Olive Leaf Immune Defence

Olive leaf is well tolerated and has more heart research than most herbs on the shelf. These are the questions our naturopaths ask in store, and most of them are about medicines you might already take.

A good fit if

• You want everyday heart and circulation maintenance, and you'll give it a couple of months
• You can read an oleuropein figure on a label, or you're happy to ask us
• You don't take medicines that lower blood pressure or blood sugar
• You'd like the mixed evidence explained honestly rather than simplified

Check with us first if

• You take any blood pressure medicine, such as ACE inhibitors, ARBs, calcium channel blockers, diuretics or beta blockers. The effects may add up.
• You take insulin or diabetes tablets, for the same reason.
• You take diltiazem or propranolol, because blood levels of these medicines may rise.
• You're pregnant or breastfeeding. The advice is to avoid it, because there isn't enough safety information.
• It's for a child, because there's no established safety information for children.
• You react to olive tree pollen, which is the only allergy recorded for this plant.

• Standardised extract, 500 mg twice daily. Best known for: The classic clinical format. Absorption: Implied by the clinical effect. Our sources have no direct absorption studies. Typical use: A flat 1,000 mg a day, used by two trials and one meta-analysis subgroup.
• Standardised extract, 500 mg once daily. Best known for: Half the dose above. Absorption: As above. Typical use: The dose that worked in the diabetes trial and in one meta-analysis. Note that the two meta-analyses disagree about which dose works.
• Extract labelled by oleuropein content. Best known for: The only fair way to compare two products. Absorption: Breakdown products of its plant compounds were found in urine 8 to 24 hours after a single dose. Typical use: Around 136 mg of oleuropein with 6 mg of hydroxytyrosol a day in the one trial that changed both blood pressure and blood fats.
• Lower-phenolic extract. Best known for: Roughly 51 mg of oleuropein a day. Absorption: As above. Typical use: One crossover trial on insulin sensitivity that has not been repeated. A separate review found low-dose extract did worse than placebo on fasting glucose.
• Dried-leaf-equivalent labelling. Best known for: The usual way Australian retail labels show it. Absorption: Not comparable with extract milligrams. Typical use: Only useful if the oleuropein figure is shown alongside it.
• Olive leaf tea or infusion. Best known for: The traditional preparation. Absorption: The amount of plant compounds varies enormously with the leaf, the water and the steeping time. Typical use: A tea can reach the levels used in trials, but one review's figure needed up to 990 mL a day to get there.
• Olive fruit and extra-virgin olive oil. Best known for: The same plant, a different part. Absorption: Mostly hydroxytyrosol rather than oleuropein. Typical use: A food with its own separate research. Don't apply olive oil evidence to an olive leaf product.
• Sorbitan olivate (item 4677). Best known for: An emulsifier made from olives, used in skin products. Absorption: Does not apply. Typical use: Used only in formulation, capped at 10% and not for use in the eye. It is not there for any health benefit.

Reference values. There's no recommended intake for olive leaf. It's a herb, not a nutrient.

Typical supplemental range. Trials used 500 to 1,000 mg a day of standardised extract, or extracts giving roughly 100 to 136 mg of oleuropein a day. Most trials ran for 8 to 14 weeks, and one went to 24.

Upper level. Australia's permitted ingredients list (Schedule 1, item 3571) sets no limit, and the NHMRC, FSANZ and the TGA haven't set a maximum daily intake. The only human report of a problem at a high dose is a single case of behaviour changes in a 67-year-old taking 5.5 g a day. High-dose animal studies showed raised liver enzymes, though human trials at the doses studied found no change in liver function.

Worth knowing. Compare products on oleuropein per daily dose, not on extract milligrams or dried-leaf equivalent grams. Those two figures can't be compared with each other or with the trials. Australian rules set no warnings for olive leaf, so the advice we give you comes from our duty of care, and that's a reason for us to be more careful, not less. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Dried olive leaf: oleuropein has been reported at levels reaching 240 mg per gram of dried leaf, though real leaf varies widely by cultivar, season and drying
• Olive leaf infusion: up to 990 mL a day in reviewed trials, delivering 320.8 mg oleuropein and 11.9 mg hydroxytyrosol
• Olives and olive oil: the same phenolic family but hydroxytyrosol-dominant, with a separate clinical literature that doesn't transfer

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• You take blood pressure medicines. Olive leaf may add to their blood-pressure-lowering effect. This is listed as a reason not to take it, and it is the interaction that matters most here.
• You take insulin or diabetes tablets. Your blood sugar may drop further, so careful monitoring is needed.
• You take diltiazem or propranolol. Blood levels of these medicines may rise when combined with olive leaf.
• Pregnancy and breastfeeding. The guidance we hold is to avoid it, because there is not enough information on safety and effectiveness.
• Children. We found no evidence in children. One trial in high-school athletes reported no safety problems, but it was not designed to test safety and enrolled only 32 people.
• High doses. One case report describes behaviour changes in a 67-year-old taking 5.5 g a day, and high-dose animal studies showed raised liver enzymes. On the other hand, human trials at studied doses found no change in liver function, total protein, albumin, urea or creatinine.
• You are allergic to olive pollen. Olive tree pollen can trigger severe breathing allergies in sensitive people. That is a pollen reaction rather than a leaf-extract one, but it is the only allergy signal recorded.
• Everyone. Schedule 1 sets no warning and no dose cap for this ingredient, so every caution here is our judgement rather than a rule. Treat that as a reason for more care, not less.