Kanna vs Ashwagandha: What the Research Shows
Both get called calming botanicals. The evidence behind each, and the cautions, are quite different.
Kanna vs ashwagandha is a natural comparison, because both appear in "calm" and "adaptogen" drinks and both are marketed with similar words. Under the marketing, they are unrelated plants with very different evidence bases. Ashwagandha has a larger set of human trials with wide variation between them. Kanna has a few small trials in healthy volunteers. This post lays out what each literature does and does not show, without claiming either does anything for any health condition.
Ashwagandha is an evergreen shrub with a larger human trial literature: a 2022 meta-analysis of 12 randomized trials reported lower anxiety and stress scores versus placebo, but with very high heterogeneity and low certainty [2]. Kanna (Sceletium tortuosum) has only a few small trials in healthy volunteers [6][7]. Both have cautions, and neither is approved by the FDA for any use.
Are kanna and ashwagandha related?
No. They are different plants from different parts of the world, used in different traditions.
NCCIH describes ashwagandha as an evergreen shrub found in parts of India, Africa and the Middle East, also called Indian ginseng, and notes that supplements are often promoted for stress and anxiety, sleep, male infertility and athletic performance [1]. Kanna is a succulent endemic to South Africa with a documented history as a masticatory and medicine among the San and Khoikhoi peoples [5][6]. Its alkaloids are mesembrine-type compounds [5]. See what is kanna for the background.
Dose numbers are not interchangeable between the two plants, or between different extracts of the same plant.
What does the research on each actually show?
Ashwagandha has more human trials, kanna has fewer and smaller ones, and both sets have meaningful limitations.
Ashwagandha
NCCIH says ashwagandha has been studied for sleep and stress outcomes, with results that vary by preparation, that evidence on anxiety is unclear, and that evidence is insufficient for areas such as cognitive function, diabetes and athletic performance [1]. A 2022 systematic review and meta-analysis in Phytotherapy Research pooled 12 randomized trials with 1,002 participants and reported lower anxiety (standardized mean difference -1.55) and stress (-1.75) scores versus placebo. The authors reported a stress effect at 300 to 600 mg per day. But heterogeneity was very high (I-squared 93.8% for anxiety and 83.1% for stress) and the certainty of the evidence was rated low. The authors themselves called for further high-quality studies [2].
That is a useful example of how to read supplement research. A pooled result can look large and still rest on trials that disagree with each other.
Kanna
Kanna's human evidence is smaller. In a 2013 crossover imaging study of 16 healthy participants, a single 25 mg dose of the Zembrin extract reduced amygdala reactivity to fearful faces [6]. In a 2020 pair of studies with 20 volunteers in total, the same dose was associated with lower self-reported anxiety before a simulated public-speaking task in one study; the other showed no treatment effect [7]. A 3-month safety trial in 37 healthy adults (8 mg or 25 mg daily) found no differences from placebo in vital signs, ECG or bloodwork, and did not assess efficacy [8]. A 2026 critical review described the overall evidence as mixed, with small samples among the limitations [10].
Several of these trials include authors affiliated with the extract's owner, and all used Zembrin, so they say little about other kanna extracts. Full detail: what the research on kanna shows.
How are kanna and ashwagandha proposed to work?
For kanna, lab studies point to the serotonin transporter and PDE4; for ashwagandha, we did not verify a mechanism and will not guess at one.
A 2011 pharmacology study found that 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 [4]. A later cell study suggested the serotonin effect may be secondary to a monoamine-releasing action, so the picture is unsettled [11]. For ashwagandha, the sources we opened (NCCIH and the meta-analysis abstract) report outcomes rather than a mechanism, so we are leaving it at that. Mechanism claims on product pages are often stronger than the evidence.
What are the safety notes for each?
Ashwagandha has NCCIH cautions that include rare liver injury and thyroid-related concerns; kanna has a serotonergic interaction concern and little long-term data.
Ashwagandha
NCCIH says ashwagandha may be safe in the short term, up to 3 months, and that long-term safety is not established. It reports that liver injury is rare but that a number of cases link it to ashwagandha supplements. It advises avoiding it in pregnancy and while breastfeeding, and says it is not recommended for people with autoimmune or thyroid disorders. People with hormone-sensitive prostate cancer should avoid it, and people scheduled for surgery should be careful. NCCIH lists possible interactions with diabetes, blood pressure, thyroid hormone, anti-seizure and sedative medications and with immunosuppressants. Drowsiness, stomach upset, diarrhea and vomiting are possible side effects [1].
A 2023 paper in Pharmaceuticals described two new cases of ashwagandha-related liver injury, each scored "probable" on the updated RUCAM causality scale. Both patients improved after stopping the supplement. The authors noted that one earlier reported case in the literature ended in liver transplantation, and described the supplement as generally considered safe despite several reported cases [3]. Case reports cannot tell us how common the problem is, which NCCIH describes as rare. If you notice dark urine, yellowing of the skin or eyes, or persistent nausea, stop and contact a clinician.
