Spearmint

Mentha spicata L. belongs to Lamiaceae, the mint family, alongside peppermint, lemon balm, rosemary, sage, and thyme. Linnaeus published the name in Species Plantarum in 1753, and Kew’s Plants of the World Online gives its native range as Europe to China, a perennial of the temperate biome. EFSA, the European Food Safety Authority, notes that it has since been introduced to North and South America and that the common name comes from the spear-like shape of the leaves; it is also called garden mint, common mint, or lamb mint, and Mrs Grieve adds mackerel mint, Our Lady’s mint, and green mint. Creeping rhizomes send up upright, square stems up to about 100 cm tall, carrying bright green leaves in opposite pairs (EFSA). Grieve describes the leaves as lance-shaped, sharply pointed, wrinkled, and finely toothed on very short stalks, and the small pinkish or lilac flowers as packed in whorls that form slender, tapering spikes at the stem tips.

Spearmint spreads easily from its underground stems; Grieve noted that every piece of root with a joint will grow, and that in America it had long escaped from gardens into moist soil, sometimes as a weed. Its family tree is less tidy than textbooks suggest. EMA’s assessment report repeats the long-standing view that peppermint (Mentha × piperita) is a hybrid of spearmint and water mint (M. aquatica). Spearmint itself has traditionally been described as a hybrid too, but Heylen and colleagues (Plants 2021), using large genetic samples, found no evidence of hybrid origin, uncovered cryptic species within the spearmint group, and argued that its taxonomic status should be revised. Curly-leaved forms, such as the one Grieve called M. crispa, are grown in gardens, and Moroccans drink tea made from M. spicata and M. viridis, an old name for spearmint, every day (El Hassani, Heliyon 2020). American growers report two commercial types to USDA, Native and Scotch spearmint.

Carvone is the defining compound. Krajewska and colleagues (Molecules 2026) report that commercially grown spearmint always yields essential oil rich in (R)-carvone, typically 30–85%, with 5–28% (R)-limonene. Caraway and dill oils are dominated by the mirror-image molecule, (S)-carvone, which has the same formula (PubChem lists (−)-carvone as CID 439570, C10H14O) but smells spicy, like caraway seeds, rather than sweet and minty. In EFSA’s 2025 analysis, steam-distilled spearmint oil contained about 49.5% carvone, 19.3% limonene, and only 2.3% menthol, while fractionally distilled oil reached 76.5% carvone; commercial specifications are based on the international standard ISO 3033. Some wild spearmints are instead rich in pulegone, piperitone, or piperitenone oxide (Krajewska). The leaves also contain polyphenols, notably rosmarinic acid (CID 5281792, C18H16O8); the memory extract tested in trials was standardized to at least 14.5% rosmarinic acid and 24% total polyphenols (Herrlinger). Grieve estimated that 350 lb of fresh plant yields about 1 lb of oil.

Mint was valued long before anyone separated spearmint from its relatives. Grieve records that Theophrastus first applied the name Mentha, after the nymph Menthe, whom the jealous Proserpine turned into the plant, and that the Romans prized garden mint highly. She quotes Pliny, via the herbalist John Gerard: ‘The smell of Mint does stir up the minde and the taste to a greedy desire of meate.’ The ancients believed mint stopped milk from curdling, and Ovid has the hospitable Baucis and Philemon scour their table with green mint before serving their divine guests. Grieve also cites the Pharisees’ tithes of mint, anise, and cumin, and notes that in Athens, where different perfumes were assigned to different parts of the body, mint was reserved for the arms. She believed that spearmint was a Mediterranean plant brought to Britain by the Romans.

Medieval and early modern Europe kept spearmint in every garden. Grieve finds it in ninth-century convent gardens and in Chaucer, and William Turner’s Herball of 1568 already calls the garden mint ‘Spere Mynte.’ Gerard wrote that ‘the smelle rejoiceth the heart of man,’ which is why mint was strewn in rooms where feasts were held, and Culpeper listed nearly forty ailments for which mint was ‘singularly good.’ In the fourteenth century mint was used to whiten teeth. By Grieve’s time spearmint was mainly a culinary herb, eaten as mint sauce with lamb, but its oil was considered a gentler alternative to peppermint, ‘better adapted for children’s maladies,’ and spearmint infusion was regarded as a specific for nausea and vomiting. She thought the Pilgrims probably brought it to America, since it appears in John Josselyn’s list of plants carried from England.

