Nasturtium

Nasturtium: A Comprehensive Encyclopedic Reference

1. Identity, Taxonomy, and Botanical Description

The common name nasturtium is applied to two botanically distinct plants that are frequently conflated in herbal literature: Nasturtium officinale R. Br. (watercress) and Tropaeolum majus L. (garden nasturtium or Indian cress). Both have independent but overlapping traditions as food plants, medicinal herbs, and dietary supplements, and both share chemically relevant glucosinolate-isothiocyanate chemistry. This article addresses each species systematically and specifies which scientific evidence applies to which plant.

1.1 Nasturtium officinale (Watercress)

Nasturtium officinale (watercress, also called yellowcress) is a species of aquatic flowering plant in the cabbage family, Brassicaceae. It is a rapidly growing perennial plant native to Eurasia and is one of the oldest known leaf vegetables consumed by humans. It is a perennial, aquatic, or semiaquatic plant species with creeping or floating stems, which colonizes gently flowing and shallow streams in its natural habitat. Well-known synonymous Latin names include Nasturtium aquaticum, Rorippa nasturtium-aquaticum, and Rorippa officinalis.

In foreign languages, N. officinale is known as watercress (English), Brunnenkresse / Wasserkresse / Brunnkresse (German), cresson de fontaine (French), berro (Spanish), and dou ban cai (Chinese, 豆瓣菜). Watercress can grow up to 60 centimetres in length; the stems are hollow and float in water, and the leaf structure is pinnately compound. Small, white, and green inflorescences are produced in clusters and are frequently visited by insects, especially hoverflies.

1.2 Tropaeolum majus (Garden Nasturtium / Indian Cress)

Tropaeolum majus is a flowering plant from the order Brassicales, family Tropaeolaceae, native from Peru to Colombia. Known as garden nasturtium or Indian cress, it occurs as a perennial plant and is used mostly as an ornamental plant, although its leaves, flowers, and unripe green seeds are used in salads and sauces where they impart a spicy flavor. It is commonly known as garden nasturtium in North America and nasturtium in Europe; in India it is also referred to as Indian cress, and in Australia as wild nasturtium.

Tropaeolum majus is a cultigen believed to have derived from South America. It is an annual that grows primarily in the subtropical biome, and it is thought to have derived from T. ferreyrae × T. minus.

1.3 Common Forms and Preparations

• Fresh plant material: Leaves, flowers, and unripe green seeds of T. majus are consumed raw in salads and sauces. Both the leaves and seeds of N. officinale are used; in the 19th century, it was sold by street vendors in the streets of Paris.
• Dried herb and powdered extract: One tablet of the licensed European product ANGOCIN Anti-Infekt N contains 200 mg of nasturtium (T. majus) and 80 mg of horseradish powder.
• Ethanolic and hydroethanolic extracts: Used in clinical research for watercress, including capsule form for supplementation studies.
• Freeze-dried preparations: A freeze-dried nasturtium drink has been used in at least one clinical intervention study of T. majus.
• Essential oils and volatile extracts: Derived from the seeds and aerial parts for research and cosmetic applications.
• Infusions and tinctures: T. majus is widely used in the form of infusions and salads in folk medicine traditions.

2. Traditional and Historical Use

2.1 Nasturtium officinale (Watercress)

The herb of Nasturtium officinale is a raw material that has long been used in the traditional medicine of Iran, Azerbaijan, Morocco, and Mauritius. In traditional medicine, N. officinale is a known remedy for hyperglycemia, hypertension, asthma, and cough, and current published studies have confirmed these applications.

Watercress is a useful medication in traditional medicine for the treatment of asthma, arthritis, bronchitis, diuresis, influenza, scurvy, pneumonia, hypercholesterolemia, hypertension, and hyperglycemia. Antiestrogenic, odontalgic, and expectorant properties of the plant are also well-known in traditional contexts.

During the 19th century, watercress gained popularity in Western herbalism, and homeopathic practitioners began using it to treat scurvy (due to its high vitamin C content), digestive disorders, and poor appetite. It was used as a salad on account of its appetizing and anti-scorbutic properties.

According to ethnobotanical surveys in Iran, watercress is a native plant there and the people of that region used it as a fresh leafy vegetable; its pharmaceutical consumption included treatment of kidney pain, as a body booster, and as a digestive system disinfectant.

