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Western herbalism

Olive leafOlea europaea

Leaf of the olive tree. We found no human gut trial; in a dish an extract inhibited H. pylori and Campylobacter at 0.31 to 0.78 percent by volume, and little else.

Botanical name
Olea europaea
Part used
leaf
Also called
Olive leaf extract, Oleuropein extract
Used in
Western herbalism
Taken for
Antimicrobial use
Sold as
capsules, tea, tincture, powder

What olive leaf is

Olive leaf comes from the same tree that gives olives and olive oil, Olea europaea, but it is a different product from the fruit or its oil. The leaves are picked in pruning, dried and either steeped whole as a tea or concentrated into a standardized extract. Extracts are usually measured by their oleuropein content, the bitter polyphenol that gives olive leaves their taste. The leaf powder and extract are sold in capsules, tablets and liquid tinctures.

Wainstein and colleagues note that olive tree leaves have been widely used in traditional remedies in European and Mediterranean countries as extracts, herbal teas and powder. The European Medicines Agency’s herbal committee has reviewed the dried leaf only for water elimination through the kidneys, not for the gut.

In gut supplements olive leaf appears in antimicrobial and cleanse blends, usually on the strength of laboratory antibacterial work rather than any trial of digestion. The human trials that exist are about blood pressure and blood sugar.

What the traditions use it for

Western herbalism

Olive leaf tea and powder belong to Mediterranean folk medicine, as Wainstein and colleagues note. The European Medicines Agency’s herbal committee (HMPC) concluded that the dried or fresh leaf can be used for water elimination through the kidneys in mild water retention, based on long-standing traditional use rather than clinical trials. No gut use was listed in that conclusion, and the committee noted that olive leaf medicines should only be used by adults.

The constituents

The signature constituent is oleuropein, a bitter polyphenol. In a laboratory fecal fermentation, Rocchetti and colleagues found that oleuropein in an olive leaf extract fell while hydroxytyrosol and other phenol metabolites rose, and the bacterial family Coriobacteriaceae (genus Collinsella) changed most. In a laboratory screen of a commercial extract against 122 microorganisms, Sudjana and colleagues found activity mainly against Campylobacter jejuni, Helicobacter pylori and Staphylococcus aureus. Vezza and colleagues linked a leaf extract’s metabolic effects in obese mice to less imbalance in their gut microbiota. These are test-tube and animal findings, not results from people.

The human evidence

We searched PubMed for randomized trials of olive leaf for constipation, diarrhea, bloating, parasites, bacterial overgrowth and Helicobacter pylori and found none. The gut case for olive leaf is therefore entirely laboratory-based.

Sudjana and colleagues tested a commercial extract against 122 microorganisms. It was most active against Campylobacter jejuni, Helicobacter pylori and Staphylococcus aureus, including methicillin-resistant strains, with minimum inhibitory concentrations as low as 0.31 to 0.78 percent by volume. For the other 79 organisms tested, most minimum inhibitory concentrations ranged from 6.25 to 50 percent, which the authors described as little activity. They concluded the extract was not broad-spectrum. Rocchetti and colleagues added the fecal fermentation work noted above. Neither study has a human trial behind it.

The human trials of olive leaf concern other conditions. Susalit and colleagues ran a double-blind, randomized, active-controlled study in people with stage-1 hypertension: an extract at 500 mg twice daily for 8 weeks lowered systolic pressure by 11.5 mmHg, against 13.7 mmHg for captopril, and the difference between groups was not significant. Wainstein and colleagues randomized 79 adults with type 2 diabetes to 500 mg of extract once daily or placebo for 14 weeks, and the extract group had lower HbA1c and fasting insulin. Both effects matter for a reader who takes blood pressure or diabetes medicines.

No study we found measures a gut symptom, an effect on H. pylori or Campylobacter infection in people, or long-term safety in the gut.

