- There are reports that combining caffeine and L-theanine has a positive effect on attention and concentration.
- The evidence score is 78, indicating that reliability is considered high.
- This information is intended for people who want to support their concentration and accuracy while working.
Caffeine + L-theanine refers to the combination of caffeine and L-theanine.
These are ingredients that are sometimes used individually, but they are also consumed together.
Combining caffeine and L-theanine may increase task accuracy and the feeling of mental clarity (alertness). There are also reports of feeling less fatigued.
This study involved 44 young adult participants. It examined how combining caffeine and L-theanine affected task-switching and concentration. 3 of the 4 studies were conducted as randomized controlled trials (a reliable research method in which participants are randomly divided to compare effects). In other words, these are attempts to scientifically verify the effects of this particular combination.
Several studies suggest the possibility of enhanced cognitive function, alertness, and concentration.
According to one systematic review (a method that compiles and analyzes many past studies), combining L-theanine and caffeine may improve cognitive function, alertness, and concentration. In another experiment, a small-scale study with 27 adult participants found that taking a specific amount reduced errors during a task.
In this study, doses of 50mg of caffeine and 100mg of theanine were used. Technically, it is reported that the error rate decreased with statistical significance (meaning the difference was not due to chance but was meaningful). In other words, concrete data exists regarding the effect of reducing mistakes.
Compared to taking caffeine or L-theanine alone, there are results suggesting that a distinct effect appears specifically when they are combined.
One study examined improvement in the ability to discriminate information (the ability to pick out the correct item from among a lot of information). The results showed that when caffeine and L-theanine were combined, the ability to correctly discriminate information improved compared with a placebo (a comparison substance with no active effect).
On the other hand, caffeine alone also improved information discrimination ability, but no change was seen in accuracy rate. There are also reports that no effect was confirmed with L-theanine alone. In other words, this suggests there may be some significance to combining the two ingredients.
| Study | Design | Number of participants | Duration | Main result |
|---|---|---|---|---|
| Nutritional Neuroscience (2010, PMID:21040626) | Randomized controlled trial (RCT) | 44 | Unknown | A positive effect was reported |
| Nutrition Research (New York, N.Y.) (2025, PMID:39854799) | Systematic review | Unknown | Unknown | A positive effect was reported |
| The Journal of Nutrition (2008, PMID:18641209) | Randomized controlled trial (RCT) | Unknown | 4 days | A positive effect was reported |
| Neuropharmacology (2012, PMID:22326943) | Randomized controlled trial (RCT) | 27 | Unknown | A positive effect was reported |
Research on this topic covers a total of 71 participants. Specifically, this includes 44 young adults and 27 adults.
These studies were conducted on people ranging from young adults to adults.
The content reported here is based on 4 studies. Of these, 3 are randomized controlled trials (RCTs), and one is a systematic review.
The fact that the study participants are limited to young adults and adults is a factor that should be taken into account.
The findings presented were obtained from studies with a limited number of participants.
Does taking caffeine + L-theanine affect attention and concentration?
Studies have reported that caffeine + L-theanine has a positive effect on attention and concentration. Results also show improved task accuracy.
What dosage has been used for caffeine + L-theanine?
One study used a condition of 50mg of caffeine and 100mg of theanine. In this case, a reduction in error rate was reported.
How reliable is the research on caffeine + L-theanine?
Based on 4 studies, reliability is considered high (evidence score 78). However, it has also been noted that there are limits regarding participant characteristics, among other factors.
There are many positive reports regarding the combination of caffeine and L-theanine for maintaining attention and concentration. This information is based on 4 studies, but since the number of studies is still limited, some people may not experience an effect, and it may not suit everyone. To find a way of using it that suits you, please also try the self-check assessment.