L-theanine: +20% cognitive improvement in 60 minutes

L theanine can improve cognitive performance and reduce stress in just 60 minutes.

The most impressive effects are produced by using L-theanine with caffeine.

Here are the studies that confirm that.

Cognitive performance

Study: https://sci-hub.mksa.top/https://www.ncbi.nlm.nih.gov/pubmed/18006208

The study involved 24 participants divided into four groups.

Each group was given 150 mg of caffeine or 250 mg L-theanine or 150 mg caffeine plus 250 mg L-theanine and a placebo.

After that, they took a series of cognitive tests 30 and 90 minutes after consumption.

The Theanine+caffeine group had the best results compared to the placebo group.

  • The reaction time improved by 6% 
  • The speed of visual information processing improved by 8% percent and the accuracy by 20%.
  • Spatial memory reaction was 5% faster.
  • Logical reasoning reaction time was 2% faster.
  • Numeric working memory reaction time was 4% faster.
  • Word recognition was 13% faster.
  • Moreover, the subjective tiredness was 33% lower and mental fatigue 27% lower.
  • The mood was improved by 14%.

Study: https://www.ncbi.nlm.nih.gov/pubmed/20079786

In another study, 29 participants took 97 mg L-theanine and 40 mg caffeine.

10 and 60 minutes after consumption, they completed two tasks that required attention.

The results showed that theanine and caffeine improved the proportion of correct answers by 1%.

Study: https://pubmed.ncbi.nlm.nih.gov/18681988/

The following study involved 27 participants taking 50 mg caffeine, with and without 100 mg L-theanine.

They took several cognitive and mood tests 60 min and 90 min after each treatment.

L-theanine and caffeine group gave two times more correct answers in the attention switching task than the placebo group.

The combined treatment also increased the number of correctly identified new words in the word recognition task. 

In addition, the ltheanine+caffeine group showed less susceptibility to distracting information in the memory task.

In another study, 16 people took the attention switching task 30 minutes after taking the mixture of 100mg l-theanine plus 50mg of caffeine.

The correct hit rate in the mixture group was 9% higher than in the placebo group.

 Stress Reduction

L theanine can significantly reduce stress levels. Here are studies that confirm that.

Study: https://www.sciencedirect.com/science/article/abs/pii/S0924224499000448

65 people were required to take 50mg, 200mg, and 250mg of l-theanine

During the study, their brains’ electrical activity was monitored.

The intensity of alpha-brain waves was significantly greater in the groups that took l-theanine.

The brain generates A-waves in the relaxed state.

In another study, 12 students were given 200mg of L-theanine and then performed an arithmetic task for 20 minutes.

The participants were asked to evaluate their subjective perception of stress.

The results showed that L-Theanine significantly reduced the stress caused by the task. 

This effect was also observed in physiological stress responses such as HR and Immunoglobulin A in the blood.

Immune system

L-theanine helps to strengthen the immune system.

Study: https://pubmed.ncbi.nlm.nih.gov/20525371/

16 long-distance runners were required to take 280 mg theanine and 700 mg cystine daily for 16 days along with their usual training

Their blood samples were on the last day of the study.

The results showed that their exercise-induced neutrophil count was 20% lower and the decline in lymphocyte count was 40% better than in the placebo group.

This confirms that supplementation may help to keep the immune system stronger.

Study: https://www.ncbi.nlm.nih.gov/pubmed/21477654

Elderly persons with normal or slight cognitive dysfunction were required to take 47.5mg of l-theanine daily for 12 months.

The results showed a significantly lower decline in cognitive function than that of the placebo group.


L theanine reduces stress, improves cognitive performance, and strengthens the immune system. The best cognitive effects are if taken with caffeine.