What is Garden nasturtium?

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.

How does Garden nasturtium work?

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.

What forms does Garden nasturtium come in?

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.

Where it comes from:

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.

What does Garden nasturtium help with?

• Repeat bladder infections, as an add-on: Folk use treated it as a flushing herb for the waterworks. One German placebo-controlled trial of the nasturtium-and-horseradish tablet reported fewer repeat infections over three months. That trial was small and funded by the maker. Treat it as early evidence, not proof. It does not replace antibiotics for an active infection.
• Sinus inflammation: German products are licensed there for short-term use in sinus infections. Support comes from one small placebo trial and from a large study that simply recorded how patients did on the tablet or on antibiotics. That second study was not randomised and used no dummy pill. So it cannot show the herb caused the result.
• Chest and airway infections: The same combination tablet is sold in Germany for acute bronchitis, a short-term chest infection. The human data is the same limited set used for sinus infection. Nothing here shows the herb clears an infection on its own. A chest infection with fever or breathlessness needs a doctor.
• Sore throat and cough: Folk healers used a peppery tea or gargle for winter colds. No human trials test this use. Any relief may come from the warm fluid rather than the plant.
• Scurvy (vitamin C lack), in the past: Sailors and gardeners ate the leaves as a fresh green. Vitamin C does prevent and treat scurvy, and that is well established. Today ordinary fruit and vegetables fill that gap. Scurvy is rare and should be handled by a doctor.
• Minor skin and wound care, folk use: Crushed leaves were laid on scrapes, boils and spots. In lab tests the mustard oils slow some skin bacteria. Whether that happens on real skin is not established. There are no human trials. The fresh juice can burn skin, so folk use is not a safe bet.

Which foods are rich in Garden nasturtium?

1. Fresh nasturtium leaves in salad
2. Nasturtium flowers as a garnish
3. Pickled nasturtium seed pods
4. Nasturtium pesto made with fresh leaves

Practical Tips:

Garden nasturtium is an ordinary salad plant. Leaves, flowers and young seed pods are all eaten.

Food amounts are small and are widely treated as safe for healthy adults. Capsules and juices are a different matter and belong under the safety advice above.

What are the side effects of Garden nasturtium?

• Burning or heartburn in the stomach
• Stomach pain or nausea
• Loose stools
• Burning in the mouth or throat
• Skin rash or itch, as an allergy
• Skin irritation from fresh juice or crushed leaves
• Worse reflux in people who already have it
• Kidney irritation with very high amounts

Good to know:

Most people who eat the leaves and flowers have no trouble at all. Problems are far more likely with strong capsules, tinctures or pressed juice.

Stomach burning is the most common complaint. It usually fades once you stop.

Allergy is uncommon but real, mainly in people who react to mustard, cress or cabbage. Swelling of the lips or face, or trouble breathing, is an emergency.

How much Garden nasturtium should you take?

• Recommended daily: This page gives no personal dose. Your right amount depends on the product, your age and your health. For scale only: German combination tablets commonly list about 200 mg of dried nasturtium herb with about 80 mg of horseradish root per tablet. Labels there direct adults to take several tablets spread across the day. Culinary use is simply a few leaves or flowers in a salad. Products differ widely in strength. Follow the label on the pack you hold, and ask a pharmacist if you are unsure.
• Best time of day: Timing does not seem to matter much. Doses in trials were spread across the day. Taking it with meals is the usual advice, mainly to spare the stomach.
• With or without food: Take it with food and a full glass of water. Mustard oils can burn an empty stomach. If you still get heartburn or stomach pain, stop.
• Time to effect: For short-term use, labels expect some change within a few days. The repeat-infection study measured results over three months. It may do nothing for you. Herbs with thin trial data often fall short of hope.
• How long to take it: Labels for acute use cover short courses, usually days up to about two weeks. The repeat-infection trial ran for about three months. Longer use has not been well studied. If symptoms are not easing after a few days, stop and see a doctor rather than carrying on.