Horseradish

Horseradish (Armoracia rusticana): A Comprehensive Reference

1. Identity, Taxonomy, and Common Forms

Botanical and Chemical Identity

Armoracia rusticana (horseradish), a member of the Brassicaceae family, has been known since ancient times as a folk medicinal herb and as a plant of nutritional value and culinary interest. The species carries the full taxonomic authority Armoracia rusticana G. Gaertn., B. Mey. & Scherb. Earlier synonyms include Cochlearia armoracia (used by Linnaeus himself) and Raphanus rusticanus, the name used by John Gerard in his 1597 herbal. Its modern Linnaean genus Armoracia was first applied to it by Heinrich Bernhard Ruppius, in his Flora Jenensis, 1745, but Linnaeus himself called it Cochlearia armoracia.

Horseradish is available under the following different brand and other names: Armoracia rusticana, Cochlearia armoracia, German mustard, great raifort, mountain radish, pepperroot, red cole, and stingnose.

Geographic Origin and Distribution

Horseradish is native to Europe and Asia (southern Russia, eastern Ukraine), but has become naturalized in North America and New Zealand, where it can be found growing along roadsides. Hooker considers that it is possibly a cultivated form of Cochlearia macrocarpa, a native of Hungary; other authorities consider it indigenous to the eastern parts of Europe, from the Caspian and through Russia and Poland to Finland.

Plant Morphology

Armoracia rusticana is a member of the Brassicaceae family that has been known since ancient times as a folk medicinal herb and as a plant of nutritional value and culinary interest. Currently horseradish is cultivated for its thick, fleshy, and white roots which have a delicious intense pungency and for its tender leaves which are frequently used in salad mixed with other vegetables.

Common Preparations and Dosage Forms

Throughout the world, horseradish is primarily used as a condiment in grated form or made into a paste or sauce to enhance the flavor of other foods, especially meats. Grated or ground roots are often combined with cream, mayonnaise, mustard, oil, salt, vinegar, or yogurt. As a dietary supplement or herbal medicine, it is available in several forms. Those different forms include horseradish powder, horseradish extracts such as horseradish powder extracts and horseradish fluid extracts; one or more active compounds of horseradish, parts of, or whole plants of horseradish, tinctures thereof, and mixtures thereof.

In pharmaceutical applications, one tablet of ANGOCIN (a licensed European herbal medicinal product) contains 200 mg of nasturtium and 80 mg of horseradish powder.

2. Traditional and Historical Use

Ancient and Classical Antiquity

Horseradish (Armoracia rusticana) is a perennial crop that has been used in Egyptian cuisine as far back as 1500 BC. In Europe, it has been used in dishes since the Middle Ages. Horseradish is probably the plant mentioned by Pliny the Elder in his Natural History under the name of Amoracia, and recommended by him for its medicinal qualities, and possibly the wild radish, or raphanos agrios of the Greeks. Dioscorides listed horseradish equally as Persicon sinapi (Diosc. 2.186) or Sinapi persicum (Diosc. 2.168), which Pliny's Natural History reported as Persicon napy; Cato discusses the plant in his treatises on agriculture.

Since the ancient Greeks, horseradish was used as an aphrodisiac and as a rub to alleviate pain in the back. It has been used historically in Europe as a cough expectorant and treatment for scurvy, food poisoning, tuberculosis, and colic.

Medieval Europe

Both roots and leaves were used as a medicine during the Middle Ages, and the root was widely used as a condiment on meats in Germany, Scandinavia, and Britain. The crop was introduced into Western Europe in the 13th century. William Turner mentions horseradish as Red Cole in his "Herbal" (1551–1568), but not as a condiment. In The Herball, or Generall Historie of Plantes (1597), John Gerard describes it under the name of raphanus rusticanus, stating that it occurs wild in several parts of England. After referring to its medicinal uses, he says: "[T]he Horse Radish stamped with a little vinegar put thereto, is commonly used among the Germans for sauce to eat fish with and such like meats as we do mustard."

