Spearmint: capsule results, a tea trial and an oil allergy

The one review-level finding on spearmint is negative. A systematic review of herbal remedies for nausea and vomiting in pregnancy found that mint did not ease symptoms. That review pooled no numbers, and its own abstract also mentions a spearmint syrup favorably, so the verdict is softer than a meta-analysis would give. The positive results come from capsules. In a 90-day trial in 90 adults with age-associated memory impairment, 900 mg a day of a proprietary spearmint extract improved quality of working memory by 15 percent against placebo (p = 0.047). That trial had one extract maker, 30 people per group and several end points. The capsule was a water extract standardized to at least 14.5 percent rosmarinic acid, which is a long way from a mint leaf in your tea. The same dose given to 142 healthy, active young adults for 90 days lifted a sustained attention score from 32.7 to 34.0, a small absolute gap, and left mood and sleep unchanged.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• Dried spearmint is listed at 87.47 mg iron per 3.5 oz (100 g), but it is eaten in amounts of a gram or two, so its iron contribution is small. — USDA reference sample, dried spearmint Evidence E source
  Iron 87.47 mg, copper 1.542 mg, vitamin B6 2.579 mg per 3.5 oz (100 g)

What your body absorbs

• In a small randomized pharmacokinetic study, rosmarinic acid, the main polyphenol of spearmint extract, peaked in blood 1 hour after a 500 mg dose taken fasted, and food delayed its absorption. — Healthy adults, single dose of a lemon balm extract containing 500 mg rosmarinic acid, fasted and fed (n = 11) Evidence B source
  Cmax 162.20 nmol/L at 1 h fasted; food increased AUC and delayed Tmax

What it does to your health

• The extract tested in the memory trial was a proprietary water extract of spearmint leaves standardized to at least 14.5% rosmarinic acid, not a culinary serving of mint. — Study product description, adults with age-associated memory impairment (n = 90) Evidence B source
  Not an outcome; defines the dose form (minimum 14.5% rosmarinic acid, 24% total polyphenols)
• In a 90-day RCT in 142 young active adults, 900 mg/day of spearmint extract raised sustained attention scores slightly above placebo, with no change in mood or sleep. — Healthy recreationally active men and women, 90 days (n = 142) Evidence B source
  Sustained attention day 90: 34.0 vs 32.7 (P = .007); no significant differences in mood, sleep or quality of life
• In a 90-day RCT in 114 adults with borderline high cholesterol, the higher dose of a supplement combining Mentha spicata leaf extract, amaranth, flavonoids and B vitamins lowered LDL cholesterol by about 22%. — Adults 18-70 with total cholesterol 200-239 mg/dL, 90 days (n = 114) Evidence B source
  LDL-C about -31.5 mg/dL (-22%) and total cholesterol about -19.5 mg/dL (-9%) with the higher dose vs placebo

Safety, limits and interactions

• In an Italian multicentre patch-test series of 54 patients with lip eczema suspected from toothpaste, spearmint oil was the most frequent allergen in the targeted test series. — Patients with eczematous lip lesions suspected to be caused by toothpaste, Italy (n = 54) Evidence C source
  17 positive reactions in 13 patients to the toothpaste series, most often to spearmint oil; toothpaste cheilitis confirmed in 15 of 54
• EFSA lists pulegone, carvone and menthone among substances of potential concern reported in spearmint essential oil. — Essential oil from aerial parts of Mentha spicata Evidence E source
  Reported ranges: (+)-pulegone up to 72.1%, carvone 59-77%, menthone 14-15.6% in some oils

What people believe that the data does not support

• In a 30-day RCT in 42 women with PCOS and hirsutism, spearmint tea twice a day lowered free and total testosterone versus placebo tea, but the objective hirsutism score did not change. — Women with polycystic ovary syndrome and hirsutism, two centers, 30 days (n = 42) Evidence B source
  Free and total testosterone reduced (p < 0.05); Ferriman-Gallwey score not significantly different (p = 0.12)

Who this works differently for

• In a 90-day RCT in adults with age-associated memory impairment, 900 mg/day of a spearmint extract improved quality of working memory by 15% versus placebo. — Adults with age-associated memory impairment, mean age 59.4, 67% female, 90 days (n = 90) Evidence B source
  Quality of working memory +15% (p = 0.0469); spatial working memory accuracy +9% (p = 0.0456) vs placebo
• A systematic review of herbal trials for nausea and vomiting of pregnancy found that mint did not improve symptoms, and it gave no pooled effect size. — Pregnant women with nausea and vomiting, trials searched to January 2019 Evidence A source
  No positive effect for Mentha; no pooled estimate reported

