Kanna

The above-ground plant is harvested from October to January. It is crushed between stones, sealed in a bag (formerly sheepskin), left to ferment in the sun for about eight days and then dried. The result, kougoed or kanna, is chewed and held in the mouth. Some people simply crush and sun-dry the fresh plant or bake it in hot sand ^{28Reference 28Brendler et al. · 2021ReviewSceletium for managing anxiety, depression and cognitive impairment: a traditional herbal medicine in modern-day regulatory systems — reviewView study →}.

It was chewed to build endurance and reduce fatigue, hunger and thirst, and used socially to raise the spirits and ease sociability ^{28Reference 28Brendler et al. · 2021ReviewSceletium for managing anxiety, depression and cognitive impairment: a traditional herbal medicine in modern-day regulatory systems — reviewView study →}. Governor Simon van der Stel’s 1685 expedition to Namaqualand recorded that the Namaqua held it “in as great esteem as the betel or areca with the Indians” ^{28Reference 28Brendler et al. · 2021ReviewSceletium for managing anxiety, depression and cognitive impairment: a traditional herbal medicine in modern-day regulatory systems — reviewView study →}.

Recorded uses also include low mood, poor memory, sleeplessness, pain, headache, toothache, nausea, colic, stomach cramps, constipation and asthma ^{28Reference 28Brendler et al. · 2021ReviewSceletium for managing anxiety, depression and cognitive impairment: a traditional herbal medicine in modern-day regulatory systems — reviewView study →}. Healers in Namaqualand use it to treat alcohol dependence, and it is known locally as onse droë drank, “our dry liquor” ^{28Reference 28Brendler et al. · 2021ReviewSceletium for managing anxiety, depression and cognitive impairment: a traditional herbal medicine in modern-day regulatory systems — reviewView study →}.

Minute amounts added to breast milk are still given to infants for colic ^{28Reference 28Brendler et al. · 2021ReviewSceletium for managing anxiety, depression and cognitive impairment: a traditional herbal medicine in modern-day regulatory systems — reviewView study →}.

Colonial farmers in the Cape took kanna as a decoction or tincture, as a sedative ^{28Reference 28Brendler et al. · 2021ReviewSceletium for managing anxiety, depression and cognitive impairment: a traditional herbal medicine in modern-day regulatory systems — reviewView study →}. Tinctures and infusions are recorded from 1857 ^{28Reference 28Brendler et al. · 2021ReviewSceletium for managing anxiety, depression and cognitive impairment: a traditional herbal medicine in modern-day regulatory systems — reviewView study →}.

In the Cape, a few drops of the fresh leaf juice were given to young children with “acidity” to settle them for a few hours ^{28Reference 28Brendler et al. · 2021ReviewSceletium for managing anxiety, depression and cognitive impairment: a traditional herbal medicine in modern-day regulatory systems — reviewView study →}.

In a double-blind, placebo-controlled crossover brain-imaging study of 16 healthy people, a single 25 mg dose of Zembrin reduced the response of the amygdala to fearful faces. It also weakened the coupling between the amygdala and the hypothalamus, part of the brain’s threat circuitry ^{4Reference 4Terburg et al. · 2013RCTAcute effects of Sceletium tortuosum (Zembrin), a dual 5-HT reuptake and PDE4 inhibitor, in the human amygdala — randomised, placebo-controlled pharmaco-fMRI crossoverView study →}.

A second placebo-controlled study in 20 healthy volunteers gave a single 25 mg dose before laboratory stress tasks. In the public-speaking task, anxiety was lower before the task began and heart rate responded differently over time. The multitasking task showed no effect ^{7Reference 7Reay et al. · 2020RCTSceletium tortuosum (Zembrin) ameliorates experimentally induced anxiety in healthy volunteers — randomised controlled trialView study →}.