2.2 Tropaeolum majus (Garden Nasturtium)

T. majus has been widely used in traditional medicine due to its antimicrobial and antiviral properties; other reports have shown anti-inflammatory and antioxidant effects related to its bioactive compounds.

T. majus has traditional uses against bacterial infections such as bronchitis, sinusitis, and urinary tract infections, as well as for its antifungal and antiviral activities. The juice of nasturtium has been traditionally used to treat lipomas, polyps, and other skin conditions; internal use of the tincture may also be useful for alopecia, while topical use as an infusion is referenced to stimulate hair growth and relieve dandruff.

Nasturtium is regarded as one of the pioneers in the usage of flowers in human food and is classified as a decorative flower in addition to having a pleasing visual appeal for consumers.

3. Key Constituents and Active Compounds

3.1 Glucosinolates and Isothiocyanates — The Primary Bioactive System

Glucosinolates and their enzymatic hydrolysis products, the isothiocyanates (ITCs), represent the most pharmacologically significant compound class in both N. officinale and T. majus.

Glucosinolates are stable water-soluble precursors of isothiocyanates located in vacuoles. When plant tissues are damaged, the endogenous enzyme myrosinase (Thioglucoside hydrolase, EC 3.2.3.1), which is stored in myrosinase grains of the myrosin cells, is released and combined with glucosinolates to produce biologically active compounds such as nitriles, thiocyanates, isothiocyanates, epithionitriles, and oxazolidine-2-thiones.

In Tropaeolum majus: The dominant glucosinolate in T. majus is benzyl glucosinolate, also called glucotropaeolin. When the plant is cut, crushed, chewed, or blended, plant enzymes help convert glucotropaeolin into benzyl isothiocyanate (BITC). The leaves and seeds of T. majus also contain fatty acids, flavonoids, tetracyclic triterpenes of cucurbitin type, and glucosinolates including sinalbin.

Analysis showed that the main volatile compounds in the extract of T. majus were benzyl cyanide (BCN) and benzyl isothiocyanate (BITC), at 37.00% and 54.35% respectively. The breakdown product BITC exhibits various biological activities such as antiproliferative, antibacterial, and anti-inflammatory effects.

Phylloxanthobilins (tetrapyrrolic pigment metabolites) have also been identified in T. majus and display strong antioxidative effects in vitro and in cellulo, and anti-inflammatory effects as assessed by COX-1 and COX-2 enzyme inhibition, similar to other bioactive ingredients of T. majus such as isoquercitrin and chlorogenic acid.

In Nasturtium officinale (Watercress): Watercress comprises the richest known natural source of gluconasturtiin, the precursor of phenethyl isothiocyanate (PEITC), which constitutes approximately 94% of watercress glucosinolate content. Glucosinolate profiling by UHPLC-DAD-MS/MS has shown that dominant compounds in watercress include glucobrassicin (493.00 mg/100 g DW at 10 days cultivation) and gluconasturtiin (268.04 mg/100 g DW at 20 days cultivation).

3.2 Polyphenols and Flavonoids

The therapeutic effects of both species are partly attributed to polyphenols, including flavonoids, phenolic acids, and proanthocyanidins. In watercress leaves, fourteen phenolic compounds have been identified, with coumaric acid and its derivatives, caftaric acid, and quercetin derivatives present in higher amounts.

3.3 Terpenoids and Carotenoids

The essential oil of flowers of N. officinale contained 15 constituents, among which limonene (43.6%), α-terpinolene (19.7%), p-cymene-8-ol (7.6%), and caryophyllene oxide (6.7%) were the major components. Nine compounds were identified in the essential oil of the leaves, with myristicin (57.6%), α-terpinolene (8.9%), and limonene (6.7%) as main components.

Administration of raw watercress has been shown to increase the accumulation of plasma antioxidants including lutein and β-carotene.

3.4 Vitamins and Minerals

The major nutritional constituents of N. officinale include vitamins B₁, B₂, B₃, B₆, E, and C, as well as various bioelements. Watercress is particularly prized for its nutrient density, offering vitamins (especially vitamin C, vitamin A, and B vitamins), minerals (such as calcium, iron, magnesium, and potassium), and antioxidants (like flavonoids and carotenoids).

