L-Theanine and Green Tea: Properties, Effects and Contraindications

Initially identified as a flavoring agent responsible for the sweet taste of some green teas, theanine has, in recent decades, been the subject of scientific studies that have uncovered its potential relaxing, anxiolytic, and hypotensive activity. An extremely rare molecule to find in nature, theanine is responsible for the relaxed and serene waking state we come to find ourselves in after drinking a cup of good green tea, such as matcha tea. But what are the mechanisms to which we can ascribe its properties? In this article we will find out what L-theanine is, why it is so beneficial, and in which teas it is found.

L-theanine: What is it?

L-theanine is an amino acid found almost exclusively in tea, and thus in Camellia sinensis, the plant whose leaves are used to make the famous infusion, particularly in green tea and matcha tea. This important molecule, often associated with glutamine (in fact, its name is N-ethyl-L-glutamine) and derived from glutamic acid, as their chemical structure is very similar, differs from other amino acids in not being proteinogenic, that is, it is not incorporated into the chains that make up proteins.

Amino acids are molecules containing an amino group, a carboxyl group and a chain that varies for different amino acids. Tea contains several amino acids, but of these only a portion are water-soluble and are retained in the brew: theanine makes up 60 percent of this amount of amino acids and is responsible for the recognizable sweet and umami taste of green tea, in which it is most abundant.

Theanine is a very significant chemical that has recently received attention due to its psychoactive properties. It can cross the blood-brain barrier and cause the brain to produce alpha waves (also known as an alpha rhythm), which are typically recorded when a subject is awake but completely relaxed.

For this reason, in this article we want to delve into the extraordinary relaxing properties of theanine, as well as its other various health effects, by finding out in which teas in particular it can be found and what benefits it has for our bodies.

Where is Theanine Found?

The main source of theanine is tea, particularly green tea, although traces have also been found in other species of the genus Camellia and in some varieties of mushrooms (Boletus badius). Tea represents the most common food in which L-theanine can be found, which is therefore a substance that is as beneficial as it is difficult to find in nature.

When the leaves are extremely young, the amino acid theanine begins to form in the tea plant. As the plant carries out chlorophyll photosynthesis through exposure to the sun, L-theanine is transformed into catechins, which are the antioxidants in tea. On a chemical level, there will therefore be more theanine in the tea plant in the younger, lighter leaves found at the top of the plant than in the older, lower leaves, which have been exposed to the sun longer and have carried out photosynthesis and developed more chlorophyll. This does not mean that the early tea leaves are totally devoid of antioxidants: as the leaf remains exposed to the sun, however, it will lose L-theanine and gain antioxidants.

Few people are aware that the amount of theanine in the tea leaf determines how sweet the tea will taste. Because of the high levels of theanine, a good matcha is distinguished by its distinctively sweet and velvety flavor. Few people know that theanine dissolves best in cold water: this is precisely why to enjoy the benefits you can opt for an iced green tea.

In pharmacies, the L-theanine produced for marketing is obtained by bacterial fermentation.

Theanine in Matcha Tea and Green Teas

Among the green teas richest in theanine are matcha tea and gyokuro tea, which are characteristic for their sweetness and balance. Theanine levels in these two teas are higher than in other green teas, but why?

Climate, leaf harvesting timing, and cultivation techniques all have an impact on the chemical makeup of leaves and, consequently, the levels of theanine.

Matcha and gyokuro tea (such as the Gyokuro for sale on Third Moon) have high amounts of this amino acid mainly because of Japan’s traditional cultivation method called kabuse: with this cultivation, tea plants are shaded under tents, plus or minus 15 days before harvest. Through shading, the plant is protected from the sun: the leaves will thus produce less chlorophyll but will still ripen. This produces a tea leaf that is very rich in L-theanine, but also in caffeine and antioxidants.

Similarly, the first harvest leaves carried out in early spring, the so-called first flush, of any green tea (e.g., sencha tea) will be richer in theanine than the second flush, second harvest leaves, which will have carried out more photosynthesis. Younger tea leaves are consequently, due to the higher theanine content, more delicate, sweet, balanced, and therefore the most valuable, and will have fewer polyphenols, a characteristic of the bitter taste.

Properties of L-Theanine

But why is theanine regarded as a sign of the quality of a tea and for what purpose is it used? Theanine has various benefits, as mentioned above. In particular, it is an amino acid that can cross the blood-brain barrier and raise the alpha rhythm, which is the baseline rhythm of electroencephalography and occurs when a person is awake yet entirely relaxed. By capturing electrical impulses on the scalp surface, electroencephalography can record brain waves. The various rhythm, frequency, and intensity of the waves correspond to distinct levels of brain activity, from awake to relaxation to sleep. Thus, alpha waves, also known as Berger’s rhythm, are characterized by gradual oscillations with a frequency of 8–13 Hz and signify a conscious, alert, but unconcerned adult. Generally this condition is overridden by visual or mental stimuli.

