which is right for you and don't necessarily rely on the suggested
number of daily servings on labels, as they, too can vary (we found the
suggestion to range from 100 mg to 400 mg per day). See the Dosage information below.
Although the Suntheanine brand of
L-theanine is the most well-studied, there do not appear to be clinically
significant differences among the types of L-theanine available in the market.
What to Consider When Using:
Amounts of L-theanine in tea
You can also get L-theanine from tea, but at lower doses than in supplements.
Amounts found in tea may vary: one cup of black tea contains approximately 20
mg of L-theanine, while certain types of green tea such as matcha, Gyokuro and
sencha may contain anywhere from 5 mg to as much as 26 to 46 mg (Keenan, Food Chem 2011; Mason, Alternat Complement Ther 2001).
Dosage:
·
To increase alpha brave waves associated with a relaxed but
alert state of mind: 50 mg (Nobre, Asia Pac Clin Nutr 2008)
·
To reduce stress or anxiety: 200 mg before or during a stressful
event (Kimura, Biol Psychol 2007)
·
To reduce anxiety and other symptoms associated with
schizophrenia or schizoaffective disorder: 200 mg taken twice daily (a total of
400 mg daily) (Ritsner, J Clin Psychiatry 2011)
·
To improve sleep quality in children with ADHD: 200 mg of
L-theanine in the morning, and again in the afternoon (a total daily intake of
400 mg)(Lyon, Altern Med Rev 2011)
Concerns and Cautions:
·
L-theanine appears to be generally safe when taken short term in
doses between 50 and 400 mg. In clinical studies, few side effects have been
reported.
·
Three versions of L-theanine have attained the self-affirmed
status of GRAS (generally recognized as safe) with the U.S. FDA, meaning that
the FDA has not raised questions regarding its use although it has not
conducted its own testing. The synthetic versions are from Taiyo International (sold
as Suntheanine) and Zhejiang Tianru
Chemical. A version produced through an enzyme-assisted
manufacturing process that uses green tea leaves as one of the starting
materials, L-Tea Active, is from Blue California.
·
L-theanine could potentially lower blood pressure and should be
used with caution when taking blood-pressure lowering medications such as
captopril (Capoten), enalapril (Vasotec), diltiazem
(Cardizem), amlodipine (Norvasc), etc., and/or when taken with other
supplements that could potentially lower blood pressure.
·
An animal study suggests L-theanine could potentially increase
the effects of the benzodiazepine drug midazolam (Heese, AANA J 2009).
·
One occurrence of a mild facial tic has been reported in a child
with ADHD who had a history of facial tics and took 400 mg of L-theanine daily;
the tic went away after treatment with L-theanine was stopped (Lyon, Altern Med Rev 2011).
Information on this site
is provided for informational purposes only. It is not an endorsement of any
product nor is it meant to substitute for the advice provided by physicians or
other healthcare professionals. The information contained herein should not be
used for diagnosing or treating a health problem or disease. Consumers should
inform their healthcare providers of the dietary supplements they take.
Latest Clinical Research Updates for L-Theanine Supplements
L-Theanine for Sleep and Cognition?
10/05/2019
Several studies have
evaluated whether a single dose of L-theanine (found in green tea) can reduce
stress and anxiety. A new study has evaluated the effect of L-theanine when
taken daily for several weeks. See the results in the What It Does section
of the L-Theanine Supplements Review. Also see our top choices for
L-Theanine.
2/05/2019
Theanine is promoted as
an anxiety-reducing supplement, but does it really work. See results of a
recent study in the What It Does section
of the L-theanine Supplements Review. Also see our top choices for
L-theanine supplements.
2/05/2019
Theanine is promoted as
an anxiety-reducing supplement, but does it really work? See results of a
recent study in the What It Does section
of the L-theanine Supplements Review. Also see our top choices for
L-theanine supplements.
Related CL Answers (7)