Daniel Safvat
Daniel Safvat

Senior Writer

Can Caffeine and L-theanine help to stabilize your mood? A scientific report
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Caffeine is the most frequently taken psychoactive element in the world, with coffee and tea representing our main dietary sources. It is a naturally occurring substance with stimulating effects and is found in more than 60 different items, including coffee, tea, cola, chocolate, guarana, and yerba mate. Caffeine is most frequently used by people for mental clarity, migraine, headache, memory, and obesity. Caffeine and L-theanine, two components of tea, may combine to affect behaviour, but there is no research on how they may affect cerebral blood flow (CBF).

Although the beneficial effects of caffeine on cognition and mood have been reported in many studies, relatively few studies have looked at the effects of caffeine in combination with other compounds, even though caffeine is seldom consumed in isolation. This study has scientifically proved the effect of caffeine and L-theanine on your mood.


Caffeine’s effects are believed to be caused by non-selective antagonism of adenosine A1 and A2A receptors, with A1 receptors being more closely associated with brain activation and A2A receptor antagonism causing vascular effects, such as vasoconstriction and a decrease in cerebral blood flow (CBF).

Functional MRI (fMRI) investigations have found that both effects have the potential to modify the blood-oxygenation-level dependent (BOLD) signal response and that the ratio of adenosine receptors (A1 to A2A) affects the overall vascular and neuronal effects. Caffeine has been demonstrated to decrease cerebral blood flow and CBF measured using a variety of methods. Caffeine’s effects on CBF are also influenced by how much of it is regularly ingested.

Health benefits of caffeine

1.  Lower Anxiety

2. You might have a longer life.

3. Your body may metabolize glucose better

4. Lower risk of heart diseases

5. Lower the chance of Parkinson`s diseases

6. Less likely to develop stroke

Caffeine and L-theanine

Let's review a scientific study to evaluate the effect of caffeine and L-theanine on our brains

1. Initial Screening;

Volunteers had to give their informed consent before they could take part, and they had to fill out a survey about their daily caffeine usage that had not yet been published. Participants in the study were invited to sign up if they fit into one of two predetermined categories: “habitual consumers” (those who drank tea and consumed more than 150 mg of caffeine daily) or “non-habitual consumers” (those who drank no more than two cups of tea or coffee per week and less than 60 mg of caffeine daily).

These cutoffs were created to ensure that habitual consumers drank the equivalent of at least three 190 ml cups of tea each day and to allow non-habitual consumers to drink a 330 ml can of most typical colas per day. Only healthy, non-smoking volunteers without a history of head trauma, learning disabilities, ADHD, neurological, vascular, or psychiatric conditions were invited to participate in the study. They also had to be non-smokers and not currently taking any dietary supplements or medications (including the contraceptive pill).

2. Treatment is given to the participant;

Participants underwent one of the following treatments during each of their four study visits, each of which was spaced at least 48 hours apart: 75 mg of caffeine, 50 mg of L-theanine, a placebo, or a combination of 75 mg of caffeine and 50 mg of L-theanine.

 The doses were chosen roughly correspond to the concentrations in two cups of tea. These were selected to complement earlier research on the effects of 100 mg L-theanine while more accurately capturing the proportion of L-theanine to the caffeine found in tea. To hide any flavour variations and guarantee that participants were unaware of the treatment they had received, each treatment was given as two capsules.

An impartial third party who was not further involved in the study manufactured and coded the capsules. Latin square and random allocation to treatment order for each group were used to determine the participants’ exposure to each treatment in the appropriate sequence.

3. People who participate in the study;

24 healthy young people between the ages of 18 and 35 were sought out, with 10 of them being men. Twelve participants were categorized as habitual consumers, whereas another 12 were non-habitual. Regular users reported consuming between 163 and 432 mg of caffeine per day according to the self-report questionnaire on caffeine use.

Non-habitual users reported consuming 0 to 56 mg of caffeine daily. Habitual tea drinkers said they drank between one and six cups a day, whereas non-habitual drinkers said they drank between zero and two cups per week. The ethical committee for the School of Psychology and Sport Sciences at Northumbria University gave its approval, and the study was carried out by the Declaration of Helsinki (1964).