The bottom line

Spearmint tea has one trial of its own. In 42 women with polycystic ovary syndrome and excess hair growth, two cups a day for 30 days lowered free and total testosterone against a placebo herbal tea, and the abstract gives no size for the drop. The hair score itself did not change significantly (p = 0.12). A month is short, and the trial was small. A 90-day trial in 114 adults with borderline high cholesterol reported LDL about 22 percent lower, roughly 31.5 mg/dL, on the higher dose of a supplement. That product mixed Mentha spicata leaf extract with amaranth, flavonoids and B vitamins, so the share owed to spearmint cannot be separated out. Rosmarinic acid, the main polyphenol in these extracts, peaked in the blood one hour after a 500 mg fasted dose in 11 healthy adults, and food delayed that peak. The dose came from lemon balm extract, and we found no absorption study of spearmint itself. Dried spearmint is listed at 87.47 mg of iron per 3.5 oz (100 g) in a single USDA sample. You use a gram or two at a time, and it is the non-heme form found in plants, so the contribution is small. Who should be careful. In an Italian case series of 54 patients with lip eczema suspected from toothpaste, spearmint oil was the most frequent allergen on the targeted patch test. That is a contact allergy to the flavoring. EFSA lists pulegone, carvone and menthone among substances of potential concern in spearmint essential oil, with pulegone reported at up to 72.1 percent in one oil source, in an opinion on the oil as an animal feed additive that sets no limit for people. Both findings are about the concentrated oil. We found no study of spearmint alongside prescription drugs, and nothing here tells you it is safe as a remedy in pregnancy.

Compared with other foods

Sources

1. spmn-daily-r1-10 · food composition data
   Spearmint, dried (FDC 172239): Iron, Fe 87.47 mg; Copper, Cu 1.542 mg; Vitamin B-6 2.579 mg per 100 g
   USDA FoodData Central, SR Legacy 2018, FDC 172239 Spearmint, dried · checked 2026-09-30
2. spmn-daily-r1-06 · RCT (pharmacokinetics)
   The serum concentration of total rosmarinic acid peaked at 1 hour after administration of Melissa officinalis extract containing 500mg rosmarinic acid in fasted state, with a maximum serum concentration 162.20 nmol/ L. ... Food intake increases area under the curve and delayed time at which the maximum serum concentration.
   PLoS One, 2015 · checked 2026-09-30
3. spmn-daily-r1-02 · RCT
   The water-extracted dry proprietary spearmint (M. spicata L. [aerial parts]) extract contained a minimum of 14.5% RA and 24% total polyphenols (Kemin Foods, L.C., Des Moines, IA).
   J Altern Complement Med, 2018 · checked 2026-09-30
4. spmn-daily-r1-03 · RCT
   Using a randomized, double-blind, placebo-controlled, parallel design, healthy, recreationally active men and women (N = 142) received 900 mg of PSE or placebo (PLA) daily for 90 days. ... wherein PSE improved sustained attention vs PLA at day 30 (PSE: 33.3 ± 0.54 vs PLA: 31.2 ± 0.98; P = .001) and day 90 (PSE: 34.0 ± 0.44 vs PLA: 32.7 ± 0.75; P = .007). ... No significant differences were observed in mood, sleep, or quality of life.
   Nutr Res, 2019 · checked 2026-09-30
5. spmn-daily-r1-05 · RCT
   Treatment B was associated with a significant reduction in LDL-C (∼31.5 mg/dL;-22%) and TC (∼19.5 mg/dL; -9%), along with an increase in high-density lipoprotein cholesterol (HDL-C).
   Nutr Metab Cardiovasc Dis, 2026 · checked 2026-09-30
6. spmn-daily-r1-07 · case series (patch testing)
   The TCS produced 17 positive reactions in 13 patients, the most frequent being to spearmint oil. ... The diagnosis of TACC was confirmed in 15/54 patients.
   Contact Dermatitis, 2000 · checked 2026-09-30
7. spmn-daily-r1-08 · agency opinion
   The EFSA Compendium of botanicals reports as substances of potential concern for human and animal health the occurrence of (+)‐pulegone (72.1%), 1,8‐cineole (1%–7%), carvone (59%–77%), d,l‐isomenthone (2.6%–32%), dihydrocarvone (1%–4%), menthone (14%–15.6%), myrcene (2.1%) in the essential oil from the aerial parts of M. spicata.
   EFSA FEEDAP Panel, EFSA Journal 2025, spearmint oil feed additive · checked 2026-09-30
8. spmn-daily-r1-04 · RCT
   Forty two volunteers were randomized to take spearmint tea twice a day for a 1 month period and compared with a placebo herbal tea. ... Free and total testosterone levels were significantly reduced over the 30 day period in the spearmint tea group (p < 0.05). ... There was, however, no significant reduction in the objective Ferriman-Galwey ratings of hirsutism between the two trial groups over the trial duration (p = 0.12).
   Phytotherapy Research, 2010 · checked 2026-09-30
9. spmn-daily-r1-01 · RCT
   Quality of working memory and spatial working memory accuracy improved after supplementation with 900 mg/day spearmint extract by 15% (p = 0.0469) and 9% (p = 0.0456), respectively, versus placebo.
   J Altern Complement Med, 2018 · checked 2026-09-30
10. spmn-daily-r1-09 · systematic review
    Mentha did not generated a positive effect on nausea and vomiting.
    J Obstet Gynaecol, 2020 · checked 2026-09-30