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Limited evidenceBrain & cognition

Rosemary Extract

Rosemary is an excellent food antioxidant with a famous but thin cognitive literature: the one controlled dose-ranging trial found 750 mg of rosemary powder helped memory speed slightly while 6000 mg made it worse. Treat the nootropic marketing as unproven.

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What the science says

  • Improves memory and alertness Limited evidence

    In a crossover trial of 28 older adults, a single 750 mg dose of dried rosemary leaf powder improved speed of memory versus placebo, while 6000 mg significantly impaired it — an inverted-U dose response from a very small study. Most other 'rosemary and memory' headlines come from aroma-inhalation experiments correlating blood 1,8-cineole with test performance, which say nothing about swallowing a capsule.

  • Neuroprotective antioxidant effects Limited evidence

    Carnosic acid and rosmarinic acid activate Nrf2 signalling and protect neurons from oxidative and excitotoxic damage in cell and rodent models, and carnosic acid crosses the blood-brain barrier in animals. No human trial has shown a clinical neuroprotective outcome such as slowed cognitive decline.

  • Anti-inflammatory and joint benefit Limited evidence

    Rosemary extracts inhibit COX-2 and inflammatory cytokines in vitro, and rosemary appears as a minor ingredient in some multi-herb joint formulas. There is no adequately powered standalone randomized trial of rosemary extract for arthritis pain or inflammatory markers in humans.

  • Hair growth for androgenetic alopecia Limited evidence

    A single 2015 trial reported topical rosemary oil matched 2% minoxidil for hair count at 6 months, but it was small, unblinded to the comparator's feel, and has not been replicated; oral rosemary extract has no hair data at all. This is a topical claim being sold on supplement labels.

Dosage & safety

Studied doseThe only controlled oral dosing data are single doses of 750 mg dried leaf powder (beneficial) up to 6000 mg (detrimental). Commercial capsules typically supply 250-500 mg of extract standardized to 5-20% carnosic acid; no chronic-dosing trial supports any specific regimen. Rosemary extract used as a food preservative (E392) is present in far smaller amounts.
SafetyCulinary and normal supplement amounts are well tolerated. Concentrated rosemary essential oil should never be swallowed — it contains camphor and has been associated with seizures and GI toxicity in overdose. High doses can cause nausea and gastric irritation. Rosemary may inhibit iron absorption from meals and has weak antiplatelet activity, so use caution with anticoagulants. Avoid medicinal doses in pregnancy (traditional emmenagogue) and in people with epilepsy. Not banned in sport.

How to take it

TimingTake it before the task — the only positive human data comes from single doses.
With food?With food; high doses cause nausea and gastric irritation on an empty stomach.
Worth knowingMore is not better: 6,000 mg impaired performance in the same experiment where 750 mg helped, and rosemary essential oil should never be swallowed.

Interactions

With medications

  • anticoagulants and antiplatelet drugs

    Rosemary has weak antiplatelet activity at medicinal doses. mention it to your prescriber and stop before surgery

With other supplements

  • iron supplements

    Rosemary polyphenols can inhibit iron absorption from a meal. separate by at least 2 hours

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

Frequently asked questions

Does rosemary improve memory?

Rosemary's memory evidence is thin (limited evidence): in a trial of 28 older adults, a single 750 mg dose of dried rosemary powder slightly improved memory speed, while 6000 mg made it worse. Most other rosemary-and-memory headlines come from aroma-inhalation experiments, which say nothing about swallowing a capsule.

Does rosemary oil or rosemary extract help hair growth?

A single 2015 trial found topical rosemary oil matched 2% minoxidil for hair count at 6 months, but it was small and has not been replicated (limited evidence). Oral rosemary extract has no hair data at all, so this is a topical claim being sold on supplement labels.

How much rosemary extract should I take?

The only controlled oral data for rosemary are single doses, with 750 mg of dried leaf powder helpful and 6000 mg detrimental; no chronic dosing trial supports any regimen. Commercial capsules typically supply 250-500 mg of extract, and rosemary essential oil should never be swallowed.

Does rosemary extract interact with blood thinners or iron?

Rosemary has weak antiplatelet activity at medicinal doses, so mention it to your prescriber if you take anticoagulants and stop before surgery. Rosemary polyphenols can also inhibit iron absorption, so separate it from iron supplements by at least 2 hours.

Scientific references

Where to buy

Swanson Vitamins, Rosemary Extract, Standardized, 500 mg, 60 Capsules

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