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Doctor's Best - Suntheanine L-Theanine 150 mg. - 90 Vegetarian Capsules

Reduces Stress & Tension

Item #: 77195
MSRP: $29.99$14.98  you save 50% Per Serving: $0.17
Serving Size: 1 Capsule(s)
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Doctor's Best - Suntheanine L-Theanine 150 mg. - 90 Vegetarian Capsules

  • Code#:77195
  • Manufacturer:Doctor's Best
  • Size/Form:90  Vegetarian Capsules
  • Packaged Ship Weight:0.25
  • Servings:90
  • Dosage Size:1  Capsule(s)

Doctors Best - Suntheanine L-Theanine 150 mg. - 90 Vegetarian Capsules

Doctors Best Suntheanine L-Theanine contains 100% Suntheanine, a patented pure form of the amino acid L-theanine produced in Japan from green tea leaves. This award-winning brand of theanine has been the subject of numerous safety studies and human clinical trials. One of green tea’s natural health-promoting compounds, L-theanine (y-glutamylethylamide) is synthesized in the roots of tea plants and transported to the leaves, comprising about 2% of the total dry weight of green tea leaves. It is the ingredient that is responsible for both the taste and the relaxing effects of green tea. Research shows that supplemental L-theanine crosses the blood-brain barrier within 30 minutes of intake and thus is able to exert its effects directly on the brain.

Features & Benefits:

  • Science-based nutrition
  • Dietary supplement
  • Promotes a relaxed state without drowsiness
  • Eases stress and everyday nervous tension
  • Promotes a positive mood and alertness
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Promotes a Relaxed State Without Drowsiness
Suntheanine L-theanine is best known for its unique ability to increase relaxation without causing drowsiness. Evidence from animal studies sheds light on this seemingly counterintuitive effect of this unique tea-based amino acid. L-theanine administered to rats by IV in relatively higher doses following the administration of approximately the same dose of caffeine has been shown to blunt the stimulating effects of caffeine as assessed by EEG recordings. However, L-theanine administered in smaller doses on its own resulted in excitatory stimulation. This reported dual action of theanine was shown to be dependent on the dose administered. Additionally, there are many anecdotal reports of L-theanine simultaneously enhancing mental alertness, and some, though not all, preliminary research in humans confirms this. Previous studies showed that Suntheanine L-theanine increases alpha brain waves, traditionally interpreted as signifying a relaxed, alert state. In a randomized, placebo-controlled, crossover study comparing placebo, 50 mg and 200 mg L-theanine, the higher dose of L-theanine increased power in the alpha frequency band (8-13Hz) of the electroencephalogram across parietal and occipital areas of the brain relative to placebo. The alpha brain waves in the resting human volunteers were generated within 40 minutes after the oral administration of L-theanine (50–200 mg), signifying a state of relaxation without drowsiness, according to the study authors.

A study performed at the Brain and Cognition Laboratory at Oxford University investigated whether a lower dose of Suntheanine L-theanine (50 mg) dissolved in tea would also affect alpha brain wave activity. The Suntheanine group consisted of 16 participants who received 50 mg of Suntheanineâ dissolved in a tea infusion, presumably containing caffeine. The control group consisted of 19 participants who received 100 mL cool water. EEG readings were taken 45 minutes after ingestion and subsequently every 15 minutes (45, 60,75, 90, 105 minutes). Participants were resting with their eyes closed during EEG recording. There was a greater increase in alpha activity across time in the Suntheanine supplemented group relative to placebo (p<0.05) indicating that this lower dose of L-theanine may also have a significant effect on the feeling of relaxation.

May Enhance Cognitive Performance and Increase Attention to Detail
Studies have been performed in which L-theanine was administered to rats daily for four months to assess its effect on memory and learning ability. Several tests were employed to determine whether L-theanine could improve memory and learning, including the Operant test in which food is released when the correct lever is pushed and a light comes on. L-theanine administration to rats resulted in an increased frequency of correct responses when compared to rats in the control group. In this experiment, the longer the L-theanine was administered, the better the response to the task. Additional tests performed on these animals included the passive and active avoidance tests. The idea here is that the animals develop the memory ability to avoid an undesirable outcome. The groups of animals receiving L-theanine again outperformed the control groups by exhibiting a greater ability to avoid undesirable events. These results demonstrate the memory and learning enhancement effects of L-theanine.