Today spearmint is an everyday flavor around the world. In Morocco, mint tea made with spearmint is drunk daily (El Hassani). Grieve noted that in America especially, mint oil flavored confectionery and chewing gum, and spearmint is also used as a flavoring in medicines, including antacids (Bulat). In 2025, USDA’s National Agricultural Statistics Service reported US spearmint oil production of 1.61 million pounds from 11,600 acres, with Washington State producing 1.03 million pounds and Indiana, Idaho, and Oregon among the other growing states; peppermint oil production was 2.47 million pounds. The modern medical story began with folk observation. Akdoğan and colleagues (Phytotherapy Research 2007) explain that doctors in a town in Isparta province, Turkey, suspected that local spearmint and peppermint teas reduced men’s libido. Rat studies followed, then small trials of spearmint tea in women with hirsutism, which are why spearmint tea is now widely discussed online for PCOS.

The best-documented effect in people is on sex hormones. In Akdoğan’s five-day study, spearmint tea lowered free testosterone and raised luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estradiol, but did not significantly change total testosterone or the adrenal androgen DHEA sulfate. In Grant’s 30-day trial, both free and total testosterone fell and LH and FSH rose compared with placebo tea. How this happens in people is unknown, and the rat studies disagree with each other. Akdoğan and colleagues (Urology 2004) found that spearmint tea lowered testosterone and raised LH and FSH in male rats, as in women. Kumar and colleagues (Food and Chemical Toxicology 2008) instead found that an aqueous spearmint extract reduced the expression of testicular enzymes needed to make testosterone and caused oxidative stress in the hypothalamus, which they suggested lowered the output of LH and FSH. Preparation also seems to matter: in older adults taking 600 or 900 mg a day of a rosmarinic-acid-rich spearmint extract for 90 days, there was no effect on FSH, LH, or thyroid-stimulating hormone (Lasrado, Regulatory Toxicology and Pharmacology 2017).

Rosmarinic acid and related polyphenols are the rationale for the memory and arthritis research. Herrlinger and colleagues cite laboratory evidence that rosmarinic acid improves antioxidant status in nerve cells and in the hippocampus, a brain region central to memory, and that salvianolic acid, another polyphenol in their extract, has anti-inflammatory and antioxidant effects in mice. Connelly and colleagues chose a spearmint variety bred for high rosmarinic acid for their osteoarthritis trial for similar anti-inflammatory reasons. These are plausible mechanisms, not demonstrated ones; no study has shown which compounds, if any, account for the small effects seen in trials.

Spearmint has long been called a carminative and antispasmodic, a herb that eases wind and gut cramping (Grieve; Bulat). For peppermint, EMA’s assessment report describes how oral peppermint oil relaxes the lower esophageal sphincter, the valve that keeps stomach acid out of the esophagus, allowing reflux. Spearmint has much less menthol, and when Bulat and colleagues (Alimentary Pharmacology and Therapeutics 1999) measured sphincter pressure and esophageal acid directly in healthy volunteers, neither a flavoring dose (0.5 mg) nor a high dose (500 mg) of spearmint changed sphincter pressure or reflux episodes compared with placebo. The high dose did cause more heartburn-type symptoms, which the authors attributed to direct irritation of the lining rather than reflux. Carvone also interacts with the skin’s immune system: Kroona and colleagues describe it as a mild skin sensitizer, which explains the allergy reports.

Hirsutism and PCOS: two small studies form the core of the evidence. Akdoğan and colleagues (Phytotherapy Research 2007) gave 21 women with hirsutism, 12 with PCOS and 9 with no identified cause, a cup of spearmint tea twice a day for five days in the first half of the menstrual cycle; free testosterone fell, without a control group. Grant (Phytotherapy Research 2010) ran a two-center randomized trial in which 42 women with PCOS and hirsutism drank spearmint tea or a placebo herbal tea twice a day for 30 days, and 41 completed it. Free and total testosterone fell significantly with spearmint, and women’s own ratings of their hirsutism on a modified dermatology quality-of-life questionnaire improved, but the objective Ferriman–Gallwey hair score did not differ significantly between groups (p = 0.12). Grant argued that 30 days is too short for hair growth to change and called for longer trials. Lower testosterone is a plausible reason to hope for benefit, but less visible hair has not been shown, and spearmint tea is not a substitute for medical assessment and treatment of PCOS.

Memory and attention: Herrlinger and colleagues (Journal of Alternative and Complementary Medicine 2018) randomized 90 adults with age-associated memory impairment, average age 59 and two-thirds women, to 900 mg, 600 mg, or no spearmint extract daily for 90 days. With 900 mg, quality of working memory improved by 15% and spatial working memory accuracy by 9% compared with placebo, both only just reaching statistical significance (p = 0.047 and 0.046), and participants reported falling asleep more easily. In a later trial by Falcone and colleagues (Nutrition Research 2019), 142 healthy, active young adults taking 900 mg a day for 90 days improved on sustained and complex attention tests, with no change in mood or sleep. Both trials tested the same proprietary extract and included researchers from Kemin Foods, which makes it; the 2018 study was funded by the company. Spearmint tea has not been tested for memory.

