Benefits
After-meal fullness and digestive comfort
In 107 adults with postprandial fullness-type functional dyspepsia, 3 g of ground aniseed after each meal for 4 weeks lowered symptom severity scores more than cornstarch placebo, and the gap held at 12 weeks. It was one center, randomization left unequal groups (47 vs 60), and an independent evidence review rated its certainty low.
Bowel comfort with enteric-coated anise oil capsules
In a 3-arm trial of 120 adults with irritable bowel syndrome, 4 weeks of enteric-coated anise oil capsules left 75% symptom free, versus 35% on placebo and 52.5% on peppermint oil capsules. The capsule (AnisEncap) was formulated for the study, and the result has not been repeated by another group.
Hot flash frequency and severity after menopause
In 72 postmenopausal women, 330 mg capsules of an alcohol extract of aniseed three times daily for 4 weeks cut daily hot flashes from about 4.2 to 1.1, while the potato-starch placebo group stayed near 4.3 (between-group P < 0.001). The placebo group barely changed at all, and no hormone levels were measured.
Mood and menopausal symptom scores in midlife women
In 60 menopausal women in India, 4 g of aniseed a day for 8 weeks lowered depression, anxiety and stress scores more than placebo. Menopausal symptom index scores also improved with anise while the placebo group showed little change. This is one small trial, and no adverse effects were reported.
Premenstrual symptom intensity
In 67 college students with premenstrual syndrome, 110 mg aniseed capsules three times daily, taken for 10 days around each period for 2 cycles, lowered premenstrual symptom scores more than starch placebo (about 14 and 10 points lower after cycles 1 and 2). It was a single small trial.
Pumped breast milk volume in mothers of preterm babies
The EMA does not recommend anise while breastfeeding because its safety has not been established, so this result is not advice to use it. In one unblinded 7-day trial in 129 mothers of preterm babies, tea from 2 g aniseed plus 1 g black tea three times daily raised pumped milk volume more than black tea or no tea. Baby weight did not differ.
Traditional carminative and expectorant use in the EU
European Medicines Agency monographs accept aniseed tea and anise oil as traditional herbal medicines for mild spasmodic digestive complaints including bloating and gas, and as an expectorant for coughs with colds, for up to 2 weeks in adults (the tea also from age 12). This status rests on long-standing use, not on clinical trials.
Mechanism of action
Trans-anethole, the main aroma compound
Anise essential oil is mostly trans-anethole, which gives the licorice flavor. In human volunteers given 1 to 250 mg of labeled trans-anethole, most was excreted in urine, over 90% of it as 4-methoxyhippuric acid, and dose size did not change how it was handled.
Estrogen-like activity at high concentrations (lab and animal work)
The EMA notes estrogenic and antifertility activity of trans-anethole at high concentrations in test tubes and lab animals, and judges it not relevant at recommended short-term doses in adults. None of the human anise trials measured hormone levels, so any hormonal role in hot flash results is untested.
Stomach lining protection in rats (animal work)
In rats, an aniseed water suspension given by stomach tube reduced stomach lesions caused by ethanol, strong salt and alkali solutions and indomethacin, and raised stomach mucus and sulfhydryl levels. When injected it lowered acid secretion. These are animal findings only.
Clinical trials
Single-center, double-blind, randomized, placebo-controlled trial in Isfahan, Iran; 3 g anise powder or cornstarch after each meal (3 times daily) for 4 weeks, follow-up to week 12. Seeds were donated by an Iranian herbal company; the paper reports no other funding. (Ghoshegir et al. 2015, J Res Med Sci)
107 adults aged 18 to 65 with postprandial distress syndrome (functional dyspepsia, Rome III); simple randomization left 47 in the anise group and 60 on placebo; 4 per group withdrew.