 4. Salivary samples were taken to check the level of caffeine.

Salivettes were used to collect saliva samples. Two samples were collected: one upon arrival and one right after the post-dose cognition test. This was done to assure overnight abstinence from caffeine and to confirm that caffeine was absorbed after caffeinated therapies (no analysis of post-treatment caffeine levels was made following placebo or L-theanine). Once taken, samples were frozen at −20 °C. The samples were then thawed and the caffeine levels in the saliva samples were measured using an Emit Caffeine Assay.

read more: New Study: Ashwagandha Benefits Brain Health!

Mood assessment

The Computerized Mental Performance Assessment System was used to offer all cognitive and emotional measurements, a specially created piece of software that allows for the flexible delivery of parallel versions of the standard and unique cognitive assessment tasks that are produced at random.

It has been demonstrated in the past that this assessment method is responsive to dietary treatments, including caffeine. The tasks were picked because they were known to be sensitive to either one of the two nutritional therapies being studied. The only difference between the tasks finished at baseline and post-dose was that baseline tasks were cut down to 2 minutes.

This minimized the discomfort caused by restricted movement by ensuring that participants were not attached to NIRS equipment for longer than 2 hours.

Caffeine and L-theanine

Caffeine improved performance on attention tasks, decreased oxygenated haemoglobin (oxy-Hb), increased deoxy-Hb, and raised ratings of overall mood. The effects of coffee on deoxy-Hb were more significant in non-consumers.

When caffeine and L-theanine were combined, some evidence for elevated deoxy-Hb persisted, but this impact was diminished and the effects of caffeine on oxy-Hb, cognition, and mood were eliminated.

Caffeine has been demonstrated to decrease cerebral blood flow and CBF measured using a variety of methods. Following dosages of 1, 2.5, and 5 mg/kg caffeine, a linear dose association has been seen between the decreases in CBF.

Caffeine’s effects on CBF are also influenced by how much of it is regularly ingested. Caffeine usage is strongly positively connected with CBF following both placebo and caffeine in a withdrawal state, chronic high users have higher resting CBF compared to low consumers. There is also proof that high users react to a 250 mg dose of caffeine provided while in a state of withdrawal more acutely than low consumers do, despite having a higher CBF overall.

The decrease in CBF caused by caffeine is in opposition to neurovascular coupling, a difficult-to-understand series of events, in which a rise in neuronal activation causes an increase in CBF to satisfy and, in the case of oxygen, exceed the metabolic needs provided by the activation. Deoxygenated haemoglobin is normally diluted in proportion to an increase in cerebral oxygenated haemoglobin as a result of this process.

Caffeine has repeatedly been proven to speed up reaction times despite the reported decrease in CBF and consequent decrease in the supply of metabolic substrates.


The main goal of the current investigation was to evaluate the independent and combined effects of caffeine and L-theanine on cerebral blood flow for the first time. By examining behavioural effects at doses lower than those employed in prior studies using a comparable methodology, which more nearly represents the ratios present in tea, the study further expanded earlier results of the two drugs’ impacts on cognition and mood.

These findings show that, when compared to a placebo, caffeine decreased the amount of oxygenated haemoglobin in the pre-frontal cortex during the absorption period minutes 3-6 and 11-18 as well as during task performance starting at 39 minutes after the caffeine dose and lasting until the end of the test. Despite L-theanine not affecting this measure when taken alone, the effect of caffeine was eliminated when combined with it.

In comparison to the placebo, the predicted decrease in deoxygenated haemoglobin during the task period was attenuated after both caffeine-containing treatments. Except for CRT, this impact was significant after caffeine alone during the whole task period, whereas after the combination, it was only significant during serial subtractions, CRT, and Stroop. A strong treatment-consumer interaction was also present, with the effects of caffeine alone on deoxygenated haemoglobin dependent on an increase in non-habitual consumers during the whole testing session.

The current study’s decline in oxy-Hb confirms findings from earlier imaging studies indicating lower CBF with greater coffee doses. Of particular note, co-administration of L-theanine with caffeine eliminated its effects on oxy-Hb but not deoxy-Hb. This set of results aligns with earlier blood pressure observations.

Caffeine significantly lowered decision reaction time, enhanced Stroop performance, and increased subjective assessments of the general mood in terms of behavioural impacts. The last two tasks finished in the cognitive paradigm were those influenced by coffee, possibly showing that impacts on behaviour didn’t show up until 55 minutes after administration.

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