Benefits
Source of glucotropaeolin, which releases benzyl isothiocyanate
Nasturtium leaf stores glucotropaeolin, which the plant enzyme myrosinase converts to benzyl isothiocyanate when the tissue is crushed or moistened. In a controlled trial, powder with active enzyme formed this compound while the same powder with heat-inactivated enzyme formed almost none, showing the enzyme step decides how much is made.
Benzyl isothiocyanate is absorbed and reaches blood, urine and breath
In 15 healthy men, one 10 g serving of freeze-dried nasturtium produced benzyl isothiocyanate conjugates in plasma within 1 to 5 hours and in urine at 4 to 6 hours. In a 7-person pilot, protein-bound forms stayed in plasma for 48 hours and the compound was exhaled in breath. These are absorption studies, not health outcomes.
Urine and airway host-defense markers after two weeks
In a crossover trial in healthy women taking 1.5 g of nasturtium twice daily, the host-defense peptide beta-defensin 1 rose in urine and exhaled breath after the benzyl isothiocyanate phase, and urine samples slightly slowed E. coli growth in a dish. These were before-and-after lab markers, not a measure of infections.
Gut hormone peptide YY after a single serving
In 15 healthy men, one 10 g serving of freeze-dried nasturtium leaf in water was followed by increased release of peptide YY, a gut hormone linked to fullness, over 6 hours in the study abstract, while insulin, GLP-1 and GIP did not change. Appetite, food intake and weight were not measured.
Gut microbiome and prostaglandin E2 in a two-week trial
In healthy women, two weeks of nasturtium with or without its benzyl isothiocyanate left mean gut microbiome composition unchanged between phases. Serum prostaglandin E2, an inflammation signal that nasturtium extract lowered in lab cells, rose by the same amount in both phases, so the compound did not explain it.
Urinary tract support in a nasturtium-led herbal blend
In maker-linked placebo-controlled trials, tablets of 200 mg nasturtium herb plus 80 mg horseradish root, with nasturtium as the lead herb, were followed by fewer recurrences in adults prone to repeated bladder infections: 0.43 versus 0.77 per person over 90 days, and 36% versus 48% of women by 6 months. Neither herb was tested alone.
Respiratory support in a nasturtium-led herbal blend
In maker-sponsored placebo-controlled trials, tablets of 200 mg nasturtium herb plus 80 mg horseradish root, with nasturtium as the lead herb, were followed by fewer new airway infections over up to 12 weeks (13.3% at 6 tablets a day versus 25.6% on placebo) and faster easing of cough and mucus in acute bronchitis. Neither herb was tested alone.
Diuretic and antibacterial effects in lab and animal studies
In rats, oral nasturtium extract increased urine output, spared potassium and lowered ACE activity and aldosterone. In lab dishes, benzyl isothiocyanate combined with horseradish mustard oils inhibited many bacteria and Candida. These are lab and animal findings and have not been shown as effects of eating nasturtium.
Mechanism of action
Myrosinase turns glucotropaeolin into benzyl isothiocyanate
Glucotropaeolin and the enzyme myrosinase are kept apart in intact tissue. Crushing, chewing or mixing the dried powder with water lets myrosinase release benzyl isothiocyanate; heat-inactivating the enzyme almost abolished it in a trial preparation. This differs from watercress, which mainly yields phenethyl isothiocyanate.
Conjugation, protein binding and exhalation
After absorption, benzyl isothiocyanate binds glutathione and is processed through the mercapturic acid pathway to N-acetylcysteine and cysteine conjugates excreted in urine. It also forms protein adducts that were still present in plasma at 48 hours and is partly exhaled, which is the traditional rationale for its use for the urinary and respiratory tracts.
Isothiocyanates inhibit bacteria in laboratory tests
Isolated benzyl, allyl and phenylethyl isothiocyanates, combined in the proportions of the nasturtium and horseradish medicine, inhibited Haemophilus, Moraxella, Proteus and Candida strongly and several other bacteria moderately, with resistant and non-resistant strains similarly affected. Concentrations reached in the body are not established.
COX and LOX signaling in immune cells
In human immune cells in culture, nasturtium extract suppressed COX-2 expression, PGE2 and LTB4 release and TNF-alpha, acting upstream through ERK and c-Jun rather than by blocking the COX-2 enzyme. A two-week human trial did not reproduce lower PGE2, so this remains a cell-level finding.
Clinical trials
Monocentric, randomized, double-blind, controlled crossover trial of dried nasturtium leaf and flower powder with active myrosinase (forms benzyl isothiocyanate) versus the same powder with heat-inactivated myrosinase; the primary outcome was serum prostaglandin E2, and a second paper on the same trial reported gut microbiome and host-defense markers; Repha GmbH supplied the powder and partly funded the trial. (Herz et al. 2023, Front Nutr)
34 healthy women; 1.5 g nasturtium powder twice daily for 2 weeks per phase, with at least a 2-week washout.