3.5 Summary of Full Phytochemical Profile

Chemical analysis of N. officinale showed the presence of alkaloids, flavonoids, saponins, terpenoids/steroids, protein, essential and volatile oils, glycosides, tannins, folic acid, vitamins, and elements.

3.6 Mechanisms of Action

The glucosinolate-myrosinase activation system is central to the pharmacological activity of both plants. Benzyl isothiocyanate (BITC) is bacteriostatic, virostatic, and is eliminated through urine and respiration, which explains the mechanism of action for nasturtium's activity in the urinary and respiratory systems.

Effects of watercress are mediated through bioactive compounds such as glucosinolates, carotenoids, and flavonoids, which modulate molecular pathways including Nrf2, NF-κB, and PI3K/Akt.

In vitro work identified that nasturtium extract caused a strong concentration-dependent suppression of a specific inflammatory signalling pathway, suggesting that the mechanism of action is unique to this plant and also different from non-steroidal anti-inflammatory drugs (NSAIDs).

Tropaeolum majus herb (nasturtium) and Armoracia rusticana root (horseradish) produce three different isothiocyanates as secondary metabolites, which exert antibacterial, anti-inflammatory, and immune-modulatory functions in humans; combined in the licensed medicinal product ANGOCIN® Anti-Infekt N, these two natural components demonstrated promising effects against acute bronchitis.

4. Scientific Evidence by Area of Use

4.1 Urinary Tract Infections (UTIs)

This is the most clinically studied application, primarily involving Tropaeolum majus in combination with horseradish root as ANGOCIN® Anti-Infekt N.

Mechanism: The antibacterial compound benzyl isothiocyanate in nasturtium is eliminated via the urinary system, which explains why this herb has a strong reputation for use in urinary tract infections.

RCT evidence (prophylaxis): In a randomized, double-blind, placebo-controlled trial, the herbal combination significantly reduced the recurrence rate of UTI compared to placebo. The mean rate of recurrent episodes in the per-protocol-treated group was 0.43 in the Angocin® group versus 0.77 in the placebo cohort (p = 0.035), without any clinically relevant differences in reported side effects.

Prospective cohort evidence: In a prospective cohort study from 251 centers in Germany, patients aged 4 years or older treated for acute sinusitis, bronchitis, or UTI between March 2004 and July 2005 were included; they were treated either with the nasturtium herb and horseradish root-containing herbal drug Angocin Anti-Infekt N (test group, n = 1,223) or with standard antibiotic therapy (control group, n = 426). In a prospective cohort study of 479 patients with UTIs, the effectiveness of Angocin® therapy was found to be comparable to treatment with standard antibiotics but with significantly fewer side effects.

Real-world observational evidence (2024): The efficacy and safety of Angocin® in treating acute and recurrent UTIs have been demonstrated in several clinical trials and prospective cohort studies involving both adults and children. In a randomized, double-blind, placebo-controlled trial, Angocin® significantly reduced the recurrence rate compared to placebo (0.43 vs. 0.77, p = 0.035) in the per-protocol analysis.

Limitations: Most positive clinical data for UTIs come from trials combining nasturtium with horseradish root; the independent contribution of nasturtium alone has not been fully isolated in these studies. Larger, more rigorously controlled trials are needed.

4.2 Respiratory Tract Infections (Acute Bronchitis, Sinusitis)

Mechanism: Nasturtium is used to treat bacterial infections in the respiratory system due to its antimicrobial activities. One of the compounds thought to be important for these bacteriostatic effects is BITC, which is eliminated via respiration, meaning it passes directly through the air sacs in the lungs.

RCT (Bronchitis, Phase IV): A randomized, two-armed, placebo-controlled, double-blind, Phase IV study included 384 patients, with 195 in the treatment group and 189 in the placebo group. The bronchitis severity score (BSS) was utilized as the primary endpoint, which sums ratings for five significant bronchitis symptoms assessed at patient clinic visits.

Prophylaxis (RCT, Phase III): A randomized, prospective, double-blind, placebo-controlled Phase III trial studied a combination product containing Tropaeoli majoris herba and Armoraciae rusticanae radix for prophylactic treatment of patients with respiratory tract diseases (Fintelmann et al., Curr Med Res Opin 2012;28(11):1799–1807).