Jewish and Christian Traditions

Horseradish for culinary use is a tradition of the Christian Easter and Jewish Passover in Eastern and Central Europe, and is an essential part of the traditional wedding dinner in the Bavarian region of Germany. Horseradish was one of the five bitter herbs (along with coriander, horehound, lettuce, and nettle) eaten historically during the feast of the Passover; in present times, horseradish is still commonly used in the Passover Seder.

Traditional Medicinal Applications

Some used horseradish syrup as an expectorant cough medicine; others were convinced it cured everything from rheumatism to tuberculosis. Externally, it is sometimes used to alleviate the pain and stiffness caused by rheumatism. Herbalists combined horseradish and honey for coughs and asthma treatments.

Nowadays, in several European countries such as Bulgaria, Romania, Poland, Russia, and Italy, horseradish is still used to prepare traditional dishes and as a popular medicinal herb. Today, horseradish has been approved in Germany for the treatment of respiratory tract infections (bronchitis, sinusitis), supportive treatment in urinary tract infections and for urinary stones, and topical use for minor muscle aches.

Traditional Antiscorbutic Use

Horseradish, a perennial herb of the family Cruciferae (mustard family), is native to Central and Southern Europe and naturalized in many parts of North America. It is grown mainly for its roots, which formerly were used medicinally, particularly as an antiscorbutic. This use is consistent with the plant's documented vitamin C content: fresh plant contains an average of 79.31 milligrams of vitamin C per 100 g of raw horseradish.

3. Key Constituents and Active Compounds

Glucosinolates

Horseradish is a rich source of a number of bioactive compounds such as glucosinolates (GLSs) and their breakdown products. Sinigrin is the dominant glucosinolate in both leaves and roots. One study found that sinigrin accounts for about 80–90% of total glucosinolate content in horseradish roots and leaves. Further glucosinolates in horseradish are glucobrassicanapin and the indole-derived glucobrassicin (plus some closely related compounds like 4-methoxy glucobrassicin and 4-hydroxy glucobrassicin). Horseradish contains two principal glucosinolates—sinigrin and gluconasturtiin—which are responsible for its pungent taste.

Isothiocyanates: Formation and Identity

AITC is stored stably in the plant as its precursor sinigrin (a type of glucosinolate), which is physically separated from myrosin cells containing myrosinase. Upon tissue disruption, myrosinase gets released and hydrolyzes the sinigrin to produce AITC and by-products. When cut or grated, enzymes from within the plant cells digest sinigrin (a glucosinolate) to produce allyl isothiocyanate (mustard oil), which irritates the mucous membranes of the sinuses and eyes. Once exposed to air or heat, horseradish loses its pungency, darkens in color, and develops a bitter flavor.

In the pharmaceutical product Angocin, the ITC ratios are PEITC (12%), AITC (38%), and BITC (50%). AITC and PEITC originate from horseradish root, while nasturtium is a rich source of BITC.

Phenolic Compounds and Other Constituents

Horseradish belongs to the Brassicaceae family, which is known for health-promoting phytochemicals, and beneficial effects as anticancer agents, due to the glucosinolates and their isothiocyanate derivatives and vitamins. It also contains coumarins, phenolic acids, and ascorbic acid. Among the non-volatile constituents, one should mention flavone glycosides (quercetin, kaempferol) and particularly ascorbic acid, which is contained to 0.6% in horseradish root. Horseradish contains potassium, calcium, magnesium, and phosphorus, as well as volatile oils, such as mustard oil.

Active compounds of horseradish include, but are not limited to, allyl-isothiocyanate, amylase, arginine, ascorbic acid, asparagine, gentisic acid, kaempferol, limonene, niacin, p-hydroxy-benzoic acid, pectin, phenylpropyl-isothiocyanate, quercetin, raphanin, riboflavin, rutoside, selenium, sinapic acid, sinigrin, tannin, thiamin, vanillic acid, and zinc.

Mechanisms of Action

During the past two decades, GLs have been reported to have several pharmacological properties, such as antibacterial, anticancer, antifungal, anti-inflammatory, and antioxidant activities. Although GLs are biologically inactive, they can be hydrolyzed by β-thioglucoside hydrolases (myrosinase) to produce bioactive compounds (e.g., thiocyanates, isothiocyanates, nitriles, etc.) that are responsible for these pharmacological activities.

