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Limited evidenceStress & mood

Holy Basil (Tulsi)

Small trials consistently report benefits for stress and blood glucose, but that consistency is itself a red flag: literally every published human study is favourable, most are small, short and industry-linked, and none are large or independently replicated.

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What the science says

  • General stress symptoms Limited evidence

    A 6-week double-blind RCT randomized 150 adults to 1200 mg/day of a standardized Ocimum tenuiflorum extract or placebo. Total self-rated stress symptom scores improved roughly 39% more than placebo, with specific gains in exhaustion, forgetfulness and recent-onset sleep problems. It is a single manufacturer-linked trial using self-rated outcomes.

  • Blood glucose and metabolic markers Limited evidence

    A systematic review of 24 human studies found reported reductions in fasting and post-prandial glucose and improvements in lipid profiles in people with type 2 diabetes or metabolic syndrome. The trials were small, short and often poorly reported, so effect sizes should not be taken at face value.

  • The uniformly positive literature is itself a warning sign Limited evidence

    The same review noted that all 24 identified human studies reported favourable clinical outcomes and none reported significant adverse events. A literature with zero negative trials is more consistent with publication bias and weak methods than with a uniformly effective herb.

Dosage & safety

Studied doseHuman trials used 300-2000 mg/day of leaf extract; the main stress trial used 1200 mg/day of standardized extract for 6 weeks, and glycaemic studies commonly used 1-2.5 g/day of leaf powder for 4-12 weeks. Preparations vary widely (aqueous extract, ethanolic extract, whole leaf powder) and are not interchangeable.
SafetyNo serious adverse events have been reported in trials, though follow-up rarely exceeds 12 weeks. Holy basil has hypoglycaemic and antiplatelet activity, so watch for additive effects with antidiabetic drugs and anticoagulants and stop before surgery. Animal studies report reversible anti-spermatogenic and anti-fertility effects at high doses in male rodents; relevance to humans is unknown but worth knowing if you are trying to conceive. Avoid in pregnancy, given traditional use as an emmenagogue and animal data suggesting anti-implantation effects. Not regulated as a medicine in most markets, so potency varies.

How to take it

TimingTiming does not matter.
With food?Take it with food to reduce mild GI upset.
Worth knowingAqueous extract, ethanolic extract and whole leaf powder are not interchangeable, so match the form to whichever trial you are relying on.

Interactions

With medications

  • insulin, sulfonylureas and other antidiabetic drugs

    Holy basil lowers blood glucose and the effects are additive. monitor your glucose when starting or changing dose

  • warfarin, DOACs and antiplatelet drugs

    Holy basil has antiplatelet activity that may add to bleeding risk. tell your prescriber and stop it before surgery

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does holy basil (tulsi) reduce stress?

The evidence is limited: one 6-week trial in 150 adults found 1200 mg/day of standardised holy basil extract improved self-rated stress scores about 39% more than placebo. It is a single manufacturer-linked trial using self-rated outcomes.

Does holy basil lower blood sugar?

A review of 24 small human studies reported lower fasting and post-meal glucose with holy basil in type 2 diabetes or metabolic syndrome, but the trials were short and often poorly reported. The evidence is limited, and the fact that every study was favourable suggests publication bias.

Is holy basil safe to take with medications?

Holy basil lowers blood glucose and has antiplatelet activity, so monitor glucose if you take diabetes medication and tell your prescriber if you take anticoagulants. Stop it before surgery, and avoid it in pregnancy.

How much holy basil should I take?

Holy basil trials used 300-2000 mg/day of leaf extract; the main stress trial used 1200 mg/day for 6 weeks. Aqueous extract, ethanolic extract and whole leaf powder are not interchangeable.

Scientific references

Where to buy

Frontier Co-op, Organic Holy Basil (Tulsi) Herb, 8 oz (226 g)

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