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Ayurveda

TulsiOcimum tenuiflorum (also written Ocimum sanctum)

Holy basil leaf, used in Ayurveda for indigestion and diarrhea. A review of human trials found 24 studies in 1,111 people, none built around a gut outcome.

Botanical name
Ocimum tenuiflorum (also written Ocimum sanctum)
Part used
leaf (the root and seed are also used in Ayurvedic texts)
Also called
Sanskrit Tulasi, Surasa; Hindi Tulsi; Holy basil, Krishna tulsi (the dark-leaved type)
Used in
Ayurveda
Taken for
Indigestion, Nausea, Loose stools and diarrhea
Sold as
tea, capsules, tablets, powder, tincture, fresh

What is meant by tulsi

Tulsi is a leafy, strongly aromatic member of the mint family (Lamiaceae) that is grown across India and is kept as a household plant. It is the plant sold in the West as holy basil, and it is a different species from the sweet basil of the kitchen. The leaf is the part most often used; Ayurvedic college monographs also list the root and the seed.

It is taken fresh as a juice or chewed, steeped as a tea, dried and powdered, or made into aqueous and alcohol extracts that are sold as capsules, tablets and tinctures. The trials reviewed below used leaf extracts, whole-plant extracts, fresh leaf and a tincture. Dark-leaved Krishna tulsi and pale-leaved Vana tulsi are both sold, and a 2014 review reports that Krishna tulsi has the higher phenolic content. The same review notes that some products in Europe have been found to contain sweet basil (Ocimum basilicum) in place of tulsi, so the species named on a label matters.

In the traditions

Ayurveda (about Ayurveda)

Ayurvedic college monographs describe tulsi in the tradition’s own four-part vocabulary: its taste (rasa) is pungent and bitter, its physical qualities (guna) are light and dry, its potency (virya), meaning whether it is felt as heating or cooling, is heating, and its after-digestion effect (vipaka) is pungent. The tradition says it calms kapha and vata, two of the three governing principles (doshas) it uses to describe how the body works, and that it kindles digestion (dipana) and kills worms (krimighna).

For the gut, the same monographs list loss of appetite, abdominal pain and intestinal worms. A seed preparation soaked in water and cooked into a milk pudding is given for dysentery. A 2014 review adds indigestion, vomiting, diarrhea and dysentery to the conditions for which tulsi is traditionally used. The monograph’s own indication list, in Sanskrit, begins with hiccups, cough, breathlessness, poisoning, joint pain, worms and irregular fever.

What the plant contains

The aroma of tulsi comes mainly from eugenol, the same compound that gives clove its smell, and a 2014 review links the plant’s anti-inflammatory effects in the laboratory to its eugenol and linoleic acid content. Phenolic compounds are credited with antioxidant effects. Ayurvedic college monographs also list methyl chavicol, limonene and caryophyllene among the volatile oils. For the gut, the laboratory finding most cited is animal work: tulsi has shown anti-ulcer and ulcer-healing activity in rodent models using aspirin, indomethacin, alcohol, histamine and stress, with proposed actions that include less acid-pepsin secretion and more mucin. These are animal findings and say nothing about doses or effects in people.

What has been tested in people

The main human source is a 2017 systematic review by Jamshidi and Cohen. It found 24 clinical studies with 1,111 participants aged 10 to 80, lasting 2 to 13 weeks, and sorted their results into metabolic disorders, cardiovascular disease, immunity and neurocognition. Gut outcomes are not one of those groups. The only digestive effect the review reports is nausea: in one study of 16 obese adults taking 250 mg leaf-extract capsules twice daily before meals, occasional, transient mild nausea was noted as a side effect. We could not find, in that review or in a PubMed search, a trial of tulsi for indigestion, diarrhea, constipation or irritable bowel syndrome.

The quality of the evidence is limited by the review’s own account. Its results section counts 3 of the 24 studies as high quality, while its discussion counts 7; the authors write that tulsi’s effects may have been overestimated because of weak trial design, and that there is insufficient evidence for any specific tulsi formulation. Most studies were small and Indian, and doses, forms and cultivars varied.