Comparative cohort evidence for sinusitis: The effectiveness of Angocin® therapy for acute rhinosinusitis (ARS) was comparable to treatment with standard antibiotics, and had an advantageous safety profile. Furthermore, Albrecht et al. conducted a randomized, double-blinded, placebo-controlled, multicenter clinical trial including 380 patients with ARS, and responder rates assessed by an ARS symptom score were significantly higher for patients receiving Angocin® compared to placebo.

Antimicrobial breadth: Both plants are known to have antimicrobial properties mainly mediated by their content of isothiocyanates (also known as mustard oils). The combination of the two plant components has been shown to produce synergistic antibacterial activity in vitro, and ongoing research is examining the antiviral potential of Angocin® against both enveloped and non-enveloped respiratory viruses.

Limitations: Again, the combination product design makes it difficult to attribute specific clinical benefit solely to nasturtium. The primary endpoint in bronchitis trials (BSS) is a composite symptom score. Larger, adequately powered head-to-head trials against antibiotics are still needed.

4.3 Gut Microbiome and Host Defense

BITC from nasturtium is known for its antimicrobial activity and is used for the treatment of infections of the draining urinary tract and upper respiratory tract. A 14-day nasturtium intervention (3 g daily, N = 30 healthy females) examined whether nasturtium could also impact the normal gut microbiota composition. Spot urinary BITC excretion highly correlated with a weak but significant antibacterial effect against Escherichia coli. A significant increase in human beta defensin 1 as a parameter for host defense was seen in urine and exhaled breath condensate upon verum intervention.

Strength of evidence: Preliminary (small sample, single crossover study in healthy women); provides mechanistic insight but insufficient to inform clinical recommendations.

4.4 Antioxidant Effects and Oxidative Stress

Despite heterogeneity in watercress formulations, dosage, follow-up, and outcomes, a systematic review found that watercress demonstrated improvements in biomarkers such as IL-1, IL-6, TNF-α, and antioxidant enzymes. These effects are mediated through bioactive compounds such as glucosinolates, carotenoids, and flavonoids.

Hemodialysis patients (RCT): In a double-blind, placebo-controlled trial, 46 hemodialysis patients were randomly recruited to consume either 500 mg/day ethanolic extract of N. officinale (EENO) (n = 23) or placebo capsule (n = 23) for 4 weeks. Biomarkers evaluated included glutathione peroxidase (GPX), superoxide dismutase (SOD), malondialdehyde (MDA), total oxidant status (TOS), total antioxidant capacity (TAC), total sulfhydryl protein (T-SH), and conventional biochemical parameters on days 0 and 28.

Healthy adults: Gill et al. demonstrated that consumption of watercress (85 g daily for 8 weeks) was associated with reductions in DNA damage, with a greater effect in smokers than non-smokers. Watercress supplementation in diet has been shown to ameliorate DNA damage and increase the blood antioxidant potential in human subjects (Gill et al. 2007).

Strength of evidence: Moderate for antioxidant biomarker improvements; evidence includes at least one RCT in hemodialysis patients and a clinical crossover study in healthy adults. Further large-scale RCTs are needed to establish clinical outcomes beyond biomarker endpoints.

4.5 Cancer-Related Research

Watercress comprises the richest known natural source of gluconasturtiin, the precursor of PEITC. PEITC has been reported to have the capacity to act as a chemopreventive agent against a broad spectrum of cancers, including prostate, leukemia, cervical, liver, colon, lung, multiple myeloma, and breast cancer. Numerous reports suggest that PEITC promotes the activation of apoptotic cascades, and as such, it is currently undergoing Phase I and II clinical trials.

Clinical evidence (smokers/carcinogen detoxification): Consumption of watercress enhanced the excretion of the NNK metabolite NNAL in smokers, suggesting inhibition of its metabolic activation, as observed in studies of PEITC and NNK in laboratory animals.

In vitro and cell line studies: Watercress extracts enriched in either PEITC or polyphenolic compounds have been shown to induce cytotoxicity in various human cancer cell lines including melanoma, prostate, leukemia, cervical, liver, colon, lung, myeloma, and breast in preclinical research.

For T. majus, the breakdown product of benzyl glucosinolate, BITC, exhibits antiproliferative activity. While BITC shows anti-cancer activity in cell cultures, no clinical trials currently confirm cancer cure or prevention in humans.

