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★☆☆Contested — the evidence disagrees with itself, or the finding carries a caution. A caution or conflict always shows one star, however strong the sources are.
The oregano shown killing Giardia in a dish is a different plant
An extract of Mexican oregano, a different genus from most oil of oregano, killed the parasite Giardia in lab cultures. It has never been tried in an animal or a person.
What the study found
Mexican oregano killed Giardia in a dish, and it is a different plant
An extract of Lippia berlandieri, known as Mexican oregano, killed the gut parasite Giardia in lab cultures. Lippia is a different genus from the Origanum vulgare in most oil of oregano, though both carry carvacrol. It shows a plant can kill Giardia in a dish, not that a capsule does.
The caveat · Dish strengths may not reach a gut
It has never been tried in an animal or a person. The strengths used, 58 to 588 µg per mL, have not been shown to be reachable in the human gut from a supplement.