Educational information, not medical advice — ask your doctor or midwife.
Garden nasturtium is a trailing garden plant with round leaves and bright orange, red or yellow flowers. The leaves, flowers and green seed pods taste hot and peppery, a bit like cress or radish. German speakers call it Kapuzinerkresse.
It is both a food and a folk remedy. In German herbal practice it is usually paired with horseradish root in tablet form. That pairing is sold for short-term bladder, sinus and chest infections.
Here is the honest verdict. There is some human trial data, but it is limited, mostly German, and nearly all of it tested the combination product rather than nasturtium alone. Long folk use is not proof that it works, and it is not proof that it is safe.
Garden nasturtium owes its bite to mustard oils, the same chemical family that makes horseradish sharp. In lab tests these oils slow the growth of some bacteria and fungi. Whether that happens inside your body is not settled.
The plant stores the compound in an inactive form. Chewing or crushing the leaf frees a plant enzyme. The enzyme turns the store into benzyl mustard oil.
In test tubes, benzyl mustard oil slows several bacteria linked to bladder and airway infections. In cell studies it also damps down some markers of swelling. Test-tube and animal results cannot tell you what a capsule does in a person.
Some of the mustard oil leaves the body in the urine. Researchers think this may be why folk use aimed the herb at the bladder. The idea is plausible, not proven.
The herb also holds vitamin C. That part is well understood, and it is simple nutrition rather than drug action.
Most people meet it first as fresh salad leaves and flowers.
- Fresh leaves, flowers and buds, eaten raw.
- Pickled green seed pods, used in place of capers.
- Dried herb for tea, though drying cuts the mustard oil.
- Pressed fresh juice, sold in some European shops.
- Tablets and capsules of dried herb, usually mixed with horseradish root.
- Tinctures, which are alcohol extracts.
The combination tablet is the form used in nearly all human trials. Nasturtium-only capsules have almost no trial data behind them.
Strength varies a lot between brands. A salad leaf and a strong capsule are not the same thing.
Garden nasturtium reached Europe from the Andes in the 1500s. German speakers named it Kapuzinerkresse, or capuchin cress, after the hood-shaped flower. It spread fast as a garden and kitchen plant.
European folk healers put the fresh leaf and seed to several uses.
- As a peppery salad green, valued as fresh food in lean months.
- As a tea or syrup for coughs and chest colds.
- As a wash or poultice for scrapes, boils and spots.
- As a hair rinse, said to slow hair loss.
- As a bladder herb, to flush the waterworks.
In the 20th century, German makers blended the herb with horseradish root. That blend became a licensed herbal medicine in Germany. It remains the main form studied today.
Stop the herb and see a doctor the same day if you get a fever, chills, pain in your back or side, or blood in your urine. These can mean a kidney infection.
Also stop and get advice if symptoms last more than three or four days, or get worse at any point.
Stop and seek urgent help for stomach pain that will not settle, vomiting, black stools, or a widespread rash.
Call emergency services for swelling of the lips, tongue or throat, or any trouble breathing.
In Germany and some other EU states, nasturtium-and-horseradish tablets are licensed herbal medicines. In the UK and the US, nasturtium is sold as a food and as a supplement. It is not approved there to treat any infection.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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