Strength of evidence: Overall, cancer-related evidence for both plants is predominantly preclinical (cell culture and animal models) with limited early-phase clinical data. Clinical trials with PEITC are at an early stage. No conclusions about anti-cancer efficacy in humans can be drawn at this time.

4.6 Metabolic Effects: Lipid Profile and Insulin Resistance

Prediabetes (pilot RCT, T. majus): Nasturtium (T. majus) is a plant rich in bioactive compounds such as phenolic compounds, glucosinolates, and their hydrolyzed metabolites isothiocyanates, which modulate signaling pathways related to lipid and carbohydrate metabolism. This randomized crossover trial explored the effect of intervention with a freeze-dried nasturtium drink on insulin response and lipid profile in prediabetic subjects. Ten patients were randomly assigned to nasturtium (NT) or placebo (PLC) for 4 weeks and then crossed for another 4 weeks. Consumption of 15 g NT (681 μmol of benzyl glucosinolate) per dose per week for four weeks resulted in a significant decrease in LDL cholesterol, Oxidized LDL (ox-LDL), Castelli's risk index I and II (TC/HDLc, and LDLc/HDLc), and the atherogenic coefficient. The results suggest nasturtium consumption might have a modulating effect on biomarkers related to cardiovascular disease.

Animal model (N. officinale): Intragastric administration of N. officinale extract (500 mg/kg bw/day) in high-fat diet rats lowered serum total cholesterol, triglycerides, and LDL-C by 34.2%, 30.1%, and 52.9%, respectively, and raised HDL-C by 27.0% after 10 days of treatment.

Strength of evidence: The human pilot study in prediabetes is very small (n = 10). Animal data cannot be directly extrapolated to humans. Evidence is preliminary; larger RCTs are required before conclusions about metabolic benefits are supportable.

4.7 Anti-inflammatory Effects

An in vitro study was carried out to investigate the potential of aqueous extract of nasturtium to inhibit inflammatory responses in primary human cells. Human peripheral blood mononuclear cells (PBMC) were treated with plant extracts or chemical fractions, and the study identified that nasturtium caused a strong concentration-dependent suppression of a specific inflammatory signalling pathway. Further clinical research is required to fully explore the potential of this herb in the management of inflammation.

A systematic review found that watercress demonstrated improvements in inflammatory biomarkers such as IL-1, IL-6, and TNF-α across randomized controlled trials, despite heterogeneity in formulations and dosages.

Strength of evidence: Mechanistic in vitro evidence supports anti-inflammatory activity; the systematic review of RCTs supports improvements in inflammatory biomarkers, but heterogeneity limits conclusions. No large, well-powered clinical anti-inflammatory trials have been completed.

4.8 Hepatoprotective and Nephroprotective Effects

Previous pharmacological studies revealed that N. officinale possesses hypolipidemic, anti-inflammatory, hepato- and reno-protective, antidiabetic, antioxidant, anticancer, antimicrobial, antigenotoxic, and anti-urolithiatic effects. In animal models, N. officinale extract also reduced serum ALT and AST levels compared to high-fat diet groups, suggesting hepatoprotective effects.

Strength of evidence: Hepatoprotective and nephroprotective data are largely from animal models; no dedicated human clinical trials have confirmed these effects.

4.9 Antimalarial Activity (Preclinical)

BITC, the main breakdown product of benzyl glucosinolate present in all parts of T. majus, has antibacterial and antiparasitic activities. To date there was no information on its effects against malaria, and a study evaluating the antimalarial activity of aqueous extracts of BITC and T. majus seeds, leaves, and stems has been conducted. This represents an early-stage area of investigation with no clinical evidence in humans.

5. Body Systems and Health Areas Associated with Nasturtium

• Urinary system: One of nasturtium's most common uses is as a natural urinary antiseptic, diuretic, and anti-inflammatory medicine. It is used to address bacterial infections in the urinary system; BITC is eliminated via the urinary system, which explains its strong reputation for UTI use.
• Respiratory system: The strong volatile components in nasturtium act as a respiratory decongestant. The glucosinolate-sulfur compounds exhibit antibacterial activity, and these effects can be valuable in fighting chronic respiratory infections characterized by mucous congestion.
• Cardiovascular and metabolic system: Evidence from preclinical and pilot human studies links both plants to improvements in lipid biomarkers and cardiovascular risk indices.
• Immune system: A significant increase in human beta defensin 1 as a parameter for host defense has been observed in urine and exhaled breath condensate upon nasturtium intervention.
• Skin health: The juice of nasturtium has been traditionally used to treat lipomas, polyps, and other skin conditions.
• Cancer prevention (preclinical): PEITC (from N. officinale) and BITC (from T. majus) are subjects of ongoing chemopreventive and cancer biology research.
• Liver and kidneys: Animal model and preclinical data suggest hepatoprotective and nephroprotective effects.