Furthermore, it seems clear that one of the mechanisms by which L-theanine supports cognitive health is through its neuroprotective potential. L-theanine acts to mitigate oxidative stress and its detrimental consequences on brain tissue. Several laboratory investigations point to L-theanine’s ability to support the health of neurons in the face of induced oxidative stress. In one such experiment, cultured rat neurons were exposed to glutamic acid, resulting in significant cellular death. When these cells were simultaneously exposed to L-theanine, the cell death was suppressed. This antioxidant effect may yield a partial glimpse into Suntheanine’s cognitive performance-enhancing actions.

Suntheanine L-theanine clearly affects brain activity and is relatively fast acting; however, many of the mechanisms of how it supports cognitive health and brain performance in humans remain to be fully determined. More recent human clinical studies (2008) have discovered that the effects of L-theanine on alpha waves are likely both dose- and caffeine- dependent, as well as dependent on whether the user is in a resting state or actively performing an attention-demanding task. This emerging research indicates that when a large dose of L-theanine is ingested by itself or when it is ingested in combination with caffeine, L-theanine actually decreases background alpha activity, but increases attention-related alpha brain wave processes during difficult attention-demanding tasks. This decrease in background alpha is associated with significant enhancement of one’s ability to actively perform tasks demanding a great deal of attention.

Another randomized, placebo-controlled, double blind crossover study published in 2008 also found differences between L-theanine alone and L-theanine with caffeine on relaxation and cognition. This study investigated the effects of L-theanine (250 mg), and caffeine (150 mg), in isolation and in combination, in 24 healthy volunteers who had abstained from caffeine for 12 hours. Results were measured 30 and 90 minutes after administration. At 30 minutes, L-theanine alone increased the participants’ subjective ratings of "calm" and "relaxed" compared to baseline, while caffeine and L-theanine combined with caffeine both decreased these feelings.

However, the L-theanine/caffeine combination had significant positive effects on delayed word recognition reaction time. These results support the idea that the combination of L-theanine and caffeine may have beneficial effects on cognition and alertness, while L-theanine alone may increase relaxation. It therefore seems that L-theanine has differential effects based on whether it is administered alone or in combination with a stimulant such as caffeine and can be used either to enhance relaxation and calmness, or to increase cognitive performance and alertness.

Helps Ease Stress and Everyday Nervous Tension
In one small investigation, eight Japanese female university students were selected as volunteers. Oral administration of 200 mg of L-theanine resulted in the generation of alpha brain waves in the occipital and parietal regions of the brains of the subjects when they were in a resting state, and resulted in a subjective feeling of relaxation. The intensity of alpha brain waves was significantly greater in the group of students with the highest levels of apprehension.

In a double-blind study illustrating L-theanine’s anti-stress effects, it was found that a single dose influences both psychological and physiological states under acute stress. This study gave 12 participants a mental math task as an acute stressor. All participants underwent four separate trials: one in which they took L-theanine at the start of an experimental procedure, one in which they took L-theanine midway, and two control trials in which they either took a placebo or nothing. L-theanine intake resulted in lower levels of perceived stress during the math task, a significantly greater reduction in perceived stress from baseline, and a reduction in the heart rate and salivary immunoglobulin A (a biomarker of stress) responses to the acute stress task relative to the placebo. By analyzing the heart rate variability, the researchers found that the reductions in these acute stress responses were likely attributable to the significantly decreased activation of the sympathetic nervous system.

Another study investigating the anti-stress effects of L-theanine found that a single dose was able to promote subjective feelings of tranquility in patients before the onset of acute nervous tension. The study also investigated the effect of L-theanine supplementation that followed the onset of apprehension and found that it did not induce relaxing behavioral effects. In this double-blind study consisting of 16 subjects, the researchers obtained behavioral measures of worry in all participants, both before and after an acute, experimentally created state of unease. L-theanine was able to promote ‘tranquil’ ratings, as measured on a visual analogue scale in rested participants. However, when participants were under conditions of increased acute apprehension, L-theanine did not have similar effects. In comparison, the placebo did not induce any relaxing effects at the initial measurement nor after the heightened state was induced. It seems L-theanine is an agent that is best used as a countermeasure to potential situations of nervousness and tension by supporting mental tranquility. Suntheanine may normalize the body’s stress response and condition the body to handle stressful situations better.

