VERIFIED CONTENTAuthor: Aleksandra Żyłowska-Mharrab, dietitian, food technologist, educator
L-Theanine is a relatively new substance in Western science and medicine. It is not to be confused with theine, although both are found in tea leaves. Research on its activity explains some of the so far mysterious effects of tea. L-theanine works primarily on the nervous system. It is best known for relaxing and enhancing learning. What else does L-theanine help with? In what doses should it be used? Is drinking tea enough? And is L-Theanine really safe?
L-teninis present in green and black tea leaves. Only these sources are of importance in the human diet. It is formed in the roots of the tea plant, but then transported to the leaves where it accumulates in the greatest amounts.
What is L-Theanine?
L-theanine (γ-glutamylethylamide) is a unique non-protein amino acid derived from glutamine. It is not found in the human body and is not essential (unlike protein amino acids). Theanine can exist in two conformations - L and D. L-theanine is a biologically active form, and D-theanine is irrelevant to he alth. Forms L and D occur together in natural sources, but D-theanine is only 1.85% of total theanine, based on an analysis of 17 types of tea.
L-theanine makes up 1 to 2.5% of the dry weight of the tea leaves. Under the influence of sunlight, L-theanine is converted into polyphenols. It affects the taste and aroma of tea - it is responsible for its umami taste, reacting with the taste receptors - T1R1 and T1R3. For this reason, some growers make sure their plants grow in the shade. All this in order not to lose the L-theanine content that shapes the taste. L-theanine should not be confused with theine, although their names sound very similar and both substances are found in tea leaves.
Research on the L-theanine content of different types of tea is not consistent. One theory is that green tea contains more of this compound than red and black (fermented) teas, because L-Theanine is converted into glutamic acid and ethylamine during fermentation.
Some authors quotehowever, the concentration of L-theanine in black tea is higher than in green tea. L-theanine does not decompose at 121 degrees Celsius. This means that even after pouring boiling water over the tea, L-Theanine remains active.
Why is science interested in L-Theanine?
It is a psychoactive compound that crosses the blood-brain barrier. Due to its structure similar to glutamine (an amino acid naturally occurring in the human body, the functions of which include the conduction of nerve impulses), L-theanine has an effect on the nervous system - it has a relaxing effect and reduces anxiety.
You can get an active dose of L-theanine from supplements as well as from a few cups of tea a day. Scientific research shows that consuming L-theanine can have great he alth benefits and positively affect the quality of life in a stressful environment.
How does L Theanine work?
The chemical structure of L-theanine is similar to the neurotransmitters glutamate and GABA. Due to its structural similarity to glutamate, L-theanine blocks the binding of L-glutamic acid to glutamate receptors in the brain.
Thus, it is believed to induce an anti-stress effect by inhibiting the excitation of cortical neurons. L-Theanine crosses the blood-brain barrier via the transport system of neutral, leucin-preferring amino acids and increases the production of both serotonin and dopamine in the brain.
However, the mechanism of dopamine release caused by L-theanine is different from blockers of the glutamate transporter or glutamic acid. It has been hypothesized that L-theanine may inhibit excitatory neurotransmission, and thus have a calming effect.
L-Theanine taken orally as a supplement or infusion of tea leaves is absorbed in the intestines. It quickly goes into the blood when absorbed.
In human studies, it was found that after oral ingestion of L-theanine, it reaches its maximum concentration in the blood between 32 and 50 minutes. Together with blood, it is easily transported to the brain and other organs, and is excreted in the urine. L-theanine has a bioavailability of 47 to 54%.
L-theanine acts on the brain by changing the levels of GABA, serotonin and dopamine, as well as increasing the activity of alpha waves in the brain, which is responsible for reducing tension and the emergence of a state of relaxation.
L-theanine - he alth effect
L-theanine reduces stress and anxiety
The action of L-theanine is compared to that of anti-anxiety drugs. L-Theanine supplementation, as well as drinking tea, relieves tension and anxiety without making you feel drowsy. At the same time, it has a positive effect on the quality of sleep thanks toanxiolytic effect. Many people with anxiety or anxiety personality disorder experience difficulty falling asleep by increasing anxiety when falling asleep. L-theanine should not be confused with sedatives. It induces a feeling of relaxation, but it does not help in states of strong, short-term stress.
Scientific research shows that L-theanine relaxes the mind when taken in a single dose of 50 mg. A significantly increased activity of the alpha frequency band in the brain is then observed. In one study involving women aged 18-22, it was found that taking L-theanine in a dose of 200 mg generates alpha brain waves and triggers a subjective sense of relaxation.
In a randomized, double-blind, placebo-controlled clinical trial, a daily intake of 400 mg of L-Theanine for 6 weeks was shown to be safe and effective in promoting falling asleep.
L-Theanine increases cognitive and learning abilities
Tea has long been thought to be due to the concentration and cognitive effects of caffeine. It turns out that it's not all about caffeine. Decaffeinated tea containing L-theanine and theogallin also has a cognitive stimulating effect. This shows that L-theanine itself is a stimulant of response and learning.
A lot of research has focused on the effects of L-Theanine in combination with caffeine. L-theanine has been shown to increase the stimulating effect of caffeine. In combination with it, it plays a beneficial role in improving performance in cognitively demanding tasks, such as word recognition or fast processing of visual information.