StudyDoseWhat it found
Double-blind randomized trial against captopril in stage-1 hypertension PMID 21036583500 mg extract twice daily for 8 weeksSystolic pressure fell 11.5 mmHg versus 13.7 mmHg on captopril; no significant difference between groups
Randomized placebo-controlled trial, 79 adults with type 2 diabetes PMID 22512698500 mg extract once daily for 14 weeksLower HbA1c and fasting plasma insulin than placebo
Laboratory screen of a commercial extract against 122 microorganisms (not a human trial) PMID 19135874Extract in agar and brothMost active against Campylobacter jejuni, H. pylori and S. aureus, MICs 0.31 to 0.78% (v/v); little activity against the other 79 organisms

Doses, in trials and in practice

The human trials above used standardized extract at 500 mg twice daily for 8 weeks (blood pressure) and 500 mg once daily for 14 weeks (blood sugar). No trial has tested a dose for a gut outcome. The traditional preparation is dried leaf as a tea or powder, and the EMA conclusion covers dried or fresh leaf as a herbal tea or in solid oral forms for adults; we did not find a standard tea amount in the sources we read.

The amounts above are what trials and pharmacopoeias record, not a dose for you; your medicines and conditions change the answer, and a clinician or pharmacist who knows them is the person to ask.

What is known about safety

The EMA page on olive leaf states that no side effects had been reported at the time of the committee’s assessment, and that olive leaf medicines should not be used by patients who have been advised to reduce fluid intake, such as those with severe heart or kidney disease, and should only be used by adults. The published trials above did not highlight adverse events in their abstracts. Pregnancy and breastfeeding are not addressed in the sources we read. The extract lowered blood pressure and blood sugar in trials, so people who already run low on either are the group those findings flag.

Where it meets prescription medicines

Blood pressure medicines: in the Susalit trial a 500 mg twice daily extract lowered systolic pressure by 11.5 mmHg, so an additive effect with antihypertensive drugs is plausible, though we found no formal interaction study. Diabetes medicines: the Wainstein trial found lower HbA1c and fasting insulin with the extract, so the same caution applies. Neither combination has been tested in a dedicated interaction study that we could find.

Medicines the site’s own interaction rules flag with olive leaf

The quiz applies these rules when someone names a medicine. They come from published interaction references and are a reason to ask a pharmacist, not a diagnosis:

Catalog entries that list olive leaf

If you want olive leaf in a product rather than as a loose herb, these are the entries that carry it, with the label amounts and the reviews read.

Gaia Herbs Olive Leaf 4.8 out of 5 from 268 ratings from Gaia Herbs · $0.94 a day Silver Fern Brand Reflux Pro 5 out of 5 from 2 ratings from Amazon · $1.92 a day

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Herbs that sit beside it

Western Oregano Origanum vulgare Ayurvedic / TCM / Western Garlic Allium sativum TCM / Western Berberine Berberis, Hydrastis, Coptis and Mahonia species (source plants)

What people want to know

Is there a human trial of olive leaf for gut infections?

We did not find one. The gut case rests on laboratory work, where an extract inhibited Campylobacter jejuni and Helicobacter pylori at 0.31 to 0.78 percent by volume and showed little activity against 79 of the other organisms tested.

What do the human trials of olive leaf measure?

Blood pressure and blood sugar. A trial of 500 mg twice daily lowered systolic pressure by 11.5 mmHg over 8 weeks, similar to captopril, and a trial of 79 people with type 2 diabetes found lower HbA1c after 14 weeks of 500 mg a day.

Is olive leaf the same as olive oil?

No. The leaf extract is a concentrate of polyphenols such as oleuropein, while olive oil is pressed from the fruit. Findings for one do not transfer to the other.

Does the EU approve olive leaf for digestion?

No. The EMA herbal committee reviewed dried and fresh olive leaf only for water elimination through the kidneys in mild water retention, on the basis of traditional use. It does not list a gut indication.

Sources