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M-03 · Sleep, Stress & Attention

L-theanine

By Andrew Kornfeld · Guide v7.2 · September 2026

l-theanine
M-03 · #bonus

L-theanine

Pure Encapsulations, L-Theanine 400 mg · 60 caps
Sleep · stress · attention

The amino acid that makes green tea calming. L-theanine raises alpha-wave activity in the brain within an hour, and in randomized trials it reduced stress-related symptoms and improved attention; paired with caffeine it sharpens focus while blunting the jittery, blood-pressure-raising side of coffee. Suntheanine-grade, single ingredient, no additives of concern. The most useful of the five products here, and the one I would try first.

Very well tolerated. May lower blood pressure slightly; note it if you already run low.
References 191–193
Andrew's notes

I take L-theanine every single day, throughout the day, always. It is an extraordinary tool: focus without the edge, and it simply feels good, especially combined with caffeine. I prefer a spray, because you can dose a puff at a time with your coffee; no spray existed on Fullscript at press time, so the capsule is linked here.

Buy on Fullscript→go.supplementsforibd.com/l-theanine
SKU
PUR-LT4 (verify)
Evidence2

RCTs for stress and attention, alone and with caffeine; none in IBD

Andrew's score5

Andrew's judgment, 1–5.

L-theanine
L-theanine · C7H14N2O3 · 174.2 g/mol · PubChem CID 439378

References

  1. Hidese S, Ogawa S, Ota M, et al. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients 2019;11(10):2362.
  2. Owen GN, Parnell H, De Bruin EA, Rycroft JA. The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutr Neurosci 2008;11(4):193–198.
  3. Haskell CF, Kennedy DO, Milne AL, Wesnes KA, Scholey AB. The effects of L-theanine, caffeine and their combination on cognition and mood. Biol Psychol 2008;77(2):113–122.

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Options to explore with your care team. These are not a recommendation to take them together. Andrew earns a commission on Fullscript purchases. US shipping only.