The mode of action for the chemopreventive activity of AITC is attributed primarily to the detoxification of carcinogens through activation of nuclear factor erythroid-related factor 2 (Nrf2). Anti-inflammatory effects by blocking lipoxygenase and cyclooxygenase pathways could be reported for nasturtium and horseradish and for the combination of both.

Upon ingestion, ITCs are rapidly conjugated to glutathione (GSH) in the gut epithelium or liver. They are then metabolized in the mercapturic acid pathway, and sequentially excreted in the urine mainly as N-acetylcysteine (NAC) conjugates.

4. Scientific Evidence by Health Area

4.1 Respiratory Tract Infections (Bronchitis and Sinusitis)

Horseradish is approved by German Commission E for treatment of respiratory tract infections and supportive treatment for urinary tract infection (UTI), as well as externally for respiratory tract congestion and minor muscle aches.

The most studied clinical formulation is the combination product ANGOCIN® Anti-Infekt N. Nasturtium herb and horseradish root have been used in combination since 1958 to treat uncomplicated acute and recurrent respiratory and urinary tract infections. A randomized, two-armed, placebo-controlled, double-blind, phase IV study included 384 patients, with 195 in the treatment and 189 in the placebo group. The "bronchitis severity score" (BSS) was utilized as the primary endpoint. The results showed that the group of patients who took the nasturtium and horseradish herbal compound showed much faster healing of their bronchitis symptoms compared to those who took the placebo.

An observational trial with 1,649 adults treated for acute sinusitis, acute bronchitis, or acute cystitis compared the efficacy and safety of ANGOCIN treatment (1,223 patients) to antibiotic therapy (426 patients). The symptom reduction was comparable for both treatment types for sinusitis, bronchitis, and cystitis. At the same time, subjects had fewer side effects with ANGOCIN treatment (1.5% versus 6.8%, respectively).

The antiviral properties of Angocin® on typical enveloped and non-enveloped viral strains are currently being extensively investigated. So far, antiviral properties have been shown for similar main components of the isothiocyanate family, like L-sulforaphane, against the common respiratory syncytial virus (RSV) and, most recently, against the SARS-CoV-2 virus.

Evidence strength: The bronchitis RCT (n=384) and the large observational cohort (n=1,649) provide moderate clinical evidence for the combination product. There are some preliminary reports indicating benefits of horseradish, but definitive scientific studies (for horseradish alone) are absent. All major clinical trials have used the combination product with nasturtium, not horseradish in isolation.

4.2 Urinary Tract Infections

A preliminary, double-blind, placebo-controlled study published in 2007 found some evidence that a standardized combination of nasturtium and horseradish might prevent new bladder infections among people with a history of recurrent bladder infections. This study, however, had numerous problems in design and statistical analysis. An even less reliable human trial found weak evidence that this combination could be helpful for children with sinusitis, bronchitis, or urinary tract infections.

Ninety-six inpatients with catheter-associated UTI successfully completed a 3-arm, 5-week observational study. Three patient groups were assessed: (1) monotherapy with Angocin® (42%), (2) Angocin® as an add-on to antibiotic therapy (29%), and (3) antibiotic therapy alone (29%).

Effects of a prophylactic treatment with horseradish root and nasturtium herb on urinary tract infections in individuals with chronic neurogenic lower urinary tract dysfunction were evaluated in a retrospective cohort study, given that recurrent urinary tract infections are common in such individuals and greatly affect their quality of life.

Evidence strength: Evidence for UTI prevention and treatment using horseradish-containing combinations is preliminary. Studies are small, often observational, and use combination products, making it impossible to attribute effects solely to horseradish.

4.3 Antimicrobial Activity

AITC reportedly has antimicrobial activity against a wide range of microorganisms. This has been confirmed by in vitro studies, which have shown efficacy against a broad spectrum of clinically relevant disease-causing bacteria including antibiotic-resistant strains. The allyl isothiocyanate isolated from horseradish roots is characterized by strong antibacterial activity — it destroys fungal and bacterial pathogens on seeds, fresh products, bread, meat, and cheese.

