{"ok":true,"entry":{"slug":"l-theanine","kind":"supplement","name":"l-theanine","aliases":["theanine","AlphaWave","Suntheanine"],"brands_sg":["California Gold Nutrition","Nutricost","NOW Foods","Doctor's Best","Life Extension"],"class":"amino acid","tags":["cognitive","sleep"],"use_for":"small cognitive effects · sleep evidence inconclusive","use_after":"200 mg at bedtime in the rct","use_duration":"the rct ran four weeks","take_with":"often paired with caffeine · gains mostly come from caffeine","pros":["theanine alone: small gains in choice reaction time","200 mg/day, 4 weeks: better psqi sleep scores (n=30)","no adverse events in the 4-week 200 mg trial"],"cons":["small trials; cis often include no effect at all","sleep evidence is inconclusive across trials","the key sleep trial was funded by the suntheanine maker"],"dose_note":"the 4-week rct used 200 mg a night — a dose its authors call high next to the 8–30 mg in a cup of green tea; no rda, ul or dv exists for theanine, and hsa's vitamin/mineral limits and prohibited/restricted lists do not cover it","dosage":{"ul":null,"unit":"mg","fda_dv":null,"rda_ai":null,"ul_status":"none_established","population":"general adult","hsa_max_daily":null},"ul_status":"none_established","sg_class":null,"cautions":["under 18, pregnant or breastfeeding — the trials were in healthy adults; no safety data seen (absence ≠ safe)","long-term use — the safety data here is 4 weeks at 200 mg/day, nothing longer"],"clashes":[{"src":["payne2025_caffeine"],"food":true,"note":"the pair is what most trials tested; gains are mostly caffeine-driven","with":"caffeine"}],"sources":[{"id":"payne2025","url":"https://europepmc.org/article/PMC/PMC12422004","label":"Effects of Tea (Camellia sinensis) or its Bioactive Compounds l-Theanine or l-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants: A Systematic Review and Meta-Analysis of RCTs (Payne et al., Nutr Rev 2025;83(10):1873–1891) — Discussion","quote":"theanine alone may confer small-to-moderate improvements, on cognitive performance measures during the first and second hours after intake … the CIs were frequently consistent with little-to-no difference … The evidence regarding the effects of … theanine alone on sleep outcomes was inconclusive","accessed":"2026-08-27"},{"id":"payne2025_caffeine","url":"https://europepmc.org/article/PMC/PMC12422004","label":"Payne et al., Nutr Rev 2025 (same review) — Introduction + Results, choice reaction time","quote":"beneficial effects of tea, or theanine plus caffeine, on cognition and mood, mostly being driven by caffeine … a small-to-moderate difference between the effects of theanine and placebo that favored theanine on choice reaction time","accessed":"2026-08-27"},{"id":"hidese2019","url":"https://europepmc.org/article/PMC/PMC6836118","label":"Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial (Hidese et al., Nutrients 2019;11(10):2362) — Abstract + Results","quote":"randomized, placebo-controlled, crossover, and double-blind trial … Participants were 30 individuals … L-theanine (200 mg/day) … for four-week administration … Pittsburgh Sleep Quality Index (PSQI) scores decreased after L-theanine administration … adverse events were not apparent during the intervention period","accessed":"2026-08-27"},{"id":"hidese2019_methods","url":"https://europepmc.org/article/PMC/PMC6836118","label":"Hidese et al., Nutrients 2019 (same trial) — Methods + Funding","quote":"Suntheanine, Taiyo Kagaku Co., Ltd … orally self-administered before sleep each night for four weeks … relatively high compared to the median amount of L-theanine per cup of green tea (8–30 mg) … funding received from Taiyo Kagaku Co., Ltd.","accessed":"2026-08-27"},{"id":"hsa_hs_guidelines","url":"https://file.go.gov.sg/hsa-hs-guidelines.pdf","label":"HSA Singapore — Health Supplements Guidelines GL-CHPB-3-001 Rev. No. 020 (January 2026), s4.8 general-adult limits, Tables 4–5 (vitamins and minerals only)","quote":"4.8 HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits stated in Tables 4 and 5","accessed":"2026-08-27"},{"id":"hsa_prohibited_2025","url":"https://file.go.gov.sg/hsa-chp-prohibited-restricted-ing-guidelines.pdf","label":"HSA Singapore — Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines, GL-CHPB-1-012 Rev. 001 (October 2025), Annex A + Annex B (theanine not listed in either)","quote":"1.3 The objective of this guideline is to highlight the substances of concern when used in HS and TM and is not meant to be an exhaustive list","accessed":"2026-08-27"},{"id":"iherb_sg","url":"https://sg.iherb.com/c/l-theanine","label":"iHerb Singapore — L-Theanine category, default order (SGD pricing)","quote":"California Gold Nutrition, L-Theanine, Featuring AlphaWave®, 200 mg, 60 Veggie Capsules … Nutricost, L-Theanine, 200 mg, 120 Capsules … NOW Foods, L-Theanine, 120 Veg Capsules … Doctor's Best, L-Theanine, 150 mg, 90 Veggie Caps … Life Extension, L-Theanine, 60 Vegetarian Capsules","accessed":"2026-08-27"}],"brand_certs":null,"updated_at":"2026-08-29T16:16:23.779398+08:00"},"disclaimer":"kozen-x is not a medical device and does not give medical advice. it lists what published sources have written down. absence of a record is not the same as safe."}