Supplement
Sweet flag, also called Vacha, is a wetland plant whose rhizome features in Ayurvedic medicine and is rich in a compound called β-asarone. The best-studied finding is a caution: long-term animal studies found that β-asarone caused intestinal tumors and organ damage with chronic exposure, though the evidence is limited. Reported effects on mood, seizures and immunity come from rodent and lab work, and that evidence is very limited.
Sources: PMID 23741157; PMID 40844059
- Updated
- How we grade
- 12 studies cited
- Best evidence
- Grade C
- Conditions studied
- 2
- Outcomes
- 8
- Graded outcomes
- 0017
Evidence by condition
- Strong
- Moderate
- Limited
- Very limited
General
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Cancer Risk (β-Asarone Toxicity) Multiple long-term animal studies confirm β-asarone, the dominant compound in Acorus calamus (up to 80.6% of rhizome essential oil), causes intestinal tumors and organ damage with chronic exposure. Reviews (Sharma et al. 2020, Middha et al. 2026) and ex vivo/in vivo studies (Parashar et al. 2026) document dose-dependent toxicity, including complete mortality at higher oral doses in mice. A 2025 Ames test (Anantha Narayana & Mukne) found no mutagenicity under acute conditions, but long-term carcinogenicity remains established. The herb is banned or restricted in food in the US and other countries due to this risk. | Worsens (the measure goes up) | Large effect | 7 studies | |||
Studies that measured cancer risk (β-asarone toxicity)
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| Antimicrobial Activity In vitro, Acorus calamus essential oil (dominated by β-asarone at 80.6%) showed bactericidal activity against Gram-positive, Gram-negative bacteria and fungi, with Micrococcus luteus most susceptible at MBC 0.032 mg/mL (Joshi 2016). Leaf extracts also demonstrated antibacterial zones against Pseudomonas aeruginosa and Staphylococcus aureus exceeding standard antibiotics in vitro (Haran et al. 2024). | Improves (the measure goes up) | Small effect | 4 studies | |||
Studies that measured antimicrobial activity
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| Depressive Symptoms In a rodent model of depression, Vacha administration prevented stress-induced behavioral deficits in ambulation and rearing, demonstrating antidepressant effects through a mechanism distinct from typical 5-HT1A receptor sensitization (Tripathi & Singh 2010). A 2020 review confirmed antidepressant properties among the documented neurological effects of Acorus calamus in preclinical models. | Improves (the measure goes down) | Moderate effect | 3 studies | |||
Studies that measured depressive symptoms
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| Seizure Susceptibility In an animal Maximal Electro Shock seizure model, both raw and traditionally processed (Shodhana) Vacha rhizomes significantly decreased the duration of the tonic extensor phase, with the processed form showing additional reductions in convulsion and stupor phases (Bhat et al. 2012). A comprehensive 2020 review corroborated anticonvulsant activity as a well-documented effect of the herb in preclinical literature. | Improves (the measure goes down) | Moderate effect | 3 studies | |||
Studies that measured seizure susceptibility
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| Blood Pressure β-Asarone exhibited vasorelaxation in isolated rat mesenteric arteries at concentrations of 1-30 μg/mL through modulation of L-type voltage-dependent calcium channels (Parashar et al. 2026). A 2020 review also listed antihypertensive effects among the pharmacological properties documented in preclinical studies. However, dose-dependent toxicity limits translational potential. | Improves (the measure goes down) | Small effect | 3 studies | |||
Studies that measured blood pressure
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| Stress-Induced Immune Suppression In a rat model, oral Vacha benzene extract (ED50 of 10 mg) administered for 4 weeks significantly prevented stress-induced reductions in total and differential leukocyte counts, immunoglobulin content, and bone marrow cellularity (p < 0.001), while also preventing structural involution of lymphoid organs (Sarjan et al. 2017). | Improves (the measure goes down) | Moderate effect | 2 studies | |||
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Neuroprotection Two comprehensive reviews (Sharma et al. 2020; Middha et al. 2026) document neuroprotective effects of Acorus calamus active compounds through modulation of Nrf-2, NF-κB, PI3K/AKT, and Ras/MAPK signaling pathways in preclinical models, reducing oxidative stress associated with neurological dysfunction. Evidence remains limited to animal and in vitro studies with no direct human clinical trials on cognition. | Improves (the measure goes up) | Small effect | 4 studies | |||
Studies that measured neuroprotection
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| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Antioxidant Capacity In vitro studies demonstrated that Acorus calamus leaf extract exhibited significant free radical scavenging activity comparable to ascorbic acid in DPPH and hydrogen peroxide assays, with dose-dependent ferric ion reduction in the FRAP assay (Haran et al. 2024). A 2020 review also noted antioxidative properties among the documented pharmacological effects. | Improves (the measure goes up) | Small effect | 3 studies | |||
Studies that measured antioxidant capacity
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Key findings
- Cancer Risk (β-Asarone Toxicity)Worsens (the measure goes up)
- NeuroprotectionImproves (the measure goes up)
- Antimicrobial ActivityImproves (the measure goes up)
Safety notes in the studies
- 2026) document dose-dependent toxicity, including complete mortality at higher oral doses in mice.
- The herb is banned or restricted in food in the US and other countries due to this risk.
- However, dose-dependent toxicity limits translational potential.
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- Grade C
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Studies cited
12 studies from PubMed
- β-Asarone-induced vasorelaxation in isolated rat mesenteric artery: An efficacy vs toxicity paradox of Acorus calamus.
- Phytochemical, Pharmacological, and Therapeutic Benefit of Acorus Calamus (Vacha): A Comprehensive Scientific Review.
- Reporting negative Ames test results for Indian Acorus calamus L., rhizome, extracts, and beta asarone.
- Free Radical Scavenging, Anti-inflammatory and Antibacterial Activity of Acorus calamus Leaves Extract Against Pseudomonas aeruginosa and Staphylococcus aureus.
- Role of Vacha (Acorus calamus Linn.) in Neurological and Metabolic Disorders: Evidence from Ethnopharmacology, Phytochemistry, Pharmacology and Clinical Study.
- The protective effect of the Vacha rhizome extract on chronic stress-induced immunodeficiency in rat.
- Acorus calamus Linn.: phytoconstituents and bactericidal property.
- Fate of β-asarone in Ayurvedic Sodhana process of Vacha.
- Anticonvulsant activity of raw and classically processed Vacha (Acorus calamus Linn.) rhizomes.
- Usage trends for memory and vitality-enhancing medicines: A pharmacoepidemiological study involving pharmacists of the Gujarat region.
- Experimental evaluation of antidepressant effect of Vacha (Acorus calamus) in animal models of depression.
- Clinical study of the Immunoglobululin Enhancing effect of "Bala compound" on Infants.