In zebrafish larvae, Zembrin reduced anxiety-like behaviour, and of its alkaloids only mesembrine contributed significantly ^{10Reference 10Gericke et al. · 2024AnimalSceletium tortuosum-derived mesembrine contributes to the anxiolytic effect of Zembrin, but the antidepressant effect may require synergy of multiple constituents — zebrafish in vivoView study →}. In another zebrafish study, all four main alkaloids reduced anxiety-like behaviour ^{11Reference 11Maphanga et al. · 2022AnimalMesembryanthemum tortuosum alkaloids modify anxiety-like behaviour in a zebrafish model — in vivo zebrafishView study →}. In chicks, an alkaloid-enriched fraction reduced distress calls in the anxiety phase of an isolation test ^{12Reference 12Carpenter et al. · 2016AnimalThe effects of a Sceletium tortuosum extract fraction in the chick anxiety-depression model — animal modelView study →}.

Gap: every human result is a single dose in healthy volunteers. There is no trial in people with an anxiety disorder, and one rat stress study found signs of intolerance ^{27Reference 27Smith · 2011AnimalThe effects of Sceletium tortuosum in an in vivo model of psychological stress — in vivo rat studyView study →}.

In a double-blind crossover trial, 21 healthy adults (average age 55) took 25 mg of Zembrin or placebo daily for three weeks. Zembrin improved cognitive set flexibility and executive function. The authors attributed this to PDE4 inhibition, which raises cAMP–CREB signalling ^{3Reference 3Chiu et al. · 2014RCTProof-of-concept randomised controlled study of cognition effects of Zembrin targeting phosphodiesterase-4 in cognitively healthy subjectsView study →}.

In a trial of 60 recreationally trained young adults, 25 mg a day for eight days improved complex reaction tasks that carried a mental load. Mood, alertness and simple reaction time did not change ^{8Reference 8Hoffman et al. · 2020RCTErgogenic effects of 8 days of Sceletium tortuosum supplementation on mood, visual tracking, and reaction — randomised controlled trialView study →}.

Sub-fractions of the plant inhibit acetylcholinesterase in vitro ^{15Reference 15Luo et al. · 2022In vitroA network pharmacology-based approach to explore the therapeutic potential of Sceletium tortuosum in neurodegenerative disorders — in silico and in vitroView study →}.

Gap: both trials are small and short and in healthy people. The effects were modest, and no trial has been run in older people with memory problems.

Mesembrine, kanna’s main alkaloid, binds the serotonin transporter with high affinity (Ki 1.4 nM), and the standardised extract blocks it in laboratory assays ^{5Reference 5Harvey et al. · 2011In vitroPharmacological actions of the South African medicinal and functional food plant Sceletium tortuosum and its principal alkaloids — in vitro receptor/enzyme studyView study →}. A high-mesembrine extract also increased VMAT2, the transporter that loads serotonin and other monoamines into storage vesicles, and acted as a monoamine-releasing agent ^{21Reference 21Coetzee et al. · 2016In vitroHigh-mesembrine Sceletium extract (Trimesemine) is a monoamine-releasing agent, rather than only a selective serotonin reuptake inhibitor — in vitroView study →}.

In the Flinders Sensitive Line rat, a genetic model of depression, single doses of Zembrin reduced despair-like behaviour, and 50 mg/kg matched escitalopram at 5 mg/kg ^{9Reference 9Gericke et al. · 2022AnimalAn acute dose-ranging evaluation of the antidepressant properties of Sceletium tortuosum (Zembrin) versus escitalopram in the Flinders Sensitive Line rat — animal model, comparative studyView study →}.

In zebrafish larvae, only the whole extract at a higher concentration showed an antidepressant-like effect. None of the single alkaloids did, which suggests several constituents act together ^{10Reference 10Gericke et al. · 2024AnimalSceletium tortuosum-derived mesembrine contributes to the anxiolytic effect of Zembrin, but the antidepressant effect may require synergy of multiple constituents — zebrafish in vivoView study →}. In chicks, an alkaloid fraction reduced anxiety-like behaviour but showed no antidepressant-like effect ^{12Reference 12Carpenter et al. · 2016AnimalThe effects of a Sceletium tortuosum extract fraction in the chick anxiety-depression model — animal modelView study →}.

Gap: there is no controlled trial in people with depression. The mood data in people are secondary observations from healthy-volunteer studies.