The antimicrobial efficacy of the isothiocyanate combination has been confirmed both in vitro and in various clinical trials, with its primary effectiveness attributed to ITCs.

Evidence strength: Antimicrobial activity is well-documented in vitro. Clinical translation specifically attributable to horseradish alone remains unconfirmed due to combination study designs.

4.4 Anticancer Properties

Glucosinolates or their breakdown products, isothiocyanates, are responsible for most of the claimed medicinal effects. Recent studies have suggested that glucosinolates provide prevention and inhibitory influences on different types of cancer. AITC has been shown to possess a broad spectrum of anticancer activities in both cultured cancer cell lines and animal tumor models.

AITC is an organosulfur compound that carries pharmacological properties, including anticancer, antibacterial, antifungal, and anti-inflammatory activities. Despite the promising anticancer effectiveness of AITC, its clinical application still possesses challenges due to several factors, i.e., low aqueous solubility, instability, and low bioavailability.

Previous data showed AITC to have a biphasic effect on cell viability, DNA damage, and migration in human hepatoma HepG2 cells. Moreover, in a 3D co-culture of HUVEC with pericytes, it inhibited tube formation at high doses but promoted this at low doses, confirming its biphasic effect on angiogenesis.

Evidence strength: Evidence for anticancer effects is currently limited to in vitro cell studies and animal models. No robust human clinical trials have evaluated horseradish or its isolated constituents for cancer prevention or treatment. This remains a promising but entirely preclinical area of investigation.

4.5 Antioxidant Activity

AITC exhibits a wide spectrum of health properties, such as antioxidant, anti-inflammatory, antibacterial, antifungal, antiangiogenic, neuroprotective, or analgesic benefits. Spectrophotometric and chromatographic analyses revealed higher concentrations of polyphenols in extracts obtained with a methanol–water mixture (1:1, v/v) compared to ultrapure water, confirming the efficiency of solvents with lower polarity. The antioxidant activity was found to be significant, with the hydroalcoholic extract achieving 96.93% and the aqueous extract reaching 89.34%.

The active compound (AITC) can also enhance the function of detoxification enzymes in the body, as well as a strong influence on the bioaccessibility of nutrients in the human gastrointestinal system.

Evidence strength: Antioxidant activity is well-documented in laboratory extracts and in vitro systems. Human clinical evidence for antioxidant benefits from dietary horseradish intake is not yet established.

4.6 Topical and Musculoskeletal Applications

The German Commission E also recommends external use of horseradish for respiratory tract congestion as well as minor muscle aches. A poultice can be prepared by grating the fresh root and spreading it on a linen cloth or thin gauze. This is then applied against the skin once or twice per day until a burning sensation is experienced.

Allyl isothiocyanate is used externally as a rubefacient (0.1 to 0.2% in 50% methanol). Its action as a topical rubefacient — a substance that causes local skin redness and warmth by increasing blood flow — underpins its traditional application for joint pain and muscle stiffness.

Evidence strength: The Commission E has issued a positive monograph for external use, lending this application official regulatory recognition in Germany. However, modern controlled clinical trial evidence for topical horseradish as a standalone therapy for musculoskeletal conditions is limited.

4.7 Digestive Health

Horseradish is a flavorful pungent herb that has been used for centuries to enhance the flavor of food, aid in digestion, and improve human health. Traditionally, it was considered a digestive stimulant, and horseradish is also described in historical sources as an excellent diuretic, and is noted for digestion problems. However, direct clinical evidence from controlled trials demonstrating a measurable benefit on digestive function is lacking.

5. Body Systems and Health Areas Associated with Horseradish

• Respiratory system: Expectorant, mucolytic, and anti-infective properties; applied for bronchitis, sinusitis, and upper respiratory tract congestion.
• Urinary tract: Supportive treatment for uncomplicated urinary tract infections; historically used as a diuretic.
• Immune system: Nasturtium herb and horseradish root produce three different isothiocyanates as secondary metabolites, which exert antibacterial, anti-inflammatory, and immunomodulatory functions in humans.
• Musculoskeletal system: Topical use as a rubefacient for minor muscle aches and joint stiffness.
• Gastrointestinal system: Traditional use as a digestive stimulant; however, its irritant compounds can also be damaging to the GI mucosa in excess.
• Oncology (preclinical): Horseradish belongs to the Brassicaceae family, which is known for health-promoting phytochemicals and beneficial effects as anticancer agents, due to the glucosinolates and their isothiocyanate derivatives.
• Antioxidant / cellular protection: AITC has sparked widespread interest due to its various biological actions, which include strong antioxidant, anti-inflammatory, antibacterial, and anticancer capabilities.