So the traditional gut uses (indigestion, diarrhea, dysentery, worms) rest on Ayurvedic texts and on rodent studies, not on human trials. What has not been tested in people, as far as we could find, is tulsi leaf or tea against any digestive complaint.

StudyDoseWhat it found
Systematic review of 24 human studies, 1,111 participants (metabolic, cardiovascular, immune and cognitive outcomes) PMID 28400848Aqueous leaf extract 300 to 3,000 mg, one to three times daily; 2 to 13 weeksNo gut outcome among the endpoints; 15 of 24 studies reported no adverse events and 8 did not report on them
One study inside the review: 16 obese adults PMID 28400848250 mg leaf-extract capsule twice daily before mealsOccasional, transient mild nausea reported as a side effect
Narrative review of tulsi in traditional and laboratory literature PMID 25624701Not applicable (review of traditional use and animal models)Anti-ulcer and ulcer-healing activity in animal models; no human gut trial described

Doses used in trials and traditional preparations

Doses in the human studies depended on the preparation: aqueous leaf extract 300 to 3,000 mg one to three times a day, ethanolic leaf extract 300 to 1,000 mg once or twice a day, whole-plant aqueous extract 6 to 14 g a day, fresh leaf 10 g a day, and a tincture of 30 drops a day split into three doses. No tea trial was among the 24; tea appears in the review only as a traditional preparation.

Ayurvedic college monographs give traditional amounts of 10 to 20 ml of fresh juice, 50 to 100 ml of a root decoction and 3 to 6 g of seed.

Treat these figures as a record of what was studied. Whether any amount of tulsi suits a particular person is a question for a clinician or pharmacist who knows their history.

Safety

In the 2017 review, 15 of the 24 studies reported no adverse events and 8 did not say; the one digestive complaint was transient mild nausea. The authors conclude that daily ingestion appears safe but add that the longest study ran 13 weeks, so long-term effects are unknown. The review contains no statement about pregnancy or breastfeeding, so we have no trial data to report for either.

Product quality is the other published concern. A 2014 review notes sweet basil substituted for tulsi in some European products and higher levels of toxic elements in leaves grown in polluted areas. Separately, JAMA studies of Ayurvedic medicines sold in the United States found lead, mercury or arsenic in 14 of 70 items bought in Boston-area stores and in 20.7% of 193 preparations ordered online; those products were mainly mineral-and-metal preparations and mixed formulas, not tulsi leaf as a class.

Drug interactions

We did not find a published drug-interaction study of tulsi, and the 2017 review does not report one. Its favorable findings were concentrated in metabolic outcomes such as blood sugar and lipids, so overlap with glucose-lowering and lipid-lowering medicines is a theoretical question rather than a documented one. No mechanism for a specific drug interaction is described in either review we read.

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Questions people ask

Is there human evidence that tulsi helps digestion?

We could not find a trial built around a digestive outcome. The 2017 review of 24 human studies covered metabolic, heart, immune and mental outcomes, and its only gut-related note was occasional mild nausea in one study. The digestive uses come from Ayurvedic texts and animal studies.

Is tulsi the same as basil from the grocery store?

No. Tulsi is Ocimum tenuiflorum, while kitchen basil is usually Ocimum basilicum. A 2014 review reports that some European products labeled as tulsi contained sweet basil instead, so the Latin name on the label is worth checking.

What does Ayurveda say tulsi does for the gut?

College monographs classify tulsi as pungent, bitter and heating, and say it kindles digestion and kills worms. They list loss of appetite, abdominal pain and worms, and a seed preparation is given for dysentery. These are the tradition’s statements, not trial results.

How long has tulsi been tested in people?

The longest study in the 2017 review lasted 13 weeks, and most lasted less. The authors note that this leaves long-term effects unknown, and they rate only a minority of the 24 studies as high quality.

Which parts of the plant do the studies use?

Mostly leaf extracts, made with water or alcohol, plus whole-plant extracts, fresh leaf and a tincture. Doses ranged from 300 mg of extract to 14 g of whole-plant extract a day, so results from one preparation do not carry over to another.

Sources