Experimental investigations have demonstrated that giving theanine to individuals with anxiety disorders caused alpha brain waves to appear 30 minutes after ingestion, which is the amount of time needed for L-theanine to enter the bloodstream and reach the brain.

Several studies have also demonstrated how theanine consumption lowers physical and mental stress while promoting a relaxed but awake mood that enhances focus and attentiveness. Theanine actually assists in enhancing focus and cognitive function by balancing the adverse and anxiolytic effects of caffeine, which is present in tea leaves.

According to evidence in the scientific literature, L-theanine generally has the following properties:

• Relaxing and Sedative
• Anxiolytic and Hypotensive
• Antidepressant
• Neuroprotective
• Anti-stress and fatigue
• Immunomodulatory

Relaxing and Anxiolytic Properties

The middle of the night, when one is relaxed but not sleeping, is when alpha waves are typically detected. This is a condition that is very beneficial to the body and brain and may be attained through the same breathing and meditation techniques. Extreme calmness is what one feels right before falling asleep; by contrast, anxiety, stress, and sleeplessness are caused by low levels of alpha waves. Studies have shown how theanine stimulates the production of alpha brain waves, and thus induces a state of relaxation and calm that can counter anxiety, agitation, and stress and hypertension.

Although the precise mechanisms by which theanine interacts with serotonin levels are unknown, the effect produced by the compound in the brain is believed to be related to higher levels of dopamine and GABA (gamma-aminobutyric acid), a crucial neurotransmitter that controls neuronal excitability in the nervous system. It is to these very mechanisms that the relaxing, antidepressant, and anti-stress properties are attributed.

According to some researchers, glutamic acid, a precursor to theanine itself, and the neurotransmitter GABA, whose high concentration at the neuronal level could very well appear to promote headaches, insomnia, and arousal as well as able to cause neuronal damage and Alzheimer’s disease, are both excitably toxic substances. Studies in laboratory rats have also shown neuroprotective effects of L-theanine.

Effects on the Immune System

L-theanine is also associated with immunomodulatory effects. Indeed, it is believed that theanine improves the immune defense response to viruses, bacteria, and other infections by enhancing the activity of gamma delta T lymphocytes, which mediate innate immunity and play a role in antigen recognition. However, this action needs further study, as existing studies, although they show a correlation between theanine and immune response, have been conducted on limited samples.

Theanine and Caffeine

Often, theanine is confused with caffeine, its name being similar to that of theine, as caffeine in tea is called. In reality, these are two distinct molecules with different functions and effects, the correlation of which is very important.

We have seen how L-theanine, which precisely counteracts the central nervous system stimulant activity of theine, is responsible for the calming effect of tea despite its caffeine content. This allows one to enter a state of calm but not drowsiness, a restful wakefulness in which the side effects of caffeine, such as anxiety, shaking and nervousness, hyperexcitability and tachycardia, are modulated.

There is often a tendency to believe that at the level of leaf chemistry, a tea that contains more L-theanine will have less caffeine, but this belief is incorrect: the balance between the two occurs only at the level of the effects they produce on the body. Caffeine-rich teas like matcha and gyokuro provide you the energy and focus boost that this chemical produces, but they’re also high in theanine, a substance whose qualities counterbalance the negative effects of caffeine use to ensure that you stay awake but still feel relaxed.

How to Take Theanine? Tea and Supplements

As we have already described, theanine is a difficult substance to find in nature, as it is found exclusively in tea, thus in the leaves of Camellia sinensis, and in some mushrooms in limited quantities.

Having discovered its benefits, the pharmaceutical industry produces dietary supplements with L-theanine for improved mood and sleep and cognitive effects: in these cases, L-theanine is replicated by bacterial fermentation.

Drinking tea remains the easiest way to take theanine, found particularly in green tea and even more specifically in shady teas such as matcha tea, gyokuro, and kabusecha.

How much theanine to take? Doses

As we shall see, there are no particular contraindications related to theanine intake, so if one is taking it through tea one must refer to the consequences of drinking too much tea. While rich in theanine, a single cup of green tea will still give a limited amount of this substance. 100 to 200 mg are the recommended dosing ranges.

Contraindications

Some studies show how theanine helps reduce blood pressure, which is why it might increase the effect of antihypertensive drugs. Also having relaxing properties, it could counteract the effect of cognitive enhancement drugs. Theanine cannot be taken through green tea by people intolerant to caffeine, as the latter is still present in the infusion, although the effects are modulated by the substance. It is also preferable to avoid theanine in cases of pregnancy and lactation.

Side Effects

Theanine intake is considered safe, and excessively high doses of theanine have no particular physical or psychological side effects. On the contrary, theanine has important effects on relaxation, anxiety, and insomnia, counteracting anxiety, stress, and improving concentration. Drinking a theanine-rich tea is optimal for those who suffer from the effects of caffeine but need a drink that will wake them up and help keep their attention high, as the amino acid counteracts the negative effects and anxiety induced by theine, while also counteracting the classic bitter taste of green tea and due precisely to caffeine.