6. Dosage Forms and Dosages Reported in Studies

Dosages vary significantly across studies, species, and preparation types. The following figures are reported directly from cited sources and should not be interpreted as recommended doses.

• In a clinical RCT in hemodialysis patients, 500 mg/day of ethanolic extract of N. officinale (EENO) was administered for 4 weeks.
• In Gill et al.'s clinical study, 85 g daily for 8 weeks of raw watercress was associated with reductions in lymphocyte DNA damage.
• In the prediabetes pilot trial with T. majus, 15 g of freeze-dried nasturtium (providing 681 μmol of benzyl glucosinolate) per dose per week for 4 weeks was used.
• A 14-day crossover study in healthy females used 3 g daily of nasturtium (T. majus) preparation (n = 30).
• One tablet of ANGOCIN® Anti-Infekt N contains 200 mg of nasturtium and 80 mg of horseradish powder; the fixed release ratio of active isothiocyanates (BITC: AITC: PEITC) is 50%: 37.9%: 12.1% (v/v).
• A single dose of 4 tablets as recommended in the package information results in a glucosinolate administration of 16 mg per administration.
• In a rat model of hyperlipidemia, intragastric administration of N. officinale extract at 500 mg/kg bw/day for 10 days produced significant lipid-lowering effects.
• In a 90-day preclinical oral toxicity study, Swiss mice and Wistar rats were treated with hydroethanolic extract of T. majus at doses of 75, 375, and 750 mg/kg orally daily for 90 days; for rabbits (dosed at 30, 150, and 300 mg/kg) doses were calculated by allometric extrapolation.

7. Safety Considerations and Interactions

7.1 General Safety Profile

A subchronic toxicity study of the hydroethanolic extract obtained from leaves of T. majus in rats showed no significant alterations in body weight gain, relative organ weight, or serum biochemical and hematological parameters of the liver, kidneys, and spleen. The plant's good toxicological profile and potential as a source of antihypertensive agent make it a candidate for clinical studies.

7.2 Gastrointestinal Effects

Glucosinolates can be irritating to some sensitive people or if given in excessive quantity, and adverse effects include irritation of the skin externally or of the digestive and urinary system internally. Excessive usage of the plant may cause upset stomach.

7.3 Goitrogenic / Thyroid Concerns

High intake of glucosinolates can interfere with iodine uptake, raising concern for people with hypothyroidism. Glucosinolates are goitrogenic components and can affect the functioning of the thyroid gland in people with hypothyroidism.

7.4 Wild-Harvested Nasturtium officinale: Specific Safety Risk

Wild-harvested plants of N. officinale can contain toxic metals and harbor dangerous parasites such as liver fluke. This is a documented and significant safety concern distinct from other dietary supplement safety considerations.

7.5 Dermatological Risk (Contact Dermatitis)

Contact dermatitis due to nasturtium has been documented in the peer-reviewed literature (Perez-Crespo et al., Contact Dermatitis, 2009;60(4):229–30). Rarely, people sensitive to Brassicaceae (mustard, horseradish) may develop rash or itching.

7.6 Contraindications in Specific Populations

Nasturtiums are not recommended for use by those experiencing gastrointestinal ulcers or kidney diseases, and are also not recommended for use by infants or small children. The use of nasturtium is not recommended during pregnancy and breastfeeding. In children under 6 years of age, it is not recommended due to goitrogenic substances and the potential for allergies.

7.7 Drug Interactions

When used alongside certain pharmaceuticals, T. majus may interfere with drug metabolism due to its bioactive compounds, potentially altering the effectiveness or side effects of medications. It may interact with anticoagulants like warfarin, increasing the risk of bleeding due to its mild blood-thinning properties.

7.8 Prolonged Use

Prolonged daily intake of nasturtium is not recommended because it can be irritating to the digestive tract, kidneys, or skin.

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