Sub-fractions of the plant scavenge free radicals and inhibit acetylcholinesterase, monoamine oxidase-B and the NMDA receptor in vitro, targets relevant to Alzheimer’s and Parkinson’s disease ^{15Reference 15Luo et al. · 2022In vitroA network pharmacology-based approach to explore the therapeutic potential of Sceletium tortuosum in neurodegenerative disorders — in silico and in vitroView study →}.

In zebrafish larvae, Zembrin reversed reserpine-induced loss of movement and reduced oxidative stress ^{16Reference 16Lepule et al. · 2026AnimalZembrin mitigates reserpine-induced motor dysfunction and oxidative stress in a Parkinson’s disease model — animal modelView study →}. In a 6-OHDA model, Zembrin protected against movement loss, and a methanol extract helped restore it ^{17Reference 17Lepule et al. · 2025AnimalNeuroprotective and neurorestorative properties of Mesembryanthemum tortuosum in a Parkinson’s disease model — animal modelView study →}.

In human astrocytes, a high-mesembrine extract was protective and anti-inflammatory, while a high-Δ7-mesembrenone extract was a stronger antioxidant ^{18Reference 18Bennett et al. · 2018Sceletium tortuosum may delay chronic disease progression via alkaloid-dependent antioxidant activity — comparative studyView study →}.

No human study has measured neuroprotection.

In primary human monocytes, a Sceletium extract raised release of the anti-inflammatory signal IL-10 and fully protected the cells’ mitochondria from bacterial endotoxin (LPS), without blocking the normal inflammatory response ^{19Reference 19Bennett et al. · 2018In vitroImmunomodulatory effects of Sceletium tortuosum (Trimesemine) elucidated in vitroView study →}.

⚠ In a rat stress study, 17 days of the extract raised IL-1β, C-reactive protein and prostaglandin E2, which the author read as intolerance to the treatment ^{27Reference 27Smith · 2011AnimalThe effects of Sceletium tortuosum in an in vivo model of psychological stress — in vivo rat studyView study →}.

The supportive data are in vitro, and the one whole-animal immune study points the other way.

Pain, headache and toothache are recorded traditional uses ^{28Reference 28Brendler et al. · 2021ReviewSceletium for managing anxiety, depression and cognitive impairment: a traditional herbal medicine in modern-day regulatory systems — reviewView study →}. In rats, mesembrine relieved pain in the hot-plate test without producing place preference (a marker of abuse potential) or loss of coordination ^{14Reference 14Loria et al. · 2014AnimalEffects of Sceletium tortuosum in rats — in vivo behavioural assays (analgesia, depression, abuse liability)View study →}.

This is one animal study of an isolated alkaloid, with no dose-response or replication.

Kanna’s reputation for libido and erectile support rests on mechanism. Its alkaloids inhibit PDE4, which raises cAMP ^{5Reference 5Harvey et al. · 2011In vitroPharmacological actions of the South African medicinal and functional food plant Sceletium tortuosum and its principal alkaloids — in vitro receptor/enzyme studyView study →}. A review of herbal sexual enhancers includes kanna, but it assessed side effects rather than benefit ^{20Reference 20Brunetti et al. · 2020ReviewPharmacology of herbal sexual enhancers: a review of psychiatric and neurological adverse effects — reviewView study →}.

Gap: no animal or human study has measured sexual function or libido.

Kava produces a similar calm, relaxed state, but it acts mainly on GABA. Kava becomes sedating at higher doses; kanna stays light.

Kratom is stronger, stimulating at low doses and sedating and pain-relieving at high ones, and it carries a risk of dependence. Kanna’s effects on mood and relaxation are milder.

Both are relaxing and mildly euphoric, but cannabis clearly alters perception and kanna does not.

Some first-time users feel nausea, tiredness or a clouded feeling instead of the expected lift in mood and focus. This is known as priming. It usually fades after the first one to three sessions, and not everyone experiences it.

