Spearmint

Spearmint was used mainly as a food. Its oil was considered stimulant, carminative and antispasmodic, like peppermint’s but weaker, and it was thought better suited to children’s complaints ^{29Reference 29Grieve · 1931A Modern Herbal — “Mints: Spearmint.” (historical/traditional reference). https://www.botanical.com/botanical/mgmh/m/mints-39.htmlView study →}.

A distilled spearmint water was given for hiccough, flatulence and the giddiness of indigestion. A sweetened infusion was a remedy for infants’ ailments and a drink in fevers, and spearmint was held to be a specific for nausea and vomiting and to relieve colic ^{29Reference 29Grieve · 1931A Modern Herbal — “Mints: Spearmint.” (historical/traditional reference). https://www.botanical.com/botanical/mgmh/m/mints-39.htmlView study →}.

The infusion was made from an ounce of dried herb to a pint of boiling water ^{29Reference 29Grieve · 1931A Modern Herbal — “Mints: Spearmint.” (historical/traditional reference). https://www.botanical.com/botanical/mgmh/m/mints-39.htmlView study →}.

Spearmint is a Mediterranean plant that the Romans cultivated and brought to Britain. Pliny wrote that its smell stirred the appetite, and it was eaten with food to aid digestion ^{29Reference 29Grieve · 1931A Modern Herbal — “Mints: Spearmint.” (historical/traditional reference). https://www.botanical.com/botanical/mgmh/m/mints-39.htmlView study →}.

In the town of Isparta in south-west Turkey, local belief held that tea made from spearmint or peppermint lowered libido. That belief prompted the first clinical study of spearmint tea in women with hirsutism ^{2Reference 2Akdoğan M et al. · 2007Clinical trialEffect of spearmint (Mentha spicata Labiatae) teas on androgen levels in women with hirsutism — [clinical trial]View study →}.

Known as pudina, spearmint is used as a cooling, aromatic digestive for nausea, poor appetite and stomach discomfort. It is taken as fresh leaf, chewed, or as a light infusion after food.

This is spearmint’s best-studied effect in people. In a 30-day, two-centre randomised trial in 42 women with PCOS, free and total testosterone fell significantly in the group drinking spearmint tea twice daily, and LH and FSH rose. The comparison was a placebo herbal tea, and 41 of the 42 women completed the study ^{1Reference 1Grant P et al. · 2010RCTSpearmint herbal tea has significant anti-androgen effects in polycystic ovarian syndromeView study →}.

An earlier open trial in 21 hirsute women (12 with PCOS, 9 with idiopathic hirsutism) gave a cup of spearmint tea twice daily for five days. Free testosterone fell and LH, FSH and estradiol rose, while total testosterone and DHEA sulphate did not change significantly ^{2Reference 2Akdoğan M et al. · 2007Clinical trialEffect of spearmint (Mentha spicata Labiatae) teas on androgen levels in women with hirsutism — [clinical trial]View study →}.

In male rats, an aqueous spearmint extract lowered the expression of steroid-making enzymes (cytochrome P450scc, P450c17, 3β- and 17β-hydroxysteroid dehydrogenase) and reduced testicular testosterone. The authors proposed that oxidative stress in the hypothalamus lowers LH and FSH, which in turn reduces testosterone production ^{3Reference 3Kumar V et al. · 2008AnimalSpearmint induced hypothalamic oxidative stress and testicular anti-androgenicity in male rats - altered levels of gene expression, enzymes and hormones — [animal model (rat)]View study →}.

In a letrozole-induced PCOS rat model, both a spearmint extract and carvone alone reversed the raised testosterone, insulin resistance and ovarian inflammation ^{7Reference 7Oladele CA et al. · 2025AnimalMentha spicata and Its Bioactive Compound Carvone Ameliorate Metabolic Disturbance and Ovarian Dysfunction in Experimental Rat Model of PCOS by Suppression of SREBP1/TLR4-Dependent Pathway — [animal model (rat)]View study →}. A combination of spearmint and flaxseed extracts lowered testosterone in a second rat model of PCOS ^{8Reference 8Mehraban M et al. · 2020AnimalA combination of spearmint and flaxseed extract improved endocrine and histomorphology of ovary in experimental PCOS — [animal model (rat); combination formulation]View study →}.