Serum PGE2 rose by a similar amount in both phases (1.76-fold and 1.78-fold), so benzyl isothiocyanate did not explain the change. In the follow-up analysis, gut microbiome composition did not differ between phases, while urinary beta-defensin 1 rose after the active phase. The control was also nasturtium, so the trial tests the compound, not the plant versus nothing.
Controlled volunteer study of one oral dose of freeze-dried nasturtium leaf suspended in water versus water alone, with hourly blood sampling for gut hormones; the same volunteers provided the benzyl isothiocyanate metabolism data. (Schiess et al. 2017, Mol Nutr Food Res)
15 metabolically healthy men; 10 g freeze-dried nasturtium (about 1000 micromoles glucotropaeolin) once.
The abstract reports increased release of peptide YY, a satiety-related gut hormone, over 6 hours, while insulin, C-peptide, GLP-1 and GIP did not change. Benzyl isothiocyanate conjugates appeared in plasma within 1 to 5 hours. A single dose in a small group, measuring hormones rather than appetite or weight.
Phase III, multicenter, double-blind, placebo-controlled trial of the German product Angocin Anti-Infekt N (200 mg nasturtium herb and 80 mg horseradish root per tablet) for continuous prophylaxis of recurrent uncomplicated cystitis, sponsored by the maker Repha GmbH, which employs two authors; the trial ended early for slow recruitment and the paper reports women only. (Albrecht et al. 2026, BMC Complement Med Ther)
217 women with recurrent bladder infections in Germany (110 blend, 107 placebo); 4 tablets three times daily for 180 days.
Recurrence was 26% versus about 40% on placebo by day 90 and 36% versus 48% by day 180 (hazard ratio 0.64, 95% CI 0.42 to 0.97). During follow-up to day 360 the difference was no longer significant. Adverse events did not differ. A blend result; nasturtium is the lead herb at 2.5 times the horseradish dose, and neither herb was tested alone.
Randomized, double-blind, double-dummy, placebo-controlled phase III trial of two doses of the nasturtium and horseradish combination, counting new respiratory tract infections; sponsored by the maker Repha GmbH according to the EU trial register. (Fintelmann et al. 2012, Curr Med Res Opin)
351 adults aged 18 to 75; 6 or 4 tablets a day, or placebo, for up to 84 days.
Excluding infections in the first 7 days, new-infection rates were 13.3% on 6 tablets a day, 18.4% on 4 tablets and 25.6% on placebo; the dose trend was significant (p = 0.0171). The character, intensity and duration of infections did not differ. A blend result; nasturtium is the lead herb at 2.5 times the horseradish dose, and neither herb was tested alone.
Randomized, two-armed, double-blind, placebo-controlled phase IV trial of Angocin Anti-Infekt N in acute bronchitis, with the change in bronchitis severity score to day 7 as primary endpoint; sponsored by the maker Repha GmbH according to the EU trial register. (Albrecht et al. 2023, Phytomedicine)
384 patients with acute bronchitis (195 blend, 189 placebo); 4 tablets three times daily for 10 days.
The severity score improved significantly faster with the blend from day 3 through day 10, with less coughing, mucus and chest pain. In the registered results the day-7 score was 3.5 versus 4.3 from a baseline of about 7.4, an adjusted difference of 0.81 points (p < 0.001); non-serious adverse events were 14.4% versus 9.0%. A blend result; nasturtium is the lead herb at 2.5 times the horseradish dose, and neither herb was tested alone.
Randomized, double-blind, double-dummy, multicenter phase III trial testing whether the nasturtium and horseradish combination was non-inferior to the antibiotic co-trimoxazole in acute uncomplicated cystitis. (Stange et al. 2017, Res Rep Urol)
96 adults randomized at 26 German centers (51 per protocol); blend 5 tablets four times daily for 7 days.
The trial was stopped early for slow recruitment. Germ-count responders were 10 of 22 with the blend and 15 of 29 with the antibiotic; non-inferiority was not shown, and symptoms took longer to resolve with the blend (median 6.5 versus 4 days). A null comparison for the blend.
Laboratory study of aqueous nasturtium extracts and their fractions on LPS-stimulated primary human blood immune cells, measuring the COX and LOX pathways. (Tran et al. 2016, Phytomedicine)
Human peripheral blood mononuclear cells in culture, not people taking nasturtium.
The extracts suppressed TNF-alpha release, COX-2 protein expression, PGE2 synthesis and LTB4 release in a concentration-dependent way without blocking COX-2 enzyme activity. When the same group later fed nasturtium to women, serum PGE2 rose rather than fell.
Animal study of oral nasturtium leaf extracts and the flavonoid isoquercitrin on urine output and the hormones that regulate it, with repeated dosing for 7 days. (Gasparotto Junior et al. 2012, J Ethnopharmacol)
Spontaneously hypertensive rats; extract 300 mg/kg by mouth.
The extract and isoquercitrin increased urine output about as much as the diuretic spironolactone, spared potassium, and lowered plasma aldosterone and ACE activity. Rat data only; no human trial has measured these effects.