L-Theanine: Why People Use It Long Term
L-theanine is an amino acid found primarily in green tea. It is known for its calming but non-sedating effect -- it increases alpha waves in the brain, associated with a relaxed yet alert state. For this reason, it is often used in combination with caffeine to achieve clear focus without anxiety. But what do we know about the safety of long-term use?
What Long-Term Use Studies Show
L-theanine has a relatively good safety record, particularly for short-term use. Data on long-term safety are more limited.
Japan's regulatory assessment that underpinned L-theanine's GRAS (generally recognized as safe) status was based on clinical studies in which theanine was used for up to 26 consecutive weeks at doses up to 400 mg per day, with no adverse effects (Juneja et al., 1999).
In one 16-week study in patients with schizophrenia, theanine at 400 mg per day was found to be safe and well tolerated (Ritsner et al., 2011). However, these are shorter-duration studies -- studies of two years or more in humans are very limited in number.
Animal toxicological studies show a very good safety profile -- even very large doses have not caused harm. But animal results are not always directly transferable to humans.
Upper Safe Limit for Long-Term Use
No formal tolerable upper intake level (UL) has been established for theanine by regulatory bodies. Typical doses used in supplements range from 100 to 400 mg per day.
In Japan, theanine is a naturally occurring amino acid in green tea and has a long history of ordinary dietary use. Based on this, the safety concern is considered minimal.
Do You Need to Cycle L-Theanine?
Based on current knowledge, cycling theanine supplementation is not necessary. No tolerance development or rebound effect has been described for theanine -- users do not report needing to increase the dose over time to achieve the same effect.
If you are using theanine in combination with caffeine, tolerance can develop to caffeine, but theanine itself does not carry this effect.
When Is Long-Term Use Most Justified?
Long-term L-theanine use may be justified for:
- People experiencing chronic stress who want nutritional support for calmness
- People who use caffeine regularly and want to reduce anxiety associated with it
- People with sleep quality issues -- theanine has shown some relieving effects
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Monitoring
For healthy people using theanine at typical doses, intensive monitoring is not required. It is sensible to:
- Periodically assess whether the supplement is still providing the desired effect
- Consult a physician if you want to combine theanine with prescription medications (particularly sedatives, blood pressure medications, or antidepressants)
Honest Verdict
L-theanine is one of the better-tolerated supplements. Long-term use at typical doses (100 to 400 mg per day) appears safe in healthy people, but rigorous clinical studies extending beyond two years are limited in number. Cycling is not necessary. If theanine delivers the desired calming effect without side effects, there is no scientific reason to discontinue use.
References
- Juneja, L.R., et al. (1999). L-theanine -- a unique amino acid of green tea and its relaxation effect in humans. Trends in Food Science and Technology, 10(6-7), 199-204. https://doi.org/10.1016/s0924-2244(99)00044-8
- Ritsner, M.S., et al. (2011). L-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder. Journal of Clinical Psychiatry, 72(1), 34-42. https://pubmed.ncbi.nlm.nih.gov/21208586/
- Nobre, A.C., et al. (2008). L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pacific Journal of Clinical Nutrition, 17(S1), 167-168. https://pubmed.ncbi.nlm.nih.gov/18296328/
FAQ
Does tolerance develop to L-theanine?
Based on current evidence, tolerance does not develop to theanine. Users do not report needing to increase the dose over time to achieve the desired effect.
Can L-theanine be taken every day?
Yes, daily use has been well tolerated in studies. Since no upper tolerable intake level has been established for theanine, typical doses (100 to 400 mg per day) are considered safe.
Is L-theanine suitable for children?
Some studies have used theanine in children with ADHD with positive results, but long-term safety data for children are limited. Always consult a pediatrician for supplements intended for children.
