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L-Theanine for Weight Loss and Memory Boost | Farr Institute

L-Theanine for Weight Loss and Memory Boost | Farr Institute

By Kire Stojkovski M.D
Editor Jonathan Hoarau Published 01 May 2023
Time to read 17 min

L-theanine is a special amino acid found mainly in green tea. It is said to have multiple beneficial effects on the mind and brain and even the potential to reduce stress and anxiety. But it is not a common compound found in our daily diet, which is why health supplements with l-theanine are becoming so popular.

In this article, we will discuss the various positive effects of l-theanine and the side effects, if any.

Key Takeaways: L-Theanine Weight Loss and Memory Boost

  • L-theanine is a naturally occurring amino acid found in green tea and has a wide range of positive effects on brain functions. These include improved memory, mental clarity, and focus.
  • L-theanine is not produced in the body and is not readily available from the diet. It is commonly found in green and black tea.
  • Some research has also shown that L-theanine is effective in boosting mental focus and cognitive alertness. The effects of long-term use are still unknown.
  • Generally, L-theanine is safe for healthy adults and is mostly free from side effects. However, it can interfere with the functioning of a few drugs.
  • Some of the popular dietary supplements containing L-theanine are Mind Lab Pro, NooCube, and Qualia Mind.

What Is L-Theanine?

L-theanine or N-ethyl-L-glutamine is a non-protein amino acid and has a chemical structure that resembles L-glutamic acid [1]. This is why some researchers suggest its action is based on the functioning of glutamate receptors. It is classified as a bioactive plant chemical rich in nutrients, in other words, a phytochemical.

It is not an essential micronutrient for humans and is not produced by the body. There are three methods for obtaining L-theanine from artificial sources, including:

  • Extraction from green tea leaves
  • Biosynthesis
  • Chemical synthesis

The process of isolation from green tea leaves involves high production costs and a low overall yield. Production by chemical synthesis is a cost-effective option.

How Does Theanine Work?

Based on animal neurochemistry studies, researchers have pointed out various possible effects of L-theanine on the brain and the central nervous system. It can help in the production of serotonin, dopamine, and gamma-aminobutyric acid (GABA) levels and also acts as a  neuroprotective agent [2].

L-theanine can modulate the monoamine levels and control the glutamate and glycine transmissions. It also affects the hippocampus to reduce the effects of stress and depression [1]. Beyond that, it can enhance the activity in the alpha brain waves to some extent, which results in the calming of the mind without causing drowsiness.

Can L-Theanine Help With Weight Loss?

Some research says that L-theanine can help in losing weight. The combined effect of L-theanine and caffeine can reduce triglyceride and non-esterified fatty acids (NEFA) levels and assist in lowering cellular fat accumulation [3].

In addition, the biochemical effects of L-theanine through green tea or supplement consumption can also reduce appetite levels and help in attaining a calorie deficit.

L-theanine can also have indirect effects on weight loss. By boosting energy levels, it can lead to better performance during workouts. Since it has positive effects on mental attention, it can also help one to focus more on exercise sessions to achieve better results.

Poor sleep quality can lead to weight gain and increase calorie intake. L-theanine helps in improving overall sleep quality, which in turn can help in weight loss.

How Does L-Theanine Boost Memory?

Studies have been conducted on patients with mild cognitive impairment to understand the effects of L-theanine. Memory enhancement effects were observed in some cases but the long-term effects were inconclusive. The results also showed enhancement in the levels of brain theta waves which helps in the overall improvement of cognitive alertness [4].

Based on the placebo-controlled clinical trial, further research is required to study the potential effects of L-theanine.

Beyond that, the combination of L-theanine and caffeine improves attention and alertness in people. However, positive effects are mostly due to the action of caffeine intake. It is possible that L-theanine interacts with caffeine to help in better performance during cognitively demanding tasks.

L-Theanine Benefits

The various health benefits of L-theanine are:

l-theanine weight loss and memory boost

  1. Relieves stress and anxiety
  2. May reduce the risk of Alzheimer’s disease
  3. May improve immunity
  4. Boosts cognitive function
  5. May enhance cancer treatment
  6. Increases focus
  7. May lower high blood pressure

Relieves Stress and Anxiety

L-Theanine can act as a therapeutic agent to reduce anxiety in many ways. However, long-term studies are required to clinically justify the fact that taking L-theanine reduces psychological stress. Studies have indicated that oral supplementation of L-theanine may reduce physical and psychological stresses [5].

