Greek Mountain Tea is the dried stems, leaves and flowers of Sideritis plants, mainly Sideritis scardica, brewed in Greece as tsai tou vounou, which simply means "mountain tea". The European Medicines Agency recognizes it as a traditional herbal tea for relief of cough with a cold and mild digestive discomfort, based on long use rather than clinical trials. Its main compounds are phenylethanoid glycosides such as verbascoside, and flavonoids. A few small human studies of extracts have looked at attention and mood, with mixed results.
What Sideritis is
Sideritis is a genus of herbs in the mint family (Lamiaceae). Sideritis scardica grows only on the Balkan Peninsula, which includes Greece, and is one of the best-known species (Todorova and Trendafilova, 2014). In English the herb is sometimes called ironwort.
In Greece, the dried herb is brewed as a tea. Several related species are used the same way, so "mountain tea" can mean more than one plant. The EMA monograph described below covers four of them.
What's in it
Like olives, Sideritis is rich in phenolic compounds. A 2014 review lists flavonoids, phenylethanoid glycosides, diterpenes and an essential oil among its constituents (Todorova and Trendafilova, 2014).
- Phenylethanoid glycosides. The best known is verbascoside, also called acteoside. A 2025 analysis of S. scardica from four countries found verbascoside was the main compound in every sample (Walasek-Janusz et al., 2025). Part of the verbascoside molecule is built from hydroxytyrosol, the olive compound described on our hydroxytyrosol page.
- Flavonoids. These include glycosides of apigenin, luteolin and related compounds.
- Phenolic acids, such as caffeoylquinic acids.
The amounts vary a lot. The same 2025 study found that composition depended on where the plant was grown, and the 2014 review called for standardized extracts for this reason. For context, the extract used in the largest human trial was reported to contain 6.25% total phenolics, including 1.2% flavonoids, 0.5% caffeoylquinic acids and 0.4% acteoside (Wightman et al., 2018). For background on how these compound families work, see the science of polyphenols.
What the EMA monograph says
In 2016 the EMA's Committee on Herbal Medicinal Products (HMPC) adopted a monograph covering four species: S. scardica, S. clandestina, S. raeseri and S. syriaca. It allows two uses, both as traditional herbal medicinal products (EMA HMPC, 2016):
- relief of cough associated with a cold;
- relief of mild gastrointestinal discomfort.
"Traditional use" has a specific meaning. The herb has been used this way for at least 30 years, including 15 in the EU, and its effectiveness is considered plausible. The EMA states that there is not enough evidence from clinical trials. Its public summary notes the lack of clinical studies on ironwort.
The monograph covers only the cut, dried herb taken as tea: 2 to 4 g in 150 to 200 mL of water, two to three times a day, up to 12 g a day, for adults. It does not cover extracts or capsules. A periodic review in 2023 checked newer studies and safety databases and found nothing that required a change (EMA HMPC, 2023).
What the human research shows
Human research on Sideritis is thin. The main studies tested extracts, not tea.
- Attention and mood in older adults. In a double-blind, placebo-controlled trial, 155 healthy adults aged 50 to 70 took 475 mg or 950 mg of a S. scardica extract, 240 mg of ginkgo extract or a placebo for 28 days. Compared with placebo, the higher dose led to fewer false alarms on one attention task and lower state anxiety at day 28. Both doses increased oxygenated blood in the front of the brain during tasks on day 1, but not on day 28. The study measured many outcomes, and differences were seen on only some of them (Wightman et al., 2018). The extract maker sponsored the study, and three authors were its employees.
- Thinking under stress. In a six-week pilot study, 64 healthy adults took a supplement containing Sideritis extract and B vitamins. The authors reported faster reaction times on some tasks and better Trail-Making Test scores (Behrendt et al., 2016). Because the product also contained B vitamins, the effect of Sideritis alone cannot be separated.
- Blood pressure and fitness markers. In a four-week placebo-controlled trial, 28 healthy adults took 1,500 mg a day of a Sideritis extract. Systolic blood pressure fell by 10.8 mmHg from baseline in the extract group, and blood markers of antioxidant status changed (Papanikolaou et al., 2024). The trial was very small, and the results need repeating.
Animal and lab studies. Much of the remaining research is in animals or cells. Mouse studies have reported better performance on memory tasks (Hofrichter et al., 2016), and a study in worms looked at the clumping of amyloid protein (Heiner et al., 2018). These are early-stage findings and do not show effects in people.
How Phenolia uses it
Phenolia Daily is a dietary supplement. Its ingredients are high-phenolic olive oil (powdered), olive leaf extract and Greek Mountain Tea (Sideritis scardica), all extracted in Greece. The capsule shell is hydroxypropyl methylcellulose (plant-based). The other ingredients are microcrystalline cellulose, magnesium stearate, silicon dioxide and arabic gum. Read about the olive leaf ingredient in our guide to olive leaf extract.
The serving is 2 capsules a day with a meal, and a box holds 60 capsules (30 servings). Each capsule provides 6 mg of polyphenols, or 12 mg per 2-capsule serving, calculated from the extract's certificate of analysis. That is about what 1.5 tablespoons (20 g) of a 600 mg/kg oil contains.
