Kanna vs L-Theanine: What Is the Difference?
One is a plant extract with a few small trials, the other a tea amino acid with more studies and a long list of caveats.
Kanna vs L-theanine is an increasingly common question because the two sit side by side in "calm" drinks and supplement stacks. They could hardly be more different. Kanna is a whole-plant extract from a South African succulent, with several active alkaloids. L-theanine is a single amino acid, best known from green tea. This post compares what each is, what the research measured, and where each body of evidence runs thin.
Kanna (Sceletium tortuosum) is a South African succulent whose alkaloids showed serotonin-transporter and PDE4 activity in lab work [5][6]. L-theanine is an amino acid found mainly in green tea; a 2020 review examined 9 randomized trials of it and stress or anxiety outcomes [1][2]. Both evidence bases are small and limited, and neither is approved by the FDA for any use.
What is the difference between kanna and L-theanine?
Kanna is a plant with many compounds; L-theanine is one specific molecule.
Kanna, Sceletium tortuosum, is a succulent endemic to South Africa. A 2021 review counted 25 alkaloids in four classes, with mesembrine-type compounds predominant [5]. L-theanine (N-ethyl-L-glutamine) is described in the pharmacology literature as a major amino acid uniquely found in green tea, long used as a relaxing agent [1]. A 2025 review adds that it is well absorbed from the intestine and can cross the blood-brain barrier [4].
That difference shapes everything downstream. A single compound can be dosed in milligrams and compared across studies. A plant extract varies by how it was made and standardized, so milligrams on one label do not equal milligrams on another. For kanna's background see what is kanna.
How is each proposed to work?
Kanna's proposed targets are the serotonin transporter and PDE4; L-theanine's come mostly from animal work and involve glutamate receptors and neurotransmitter levels.
In a 2011 study, a standardized Sceletium extract blocked the serotonin transporter (IC50 4.3 ug/ml) and inhibited PDE4 (IC50 8.5 ug/ml), with mesembrine the most potent alkaloid at the transporter [6]. A later cell study suggested the serotonin effect may be secondary to a monoamine-releasing action, so this is not settled [10].
A 2006 review of L-theanine's pharmacology reported that animal neurochemistry studies suggested it raises brain serotonin, dopamine and GABA levels and has micromolar affinity for AMPA, kainate and NMDA receptors. The authors concluded it warranted further investigation in animals and humans [1]. That is an animal-based picture, and it should not be read as a description of what happens in a person drinking a can.
What do the human studies show?
L-theanine has more randomized trials than kanna, but a recent review still calls the human evidence for relaxation and sleep inconsistent.
L-theanine
A 2020 systematic review in Plant Foods for Human Nutrition identified 9 randomized trials comparing L-theanine supplements with a control. The review looked at stress and anxiety outcomes in trials that mostly used 200 to 400 mg a day, and the authors said larger, longer studies are still needed [2].
A 2019 randomized, placebo-controlled, double-blind crossover trial in Nutrients gave 30 healthy adults (mean age about 48) 200 mg per day or placebo for 4 weeks. Scores on a depression self-rating scale, trait anxiety and a sleep-quality index decreased after L-theanine, and the authors reported improvements in verbal fluency and executive function scores. The caveats: 30 people, a subgroup analysis behind the verbal-fluency finding, and funding from, and two authors employed by, the company that supplied the L-theanine [3].
The 2025 review in Nutrition Research sums up the field this way: findings are mixed, human evidence for relaxation and sleep is inconsistent, and there is "a lack of rigorous human clinical trials." It also says the science does not yet match the hype. It treats L-theanine plus caffeine improving performance and focus as a reported effect rather than a settled finding [4].
Kanna
Kanna's human research is smaller. In a 2013 imaging study of 16 healthy participants, a single 25 mg dose of the Zembrin extract reduced amygdala reactivity to fearful faces [7]. In a 2020 pair of studies in 20 volunteers, the same dose was associated with lower self-reported anxiety before a simulated public-speaking task in one study, while the other showed no treatment effect [8]. A 3-month safety trial in 37 healthy adults (8 or 25 mg daily) found no differences from placebo in vital signs, ECG or bloodwork [9]. These were short, small and Zembrin-specific, and several involved authors tied to the extract's owner. The 2026 critical review described the evidence as mixed [11]. Full detail: what the research on kanna shows.
No trial we found compared kanna and L-theanine directly. Anyone ranking one above the other is giving an opinion.
What are the safety notes for each?
L-theanine appears well tolerated in the studies we reviewed, with long-term data lacking; kanna has a serotonergic interaction concern and little long-term data.
The 2025 review states that toxicology studies suggest L-theanine has "a good safety profile," while advising caution about pharmacologic doses in the general population until better human trials exist [4]. We did not find an NIH fact sheet on L-theanine to cite for interactions or pregnancy, so we will not make claims on those points. Ask a doctor if you take prescription medicines or are pregnant or nursing.
For kanna, WebMD lists headache and upset stomach as common side effects, flags possible interactions with SSRIs, SNRIs, MAOIs, tricyclics, antipsychotics, triptans and St. John's wort, and says pregnancy and breastfeeding data are lacking [12]. Details at is kanna safe.