Furthermore, L-theanine helps in modulating alpha activity in the brain that results in an overall positive effect on mental health. The reduction of stress-related symptoms was also observed during a placebo-controlled clinical trial [1]. L-Theanine also helped in improving overall sleep quality and reducing sleep-related disturbances.

l-theanine weight loss and memory boost Anti-stress effects of L-Theanine compared to a placebo
L-Theanine improved stress during the first hour after dose. The effects were less significant at the three-hour mark
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4728665/

May Reduce Risk of Alzheimer’s Disease

Research has established a link between the reduction in the risk of developing Alzheimer’s disease and tea consumption [6]. L-theanine can help in reducing Amyloid-beta (Abeta)-induced neurotoxicity which is a major cause of Alzheimer’s disease [7].

L-theanine may reduce protein and lipid damage related to oxidative stress in the brain [7]. The overall levels of macromolecular damage due to oxidation are also reduced. Moreover, it raises glutathione levels and reduces the levels of compounds like ERK/p38 and NF-kappaB which can help in reducing the effects of degenerative diseases like Alzheimer’s.

May Improve Immunity

L-theanine has multiple effects on the immune system. Studies conducted on rats have shown that L-theanine improves immune function by increasing the spleen cell number by changing the splenic weight [8]. L-theanine may also boost the rate of antibody generation and can have anti-inflammatory effects.

Supplementation with L-theanine can help in boosting the immune system and raising the overall granulocyte percentage [9]. Some research has pointed out that it can help in the prevention of respiratory tract infections and conditions like influenza [10].

Boosts Cognitive Function

One important benefit of L-theanine is boosting cognitive functioning and subjective alertness. Since caffeine improves cognitive performance in some limited ways, it is often used with L-theanine. Therefore, taking L-theanine may help in improving attention levels while improving working memory.

Studies have also indicated that L-theanine improves performance in attention tasks and working memory-related tasks in middle-aged and older individuals [11]. It also helps in improving reaction time and visual attentional performance. However, the results were more pronounced on test subjects with higher levels of anxiety symptoms [12].

l-theanine weight loss and memory boost
The L-Theanine group had significantly better response scores than the placebo up to 60 minutes after dose
Source: https://www.sciencedirect.com/science/article/pii/S1756464611000351#f0010

Beyond that, L-theanine supplementation also resulted in better verbal fluency and executive functioning among test subjects.

May Enhance Cancer Treatment

Studies have shown that L-theanine in green tea can improve cytotoxicity in tumor cells. L-theanine can induce cancer cell death rate through acute glutamine deprivation with no negative effects on healthy cells [13].

Positive effects of L-theanine have also been found on human lung cancer and leukemia cells. With further research, L-theanine may find wide-scale therapeutic applications for cancer treatment [14]. Additionally, L-theanine can also help in sensitizing specific cells to cytotoxic agents and radiation therapy in patients with liver cancer.

Increases Focus

The relaxing effects of L-theanine may help in boosting mental focus and attention levels. This also makes it an important nootropic for memory enhancement.

The combined effect of L-theanine and caffeine intake can help in boosting subjective alertness levels. The combined effect of the two can also lead to better performance during demanding cognitive tasks [15].

L-theanine can have a positive effect on the activity of alpha waves in the brain and help in improving the critical aspects of mental focus. Research suggests that the influence of L-theanine on alpha brain waves also promotes alert relaxation of the mind and helps in maintaining focus levels under external stress.

The effects can also be related to the better objective sleep quality resulting from L-theanine.

Studies involving male children have also shown that daily dosage of L-theanine is effective in the treatment of attention deficit hyperactivity disorder (ADHD) [16].

May Lower High Blood Pressure

L-theanine helps in the reduction of cortical neuron excitation and helps to decrease blood pressure levels in adults with a high-stress response.

