Kanna

What it is

Sceletium tortuosum, today also called Mesembryanthemum tortuosum in botany, is a member of the ice plant family from the Karoo. The Afrikaans word kougoed, “chewing stuff”, describes the traditional use: the leaves were crushed, fermented, dried and chewed, and later also used as a tea or tincture. In a description from 1738, kanna is called the greatest enlivener of the spirits.

The plant contains 25 known alkaloids; the most important are mesembrine, mesembrenone, mesembrenol and mesembranol. Their content varies greatly between plants and origins. A standardized extract, Zembrin, set to a fixed alkaloid content, was therefore developed for research. Almost all human studies were done with this extract.

How it is supposed to work

In the laboratory, the extract inhibits the serotonin transporter, the same target protein as classic antidepressants of the SSRI type. Mesembrine is the most potent alkaloid here. In addition, the extract selectively inhibits phosphodiesterase 4, an enzyme that breaks down the cellular messenger cAMP and is associated with mood, inflammation and memory. A cell study suggests that mesembrine-rich extracts also trigger the release of monoamines, so they do not merely slow reuptake.

In humans there is direct evidence of an effect in the brain. In a study with functional MRI, the amygdala, the brain’s alarm center, responded more weakly to fearful faces after a single dose, and its coupling to the hypothalamus decreased. Two EEG studies from the manufacturer’s circle found altered brainwave rhythms during thinking and emotional tasks.

It is open how the alkaloids get there. According to the manufacturer’s documents, the main alkaloids are hardly available in the blood after swallowing; they are heavily transformed in the liver. A laboratory study showed that they penetrate the mucous membranes of the mouth and tongue well. The traditional long chewing could therefore be more than folklore.

What comes next

The developer of the Zembrin extract has submitted an application to the EU for authorization as a novel food, intended for food supplements for adults. The application documents cite several genotoxicity tests without findings and two 90-day feeding studies in rats in which even the highest dose showed no harm. No decision on the application has been made yet. In parallel, further human studies are registered, including an 8-week study on the psychological effects of the extract.

What users describe

In traditional use, kanna is considered a mood enhancer, a remedy against tension, hunger and thirst, and in larger amounts mildly intoxicating and euphoric. In the 3-month study, some participants noted unprompted in their diaries that they coped better with stress and slept better. These are reports, not measurements, but they fit what the small studies suggest.

What the studies show

Fear center on a brain scan (2013)

Double-blind, placebo-controlled crossover study with 16 healthy participants. After a single dose of 25 mg Zembrin, the amygdala responded more weakly to fearful faces, and its functional coupling to the hypothalamus was reduced. The authors see this as an indication of anxiety-relieving potential. What was measured was a brain signal, not the feeling of anxiety.

Cognition in healthy people (2014)

Randomized, double-blind crossover study with 21 cognitively healthy people, on average 54.6 years old, each taking extract and placebo for 3 weeks. With Zembrin, cognitive flexibility (p < 0.032) and executive function (p < 0.022) improved, and mood and sleep changed positively. The study was small and was conducted with the involvement of the developer.

Reaction under load (2020)

60 trained adults between 20 and 35 years of age received kanna extract or placebo for 8 days. In complex reaction tasks with cognitive load, the kanna group performed better. In simple reaction tests and in mood, there was no difference.

Where the data stop

The biggest gap: there is not a single published study in people with an anxiety disorder or depression. All human studies were done in healthy people, with 16 to 60 participants and from a single dose up to at most 3 months. Many endpoints are brain signals from MRI and EEG, not what affected people feel in everyday life. And not everything was positive: in one of the two laboratory studies on anxiety there was no effect, and in the athlete study no effect on mood. A 2026 review therefore speaks of mixed evidence.

Almost all studies used the same brand-name extract, and the developer was involved in most of them. Independent replications are largely lacking. The pharmacokinetics in humans are also unresolved, including the question of which substances carry the effect after swallowing. The results cannot simply be transferred to the raw plant, fermented herb or other extracts whose alkaloid profile is different. Further studies are registered; results are pending.

Status, approval and legal

In the EU, kanna is an unauthorized novel food. The European Commission’s Novel Food Catalogue does not list the plant, and it is not on the Union list of authorized novel foods. German authorities reported kanna in food supplements as an unauthorized novel ingredient in the European rapid alert system RASFF in 2020, 2025 and 2026, and Austria most recently in 2026. The manufacturer of the Zembrin extract has submitted a novel food application for food supplements for adults, on which no decision has yet been made. Kanna is not approved as a medicine and is not listed in the German Narcotics Act. In the US, a particular extract has been marketed since 2011 on the basis of a GRAS self-affirmation. Kanna is not named on the World Anti-Doping Agency’s 2026 Prohibited List.

Safety

In the controlled studies, the standardized extract was well tolerated; over 3 months there were no abnormalities in lab values, ECG or vital signs. Because of its action on the serotonin transporter, kanna should not be combined with SSRIs, SNRIs or other serotonergic psychotropic drugs; caution is also needed with PDE4 inhibitors such as roflumilast. There are no data for pregnancy and breastfeeding; the application for authorization explicitly excludes these groups. A practical risk lies in the products: the alkaloid content varies greatly, and the banned substance ephedrine was found in a commercially available kanna product. Anyone suffering from persistent anxiety or low mood should have this clarified by a physician and should not replace current medication on their own.

Sources

• Terburg et al., Neuropsychopharmacology 2013 – amygdala response after a single dose of Zembrin
• Chiu et al., Evidence-Based Complementary and Alternative Medicine 2014 – cognition in healthy people
• Nell et al., Journal of Alternative and Complementary Medicine 2013 – safety study over 3 months
• Reay et al., Human Psychopharmacology 2020 – experimentally induced anxiety in healthy people
• Hoffman et al., Journal of Strength and Conditioning Research 2020 – reaction and mood in athletes
• Harvey et al., Journal of Ethnopharmacology 2011 – serotonin transporter and PDE4
• Brendler et al., Current Neuropharmacology 2021 – Sceletium between tradition and regulation
• de Jong et al., Planta Medica 2026 – mixed evidence from animal and human studies
• European Commission – summary of the novel food application for Sceletium extract
• RASFF 2025.7263 – kanna as an unauthorized novel ingredient