Caffeine and theine: are they the same substance?

Yes, caffeine and theine are the same substance. The French Academy of Agriculture considers the names theine, guaranine and mateine outdated, precisely because they all refer to the same compound: caffeine, an alkaloid of the methylxanthine family. The recommendation is to keep only the name caffeine, to avoid confusion. So when you read "theine" on a packet of tea, you are reading "caffeine" under another name.

The confusion comes from the old names. The old name stuck, but the chemistry did not change. If someone tells you that tea "doesn't have caffeine, it has theine", they are using an outdated name for the same substance.

Why does tea seem not to give the same stimulation as coffee?

Because the drink is different, not the molecule. A 220 ml cup of black tea contains, according to the EFSA, about 50 mg of caffeine. A 200 ml cup of filtered coffee contains about 90 mg. Nearly double. The amount and the portion size vary, but the order of magnitude explains a lot of the sensation.

There is also enormous variation within tea itself. An analysis of 20 commercial products found concentrations of 14 to 61 mg per portion in white, green and black teas, with no clear trend by variety. Brewing time affected the caffeine concentration. Decaffeinated teas were below 12 mg per portion, and in herbal teas no caffeine was detected. In other words: the same tea can give you a quite different dose depending on how you prepare it.

The difference you feel has to do with the dose and with the rest of the drink, not with a special property of the molecule when it comes from a tea leaf.

What caffeine does in the body, in plain language

The EFSA describes caffeine as a compound that stimulates the central nervous system. In moderate doses, it increases alertness and reduces drowsiness. That is what the established evidence allows us to say, and no more than that. It is not a source of energy: it is a stimulant of the nervous system.

That distinction matters. If you are exhausted because you slept badly for a week, caffeine does not solve the sleep debt. And, according to the EFSA, single doses of 100 mg can affect the sleep of some adults, especially if taken near bedtime. A coffee in the late afternoon may be sabotaging the night that should have solved the problem.

How much caffeine is reasonable in a normal day

The EFSA concluded that intakes up to 400 mg per day, spread throughout the day, do not raise safety concerns for healthy adults. The exception is pregnant women. For pregnant and breastfeeding women, the EFSA concluded that intakes up to 200 mg per day do not raise safety concerns for the fetus; talk to your doctor.

To put 400 mg in perspective: that is about eight cups of black tea or four filtered coffees, roughly, according to the average values above. The problem is that we rarely drink just one thing. Soft drinks, energy drinks, chocolate and supplements with guarana also count. Caffeine is the same, wherever it comes from.

If you are pregnant, breastfeeding, or if you have a health condition or take medication, the calculation stops being a curiosity and becomes a conversation with your doctor or pharmacist.

And L-theanine? That is another substance

L-theanine is an amino acid, it is not caffeine and it has no chemical relationship with it. We know they are different substances; the rest is not established.

It is worth knowing this because many labels mix the two and suggest a synergy that science has not yet confirmed. If you are looking for a specific effect, be wary of promises of certain results.

Where a supplement fits — and where it does not

A supplement does not replace habits. If you sleep badly, if you drink too much coffee late in the day or if you expect a gummy to make up for sleepless nights, no product will solve that. That said, there are situations where it makes sense to know what you are taking.

Energy Gummies with Guarana from TuttiBear contain, per dose of two gummies, 200 mg of guarana extract, of which 44 mg is caffeine, plus 200 mg of L-theanine, 100 mg of L-tyrosine, vitamin B6, B12 and C. The recommended daily dose is two gummies. The packaging warns that it contains caffeine and that it is not recommended for children, pregnant or breastfeeding women.

Notice the number: 44 mg is less than a cup of black tea. If you already drink three coffees a day, this supplement will not radically change your total intake — and that is what you should count. Guarana is just another plant that contains caffeine, as the EFSA notes when listing the natural sources of the compound. It is not a "better" caffeine.

There are also Active Metabolism Gummies, with green tea extract and green tea seed, among other ingredients. Green tea contains caffeine, and the packaging warns not to consume it together with other products containing green tea on the same day. If you are doing a caffeine count, this is a detail you should not ignore.

Neither of these products treats, prevents or cures any disease. They are food supplements. And there is no reason, in the available evidence, to prefer them to a well-made cup of tea if the goal is simply to be awake.

The mistakes worth avoiding

The first is trusting the "caffeine-free" label without reading the rest. The decaffeinated teas that were analysed had less than 12 mg per portion — less, but not zero. If you are very sensitive, you may still notice it.

The second is forgetting hidden sources. Chocolate, cola soft drinks, energy drinks and supplements with guarana or green tea add to coffee and tea. The 400 mg account is daily and includes everything.

The third mistake is the opposite: worrying too much about tea and ignoring coffee. A cup of black tea has about half the caffeine of a filtered coffee. If you are trying to reduce, coffee is the first place to look.

There is also a mistake of expectation: thinking that theine, because it has another name, does not count towards sleep. It does. It is the same molecule, with the same effect on the central nervous system.

When this stops being a curiosity and becomes a medical matter

If you are pregnant or breastfeeding, the limit drops to 200 mg per day and the conversation should be had with a professional. If you take medication, especially for the heart, for anxiety or for sleep, ask the pharmacist before increasing your caffeine intake. If you feel palpitations, tremors or persistent insomnia after drinking tea or coffee, that is a sign to talk to someone — not to change brands.

And if the underlying complaint is tiredness that does not go away, caffeine is not the answer. Increasing the dose to compensate is the wrong path. Persistent tiredness has causes that a supplement does not solve.

What to do next

Start by counting what you drink on a typical day, including tea, coffee, soft drinks and supplements. Then, if you want to reduce caffeine, swap coffee for tea — the difference in dose is real and significant. If you want to keep the tea habit, control the brewing time: it affects the amount of caffeine that passes into the cup. And if you are thinking of buying a supplement with caffeine or guarana, check the label and add that caffeine to what you already consume.

The distinction between caffeine and theine is not a question of chemistry: it is a question of vocabulary. Once that is resolved, what remains is the practical question — how much you take, when, and whether it is helping or just hiding the problem.