Kanna
WebMD lists headache and upset stomach as common side effects, flags possible interactions with MAOIs, SSRIs, SNRIs, tricyclics, antipsychotics, triptans and St. John's wort, and says it is not known whether sceletium affects pregnancy or breastfeeding [9]. The 3-month trial above supports tolerability in 37 healthy adults, which is a small base [8]. See is kanna safe.
Kanna vs ashwagandha at a glance
| Kanna | Ashwagandha | |
|---|---|---|
| Plant type and origin | Succulent, South Africa [5] | Evergreen shrub; India, Africa, Middle East [1] |
| Key compounds | Mesembrine-type alkaloids [5] | Not covered in sources we opened |
| Human trial base | A few small trials in healthy volunteers, mostly Zembrin [6][7][8] | 12 randomized trials in one 2022 meta-analysis, 1,002 participants [2] |
| Quality of evidence | 2026 review: mixed, small samples [10] | Very high heterogeneity; certainty rated low [2] |
| Doses in trials | 25 mg Zembrin single dose; 8 or 25 mg daily for up to 3 months [6][7][8] | Authors report a stress effect at 300 to 600 mg/day [2] |
| Short-term safety statement | Tolerated in a 3-month trial of 37 healthy adults [8] | May be safe up to 3 months [1] |
| Main caution flags | Serotonergic medicines; pregnancy data lacking [9] | Rare liver injury; thyroid, autoimmune, pregnancy; several drug interactions [1][3] |
| FDA status | Not approved or reviewed [9] | Dietary supplement; see NCCIH [1] |
Do kanna and ashwagandha feel different or work on different timelines?
The trial designs suggest different expectations, but there is no head-to-head study, so we cannot say how they compare in a person.
The kanna studies above looked at a single dose within hours (amygdala reactivity, an anxiety task) and at daily use for up to three months (safety). The ashwagandha trials in the meta-analysis were multi-week supplementation studies, and NCCIH mentions 2 to 4 months in the context of testosterone and sperm outcomes rather than stress [1][2]. Any claim that one is "fast" and the other "slow" would be a reading of how the studies were designed, not a finding. We found no study comparing the two.
Can you take kanna and ashwagandha together?
Some drinks and capsules combine them, but we found no studies of the combination, so there is no evidence on how they interact.
Each has its own caution list: serotonergic medicines for kanna [9], and sedatives, thyroid, diabetes, blood pressure and other medicines for ashwagandha [1]. A blend inherits both. If you take any prescription medication, are pregnant or nursing, or have a thyroid or liver condition, talk to a doctor before adding either. If you are weighing other calming-category ingredients, our comparison of kanna vs L-theanine covers a third, very different option, and kava vs kratom vs kanna covers the plants that get grouped with kanna most often.
This page is general information, not medical advice. These statements have not been evaluated by the FDA. Kanna and ashwagandha products are not intended for any disease or health condition. kannadrinks.com is published by Psilly Goose, a kanna drink maker.
References
- National Center for Complementary and Integrative Health. Ashwagandha (content last updated March 2023). nccih.nih.gov
- Akhgarjand C, et al. Does ashwagandha supplementation have a beneficial effect on the management of anxiety and stress? A systematic review and meta-analysis of randomized controlled trials. Phytother Res 2022. PubMed
- Bokan G, et al. Herb-induced liver injury by Ayurvedic ashwagandha as assessed for causality by the updated RUCAM: an emerging cause. Pharmaceuticals (Basel) 2023;16(8):1129. 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
- Olatunji TL, et al. Sceletium tortuosum: a review on its phytochemistry, pharmacokinetics, biological and clinical activities. J Ethnopharmacol 2021;280:114476. 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
- WebMD. Sceletium: Uses, side effects, interactions. webmd.com
- 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
- Coetzee DD, et al. Effects of a high-mesembrine Sceletium extract on monoamine transporters (cell study). J Ethnopharmacol 2016;177:111-6. PubMed
Frequently asked questions
Is kanna the same as ashwagandha?
No. Kanna is a South African succulent, Sceletium tortuosum [5]. NCCIH describes ashwagandha as an evergreen shrub found in parts of India, Africa and the Middle East [1]. They are unrelated plants with different compounds.
Which has more research, kanna or ashwagandha?
Ashwagandha has a larger human literature. A 2022 meta-analysis pooled 12 randomized trials with 1,002 participants [2], while kanna's human research is a handful of small trials, mostly of one extract [6][7][8]. Both bodies of evidence have limits.
Is ashwagandha safe to take long term?
NCCIH says it may be safe in the short term, up to 3 months, and that long-term safety is not established [1]. It also notes rare cases of liver injury [1][3]. Talk to a doctor, especially with thyroid or liver conditions.
Can you take kanna and ashwagandha together?
We found no studies of the combination. Kanna has serotonergic drug-interaction cautions [9], and NCCIH lists interactions for ashwagandha with sedatives, thyroid, diabetes and blood pressure medicines among others [1]. Ask a doctor first.
Who should avoid ashwagandha?
NCCIH says to avoid it in pregnancy and while breastfeeding, not to use it with autoimmune or thyroid disorders, and that men with hormone-sensitive prostate cancer should avoid it [1]. Anyone with liver disease or on prescription medicines should ask a doctor first.