Suggested Use

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Take 1 capsule daily, away from food, or as directed by a health care professional.

Suntheanine L-theanine has undergone extensive safety evaluations which include tests for mutagenicity (ability of the product to induce genetic mutations in DNA) and acute toxicity. In addition, a 28-day subacute toxicity study and a 78-week evaluation of toxicity and carcinogenicity of L-theanine have been conducted in mice. According to the results of the acute toxicity evaluation, Suntheanine was reported to have an LD50 of greater than 5,000 mg per kilogram of body weight. In essence, no toxic effects were noted. The Ames test for mutagenicity showed Suntheanine to be non-mutagenic, while no treatment-related side effects were observed in either the 28-day study or the 78-week evaluation, with findings indicating a lack of carcinogenic potential of L-theanine. In addition, a 90-day toxicity evaluation has been performed on Suntheanine in which rats were given daily doses of 1500, 3000 or 4000 mg per kilogram of body weight. The no-observed-adverse-effect-level (NOAEL) as determined based on the findings of the study was established at 4000 mg per kilogram of body weight per day, the highest dose tested.

Doctor's Best - Suntheanine L-Theanine 150 mg. - 90 Vegetarian Capsules
Supplement Facts
Serving Size: 1 Capsule
Servings Per Container: 90 Servings
Amount Per Serving %DV*
Suntheanine L-theanine 150 mg *
*Daily Value Not Established.
†Percent Daily Values are based on a 2,000 calorie diet. Your diet values may be higher or lower depending on your calorie needs.
Other Ingredients: Rice powder, modified cellulose (vegetarian capsule)

Average Rating

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100%8 out of 8 reviewers would recommend this product to a friend.
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By Doris (Oakwood , GA )

Product was recommended as helpful with ADD and OCD. I've only taken it for a couple of weeks but so far, I can't tell that it's having any effect on me. However, I take anti-depressants and they could affect the efficacy of the product. I will continue on them for a few months to see if long term use will be beneficial.

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By Martha (Medford , MA )

This is my second bottle and I think it's been beneficial. No major effects but I think it is working subtly. I take melatonin (3 mg) at night and this in the morning.

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By penny (Springdale , AR )

Suntheanine is the only L-theanine I trust and Doctor's Best had a great price. I works wonders when combined with 5-HTP for anxiety. I have used it for years when I have and anxiety attack. It doesn't work instantly but given a little time it is a life saver.

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By DEBRAH (Fort Wayne , IN )

I got this for my daughter and she reports that it has helped a lot with her anxiety and sleep and for the price this seemed the best deal of the l-theanines

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By Terri (Langhorne , PA )

suntheanine works better than other brands. Lucky vitamin always has it in stock.

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Disclaimer: The views and opinions expressed by contributors of the product reviews are their own and not necessarily those of LuckyVitamin.com. LuckyVitamin.com does not endorse or imply any medical claims from these reviews. These reviews should not be taken as recommendations but rather customer opinions of the products that they may or may not have used. Reviews are not intended as a substitute for appropriate medical care or advice and are not intended to diagnose, treat, cure, or prevent any disease. Read the full product reviews disclaimer here.

Manufacturer Info

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197 Avenida La Pata
San Clemente, CA,
Phone: 949-498-3628 Fax: 949-498-3952 Visit website

About Doctor's Best

Founded in 1990 by a pioneering physician committed to science-based alternative health care, Doctor’s Best offers only the most important nutritional supplements. Containing the finest quality raw materials from around the world, Doctor’s Best supplements embody the best that traditional knowledge and current scientific research have to offer in the field of therapeutic nutrition. Each of their products is accompanied by an annotated "fact sheet" with detailed background information, structure-function statements, and scientific references that substantiate these statements. All structure-function statements have been filed with FDA in accordance with DSHEA regulations.

*The products and the claims made about specific products on or through this site have not been evaluated by LuckyVitamin.com or the United States Food and Drug Administration and are not approved to diagnose, treat, cure or prevent disease. The information provided on this site is for informational purposes only and is not intended as a substitute for advice from your physician or other health care professional or any information contained on or in any product label or packaging. You should not use the information on this site for diagnosis or treatment of any health problem or for prescription of any medication or other treatment. You should consult with a health care professional before starting any diet, exercise or supplementation program, before taking any medication, or if you have or suspect you might have a health problem.

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