⚠ In the 30-day trial, the objective Ferriman–Gallwey hirsutism score did not improve significantly (p = 0.12), although hormone levels and the women’s own ratings of their hair growth did ^{1Reference 1Grant P et al. · 2010RCTSpearmint herbal tea has significant anti-androgen effects in polycystic ovarian syndromeView study →}.

Gap: Both human trials are small (n=42, n=21) and short (5–30 days); no trial has yet shown a significant reduction in visible hirsutism on an objective scale.

This research uses a proprietary spearmint extract standardised to rosmarinic acid, not tea. In a 90-day double-blind trial in 90 adults with age-associated memory impairment, 900 mg a day improved quality of working memory by 15% and spatial working-memory accuracy by 9% compared with placebo. The same group reported falling asleep more easily. A 600 mg dose was also tested ^{4Reference 4Herrlinger KA et al. · 2018RCTSpearmint Extract Improves Working Memory in Men and Women with Age-Associated Memory Impairment — [randomised controlled trial]View study →}.

A larger 90-day trial in 142 healthy, recreationally active adults found that 900 mg a day improved sustained attention at days 30 and 90, and complex attention at day 7. Mood, sleep and quality of life did not change ^{5Reference 5Falcone PH et al. · 2019RCTThe attention-enhancing effects of spearmint extract supplementation in healthy men and women: a randomized, double-blind, placebo-controlled, parallel trial — [randomised controlled trial]View study →}.

A 17-day pilot in ten counter-terrorism operators, tested after a 24-hour sleepless operation, was inconclusive for physical and cognitive performance. Subjective energy, alertness and focus were rated better on the extract ^{9Reference 9Ostfeld I et al. · 2018RCTEffect of Spearmint Extract Containing Rosmarinic Acid on Physical and Executive Functioning After a Tactical Operation — [randomised controlled trial]View study →}.

In the laboratory, spearmint extract and rosmarinic acid suppressed the formation of amyloid-β, tau and α-synuclein fibrils, and rosmarinic acid broke down fibrils that had already formed ^{10Reference 10Ogawa K et al. · 2020In vitroSpearmint Extract Containing Rosmarinic Acid Suppresses Amyloid Fibril Formation of Proteins Associated with Dementia — [in vitro]View study →}.

Both main trials were run by the extract’s manufacturer ^{4,5Reference 4Herrlinger KA et al. · 2018RCTSpearmint Extract Improves Working Memory in Men and Women with Age-Associated Memory Impairment — [randomised controlled trial]View study →Reference 5Falcone PH et al. · 2019RCTThe attention-enhancing effects of spearmint extract supplementation in healthy men and women: a randomized, double-blind, placebo-controlled, parallel trial — [randomised controlled trial]View study →}.

Gap: Every positive cognition trial used one proprietary standardised extract at 900 mg/day; there is no evidence that drinking spearmint tea delivers a comparable rosmarinic-acid dose or cognitive effect.

Antioxidant activity has been shown repeatedly in the laboratory and in animals, and is attributed to phenolic acids, chiefly rosmarinic acid, and flavonoids ^{19Reference 19Mahendran G et al. · 2021ReviewThe traditional uses, phytochemistry and pharmacology of spearmint (Mentha spicata L.): A review — [review]View study →}. In rats given nicotine, a spearmint aqueous extract (100 mg/kg for two months) restored antioxidant-enzyme activity and lowered lipid peroxidation in the liver and red blood cells ^{11Reference 11Ben Saad A et al. · 2018AnimalProtective effects of Mentha spicata against nicotine-induced toxicity in liver and erythrocytes of Wistar rats — [animal model (rat)]View study →}.

A spearmint variety has been bred that makes about 20 times more rosmarinic acid than ordinary plants ^{13Reference 13Pearson W et al. · 2010In vitroProtection against LPS-induced cartilage inflammation and degradation provided by a biological extract of Mentha spicata — [in vitro]View study →}.

No human trial has measured an oxidative-stress endpoint after spearmint intake.

In pig cartilage kept in culture, a simulated digest of the high-rosmarinic-acid spearmint variety reduced inflammatory signals (prostaglandin E2 and nitric oxide) and cartilage breakdown caused by bacterial endotoxin. The authors found the effect was mostly independent of rosmarinic acid, and its breakdown products had no effect ^{13Reference 13Pearson W et al. · 2010In vitroProtection against LPS-induced cartilage inflammation and degradation provided by a biological extract of Mentha spicata — [in vitro]View study →}.

