L-theanine: Can a compound in tea lower anxiety and help you focus?

L-theanine is an amino acid predominantly found in tea leaves. This compound was first associated with tea’s relaxing effects in the 1940s and is now widely sold as a supplement for promoting stress relief, enhanced focus, and improved sleep. Although the research into its efficacy is still nascent, there are several intriguing suggestions that L-theanine may confer various cognitive benefits, particularly for those experiencing anxiety.

What Beneficial Effects Might L-theanine Have?

Though still limited, research on L-theanine presents promising observations. “The existing research is limited, and results are mixed,” explains Crystal Haskell-Ramsay from Northumbria University in the UK.

Small-scale studies indicate that L-theanine may have the potential to lower blood pressure during focused tasks and may also contribute to reduced heart rate and stress hormone cortisol spikes in stressful situations. Initial findings also suggest it could promote relaxation and enhance focus.

What Effects Does L-theanine Have on the Brain?

Once L-theanine is absorbed into the bloodstream, it crosses the blood-brain barrier. Its structure is similar to that of the brain’s neurotransmitters, glutamate and GABA, which are responsible for modulating signaling throughout the brain. Animal studies indicate that L-theanine might elevate levels of dopamine and serotonin, which are critical for multiple brain functions, including mood regulation and reward processing.

Furthermore, L-theanine appears to increase alpha brain wave activity, a state associated with calm yet alert wakefulness. “When you close your eyes, alpha activity increases suddenly,” says Manuel Gomez-Ramirez from the University of Rochester in New York.

Is This Beneficial for Mood and Well-being?

In increasing alpha brain wave activity, L-theanine may help improve focus and reduce distractions. “The higher the alpha activity, the more effectively you’re tuning out extraneous noise,” explains Gomez-Ramirez. These calming effects appear to intensify with caffeine, as L-theanine and caffeine reportedly produce a synergistic effect.

The impact of L-theanine on alpha waves tends to be more pronounced in anxious individuals, with research showing that its effects on dopamine and serotonin levels in the brain led to fewer symptoms of depression in stressed rodents. However, human studies yield mixed results, indicating that while some find L-theanine beneficial for generalized anxiety disorder, others report no significant improvement in stress and anxiety levels at all.

If L-theanine does alleviate anxiety, this may also elucidate its purported effects on sleep quality. According to one analysis, it can accelerate sleep onset and improve overall sleep quality.

Is There Enough L-theanine in Tea to Have an Effect?

Teas—both black and various green teas including matcha—contain L-theanine in amounts ranging from approximately 5 mg to 40 mg per cup. While these levels may impart mild effects, most research utilizes dosages around 200 mg, synonymous with those taken in supplement form.

How Good is the Evidence on L-theanine?

The majority of studies investigating L-theanine utilize modest sample sizes, often focusing on short-term outcomes from single doses or limited supplementation periods. “While promising, we still need more comprehensive research in this field,” remarks Amanda Bulman of the University of Canberra in Australia.

An additional complexity arises when combining L-theanine with other ingredients during testing, which complicates the ability to isolate effects. “It’s difficult to determine what is truly responsible for the results,” cautions Haskell-Ramsay. Moreover, she emphasizes the importance of noting that long-term effects of daily L-theanine use are yet to be rigorously studied.