← Tea guide

L-theanine, caffeine, catechins (EGCG) - the trio of tea

Tea stimulates differently from coffee - it gives a calm, focused energy, with no nervous spike and sudden crash. It is no accident nor suggestion, but the effect of chemistry. Behind the flavour and the action of tea stand three key compounds that form a unique trio: L-theanine, caffeine and catechins, with the most famous EGCG. L-theanine gives umami and calm, caffeine energy, and catechins astringency and antioxidant power. Most interestingly, they do not act separately but work together, softening each other’s extremes. This is why tea stimulates gently, and its flavour is so complex. Here is a guide to the trio of tea compounds: what each of them is, how it affects flavour and action and why together they give an effect impossible to reach separately.

The three pillars of tea

The flavour and action of tea rest on three main compounds, worth getting to know together, because they work as a team. They are L-theanine, an amino acid giving umami and a feeling of calm; caffeine, an alkaloid responsible for stimulation; and catechins, a group of antioxidants giving astringency and bitterness, with EGCG at the head. Each of them brings something different to the flavour and to how we feel after drinking. But the real magic of tea hides not in them separately but in their mutual interaction. It is a team in which one softens the other, creating a balance unreachable for caffeine alone or an antioxidant alone. Understanding this trio is the key to grasping why tea acts and tastes as it does. They all come from the leaf of the same plant, Camellia sinensis. We cover caffeine itself more in caffeine in tea.

L-theanine: umami and calm

L-theanine is a unique amino acid, discovered in the leaves of green tea in 1949. It is responsible for two important things. First, for flavour: it is it that gives tea its characteristic umami, that full, brothy, slightly sweetish aftertaste, strongest in shaded teas like matcha or gyokuro. Second, for action: L-theanine affects the brain, favouring a state of calm focus. It raises the level of certain neurotransmitters associated with relaxation, giving a feeling of calm without drowsiness. This is why tea, despite the caffeine, does not cause the nervousness typical of coffee. L-theanine also balances the flavour, softening the astringency and bitterness of the catechins with its umami. It is a compound that makes tea at once tastier and calmer in action. Without it tea would be just a bitter brew with caffeine. L-theanine is the secret of its uniqueness.

Caffeine: the energy of tea

Caffeine is the alkaloid responsible for the stimulating action of tea - the same substance found in coffee. It is it that gives energy, alertness and clears the mind, blocking the signals of tiredness in the brain. But caffeine in tea acts differently from in coffee, even though it is the same molecule. The reason lies in the company of the other compounds, especially L-theanine and catechins, which change the way caffeine affects us. Caffeine alone would give a sharp spike of energy and an equally sharp crash, sometimes with nervousness. In tea this effect is softened and lengthened. This is why the stimulation from tea is often described as calmer and more balanced. Caffeine is the engine of tea’s energy, but it is its co-workers that decide how gently this engine runs. The amount of caffeine alone is not everything - the context counts.

Catechins and EGCG: astringency and antioxidants

Catechins are a group of strong antioxidants present in tea, and the most abundant and best-studied of them is EGCG (epigallocatechin gallate). They are responsible for two things. In flavour they give astringency and part of the bitterness - it is they that pucker the mouth and create the dry, tannic character, especially in strongly brewed green tea. In action they are prized for their antioxidant power: they neutralise free radicals and are the subject of numerous studies on health. EGCG is the star here, studied for its potential protective action, including for the brain. Catechins are abundantly present in less oxidised teas, like green, and decrease with stronger oxidation. It is they that give tea its dry edge and most of its health reputation. Drawn out too strongly, though, they give an unpleasant bitterness. We cover bitterness more in bitter tea.

A table: three compounds

Let us gather the trio in one place:

The table shows that each compound brings a different flavour and a different action. Only together do they create the full picture of tea - its characteristic flavour and its unique way of stimulating.

Synergy: calm energy

The most interesting thing in tea is how these compounds work together. Caffeine alone gives a sharp, sometimes nervous stimulation. But in tea L-theanine softens its action, and catechins additionally slow it - catechins bind with caffeine, creating a slow, even release of energy instead of a violent spike. The result is a state described as calm alertness: at once stimulated and soothed, focused without the jitters. Research shows that L-theanine and caffeine together improve attention and working memory more effectively than either alone. It is a classic example of synergy: the whole gives an effect better than the sum of its parts. It is precisely this cooperation that sets tea apart from coffee, despite the same caffeine. It is not the amount of the substances but their team action that creates the unique character of tea. Synergy is the heart of its phenomenon.

How brewing changes the proportions

The proportions of these compounds in the brew are not fixed - they depend on the way of brewing, and this gives real control over flavour and action. Hotter water and longer brewing draw out more catechins and caffeine, giving a stronger, more astringent and stimulating brew, but also a more bitter one. Cooler water and a shorter time draw out more of the delicate L-theanine relative to the catechins, giving a gentler, sweeter brew, with clearer umami and a calmer action. This is why the same tea brewed cold or cool tastes sweet and soothing, and flooded with boiling water for long - bitter and strong. Knowing this mechanism, you can deliberately steer the profile: want calm and umami, brew cooler and shorter; want energy and edge, hotter and longer. Brewing is a tool for regulating the trio of compounds. We cover the kinds of green more in green tea types.

How to sense it in the brew

The action of the trio is easy to sense once you know what to look for. The full, brothy, slightly sweetish aftertaste that stays on the tongue is umami from L-theanine - strongest in high-quality green teas and matcha. The mouth-puckering astringency and dry bitterness are the catechins, especially in a strongly brewed green. The stimulation after drinking, but calm and even, with no nervous spike, is the effect of the synergy of caffeine with L-theanine and catechins. If after tea you feel focused and soothed at once, that is precisely their joint work. It is worth comparing a matcha rich in L-theanine with a strong, astringent black brew, to feel the different proportions of the trio. Over time you will start to recognise the flavour of each compound and deliberately choose your tea for your mood. We cover the whole family more in types of tea.

The essentials in brief

Let us gather it up. Behind the flavour and action of tea stands a trio of compounds from the leaf of Camellia sinensis: L-theanine, caffeine and catechins. L-theanine is an amino acid giving umami and calm focus; caffeine is an alkaloid giving energy; catechins, with EGCG at the head, give astringency and antioxidant power. Their magic lies in synergy: L-theanine softens the caffeine, and catechins slow it, giving calm alertness instead of a nervous spike - this is why tea stimulates differently from coffee. The proportions in the brew depend on the brewing: cooler and shorter gives umami and calm, hotter and longer gives edge and energy. It is this joint action, not the amount alone, that creates the phenomenon of tea. Now you know why tea stimulates gently and where its complex flavour comes from.

Note every tea in GustoNote - including the umami, astringency and the way it acts that you sense. Over time you will start to recognise the trio of compounds and deliberately steer it through brewing.