PubMed lists 1,069 records on holy basil, yet only 4 of its 21 tagged clinical trials gave people the herb alone to swallow. The rest include mouthwash, toothpaste, eye drops, hens and cows.
That is worth knowing before you buy anything, so this page counts what the human evidence does show and what it does not.
Quick Answer: What Is Holy Basil?
Holy basil, or tulsi, is Ocimum tenuiflorum, a different species from the sweet basil used in cooking. It is sold as an adaptogen for stress. PubMed holds 1,069 records on it, and 4 of the 21 tagged as trials gave people tulsi alone by mouth. A 2017 systematic review found 24 small human studies, all favourable.
Key Takeaways
- Holy basil is Ocimum tenuiflorum, 1 species apart from kitchen sweet basil.
- PubMed lists 1,069 records, and 21 of them are tagged as trials.
- Only 4 of those 21 gave people tulsi alone to swallow.
- The 2017 review found 24 human studies, all favourable, none alarming.
- Fertility cautions come from 23 records, and 0 are human trials.
Related Products
Holy Basil Is Not Kitchen Basil
Holy basil is Ocimum tenuiflorum, also listed as Ocimum sanctum. The sweet basil in pesto and the Thai basil in many takeaways are Ocimum basilicum, a different species with different chemistry. Tulsi is sacred in Hindu homes and central to Ayurveda, and it is the plant every study on this page used.
- Holy basil: Ocimum tenuiflorum, with serrated leaves and hairy, often purple-tinged stems.
- Two common types: Rama tulsi with green leaves, Krishna tulsi with purple ones.
- Sweet basil: Ocimum basilicum, with large smooth leaves, used in cooking.
- Taste: Holy basil is peppery and clove-like rather than sweet.
- Our capsule: 1,000 mg of holy basil leaf and stem.
Even the holy basil label is not always one plant. A 2026 chemistry study compared Ocimum tenuiflorum with Ocimum gratissimum, both discussed under the same name, and found clear differences between them.[1]Species-Specific Phytometabolite Composition of Ocimum (Holy Basil) Inflorescences Underlies Differential Biological Activities — Chemistry and Biodiversity (2026) View source Most people buy tulsi for stress, and what the stress trials measured deserves its own page.
The Size of the Evidence
Holy basil is often described as well researched. There is a lot of research, but very little of it involves a person swallowing the herb, and that distinction explains almost every claim you will read about it.
| What PubMed holds on holy basil (tulsi) | Count |
|---|---|
| Records mentioning holy basil or tulsi | 1,069 |
| Records tagged as human | 238 |
| Records on animals only | 247 |
| Records tagged as clinical trials | 21 |
| Of those, tulsi alone swallowed by people | 4 |
| Records on fertility, sperm or pregnancy | 23 |
| Human trials on fertility or pregnancy | 0 |
The best single summary is a 2017 systematic review of human studies in which people ingested tulsi. It found 24 studies covering metabolic, cardiovascular, immune and cognitive outcomes, all favourable, and none reporting a significant adverse event.[2]The Clinical Efficacy and Safety of Tulsi in Humans: A Systematic Review of the Literature — Evidence-Based Complementary and Alternative Medicine (2017) View source
That sounds conclusive and it is not. The same review asked for further studies to clarify the dose, the dose form and who is most likely to benefit.
What the 21 Trial Records Actually Are
We read every record PubMed tags as a clinical trial on holy basil. Most are not what a supplement buyer would picture, and the count below is the part no competitor page prints.
| What was tested | Records |
|---|---|
| Tulsi alone, swallowed by people | 4 |
| Multi-herb formulas that include tulsi | 3 |
| Mouthwash, toothpaste, dental fillings, eye drops, skin cream | 10 |
| Not a human trial of the herb (teeth soaked in tea, a survey, hens, cows) | 4 |
The tag misses in the other direction too. The 2 best stress trials are not tagged as trials at all, and 1 of them is filed as a case report. That is why a raw count on its own misleads, and why each trial on this page is named.
What the Human Trials Found
Taken together, the human evidence for swallowed tulsi is a handful of small, short trials, one of which produced the blood sugar signal. Each is worth knowing by its dose and length, because no two used the same preparation.
- Stress, 2012: 150 people, 1,200 mg of an extract daily, 6 weeks.[3]Efficacy of an Extract of Ocimum tenuiflorum (OciBest) in the Management of General Stress: A Double-Blind, Placebo-Controlled Study — Evidence-Based Complementary and Alternative Medicine (2012) View source
- Stress, 2022: 100 adults, 125 mg of an extract twice daily, 8 weeks.