6. Dosage Forms and Reported Dosages

The German Commission E monograph suggests an average daily intake of 4 teaspoons (20 grams) of the fresh root for adults. Alternatively, 1/2–1 teaspoon (3–5 grams) of the freshly grated root can be eaten three times per day. Horseradish tincture is also available and is sometimes taken at 1/2–3/4 teaspoon (2–3 ml) three times daily.

In the combination pharmaceutical product studied in clinical trials, Angocin comprises horseradish root (Armoracia rusticanae radix, 80 mg) and nasturtium (Tropaeoli majoris herba, 200 mg) and is authorized for treating inflammatory diseases affecting the respiratory and urinary tract.

Horseradish is generally recognized as safe (GRAS) when consumed in food amounts but may irritate the stomach, throat, or urinary tract in large doses. Despite the potential for severe irritation, horseradish is generally recognized as safe for human consumption as a natural seasoning and flavoring by the FDA.

For topical use, a poultice can be prepared by grating the fresh root and spreading it on a linen cloth or thin gauze. This is then applied against the skin once or twice per day until a burning sensation is experienced.

7. Safety Considerations and Interactions

Gastrointestinal Irritation

Irritant effects on the lining of the mouth, stomach, and intestines have been documented. If used in amounts higher than recommended, horseradish can cause stomach upset, vomiting, or excessive sweating. Ingestion of large amounts may cause bloody vomiting and diarrhea. Horseradish can irritate the digestive tract and should not be used by those with stomach or intestinal ulcers, inflammatory bowel disease, infections, or other digestive tract conditions.

Topical Safety

Direct application to the skin or eyes may cause irritation and burning. Topical use can cause skin irritation or burns if applied undiluted or left on for too long. Crushed horseradish may irritate mucous membranes upon contact or inhalation.

Thyroid Disorders

Horseradish is part of the cabbage and mustard family, and may impair thyroid function. There is concern that using horseradish might worsen hypothyroidism (underactive thyroid gland). Horseradish might decrease thyroid activity, and taking horseradish along with thyroid hormone might decrease the effects of thyroid hormone.

Kidney Disorders

There is concern that horseradish might increase urine flow. This could be a problem for people with kidney disorders. Avoid using horseradish if you have kidney problems.

Pregnancy and Breastfeeding

It is likely unsafe to take horseradish by mouth in large amounts if pregnant or breastfeeding. Horseradish contains mustard oil, which can be toxic and irritating. Horseradish tincture is also likely unsafe when used regularly or in large amounts because it might cause a miscarriage. Use should be avoided during pregnancy and lactation because toxic irritants are released upon crushing.

Children

Horseradish should not be used by children under four years of age. Horseradish is likely unsafe when taken by mouth in children under 4 years of age and can cause stomach problems in young children.

Drug Interactions

There is a moderate interaction concern between horseradish and levothyroxine (thyroid hormone replacement); caution with this combination is advised. The allyl isothiocyanate in horseradish can enhance the effects of blood thinners, such as warfarin, and increase the risk of bleeding or bruising. Additionally, horseradish may decrease the effectiveness of medications used to manage thyroid conditions, such as hypothyroidism, by interfering with the absorption of thyroid hormones.

Overall Safety Profile in Clinical Use

In the large observational cohort study of ANGOCIN (which includes 80 mg horseradish powder per tablet), the symptom reduction was comparable for both treatment types (ANGOCIN and antibiotic therapy) for sinusitis, bronchitis, and cystitis. At the same time, subjects had fewer side effects with ANGOCIN treatment (1.5% versus 6.8%, respectively). This favorable tolerability profile was observed in a combination product and cannot be attributed solely to the horseradish component.

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