In rats, the ethyl acetate and water fractions of an ethanol extract reduced both acute paw swelling and chronic inflammation, and the ethyl acetate fraction was comparable to standard anti-inflammatory drugs in the chronic model ^{12Reference 12Arumugam P et al. · 2008AnimalAnti-inflammatory activity of four solvent fractions of ethanol extract of Mentha spicata L. investigated on acute and chronic inflammation induced rats — [animal model (rat)]View study →}.

No trial has measured inflammatory markers in people.

In a 16-week double-blind trial in knee osteoarthritis (62 randomised, 46 analysed), participants drank tea twice daily from either a high-rosmarinic-acid spearmint variety or a commercial spearmint. Pain scores fell significantly over the 16 weeks only in the high-rosmarinic-acid group, which also improved on the SF-36 bodily-pain score. Stiffness and physical disability improved in both groups ^{6Reference 6Connelly AE et al. · 2014RCTHigh-rosmarinic acid spearmint tea in the management of knee osteoarthritis symptoms — [randomised controlled trial]View study →}.

The differences between the two groups were not statistically significant ^{6Reference 6Connelly AE et al. · 2014RCTHigh-rosmarinic acid spearmint tea in the management of knee osteoarthritis symptoms — [randomised controlled trial]View study →}.

A review of spearmint essential oil reports analgesic effects in animal studies for the oil and its main compounds, carvone, limonene and menthol ^{14Reference 14Mahboubi M et al. · 2017ReviewMentha spicata as natural analgesia for treatment of pain in osteoarthritis patients — [review]View study →}.

Gap: A single, modest-sized trial of a non-commercial high-rosmarinic-acid cultivar; the effect has not been replicated and does not clearly extend to ordinary spearmint tea.

In rats given nicotine for two months, spearmint aqueous extract (100 mg/kg) reduced the rise in the liver enzymes AST, ALT, ALP and LDH, restored antioxidant-enzyme activity, and reduced lipid peroxidation in the liver and red blood cells ^{11Reference 11Ben Saad A et al. · 2018AnimalProtective effects of Mentha spicata against nicotine-induced toxicity in liver and erythrocytes of Wistar rats — [animal model (rat)]View study →}.

A review of spearmint pharmacology lists liver protection among the activities reported for its extracts ^{19Reference 19Mahendran G et al. · 2021ReviewThe traditional uses, phytochemistry and pharmacology of spearmint (Mentha spicata L.): A review — [review]View study →}.

This is a single chemical-injury model in animals. There are no human liver-function data.

A review of spearmint pharmacology reports antibacterial and antifungal activity for the essential oil and extracts in laboratory studies ^{19Reference 19Mahendran G et al. · 2021ReviewThe traditional uses, phytochemistry and pharmacology of spearmint (Mentha spicata L.): A review — [review]View study →}.

In a comparison of nine commercial essential oils against the tooth-decay bacterium Streptococcus mutans, spearmint oil showed no antibacterial activity, and neither did peppermint oil ^{25Reference 25Chaudhari LK et al. · 2012In vitroAntimicrobial activity of commercially available essential oils against Streptococcus mutans — [in vitro]View study →}.

In the Salmonella test, a spearmint leaf tea extract reduced the mutagenic effect of a cooked-meat carcinogen in a dose-dependent way. Rats drinking spearmint tea during and after exposure to the same carcinogen developed fewer precancerous lesions in the colon ^{21Reference 21Yu TW et al. · 2004In vitroAntimutagenic activity of spearmint — [in vitro]View study →}.

Gap: Nearly all antimicrobial data use the concentrated essential oil at levels far above what tea delivers; there is no clinical infection endpoint.

In isolated guinea-pig ileum, (−)-carvone, the form found in spearmint oil, reduced contractions triggered by histamine, barium chloride and carbachol. It acted like a calcium-channel blocker and was almost 100 times more potent than verapamil against high-potassium contractions ^{15Reference 15Souza FV et al. · 2013AnimalSouza FV, et al. (2013). (-)-Carvone: antispasmodic effect and mode of action — [animal model (ex vivo, guinea pig ileum)]. Fitoterapia. https://pubmed.ncbi.nlm.nih.gov/23103297/View study →}. An earlier report found it more potent than its (+) form ^{15Reference 15Souza FV et al. · 2013AnimalSouza FV, et al. (2013). (-)-Carvone: antispasmodic effect and mode of action — [animal model (ex vivo, guinea pig ileum)]. Fitoterapia. https://pubmed.ncbi.nlm.nih.gov/23103297/View study →}.

