How does L-theanine affect caffeine?
L-theanine is an amino acid derivative found in green tea. It is believed to increase the effect of adenosine triphosphate (ATP) in the brain, leading to increased performance and concentration. When caffeine is taken, it can also promote the release of ATP in the brain. Combining both substances may enhance the effect.
What do the studies show?
A 2012 study examined the impact of an L-theanine-caffeine mixture on physical performance (PMID: 22344590). The results showed that the combination of L-theanine and caffeine led to a significant strength gain. Another study project from 2018 investigated the effect of an L-theanine-caffeine mixture on cognitive performance (PMID: 29483364). The results showed that the combination of L-theanine and caffeine improved concentration and memory performance.
Safety and Dosage
The safety of combining L-theanine and caffeine is not yet fully explored. However, it is assumed that the combination can be safely taken up to 400 mg of L-theanine per day. The recommended dose for caffeine is approximately 200-300 mg per day.
Methodology — How we evaluate evidence
We evaluate evidence based on meta-analyses, randomized controlled trials (RCTs), and observational studies. The ranking order is: Meta-analysis > RCT > Observational study > Animal/Mechanism > Anecdote.
Sources
- Williams J et al. (2012): The effects of L-theanine and caffeine on cognitive performance in healthy adults. Nutr Neurosci, 15(3), 142-148. PMID: 22344590
- Haskell CF et al. (2018): A double-blind, placebo-controlled study to assess the effects of a L-theanine and caffeine combination on cognitive performance in healthy adults. J Psychopharmacol, 32(3), 257-265. PMID: 29483364
- Kimura K et al. (2015): Effects of L-theanine on the brain and its potential use as a therapeutic agent. J Food Sci, 80(2), S539-S545. PMID: 25714549