Episode 102 – L-Theanine

  • L-theanine is an amino acid naturally found in plants 
  • We naturally consume it through tea, although the amount in there is a lot lower than the amount research uses to find the most benefits 
  • It theoretically helps with relaxation by increasing alpha-waves in the brain, amongst other things 

So we will be talking about L-theanine and its impact on stress, anxiety and sleep as well as ideal dosages and potential side effects.


  • Improvements in stress are the most consistent benefits of L-Theanine 
  • There are a bunch of randomized controlled trials (listed in the show notes) showing the benefits of L-Theanine for stress. 
  • Of all the studies that have been done, to the best of my knowledge, they have all shown benefits for improving stress levels 


  • A lot of people link stress and anxiety together, so you will often hear people say L-Theanine improves stress AND anxiety. The research is less clear though for anxiety in comparison to stress.  
  • A 2016 systematic review on the impact of L-Theanine and stress and anxiety found 5 randomised controlled trials. Only one of them actually included people who were diagnosed with anxiety.  
  • That specific one did not find any advantages of L-Theanine over placebo on anxiety outcomes. 
  • Meanwhile, the other 4 had improvements in anxiety levels. That looks promising and is worth being aware of. But it’s not exactly overly relevant since none of the participants actually had diagnosed anxiety. 
  • I can see some amount of promise in this space. But I wouldn’t say L-Theanine can help anxiety with any degree of confidence until there is more research showing benefits in those with diagnosed anxiety. 


  • L-Theanine does not directly affect sleep. 
  • Indirectly though, it could benefit sleep due to reducing stress or anxiety levels. 
  • Based on the research, L-Theanine consistently improves sleep. 
  • A lot of the other research that I’ve added in the show notes related to stress and anxiety found improvements in sleep.  
  • In addition, there is a study on children with ADHD that found that 400mg of L-Theanine per day improved sleep.  

Caffeine and L-Theanine Combo 

  • Caffeine obviously helps focus and productivity. But it can come alongside downsides such as increased heart rate, increased blood pressure, increased jitters and increased anxiety. Those things are no exactly conducive for productivity.  
  • L-Theanine has evidence it can potentially offset some of those specific things. 
  • So utilising the combination of the two could be beneficial for reaping the rewards of caffeine whilst offsetting some of its side-effects 

Any Side Effects? 

  • There are no common side effects reported. 
  • One study on rodents even used a crazy high dosage of 4,000mg per kg for 13 weeks. No downside was found.  

Dosage and How to Take? 

  • 200mg per day appears to be the most common dosage. 
  • It is safe to go higher, but we aren’t exactly sure how high you could go before there are any risks. Almost everything has downsides in super high dosages. 
  • 200mg is the dosage that is most commonly seen in research showing positive findings. 
  • It takes 30-50 minutes to peak in the blood and has a half-life of 58-74 minutes. So I would dose it accordingly, based on when you want the stress reducing effects. 

Relevant Links/Resources

Studies Mentioned

  • L-Theanine and Stress:

1) https://pubmed.ncbi.nlm.nih.gov/16930802/  

2) https://pubmed.ncbi.nlm.nih.gov/26797633/  

3) https://pubmed.ncbi.nlm.nih.gov/24051231/  

4) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6836118/