Research indicates that oral administration of L-theanine resulted in the reduction of systolic and diastolic blood pressure levels related to high-stress tasks [17]. However, it did not reduce blood pressure levels in situations related to high physical stress.

Since stress is an indirect cause of hypertension, the reduction in stress levels brought about by L-theanine can help in the treatment of hypertension.

What Is the Evidence Saying?

There has been no conclusive research to point out any negative side effects of L-theanine or chronic effects in healthy adults. In general, the consumption of green tea is considered safe for most people.

Is L-Theanine Safe?

Oral consumption of L-theanine is possibly safe when taken short term. There is not enough research to confirm its safety when consumed for long periods.

It is necessary to remember that no L-theanine dietary supplement is regulated or reviewed by the FDA. The safety of any supplement is solely the responsibility of the manufacturer.

Precautions and Warnings

Although L-theanine is mostly safe, some precautions are necessary while consuming nootropics for energy or memory enhancement.

Side Effects

Daily dosages between 200 to 400 mg of L-theanine have been used to treat stress and anxiety symptoms without any side effects [5]. In some cases, the caffeine content in an L-theanine supplement can lead to some discomfort, irritability, and nausea related to caffeine stimulation.

Here are some precautions that need to be taken while consuming L-theanine:

  • There is no data to confirm the safety of L-theanine during pregnancy and breastfeeding. It’s best to take precautions and consult a physician before using any supplement in these conditions.
  • People with low blood pressure should exercise caution before consumption. To prevent your blood pressure from dropping too low, consult your healthcare provider before choosing an L-theanine supplement.
  • Generally, L-theanine is considered safe for children. Doses of 200 mg of theanine have been safely used in male children for up to 6 weeks. Consult a physician before choosing any clinically unproven supplement for children.


Drug interaction risks related to L-theanine are:

  • Interactions with medications related to both high and low blood pressure are possible. If you take any such medication, consult with your healthcare provider before consuming L-theanine.
  • It can interact with medications that stimulate the nervous system. Since L-theanine slows down the nervous system leading to stress reduction, it can impact the effect of such medications. Consult your healthcare provider to find the right combination.
  • L-theanine can interact with sedatives. Therefore, if you consume sedatives regularly, consult your physician before supplementing with L-theanine.

Best L-Theanine Supplements

There are quite a few L-theanine supplements in the market. We have chosen three of the best options.

l-theanine weight loss and memory boost

Mind Lab Pro

This nootropic supplement is made from completely natural products and contains 11 effective nootropics including Suntheanine. Suntheanine is an L-theanine powder produced by enzymatic fermentation.

All the major components claim to play an important role in improving memory, performance, energy, and neuroregeneration by promoting nerve cell growth and help in oxygenating the brain cells. The overall effect leads to an improvement in memory functioning.

Mind Lab Pro helps in improving performance and productivity in professionals, students, and athletes. With higher energy levels, you can expect better results from exercise sessions. This can lead to better results when you are trying to lose weight or gain muscle.

Another positive aspect of Mind Lab Pro is it is free from synthetic compounds and any form of stimulant. However, the manufacturers have not mentioned any independent clinical trials to support their claims.

With a quality-driven design, it is one of the best nootropics for motivation in the market. Read more in our Mind Lab Pro review.


  • It contains premium quality components that deliver results
  • The capsules are made from 100% natural vegan products
  • It is free from gluten, synthetic additives, and caffeine
  • Safe and clean with no proprietary blends
  • Proper quality control to ensure potency and purity of ingredients


  • Some minor side effects were reported
  • A few users found no results after use


NooCube comes with a combination of multiple vitamins, herbs, plant extracts, and minerals. It is made of completely natural products that claim to provide all-day mental energy for professionals.

The components help in improving learning and memory capabilities while reducing stress and anxiety levels to ensure better mental clarity. NooCube also improves cerebral blood flow and reduces cellular inflammation.

The combination of L-tyrosine and L-theanine in NooCube helps in improving attention and focus in some randomized controlled trials. The brand mentions that NooCube can help in improving multitasking skills and keeps the mental energy levels high.

In addition, it can help in improving concentration levels during intense mental and physical activities. This can be beneficial for individuals looking to lose weight through rigorous exercise sessions.