Nausea: spearmint is traditionally given for nausea (Grieve), but the trials are weak. Tayarani-Najaran and colleagues (Ecancermedicalscience 2013) gave people starting chemotherapy capsules containing two drops of spearmint or peppermint oil every four hours, alongside their usual anti-sickness drugs, with 50 per group. Vomiting episodes in the first 24 hours were lower with spearmint (0.6) and peppermint (0.7) than with placebo (1.8), but the published tables are internally inconsistent: placebo patients had lower nausea-intensity scores than those taking spearmint, and the oil analysis labeled as spearmint was mostly pulegone, with no carvone listed. EMA judged the study not relevant for its peppermint monograph. Inhaled blends containing spearmint have done better: in a trial of 301 patients with nausea after ambulatory surgery, Hunt and colleagues (Anesthesia and Analgesia 2013) found that sniffing a blend of ginger, spearmint, peppermint, and cardamom oils reduced nausea and requests for anti-sickness medicine more than saline. Because the blend contained four oils, spearmint’s own contribution is unknown, and Cochrane’s 2018 review of aromatherapy found no clear effect on postoperative nausea severity.

Knee osteoarthritis: Connelly and colleagues (Journal of Medicinal Food 2014) randomized 62 adults with knee osteoarthritis to drink either a specially bred high-rosmarinic-acid spearmint tea or ordinary commercial spearmint tea twice a day for 16 weeks; 46 were analyzed. Stiffness and physical disability scores improved in both groups, and pain improved only with the high-rosmarinic-acid tea. There was no placebo group, and the abstract reports changes within each group rather than a clear difference between them, so the results are at best preliminary.

Digestion and other uses: Grieve records traditional use of spearmint for wind, hiccups, colic, and indigestion, and Kew notes use for digestive disorders. A small controlled gut trial tested a combination: Vejdani and colleagues (Digestive Diseases and Sciences 2006) gave 32 people with irritable bowel syndrome Carmint, an extract of lemon balm, spearmint, and coriander, or placebo, alongside loperamide or psyllium for eight weeks, and reported less pain and bloating. As a three-herb pilot it cannot show what spearmint itself does. Laboratory and animal studies report antimicrobial, antioxidant, and blood-sugar effects (Mahendran, Journal of Ethnopharmacology 2021), but none has been confirmed in people.

Tea is the traditional form, and there is no official medicinal dose. The hormone studies used a cup of spearmint tea twice a day, for five days (Akdoğan) or 30 days (Grant), and the osteoarthritis trial used two cups a day for 16 weeks (Connelly); the published abstracts do not specify how much leaf went into each cup. Grieve’s 1931 recipe was an ounce of dried herb to a pint of boiling water, taken a wineglassful at a time. Moroccan mint tea, which historian Graham Cornwell describes as green tea, sugar, and fresh mint, usually spearmint, also contains caffeine from the green tea. Fresh leaves in salads, sauces, and drinks are food, not medicine. Whatever the form, stop if it brings on heartburn.

Extracts: the memory and attention trials used a proprietary dried water extract of spearmint leaves standardized to at least 14.5% rosmarinic acid, taken as two capsules once a day to give 900 mg (or 600 mg) daily for 90 days. In a 90-day rat study by the manufacturer, doses up to 1,948 mg per kg of body weight a day caused no adverse effects, and the extract was not mutagenic in standard laboratory tests (Lasrado, Regulatory Toxicology and Pharmacology 2015). This product’s results cannot be applied to tea, to other extracts, or to spearmint oil, which have very different chemistry.

Essential oil: spearmint oil is concentrated, at roughly 30–85% carvone, and is meant for flavoring and fragrance in tiny amounts. The two drops in a sugar-filled capsule used in the chemotherapy trial are not a home recipe, and undiluted essential oil should not be swallowed or applied to the skin. EFSA considers spearmint oil an irritant to the skin and eyes and a skin and respiratory sensitizer for people handling it. EMA’s assessment report records a 9-year-old boy who developed a racing heart and agitation, which settled within 24 hours, after drinking an infusion made from 30 leaves of a carvone-type mint. Store oils out of children’s reach, and avoid stacking several mint products, such as oil capsules, strong teas, and lozenges, at once.