Traditional kougoed is fermented, and fermented products are often advertised as stronger ^{1Reference 1Patnala et al. · 2009Investigations of the phytochemical content of Sceletium tortuosum following the preparation of “Kougoed” by fermentation of plant materialView study →}. In a controlled study, fermentation converted most of the mesembrine into Δ7-mesembrenone ^{1Reference 1Patnala et al. · 2009Investigations of the phytochemical content of Sceletium tortuosum following the preparation of “Kougoed” by fermentation of plant materialView study →}. Fermented kanna tastes worse than raw.

Tolerability. A randomised, double-blind, placebo-controlled trial gave 37 healthy adults 8 mg or 25 mg of Zembrin daily for three months. It found no changes in vital signs, ECG, blood tests or body weight, and side effects were more common with placebo ^{13Reference 13Nell et al. · 2013RCTA randomised, double-blind, parallel-group, placebo-controlled trial of extract Sceletium tortuosum (Zembrin) in healthy adults — 3-month safety RCTView study →}. In rats, 14-day and 90-day studies found no adverse effects at the highest doses tested (5,000 and 600 mg/kg a day) ^{22Reference 22Murbach et al. · 2014AnimalA toxicological safety assessment of a standardised extract of Sceletium tortuosum (Zembrin) in rats — animal toxicology studyView study →}.

Side effects. Common short-term effects are mild: nausea, headache, tiredness, dizziness or a clouded feeling, most often in the first few sessions. In rats, an alkaloid-rich fraction caused loss of coordination ^{14Reference 14Loria et al. · 2014AnimalEffects of Sceletium tortuosum in rats — in vivo behavioural assays (analgesia, depression, abuse liability)View study →}, and a 17-day study found raised inflammatory markers ^{27Reference 27Smith · 2011AnimalThe effects of Sceletium tortuosum in an in vivo model of psychological stress — in vivo rat studyView study →}.

Serotonergic medicines. Because kanna blocks serotonin reuptake, it should not be used with antidepressants, including SSRIs (fluoxetine, paroxetine, sertraline, citalopram, escitalopram), SNRIs (duloxetine, venlafaxine) and MAOIs ^{28Reference 28Brendler et al. · 2021ReviewSceletium for managing anxiety, depression and cognitive impairment: a traditional herbal medicine in modern-day regulatory systems — reviewView study →}.

PDE inhibitors. Kanna inhibits PDE4 ^{5Reference 5Harvey et al. · 2011In vitroPharmacological actions of the South African medicinal and functional food plant Sceletium tortuosum and its principal alkaloids — in vitro receptor/enzyme studyView study →}. Take care with the PDE4 drug roflumilast ^{28Reference 28Brendler et al. · 2021ReviewSceletium for managing anxiety, depression and cognitive impairment: a traditional herbal medicine in modern-day regulatory systems — reviewView study →}. Erectile-dysfunction drugs inhibit the related enzyme PDE5, so take care combining them with kanna, including within about 48 hours of taking one.

Blood pressure. Kanna may add to the effect of blood-pressure medicines and cause dizziness or fainting.

Oxalates and snuffing. The plant contains oxalates, which in very large amounts could burden the kidneys. Repeated snuffing irritates the nasal passages.

Dependence. It is not physically addictive, though, like anything that lifts mood, it can become a habit. Namaqualand healers use it to treat alcohol dependence, and no withdrawal symptoms are recorded from long-term use ^{28Reference 28Brendler et al. · 2021ReviewSceletium for managing anxiety, depression and cognitive impairment: a traditional herbal medicine in modern-day regulatory systems — reviewView study →}.

Pharmacokinetics. In mice, mesembrine and mesembrenone were poorly absorbed by mouth, and blood levels after oral dosing were below detection ^{23Reference 23Manda et al. · 2017AnimalQuantification of mesembrine and mesembrenone in mouse plasma using UHPLC-QToF-MS: application to a pharmacokinetic studyView study →}. A computer-based toxicity prediction placed mesembrine in a moderate acute-toxicity class; it has not been confirmed by measurement ^{24Reference 24Niżnik et al. · 2025First toxicity profile prediction for mesembrine — a multi-faceted in silico approachView study →}.