The label lists the blend. The polyphenol total is the verified figure; we do not publish a separate amount for the Sideritis extract. The human studies above used 475 mg to 1,500 mg of extract a day, and the EMA monograph covers 2 to 12 g of dried herb as tea. Their results cannot be transferred to Phenolia.
Phenolia Recovery is the same base plus Greek beetroot extract, with 12 mg olive polyphenols per serving. Our article on beetroot nitrates and olive polyphenols explains that addition.
Phenolia is made by Doctors Labs in Greece, a GMP facility licensed by Greece's National Organization for Medicines (EOF), ISO 22000:2018. PharmaGnose S.A. (Greece) makes the extracts and certifies the extract lots, and final packaging is in Bettendorf, Iowa. Heavy metals and pesticides were tested on the capsule powder in August 2026. Finished-capsule HPLC testing and banned-substance screening are under way. See the full list of what's in Phenolia.
Safety and who should check with a doctor
The EMA monograph lists no known side effects, no reported interactions and no reported cases of overdose. Its 2023 review found no reports in the EU's EudraVigilance database. People who are allergic to plants in the mint family (Lamiaceae) should not use it. Use in pregnancy and breastfeeding is not recommended because safety has not been established, and use under age 18 has not been established (EMA HMPC, 2016).
The data are limited. The monograph notes that tests on reproductive toxicity and carcinogenicity have not been performed, and it does not cover extracts. A rat study of one S. scardica extract found no signs of toxicity at the doses tested and no mutagenic effect in lab tests (Feistel et al., 2018). The human trials were small and lasted four to six weeks.
Check with your doctor before taking a Sideritis supplement if you are pregnant or breastfeeding, take prescription medicine, or have a long-term health condition. One small trial reported lower blood pressure, so this includes people taking blood pressure medicine. If a cough lasts more than a week or stomach symptoms last more than two weeks, see a doctor rather than relying on tea.
Frequently asked questions
What does tsai tou vounou mean?
It is Greek for "mountain tea". It refers to tea made from the dried stems, leaves and flowers of Sideritis plants.
What is Greek Mountain Tea traditionally used for?
The European Medicines Agency recognizes it as a traditional herbal tea for relief of cough with a cold and mild digestive discomfort. This is based on long use, not on clinical trials.
Is Greek Mountain Tea a true tea?
No. Sideritis is a herb in the mint family. Black and green tea come from a different plant, Camellia sinensis.
Do the Sideritis studies apply to Phenolia?
No. The human studies used 475 mg to 1,500 mg of extract a day. Phenolia does not publish a separate Sideritis amount, so the study results cannot be transferred to it.
Sources
- European Medicines Agency, Committee on Herbal Medicinal Products. European Union herbal monograph on Sideritis scardica Griseb.; Sideritis clandestina (Bory & Chaub.) Hayek; Sideritis raeseri Boiss. & Heldr.; Sideritis syriaca L., herba (EMA/HMPC/39453/2015). 2016. ema.europa.eu
- European Medicines Agency, Committee on Herbal Medicinal Products. Addendum to assessment report on Sideritis herba (EMA/HMPC/320997/2023). 2023. ema.europa.eu
- Todorova M, Trendafilova A. Sideritis scardica Griseb., an endemic species of Balkan peninsula: traditional uses, cultivation, chemical composition, biological activity. Journal of Ethnopharmacology. 2014;152:256-265. doi.org/10.1016/j.jep.2014.01.022
- Walasek-Janusz M, Wojtanowski KK, Papliński R, et al. Polyphenol profile and biological activity of the extracts from Sideritis scardica Griseb. (Lamiaceae) herb. Pharmaceuticals. 2025;18:1121. doi.org/10.3390/ph18081121
- Wightman EL, Jackson PA, Khan J, et al. The acute and chronic cognitive and cerebral blood flow effects of a Sideritis scardica (Greek mountain tea) extract: a double blind, randomized, placebo controlled, parallel groups study in healthy humans. Nutrients. 2018;10:955. doi.org/10.3390/nu10080955
- Behrendt I, Schneider I, Schuchardt JP, et al. Effect of an herbal extract of Sideritis scardica and B-vitamins on cognitive performance under stress: a pilot study. International Journal of Phytomedicine. 2016;8:95-103. ijp.arjournals.org
- Papanikolaou K, Kouloridas K, Rosvoglou A, et al. Characterization of the Sideritis scardica extract SidTea+ and its effect on physiological profile, metabolic health and redox biomarkers in healthy adults: a randomized, double-blind, placebo-controlled study. Molecules. 2024;29:1113. doi.org/10.3390/molecules29051113
- Hofrichter J, Krohn M, Schumacher T, et al. Sideritis spp. extracts enhance memory and learning in Alzheimer's β-amyloidosis mouse models and aged C57Bl/6 mice. Journal of Alzheimer's Disease. 2016;53:967-980. doi.org/10.3233/JAD-160301
- Heiner F, Feistel B, Wink M. Sideritis scardica extracts inhibit aggregation and toxicity of amyloid-β in Caenorhabditis elegans used as a model for Alzheimer's disease. PeerJ. 2018;6:e4683. doi.org/10.7717/peerj.4683
- Feistel B, Wegener T, Rzymski P, Pischel I. Assessment of the acute and subchronic toxicity and mutagenicity of Sideritis scardica Griseb. extracts. Toxins. 2018;10:258. doi.org/10.3390/toxins10070258
