Kanna and Caffeine: What Is Known About Combining Them

Coffee, energy drinks and pre-workout are everywhere, and so are kanna drinks. Whether the two interact has not been studied in people that we could find.

Kanna and caffeine is a question that comes up because both show up in the same aisle. Kanna drinks sit next to coffee sodas and energy cans, and some products blend the two. So can you combine them? The honest answer is that we do not know. We searched for human studies of kanna together with caffeine and found none. This post lays out what is known about each, what is missing, and how to read a label so you know what you are actually drinking.

Is there research on kanna and caffeine?

Not that we could find. The human kanna studies we reviewed did not test caffeine alongside it.

The published human work on kanna is small. It includes a 2013 brain-imaging study of 16 healthy people given one 25 mg dose of the Zembrin extract [6], a 3-week cognition study in 21 adults [7], a 3-month safety trial in 37 adults taking 8 mg or 25 mg daily [3], and two 2020 studies, one in 20 volunteers [8] and one in 60 young adults [9]. As far as we can tell from their published abstracts and the reviews that summarize them, none gave participants caffeine as part of the design, and none reported a caffeine interaction. A 2026 critical review of animal and clinical studies calls the evidence "mixed" and notes small samples [10]. A 2021 review notes the plant had not been studied in a clinical population [5].

We also looked for interaction references. WebMD's sceletium page lists medicines of concern and says interactions are not fully understood. It does not mention caffeine [2]. Absence from a list is not proof of safety, and it is not proof of a problem. It means the question has not been answered. For the full picture of what has been tested, see what the research on kanna shows.

What is known about each one on its own?

Caffeine is well documented; kanna is much less so.

Caffeine

The FDA says that for most adults, 400 mg a day is an amount not generally associated with negative effects, and that sensitivity and the speed at which the body clears caffeine vary widely [1]. It lists symptoms of too much: faster or fluttering heartbeat, higher blood pressure, trouble sleeping, nervousness or shakiness, stomach upset and headache [1]. It also says some medications can make people more sensitive and advises talking to a health care provider if you take medication, have a condition, or are pregnant or breastfeeding [1].

Kanna

Kanna (Sceletium tortuosum) is a South African succulent whose main alkaloids are mesembrine-type compounds [5]. In a 2011 lab study, a standardized extract blocked the serotonin transporter and inhibited the enzyme PDE4 [4]. Caffeine does not appear among the alkaloids described in the reviews we read [5]. In the 3-month safety trial, vital signs, ECG and bloodwork did not differ from placebo at 8 mg or 25 mg daily, and headache was the most common adverse event, more often in the placebo group [3]. That trial involved healthy adults, one extract, and no caffeine arm. See what is kanna for background.

What is known and unknown about combining them?

The combination itself is unstudied, so most of what people say about it is guesswork, including guesses in forums and on product pages.

It can be tempting to reason from mechanisms, for example by noting that kanna and caffeine both act on signaling pathways in the brain. We are not going to do that. Lab mechanisms in a dish or rodent do not tell you what a combination does in a person, and no one has published the human experiment. If you see a confident claim that the pair is "synergistic" or "dangerous," ask what study it comes from.

One more unknown matters for real products. WebMD notes that some dietary supplements containing sceletium have been found to contain other ingredients, such as ephedrine, a stimulant [2]. A separate 2016 lab analysis of commercial kanna products found ephedrine in one sample [11]. That is a contamination or adulteration issue, not a caffeine interaction, but it is a reminder that a "kanna" product is not always only kanna.

Which kanna products contain caffeine?

Some do, some do not, and the only way to know is the label.

Kanna is sold as drinks, shots, capsules, powders and tinctures. Some drinks pair it with other botanicals such as kava or L-theanine, and some products are reported to contain added caffeine, so check each label. The FDA also points out that dietary supplements and over-the-counter medicines may contain added caffeine [1], so the stimulant can appear in places you do not expect. If a label lists "guarana," "green tea extract," "yerba mate" or "natural caffeine," those are caffeine sources.

For context on how different kinds of functional drinks are put together, see our explainer on functional beverages. For one that has no caffeine, Silly lists none in its ingredients.

What about energy drinks, pre-workout and nicotine?

We found no data on any of them paired with kanna, and each has its own caution.

The FDA says energy drinks generally contain 54 to 328 mg of caffeine per 16 fluid ounces and that there is no FDA regulation specific to "energy drinks" [1]. It also notes that medical experts advise against energy drinks for children and teens [1]. Pre-workout powders often contain caffeine and other stimulants, with amounts that vary by product. Nicotine is a separate stimulant. We found no study of kanna with any of these, and no reason to assume the answer is the same across them.

The same logic applies to alcohol, which is a depressant and behaves differently from caffeine. Our post on kanna and alcohol covers what is known there.

What should you check before combining them?

You can reduce the unknowns even though you cannot remove them.

• Read the whole ingredient list. Add up caffeine from every source in a day, not only the kanna product.
• Look for added stimulants. Ephedrine, synephrine and similar compounds should not be hidden in a supplement, and finding one is a reason to stop and ask.
• Know your own sensitivity. The FDA notes that people vary widely in how they respond to caffeine [1].
• Mind your medicines. Anyone taking an SSRI, SNRI, MAOI, tricyclic, antipsychotic or triptan, or using St. John's wort, should talk to a doctor or pharmacist before using kanna at all [2]. See kanna and drug interactions.
• Pregnancy and nursing. WebMD says it is not known whether sceletium is safe in pregnancy [2], and the FDA advises talking to a provider about caffeine in pregnancy [1]. Ask a clinician.

This is information, not a recommendation to combine or avoid anything. For the wider safety picture, read is kanna safe, and for what trials used, kanna dosage.

This page is general information, not medical advice. These statements have not been evaluated by the FDA. Kanna products are not intended for any disease or health condition. kannadrinks.com is published by Psilly Goose, a kanna drink maker.

References

1. U.S. Food and Drug Administration. Spilling the Beans: How Much Caffeine Is Too Much? fda.gov
2. WebMD. Sceletium: Uses, side effects, interactions. webmd.com
3. 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
4. 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
5. Olatunji TL, et al. Sceletium tortuosum: a review on its phytochemistry, pharmacokinetics, biological and clinical activities. J Ethnopharmacol 2021;280:114476. PubMed
6. 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
7. Chiu S, et al. Proof-of-concept randomized controlled study of cognition effects of the proprietary extract Sceletium tortuosum (Zembrin) targeting phosphodiesterase-4 in cognitively healthy subjects. Evid Based Complement Alternat Med 2014;2014:682014. PubMed
8. Reay J, et al. Sceletium tortuosum (Zembrin) ameliorates experimentally induced anxiety in healthy volunteers. Hum Psychopharmacol 2020;35(6):1-7. PubMed
9. Hoffman JR, et al. Ergogenic effects of 8 days of Sceletium tortuosum supplementation on mood, visual tracking, and reaction in recreationally trained men and women. J Strength Cond Res 2020;34(9):2476-81. PubMed
10. 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
11. Lesiak AD, et al. Direct analysis in real time high resolution mass spectrometry as a tool for rapid characterization of mind-altering plant materials and revelation of supplement adulteration: the case of Kanna. Forensic Sci Int 2016;260:66-73. PubMed

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