- Attention, 2015: 300 mg of an extract daily, 30 days.
- Blood sugar, 1996: holy basil leaves in type 2 diabetes.
The 2012 trial reported 39% more improvement in self-rated stress symptoms than placebo. The 2022 trial found lower perceived stress and lower hair cortisol after 8 weeks.[4]A randomized, double-blind, placebo-controlled trial investigating the effects of an Ocimum tenuiflorum (Holy Basil) extract on stress, mood, and sleep in adults experiencing stress — Frontiers in Nutrition (2022) View source
The 1996 trial found fasting glucose 17.6% lower during the holy basil period than on placebo leaves.[5]Randomized placebo-controlled, single blind trial of holy basil leaves in patients with noninsulin-dependent diabetes mellitus — International Journal of Clinical Pharmacology and Therapeutics (1996) View source
Where the Real Cautions Sit
Short human trials report holy basil as well tolerated. The cautions that matter come from how it interacts with medicines and from animal studies nobody has repeated in people, and together they decide who should avoid it.
- Blood sugar medicine: effects could add up, based on the 1996 trial.
- Fertility: lower sperm counts in rats and rabbits, never tested in people.
- Pregnancy: 0 human trials, so the only sensible answer is to avoid it.
- Thyroid: 1 mouse study found lower thyroxine after 15 days.
A 2002 rat study found lower sperm counts that recovered 2 weeks after treatment stopped.[6]Reversible anti-fertility effect of benzene extract of Ocimum sanctum leaves on sperm parameters and fructose content in rats — Journal of Basic and Clinical Physiology and Pharmacology (2002) View source Every caution on this list names the animal or the trial it came from.
Who Might Reasonably Try It
Holy basil is a mild, traditional herb with a small but consistently positive human literature. On those terms it is reasonable for some people and plainly wrong for others, and the difference is mostly about medicines and pregnancy.
- Reasonable: A healthy adult curious about everyday stress, for 8 weeks.
- Reasonable: Someone who likes tulsi tea and wants a measured form.
- Not reasonable: Anyone pregnant or trying to conceive.
- Not without advice: Anyone on glucose-lowering or thyroid medicine.
On those terms a 1000 mg holy basil capsule is a measured amount of a traditional herb, sold without a disease claim attached.
Speak to a Clinician Before Taking Holy Basil If
- You are pregnant, breastfeeding or trying to conceive, where the only data comes from animals
- You take insulin, a sulfonylurea, metformin or any other glucose-lowering medicine
- You have a thyroid condition or take thyroid medication
- You have surgery planned within the next 2 weeks
- You already take a blend that contains holy basil, so you would be doubling it
Frequently Asked Questions
What does holy basil do to the body? +
In small trials it was linked with lower self-rated stress and, in 1 trial from 1996, lower fasting blood sugar. Most other claims come from animal or laboratory work.
What organ is basil good for? +
No human trial shows holy basil targets 1 organ. The trials measured stress scores, blood sugar, reaction times and immune cells in blood, not a single organ.
Does holy basil give you energy? +
It contains no caffeine and 0 trials measured energy as a main outcome. The 2012 stress trial did report less frequent exhaustion on a self-rated symptom scale.
Does holy basil help with sleep? +
1 trial in 2022 found better self-rated insomnia scores after 8 weeks. Its authors said objective sleep measures are still needed before calling that proven.
What are the benefits of holy basil capsules? +
A capsule gives a fixed amount, 1,000 mg in ours, without the taste. Trials used extracts at other doses, so a capsule is a measured amount rather than a trial replica.
Is holy basil the same as regular basil? +
No. Holy basil is Ocimum tenuiflorum and sweet basil is Ocimum basilicum, 2 different species with different chemistry and flavour.
Is tulsi the same as Thai basil? +
No. Thai basil is a variety of sweet basil. Thai cooks also use holy basil, in dishes such as pad kra pao, which is why the 2 names get confused.
What are Rama and Krishna tulsi? +
They are 2 types of the same plant told apart by leaf colour: Rama tulsi has green leaves and Krishna tulsi has purple-tinged ones.
Is holy basil an adaptogen? +
It is described as 1, meaning a herb said to help the body handle stress. Adaptogen is a traditional category, not a measured or regulated one.
How strong is the evidence for holy basil? +
Modest. A 2017 systematic review found 24 human studies, all favourable, but most were small and short, with doses and forms that differ.
Related Reading
Related Products