Functional dyspepsia severity scores fell from 10.6 to 2.44 at week 4 with anise and rose from 10.96 to 13.05 on placebo (P = 0.0001), with the gap held at week 12 (1.08 vs 13.30). A companion paper on the same patients reported better SF-36 quality of life at week 12. The abstract's conclusion names the wrong condition, an evident editing error; the measured outcomes were digestive symptoms. A Cochrane review rated this single trial low certainty.
Three-arm, double-blind, randomized trial in Shiraz, Iran, comparing enteric-coated anise oil capsules (AnisEncap) formulated for the study with placebo and peppermint oil capsules (Colpermin), 3 capsules a day for 4 weeks plus 2 weeks of follow-up. (Mosaffa-Jahromi et al. 2016, J Ethnopharmacol)
120 adults with irritable bowel syndrome, divided into three groups.
By intention to treat, 75% on anise oil, 35% on placebo and 52.5% on peppermint oil were free of symptoms (P < 0.001), and quality of life scores favored anise oil at 4 and 6 weeks. The authors report a number needed to treat of 4. Not yet repeated by an independent group.
Double-blind, randomized, placebo-controlled trial at health centers in Qazvin Province, Iran; 330 mg capsules of an ethanol extract of aniseed blended with potato starch, or potato starch alone, 3 times daily for 4 weeks, then 4 weeks of follow-up; the authors thank the research office of Shahid Beheshti University of Medical Sciences for facilities, and no other funding is stated. (Nahidi et al. 2012, Iran J Pharm Res)
72 postmenopausal women aged 45 to 60 with hot flashes, 36 per group.
Daily hot flash frequency fell from 4.21 to 1.10 by week 4 with anise and was 4.38 on placebo (P < 0.001); severity scores fell from 56.21 to 14.44 versus 56.25 on placebo. Effects partly persisted 4 weeks after stopping (1.60 vs 4.22). The placebo group showed almost no change, and hormone levels were not measured.
Double-blind, randomized, placebo-controlled trial in Iran; 110 mg aniseed capsules or starch 3 times daily from 7 days before to 3 days after menstruation starts, for 2 cycles. (Farahmand et al. 2020, J Complement Integr Med)
67 college students aged 18 to 35 with premenstrual syndrome.
Premenstrual Symptoms Screening Tool scores were lower with anise than placebo by about 13.9 points after the first cycle and 9.8 points after the second (both P < 0.001). Small and short; the abstract does not report adverse events.
Double-blind, randomized, placebo-controlled add-on trial in Shiraz, Iran, with 1:4 allocation; 25 g sachets of aniseed and rock-candy powder (2:1) or a flour and sugar placebo, twice daily for 2 weeks. The sachet size was raised from 5 g to 25 g after registration, before recruitment. No financial support was received. (Mosaffa-Jahromi et al. 2024, Front Pharmacol)
225 non-hospitalized adults with acute COVID-19 and at least one digestive symptom (45 aniseed, 180 placebo).
More people on aniseed reported improvement in abdominal pain, poor appetite and diarrhea, but not in nausea or vomiting or in bloating, where the differences were not significant. Mild to moderate adverse events occurred in 2 aniseed and 3 placebo participants. The aniseed group started with worse nausea and bloating scores, the powders were not matched for taste, and there was no correction for testing several symptoms.
Randomized, unblinded controlled trial in Tehran, Iran; tea from 2 g aniseed plus 1 g black tea, or 3 g black tea placebo, 3 times daily for 7 days, or no tea; funded by Iran University of Medical Sciences as part of a master's thesis. (Khalili et al. 2023, BMC Complement Med Ther)
129 mothers of preterm babies analyzed (45 anise tea, 45 black tea, 39 no tea).
Pumped milk volume was higher with anise tea than with black tea or no tea on days 3 to 7 (day 7: about 268 vs 170 vs 155 ml, P < 0.001); on day 2 there was no difference. Baby weight did not differ between groups. No side effects were reported. The EMA does not recommend anise during breastfeeding because its safety has not been established.