{"entity":{"id":"l-theanine-supplements","kind":"technology","name":"L-theanine","aka":["Theanine","Suntheanine"],"tldr":"L-theanine is an amino acid from green tea sold for relaxation and sleep. Small studies suggest it may help sleep, with mixed results for anxiety, and early studies in chemotherapy are preliminary. No side effects are reported for the purified form, but green tea products can interfere with the myeloma drug bortezomib.","summary":"L-theanine is a water-soluble amino acid found in green tea and some mushrooms and sold purified as a relaxant. Memorial Sloan Kettering's About Herbs entry describes limited human data: small studies suggest improvements in sleep, while effects on anxiety are mixed. In cancer, preliminary data suggest that oral theanine taken with cystine may reduce neuropathy with oxaliplatin and oesophagitis during chemoradiotherapy; laboratory studies suggest enhanced chemotherapy effects and reduced toxicity, which have not been shown in people. MSK advises patients having chemotherapy to discuss it with their physicians because most purported effects are not based on clinical trials, and because epigallocatechin gallate in green tea reduces the activity of bortezomib, which matters for green tea extracts containing theanine. No side effects are reported for L-theanine itself; it is contraindicated in pregnancy and breastfeeding and with sedatives, and in animals it added to the effect of midazolam.","status":"phase-2","asOf":"2026-11-04","links":[{"label":"MSK About Herbs: L-theanine (page last updated 14 July 2026)","url":"https://www.mskcc.org/cancer-care/integrative-medicine/herbs/l-theanine"}],"tags":["complementary","supportive-care","evidence:insufficient"],"related":["five-htp-supplements","melatonin-cancer"],"cancers":[],"sections":["supportive-care"],"technologies":["integrative-oncology","dietary-supplements-treatment-interactions","green-tea-egcg"],"targets":[],"drugs":["bortezomib","oxaliplatin"],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":["b-toxicity-qol"],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"principle":"Crosses into the brain and alters levels of GABA, serotonin and dopamine, which is the proposed basis of its calming effect.","strengths":["No reported side effects for the purified form","Small sleep studies positive"],"limitations":["Limited, small human studies","Green tea products interact with bortezomib","Avoid with sedatives and in pregnancy"]},"route":"/technologies/l-theanine-supplements/","neighbours":{"technology":[{"id":"five-htp-supplements","kind":"technology","name":"5-HTP (5-hydroxytryptophan)","route":"/technologies/five-htp-supplements/"},{"id":"dietary-supplements-treatment-interactions","kind":"technology","name":"Dietary supplements during cancer treatment: interactions and harms","route":"/technologies/dietary-supplements-treatment-interactions/"},{"id":"integrative-oncology","kind":"technology","name":"Evidence-based integrative oncology","route":"/technologies/integrative-oncology/"},{"id":"green-tea-egcg","kind":"technology","name":"Green tea and EGCG extracts","route":"/technologies/green-tea-egcg/"},{"id":"melatonin-cancer","kind":"technology","name":"Melatonin as a cancer adjunct","route":"/technologies/melatonin-cancer/"}],"section":[{"id":"supportive-care","kind":"section","name":"Supportive Care & Survivorship","route":"/fronts/supportive-care/"}],"drug":[{"id":"bortezomib","kind":"drug","name":"Bortezomib","route":"/drugs/bortezomib/"},{"id":"oxaliplatin","kind":"drug","name":"Oxaliplatin","route":"/drugs/oxaliplatin/"}],"bottleneck":[{"id":"b-toxicity-qol","kind":"bottleneck","name":"Toxicity and quality of life are undervalued","route":"/bottlenecks/b-toxicity-qol/"}]}}