Supplement
Tulsi (Holy Basil)
Adaptogen · Holy Basil, Heiliges Basilikum, Ocimum tenuiflorum, Ocimum sanctum, Tulasi, Krishna Tulsi, Thai basil
Tulsi, holy basil, is a sacred plant, a tea and a medicinal herb all at once in India. In Ayurveda it is regarded as an “elixir of life”, in the West as an adaptogen against stress. The body of studies is small but remarkably consistently positive, and the best study is fairly recent.
In short
Tulsi (Ocimum tenuiflorum, formerly Ocimum sanctum) is a basil from India that is taken as a tea and extract against stress. In a double-blind study with 100 stressed adults, perceived stress fell by 37 percent over 8 weeks under a tulsi extract and by 19 percent under placebo, and sleep improved subjectively. There are also small positive studies on blood sugar and immune markers. The catch: the studies are few, short and often of low quality, and the best ones come from an extract manufacturer. The herb may be marketed as a food in the EU and was well tolerated in studies.
What it is
Tulsi is a member of the mint family, botanically Ocimum tenuiflorum, in older literature Ocimum sanctum. It is related to our culinary basil. In India the plant is highly revered, drunk as a tea and used in Ayurvedic and Siddha medicine. A distinction is made between green tulsi and purple tulsi, also called Krishna tulsi.
The plant contains essential oil with eugenol and methyleugenol, as well as rosmarinic acid, ursolic acid, oleanolic acid and the flavonoid luteolin. Capsules usually contain an extract of the leaves or the whole herb, tea contains the dried herb. In the EU catalogue of novel foods, tulsi is also listed in German as Thai basil.
How it is supposed to work
Tulsi is considered an adaptogen, that is, a plant intended to help the body cope better with stress. The most likely point of action is the stress axis of hypothalamus, pituitary gland and adrenal gland. In cell experiments from 2023, a tulsi extract inhibited cortisol release and blocked the CRF1 receptor, to which the stress hormone CRH binds. Mice treated with it swam longer, and in rats the rise in the stress hormone corticosterone in the swim test did not occur.
In humans, it fits that in the 2022 study hair cortisol was lower after 8 weeks and the response to a laboratory stress test was dampened, with less salivary cortisol and lower blood pressure. How tulsi influences blood sugar or immune cells has not been clarified in humans; the pathways discussed come mainly from animal and cell experiments.
Tea, powder or extract
Tulsi has been studied in very different forms, and that makes comparisons difficult. The 2017 review found aqueous leaf extracts of 300 to 3000 mg per day, ethanolic leaf extracts of 300 to 1000 mg and whole-plant preparations of 6 to 14 g. The 2022 stress study used 250 mg of a standardized extract, the 1996 diabetes study 2.5 g of leaf powder. Which variety was used was not stated in most papers.
For you, this means: the results apply first of all to the preparation studied in each case. A tea from the supermarket is not automatically the same as a standardized extract from a study.
What is well supported
The best supported effect is on perceived stress. In a double-blind, placebo-controlled study with 100 adults, the stress score fell by 37 percent over 8 weeks under 250 mg of extract per day compared with 19 percent under placebo, and the insomnia scale by 48 compared with 27 percent. An older double-blind study with 150 participants found a 39 percent greater improvement in stress symptoms after 6 weeks than under placebo.
In addition, there are small studies on blood sugar and the immune system. A 2017 systematic review found 24 human studies with 1,111 participants, and all reported favorable results without serious side effects. This consistency is remarkable, even if it should be read with caution.
What the studies show
Stress and sleep, 2022
Australian study, double-blind, randomized and registered. 100 adults with persistent stress and sleep problems took 125 mg of a standardized tulsi extract or placebo twice daily for 8 weeks. The stress score fell by 37 versus 19 percent, so the primary endpoint was met. Hair cortisol and the response to a laboratory stress test turned out more favorably. Sleep efficiency measured with Fitbit, however, did not differ between the groups. The study was funded by the manufacturer of the extract.
Blood sugar in type 2 diabetes, 1996
40 people with type 2 diabetes each received 2.5 g of tulsi leaf powder or spinach powder as placebo for 5 weeks, single-blind in alternation. Under tulsi, fasting blood sugar fell by 21.0 mg/dl, corresponding to 17.6 percent, and the post-meal value by 7.3 percent. Cholesterol decreased slightly. A small, old study, but with a control condition.
Stress symptoms, 2012
150 people with general stress took a tulsi extract with 1200 mg of active ingredients per day or placebo for 6 weeks, double-blind. Forgetfulness, exhaustion and sleep problems decreased more markedly under tulsi; overall, the improvement was 1.6 times as large as under placebo. Measurement was by self-report only, and this extract also comes from the same manufacturer as the one from 2022.
Concentration, 2015
Healthy adults took 300 mg of ethanolic leaf extract or placebo for 30 days. In two concentration tests, the Sternberg and the Stroop test, reaction time and error rate improved more under tulsi than under placebo. A 2026 systematic review confirms faster responses for tulsi in a task on executive functions, but is based on only a few studies.
Immune markers in healthy people, 2011
24 healthy volunteers took 300 mg of ethanolic leaf extract or placebo for 4 weeks in a double-blind crossover study; 22 were analyzed. Under tulsi, the messenger substances interferon-gamma and interleukin-4 in stimulated blood rose, as did the proportion of T helper cells and natural killer cells. Whether fewer infections result from this was not measured.