Kanna vs L-theanine at a glance
| Kanna | L-theanine | |
|---|---|---|
| What it is | Plant extract; 25 alkaloids in four classes [5] | Single amino acid, mainly from green tea [1] |
| Origin | South Africa [5] | Green tea [1] |
| Proposed mechanism | Serotonin transporter and PDE4, lab studies [6] | Animal data: neurotransmitter levels, glutamate receptors [1] |
| Doses in studies | 25 mg Zembrin single dose; 8 or 25 mg daily up to 3 months [7][8][9] | 200 mg daily for 4 weeks [3]; 200 to 400 mg daily in most reviewed trials [2] |
| Human trial base | A few small trials, mostly one extract [7][8][9] | 9 randomized trials in a 2020 review [2]; inconsistent per 2025 review [4] |
| Caffeine? | Not part of the extract; drinks vary, so check labels | No; studied alongside caffeine from tea [4] |
| Main caution | Serotonergic medicines; pregnancy data lacking [12] | Long-term and special-population data limited; no NIH fact sheet found |
| FDA status | Not approved or reviewed [12] | No approval for any use found in sources reviewed |
Why do some drinks combine kanna and L-theanine?
Mostly because both are marketed in the same "calm" category, not because anyone has tested the pair together.
Some canned drinks list both ingredients. We found no studies of the combination, so there is no evidence on how they interact or whether the sum differs from the parts. If you want to see what each kanna drink actually discloses, including any added L-theanine, our kanna drink ranking lists amounts and ingredients side by side. For transparency: kannadrinks.com is published by Psilly Goose, whose Silly drink (35 mg kanna, 3,000 mg lion's mane, no caffeine, no kava) is on that ranking alongside competitors.
If you are comparing other ingredients, see kanna vs ashwagandha, kanna and lion's mane and kanna vs kava.
This page is general information, not medical advice. These statements have not been evaluated by the FDA. Kanna and L-theanine products are not intended for any disease or health condition.
References
- Nathan PJ, Lu K, Gray M, Oliver C. The neuropharmacology of L-theanine (N-ethyl-L-glutamine): a possible neuroprotective and cognitive enhancing agent. J Herb Pharmacother 2006;6(2):21-30. PubMed
- Williams JL, et al. The effects of green tea amino acid L-theanine consumption on the ability to manage stress and anxiety levels: a systematic review. Plant Foods Hum Nutr 2020;75(1):12-23. PubMed
- Hidese S, 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. PubMed
- Dashwood R, Visioli F. L-theanine: from tea leaf to trending supplement, does the science match the hype for brain health and relaxation? Nutr Res 2025;134:39-48. PubMed
- Olatunji TL, et al. Sceletium tortuosum: a review on its phytochemistry, pharmacokinetics, biological and clinical activities. J Ethnopharmacol 2021;280:114476. PubMed
- Harvey AL, et al. Pharmacological actions of the South African medicinal and functional food plant Sceletium tortuosum and its principal alkaloids. J Ethnopharmacol 2011;137(3):1124-9. PubMed
- Terburg D, et al. Acute effects of Sceletium tortuosum (Zembrin), a dual 5-HT reuptake and PDE4 inhibitor, in the human amygdala and its connection to the hypothalamus. Neuropsychopharmacology 2013;38(13):2708-16. PubMed
- Reay J, et al. Sceletium tortuosum (Zembrin) ameliorates experimentally induced anxiety in healthy volunteers. Hum Psychopharmacol 2020;35(6):1-7. PubMed
- Nell H, et al. A randomized, double-blind, parallel-group, placebo-controlled trial of Extract Sceletium tortuosum (Zembrin) in healthy adults. J Altern Complement Med 2013;19(11):898-904. PubMed
- Coetzee DD, et al. Effects of a high-mesembrine Sceletium extract on monoamine transporters (cell study). J Ethnopharmacol 2016;177:111-6. PubMed
- de Jong M, et al. Mesembryanthemum tortuosum and Zembrin: mixed evidence from in vivo animal and clinical studies on their antidepressant and anxiolytic effects. Planta Med 2026;92(8):806-823. PubMed
- WebMD. Sceletium: Uses, side effects, interactions. webmd.com
Frequently asked questions
Is kanna the same as L-theanine?
No. Kanna is Sceletium tortuosum, a South African succulent with a mix of alkaloids [5]. L-theanine is a single amino acid found mainly in green tea [1]. They differ in chemistry, source and proposed mechanism.
How much L-theanine was used in studies?
A 2020 systematic review examined 9 randomized trials of L-theanine and stress or anxiety outcomes, mostly at 200 to 400 mg a day, and called for larger studies [2]. A 2019 crossover trial of 30 adults used 200 mg per day for 4 weeks [3]. Both authors call for larger, longer studies.
Which has better evidence, kanna or L-theanine?
L-theanine has more randomized trials, but a 2025 review called the human evidence for relaxation and sleep inconsistent [4]. Kanna has fewer, smaller trials, mostly of one extract [7][8][9]. Neither is established.
Does L-theanine have caffeine in it?
No. L-theanine is an amino acid, not caffeine [1]. Tea contains both, which is partly why it is studied alongside caffeine, but that is a separate question from either ingredient on its own [4].
Can you combine kanna and L-theanine?
Some drinks do, but we found no studies of the combination. Kanna has serotonergic drug-interaction cautions [12]; talk to a doctor about any supplement, especially if you take prescription medicines or are pregnant or nursing.