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Herb library · Herb · Nasturtium officinale

Watercress

A water green eaten in salads and soups and used in Iranian folk medicine for coughs and asthma. Trials of freeze-dried watercress and a watercress extract changed blood and urine markers in people; none has shown a health outcome.

Traditional use

Eaten as a salad green. In Iranian folk medicine it has been used for bronchitis and asthma, as the authors of an asthma trial describe. Dried watercress is one of the extra herbs in Flor Essence, an eight-herb version of the Essiac tea mixture.

What studies show

  • Limited· a lab measure, not a health outcome

    Toxin breakdown: in a two-site crossover trial, 188 people who drank freeze-dried watercress three times a day for two weeks excreted more of the breakdown products of acrolein, benzene and four other airborne toxins than on a placebo drink. It measured urine markers, not health.

  • Limited· a lab measure, not a health outcome

    Asthma: in a double-blind placebo-controlled trial in Iran, 500 mg watercress extract capsules twice a day for four weeks lowered blood markers of oxidative stress in people with asthma. The trial's abstract does not report a change in asthma control.

Be careful of

Cautions

  • NoteEat watercress only from a trusted grower, and never raw from wild streams near livestock. The CDC says people most often catch Fasciola liver flukes by eating raw watercress or other freshwater plants carrying the larvae.
  • PregnancyWatercress as food is not the concern. No safety information for concentrated extracts in pregnancy or breastfeeding was found; avoid them then.
  • Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.

Sources

  1. A watercress drink increases detoxification of common environmental carcinogens such as acrolein and benzene: results of a randomized clinical trial (Carcinogenesis, 2025) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
  2. The hydroalcoholic extract of Nasturtium officinale reduces oxidative stress markers and increases total antioxidant capacity in patients with asthma (J Ethnopharmacol, 2024) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
  3. About Liver Flukes (CDC) (opens in a new tab) · CDC · read September 25, 2026
  4. Essiac/Flor Essence (PDQ®) — Patient Version (National Cancer Institute) (opens in a new tab) · NIH · read September 25, 2026
  5. The hydroalcoholic extract of Nasturtium officinale reduces oxidative stress markers and increases total antioxidant capacity in patients with asthma (J Ethnopharmacol, 2024) — PubMed record (opens in a new tab) · NIH · read September 25, 2026

Reviewed September 25, 2026.