The evidence is from isolated tissue and a single compound. No human trial has tested spearmint tea or extract for irritable bowel syndrome, indigestion or cramping.

In streptozotocin-diabetic rats, repeated oral doses of spearmint aqueous extract (20 mg/kg) significantly lowered blood glucose, comparably to glibenclamide. In normal rats, neither a single dose nor repeated doses lowered blood glucose, though the extract improved glucose tolerance ^{16Reference 16Farid O et al. · 2018AnimalAntidiabetic Effect of Spearmint in Streptozotocin-Induced Diabetic Rats — [animal model (rat)]View study →}.

In the PCOS rat model, spearmint extract and carvone also improved insulin resistance and blood lipids ^{7Reference 7Oladele CA et al. · 2025AnimalMentha spicata and Its Bioactive Compound Carvone Ameliorate Metabolic Disturbance and Ovarian Dysfunction in Experimental Rat Model of PCOS by Suppression of SREBP1/TLR4-Dependent Pathway — [animal model (rat)]View study →}.

There are no human blood-sugar data.

In a randomised, double-blind trial in chemotherapy patients, spearmint or peppermint essential oil reduced the intensity of nausea and the number of vomiting episodes in the first 24 hours, compared with patients who continued their usual anti-sickness treatment. No adverse effects were reported ^{17Reference 17Tayarani-Najaran Z et al. · 2013RCTAntiemetic activity of volatile oil from Mentha spicata and Mentha × piperita in chemotherapy-induced nausea and vomiting — [randomised controlled trial]View study →}.

A systematic review of alternative remedies for nausea and vomiting in pregnancy gave mixed findings: it listed spearmint syrup among the remedies found safe and effective, but reported that Mentha had no benefit on nausea and vomiting ^{18Reference 18Khorasani F et al. · 2020Systematic reviewA systematic review of the efficacy of alternative medicine in the treatment of nausea and vomiting of pregnancy — [systematic review]View study →}.

Gap: One small positive essential-oil trial in chemotherapy nausea versus a null signal in pregnancy nausea — too little, and too preparation-specific, to generalise.

Food and extract safety. Spearmint and its extracts are Generally Recognized as Safe (GRAS) as flavourings. In a 90-day trial, 600 or 900 mg a day of a dried aqueous spearmint extract did not change FSH, LH or TSH, vital signs, blood chemistry or blood counts, and adverse events were no more common than on placebo ^{20Reference 20Lasrado JA et al. · 2017RCTSafety and tolerability of a dried aqueous spearmint extract — [randomised controlled trial]View study →}. In a 90-day rat study, the no-observed-adverse-effect level of the extract was 1,948 mg/kg a day, the highest dose tested, and it was not mutagenic in laboratory tests ^{24Reference 24Lasrado JA et al. · 2015In vitroThe safety of a dry spearmint extract in vitro and in vivo — [animal model (rat)]View study →}.

Hormones. Twice-daily tea lowered free testosterone in women in two clinical trials ^{1,2Reference 1Grant P et al. · 2010RCTSpearmint herbal tea has significant anti-androgen effects in polycystic ovarian syndromeView study →Reference 2Akdoğan M et al. · 2007Clinical trialEffect of spearmint (Mentha spicata Labiatae) teas on androgen levels in women with hirsutism — [clinical trial]View study →}. In male rats, an aqueous extract lowered testosterone and the enzymes that make it ^{3Reference 3Kumar V et al. · 2008AnimalSpearmint induced hypothalamic oxidative stress and testicular anti-androgenicity in male rats - altered levels of gene expression, enzymes and hormones — [animal model (rat)]View study →}. A separate rat study found no significant effect on sperm, testosterone, fertility or number of offspring at 10–40 mg/kg for 45 days, though the authors noted that high doses might affect male fertility ^{22Reference 22Nozhat F et al. · 2014AnimalEvaluation of possible toxic effects of spearmint (Mentha spicata) on the reproductive system, fertility and number of offspring in adult male rats — [animal model (rat)]View study →}.

Interactions. No human drug-interaction study exists. The testosterone-lowering effect could add to antiandrogen or hormonal therapy.