Where the data stop
The body of studies is thin. Of the 24 studies in the review, only 8 had a placebo group, only 7 were rated as high quality, and almost all ran without double-blinding in India. The authors themselves write that the effect could be overestimated and that negative studies may never have been published. The two best stress studies use extracts from the same manufacturer. We did not find a meta-analysis that pools the effects.
Cortisol, immune cells and blood sugar are intermediate markers, not hard endpoints. Objectively measured sleep did not improve more than under placebo. The studies lasted 2 to 13 weeks; statements about long-term effects are not possible. For the promise that tulsi prolongs life, there are no human data.
Status, approval and legal
According to the EU Novel Food Catalogue, the aerial parts of Ocimum tenuiflorum are considered not novel; member states report their use in food supplements. Tulsi herb, tea and leaf extracts may therefore be marketed as food in Germany. Only the seeds are a novel food that has not yet been authorized. Health claims on stress, the immune system, the heart and the airways are on hold at EFSA and are not authorized, so advertising with them is not permitted. There is no doping relevance.
Safety
In the studies of up to 13 weeks, tulsi was well tolerated; no serious side effects were reported. In the 2022 study, 83 percent remained free of any complaints; digestive problems and headache occurred about as often under placebo. Caution when trying to conceive: in animal experiments, sperm count and motility fell in rabbits and rats, reversibly in rats, and hormones changed in female rats. Human data on this are lacking, so you should avoid tulsi during pregnancy and breastfeeding. Anyone taking blood-sugar-lowering drugs should keep an eye on their values. Purple tulsi contains more methyleugenol, which is considered potentially carcinogenic and may not be added to foods as a pure substance; in a laboratory study, 80 percent of 30 market samples were purple. The essential oil does not belong in capsules or drinks. There are no official upper limits.
BK-Score Thin human evidence
| Human evidence | 5 | |
|---|---|---|
| Mechanism | 4 | |
| Safety data | 5 | |
| Hype gap | 5 | |
| Track record of use | 7 |
Evidence 5, because there are several small placebo-controlled studies, one of which, a registered double-blind RCT with 100 adults, met its primary endpoint (stress −37 % versus −19 %, Lopresti 2022), but the overall picture is weak: 24 studies with 1,111 participants, only 8 with placebo and only 7 of high quality (Jamshidi 2017), no meta-analysis with pooled effects, and the two best stress studies come from the same manufacturer (Saxena 2012). Mechanism 4, because the dampening of the stress axis comes mainly from cell and animal experiments (CRF1 antagonism, less corticosterone; 2023), and in humans only surrogate markers such as hair and salivary cortisol or immune cells have been measured (Mondal 2011). Safety 5, because controlled data cover only 2 to 13 weeks, without serious events there (83 % without complaints, Lopresti 2022), while animal data on fertility (Sethi 2010) and the methyleugenol content of purple varieties (Balaji 2024) leave open questions. Hype 5, because the stress effect is advertised roughly at the level of the data, but the promise of an elixir of life has no human data behind it. Use 7, because tulsi has a long tradition in India as a tea and medicinal herb and is on the market in the EU as a non-novel food. Direction positive, because all controlled studies point in the same favorable direction, with a thin body of data overall.
The score rates the state of knowledge, not the substance. “Safety data 9” means well studied – not harmless.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)
Frequently asked questions about tulsi (holy basil)
What is tulsi?
Tulsi is holy basil, botanically Ocimum tenuiflorum. It comes from India, is used there as a tea and medicinal herb, and is considered an adaptogen in Ayurveda. In Europe it is available as tea, powder and extract in capsules.
Does tulsi help against stress?
The best study to date suggests so. In 100 stressed adults, the stress score fell by 37 percent over 8 weeks, compared with 19 percent under placebo. The study was double-blind but was funded by the manufacturer of the extract.
Does tulsi improve sleep?
Subjectively, yes: in the 2022 study, the score on an insomnia scale fell by 48 percent compared with 27 percent under placebo. Sleep efficiency measured by fitness tracker, however, did not differ between the groups.
Does tulsi lower blood sugar?
In small studies in type 2 diabetes, yes; in one controlled study, fasting blood sugar fell by 17.6 percent. The studies are small and mostly older. Anyone taking diabetes medication should add tulsi only after consulting a physician.
Is tulsi tea the same as capsules?
Both come from the same plant, but the studies mostly used extracts or leaf powder in a fixed amount. How much active substance a tea delivers depends on quantity and steeping time and has not been studied. Most of the stress data apply to standardized extracts.
Can tulsi be taken during pregnancy?
Better not. In animal experiments, tulsi affected sperm and reproductive hormones; there are no data from pregnancy. Restraint also makes sense when trying to conceive.
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Sources
- Jamshidi & Cohen, Evid Based Complement Alternat Med 2017
- Lopresti et al., Front Nutr 2022
- Saxena et al., Evid Based Complement Alternat Med 2012
- Agrawal et al., Int J Clin Pharmacol Ther 1996
- Mondal et al., J Ethnopharmacol 2011
- Sampath et al., Indian J Physiol Pharmacol 2015
- Sethi et al., Int J Ayurveda Res 2010
- Marsh et al., Int J Neuropsychopharmacol 2026
- Balaji & Parani, Mol Biol Rep 2024
- European Commission, Novel Food Catalogue: Ocimum tenuiflorum
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Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-09-30.