One study found that a combination of caffeine (150 mg) and L-theanine (250 mg) led to faster simple reaction times, faster numerical working memory reaction times, and improved sentence verification accuracy.
L-theanine has one more advantage. It is well known that high doses of caffeine cause excessive agitation, nervousness and trouble falling asleep. L-theanine reduces the sleep-disrupting and over-stimulating effects of caffeine.
L-theanine reduces physical fatigue
L-theanine causes an increase in the concentration of dopamine in the brain and liver glycogen (which stimulates the body), and a decrease in the activity of 5-HT serotonin receptors and serum urea concentration.
This results in the relief of physical fatigue. L-theanine can be used as a sports supplement, allowing you to extend training and increase its intensity, or to reduce physical fatigue faster after training.
L-theanine in diseases of the nervous system
L-Theanineshows neuroprotective effects in many fields. Scientific research conducted on animals and human cell lines shows that:
- L-theanine has neuroprotective effects by interacting with the GABA receptor.
- L-theanine can help prevent memory impairment caused by recurring cerebral ischemia.
- L-theanine inhibits the death of nerve cells in the hippocampus.
- L-theanine protects against neurotoxin-induced Parkinson's disease.
- L-theanine lowers the level of amyloid in the brain. Their accumulation is characteristic of Alzheimer's disease.
- Moreover, L-theanine has been proven to alleviate activation and anxiety symptoms in patients with schizophrenia and schizoaffective disorders. It probably has an antidepressant effect along with an antipsychotic effect.
L-Theanine supports the immune system
Not necessarily L-theanine supplementation, but just drinking tea strengthens immunity. L-theanine may play a role in strengthening the immune system because its metabolite, ethylamine, activates one of the components of the immune system, namely gamma-delta T lymphocytes.
Depending on the source of the infection, L-theanine metabolite may induce both specific and non-specific immune system responses. The discovery of this process allows us to at least partially explain the beneficial effects of tea in diseases.
Co-administration of L-theanine (80 mg / kg) and L-cystine (200 mg / kg) has also been found to increase the production of ethylamine-specific immunoglobulin G, in part by increasing glutathione levels and the immune response mediated by Th2 T-helper cells.
Oral dosing of 490 mg L-cystine and L-theanine twice daily has been shown to be useful in the prevention of the common cold.
L-theanine in cardiovascular diseases
Epidemiological and clinical studies in recent years have shown that regular consumption of green or black tea significantly reduces the risk of cardiovascular disease. One of the key ingredients in tea that supports the cardiovascular system, in addition to antioxidants, is L-theanine.
L-theanine reduces blood pressure in hypertension and inhibits the increase in blood pressure caused by caffeine. Moreover, L-theanine has been shown to promote the activation of the ERK / eNOS signaling pathway in vitro in the human vascular endothelial cell line, resulting in increased nitric oxide production. The role of nitric oxide in the proper functioning of the circulatory system is huge.
Other activities of L-Theanine
- In vitro and in vivo tests on animalsshow that L-theanine may have anti-cancer effects.
- In animal studies, L-theanine has been shown to be effective in the treatment of gastric and duodenal ulcers.
- L-theanine may prevent alcohol-induced liver damage by increasing the antioxidant capacity of hepatocytes.
- L-theanine may reduce symptoms related to PMS.
Is L-Theanine safe?
According to the US FDA (Food and Drug Administration), L-theanine has the GRAS status, meaning "Generally Recognized as Safe" and is considered non-toxic. No dietary limits have been recommended for L-theanine intake. Taking L-Theanine orally is possibly safe in the short term.
No significant side effects of L-theanine supplementation were found in human research studies up to 8 weeks. The only side effects that may occur after consuming L-Theanine are headache and drowsiness. There is a lack of research on the long-term use of L-theanine as a supplement and its safety.
The doses of L-theanine administered to research participants were usually up to 900 mg per day, although it is believed that even 5 g per day does not adversely affect the human body. It can be considered that such an amount used daily is not harmful to he alth. Short-term and in lower doses, L-theanine is also safe for children aged 8-12 years.
The conducted analyzes lasted up to 6 weeks with a daily dose of up to 200 mg. However, there are no studies that would confirm the safety of L-theanine in pregnant and breastfeeding women.
Due to the fact that L-theanine can cause blood pressure drops, people with low blood pressure or taking antihypertensive drugs should not use the supplement without consulting a doctor. L-theanine interacts with drugs that stimulate the nervous system, so they should not be combined with each other.
How to use L-Theanine?
L-theanine can be provided by drinking tea or using dietary supplements. How much L-theanine in tea? Assuming that we prepare the infusion from 1 teaspoon, which contains 2 g of tea, you can find from 20 to 40 mg of L-theanine in it.
There are no official recommendations regarding the use of L-theanine in diseases, however, based on the results of scientific research, a dosage of L-theanine can be proposed.
How to use L-Theanine?
- To relieve tension and relax- 50 to 200 mg of L-theanine daily.
- Anti-anxiety- 250 to 1250 mg of L-theanine per day.
- For improving memory and abilities - 100 mg of L-Theanine before a mental task OR 200 mg daily for 4 weeks. L-theanine has also been used in combination with caffeine. The combination doses ranged from 30-150 mg of caffeine and 12-250 mg of L-theanine.
- For strengthening the immune system- 490 mg of L-theanine 2 times a day.