Health Reference Library

L-theanine vs ashwagandha: which should you take for stress?

This entry is part of the Nutri Tailor Health Reference Library — cited research on supplements, nutrients and adjacent areas of health.

Summary

They work on different clocks. L-theanine, the amino acid from tea, takes the edge off within about an hour: in the trials, 200 mg a day lowered stress scores over four weeks and single doses steadied attention under pressure without drowsiness, so it suits the working day. Ashwagandha, a root extract, builds over weeks: 240 to 600 mg a day of a standardised extract lowered stress scores and morning cortisol in eight week trials and improved sleep in a 2021 review of five trials, so it suits a run of stressful months and poor sleep. Theanine for the moment, ashwagandha for the season; many people take theanine by day and ashwagandha at night.

How it works

Theanine crosses into the brain and raises alpha wave activity, the pattern seen in relaxed wakefulness, and nudges GABA, serotonin and dopamine, which is why it calms without sedating. The 2016 study measured the brain effect with magnetoencephalography and the reduced stress response to a task. Ashwagandha acts on the stress hormone axis: the 2019 trials found morning cortisol fell against placebo over eight weeks, alongside lower scores on stress questionnaires, and the sleep review found better sleep quality, most clearly in people with insomnia at 600 mg for eight weeks or more.

Effective dose

L-theanine: 200 mg a day for four weeks in the 2019 Japanese trial; 200 mg as a single dose in the acute studies. Ashwagandha: 240 mg a day of a high withanolide extract for 60 days, or 250 and 600 mg a day of a 5 percent extract for eight weeks in the 2019 trials; the sleep review favoured 600 mg or more for eight weeks or longer. Neither has a UK reference intake, and neither is a food.

Forms compared

L-theanine is a single amino acid, chemically simple, and most products are the same 100 or 200 mg. Ashwagandha is a plant extract, and products vary by the part of the plant used, how concentrated the extract is and the withanolide content it is standardised to; the trials used root extracts standardised to withanolides, at 240 mg of a 35 percent extract or 250 to 600 mg of a 5 percent extract. Read the standardisation on the label, because the milligrams alone do not tell you what you are getting.

Timing

Theanine in the morning or before a demanding task; it can also be taken in the evening because it does not disturb sleep. Ashwagandha with the evening meal if sleep is the target, or split morning and evening if stress across the day is the target. Give ashwagandha eight weeks before judging it.

Safety profile

Theanine has a clean safety record at trial doses, with no reported dependence or withdrawal. Ashwagandha is generally well tolerated over eight to twelve weeks; mild stomach upset and drowsiness are the common complaints, and it should be stopped before surgery. Rare liver reactions have been reported with some ashwagandha products, so stop and see your GP if you notice yellowing of the eyes, dark urine or severe tiredness. Ashwagandha is not advised in pregnancy, and people with thyroid conditions should ask their GP first because it can nudge thyroid hormone levels.

Guideline positions

Effects of L-theanine on stress related symptoms and cognitive function, randomised trial (2019). Anti stress and magnetoencephalography effects of an L-theanine based drink (2016). Stress relieving actions of an ashwagandha extract, randomised trial (2019). Adaptogenic and anxiolytic effects of ashwagandha root extract, randomised trial (2019). Effect of ashwagandha extract on sleep: systematic review and meta analysis (2021).

Practical framework

Need to feel steadier today: theanine. Three months of pressure and broken sleep: ashwagandha, and give it eight weeks. Nutri Tailor stocks [L-theanine capsules](/products/theanine) at 200 mg per capsule, theanine only, and [ashwagandha capsules](/products/ashwagandha) at 450 mg of root extract per capsule, concentrated 10 to 1 and standardised to 1.5 percent withanolides, both made in the UK. Taking both together is common and no interaction between them has been reported; keep each at its trial dose. This is a summary of published research, not personal health advice. Talk to your GP or a registered nutritional therapist before changing what you take, especially if you are pregnant, have a diagnosed condition or are under ongoing care.

Common misconceptions

That ashwagandha works on the first night: the trials measured change at eight weeks. That theanine is a sedative: it lowers stress scores without lowering alertness, which is the point. That any ashwagandha is the same: extracts differ several fold in withanolides. That either replaces help for anxiety that stops you functioning: that belongs with your GP.

Forms compared

L-TheanineAshwagandha

Sources

  1. Hidese S, Ogawa S, Ota M, Ishida I, Yasukawa Z, Ozeki M, Kunugi H 2019. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients (MDPI).
  2. White DJ, de Klerk S, Woods W, Gondalia S, Noonan C, Scholey AB 2016. Anti-Stress, Behavioural and Magnetoencephalography Effects of an l-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial. Nutrients (MDPI).
  3. Lopresti AL, Smith SJ, Malvi H, Kodgule R 2019. An investigation into the stress-relieving and pharmacological actions of an ashwagandha extract. Medicine (Baltimore). PMID: 31517876
  4. Salve J, Pate S, Debnath K, Langade D 2019. Adaptogenic and Anxiolytic Effects of Ashwagandha Root Extract in Healthy Adults. Cureus. PMID: 32021735
  5. Cheah KL, Norhayati MN, Husniati Yaacob L, Abdul Rahman R 2021. Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis. PLoS One. PMID: 34559859

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