NooCube does not contain any components that are proven to have any side effects. However. no complete list of the ingredients and their dosage is provided. Read on to learn more about this supplement in our NooCube review.


  • Delivers a smooth climb of mental energy and reduction in subjective stress
  • Natural ingredients are easily absorbed and safe
  • It is free from gluten and caffeine
  • The natural ingredients are backed by clinical data
  • It comes with a 30-day money-back warranty


  • It has no upfront label of ingredients
  • Lack of research to determine long-term side effects if any

Qualia Mind

Qualia Mind is another popular nootropic for enhancing brain function. It contains a complex mixture of 28 different herbs, vitamins, minerals, and amino acids.

Apart from L-theanine, Qualia Mind contains multiple ingredients that boost energy levels and helps in maintaining mental clarity. It also contains powerful antioxidants that have neuroprotective properties and can assist in better memory functioning. The overall effects can be beneficial in boosting exercise performance and weight reduction.

There have been some clinical studies to judge the exact efficacy of Qualia Mind. Preliminary results from one independent study have indicated that it boosted memory, concentration, and reasoning skill levels in the participants [18].

Keep in mind the product contains caffeine which is a stimulant. The brand claims that the product does not cause any jitters, however. Qualia Mind supplement is to be taken for five days at a stretch, followed by two days of break.

Furthermore, the performance of the supplement depends on the subject’s sleep quality. If you are experiencing sleep disorders, Qualia Mind will not work for you.


  • Helps to improve focus and short-term memory
  • It does not rely solely on caffeine and there is no energy crash
  • The positive effects are verified by independent research
  • It comes with a 100-day money-back warranty


  • Expensive
  • Contains caffeine as a stimulant
  • Standard dosage is seven capsules per day


Here are some of the common queries related to L-theanine.

What Does Taking L-Theanine Do?

L-theanine can help in improving brain function, focus, memory and can also have anti-obesity effects. It can also be effective in relieving stress and anxiety and help in conditions like attention deficit hyperactivity disorder. Research suggests that other benefits may include the prevention of cancer and hypertension.

How Do You Take Theanine for Anxiety?

It is usually taken in the form of an oral supplement. The recommended dosage can be between 200 to 400 mg per day. You can also drink green tea as a source of L-theanine.

Can L-Theanine Make Anxiety Worse?

There is no such evidence at present. As per research data, L-theanine assists in improving brain alpha wave patterns and also acts as a natural sleep aid, which helps in reducing stress and anxiety levels.

Does L-Theanine Affect Serotonin?

Neurochemistry studies on animals have indicated that L-theanine increases serotonin and dopamine levels. More studies are required to confirm the effect on humans.


L-theanine has become a popular nutritional supplement and is also a reason for the rise in the popularity of green tea. Due to its wide range of benefits, it is presently included in a variety of nootropic supplements.

Keep in mind that there is no conclusive clinical evidence on many of the positive effects of L-theanine. Therefore, consulting a medical practitioner before starting on any supplement is necessary.


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  2. C;, Nathan PJ;Lu K;Gray M;Oliver. “The Neuropharmacology of l-Theanine(n-Ethyl-l-Glutamine): A Possible Neuroprotective and Cognitive Enhancing Agent.” Journal of Herbal Pharmacotherapy, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/17182482/.
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  6. Polito, Curt Anthony, et al. “Association of Tea Consumption with Risk of Alzheimer’s Disease and ANTI-BETA-AMYLOID Effects of Tea.” Nutrients, MDPI, 22 May 2018, www.ncbi.nlm.nih.gov/pmc/articles/PMC5986534/#sec4-nutrients-10-00655title.
  7. Kim TI;Lee YK;Park SG;Choi IS;Ban JO;Park HK;Nam SY;Yun YW;Han SB;Oh KW;Hong JT; “l-Theanine, an Amino Acid in Green TEA, ATTENUATES Beta-Amyloid-Induced Cognitive Dysfunction AND Neurotoxicity: Reduction in Oxidative Damage and Inactivation of ERK/p38 Kinase and NF-KAPPAB PATHWAYS.” Free Radical Biology & Medicine, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/19766184/.
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