Zingiberaceae
Curcuma longa
Turmeric · Haldi
- Part used
- rhizome
- Native range
- South Asia; a cultigen, not known in the wild
- Morphology
- A perennial to a metre with broad leaves rising from a branched rhizome whose flesh is deep orange. Sterile and triploid, propagated entirely by division.
What is in it
Evidence
One of the most-studied natural products in the world and one of the most disappointing. Curcumin is very poorly absorbed orally, rapidly metabolised, and is a notorious assay-interference compound that produces false positives in laboratory screens — a documented problem serious enough that medicinal chemists cite it as a cautionary class. Modest evidence for osteoarthritis pain; little that survives at the level of hard outcomes.
Safety
Culinary use is benign. High-dose supplements are associated with hepatotoxicity, and case reports have risen sharply with the popularity of enhanced-absorption formulations, particularly those containing piperine. Gallbladder contraction makes it inadvisable in biliary obstruction. Oxalate content is relevant in kidney stone formers.
Interactions: Additive bleeding risk with anticoagulants and antiplatelets; Piperine-enhanced products raise levels of many drugs by inhibiting metabolism
Regulatory: Permitted as a food and as a listed medicine ingredient. Several regulators have issued liver injury warnings on high-dose supplements.
How the traditions classify it
Three systems, rating the same plant. Where they disagree, none of them is correcting the others — they are separate frameworks that arrived at their categories independently.
Historical use
Used in South Asia for several thousand years as food, dye, cosmetic and medicine, and central to Hindu ritual. Recorded in Ayurvedic texts and traded to China and the Mediterranean in antiquity.
Recorded as history and attributed where possible. Long use establishes that a plant was widely used, not that it worked, and not that it was safe.
Worth knowing
Turmeric is the best modern illustration of a compound that looks active in every laboratory assay and does almost nothing in a person.
Curcumin binds, inhibits or modulates apparently everything, which should have been the warning rather than the promise. It is a pan-assay interference compound — it interferes with the detection methods themselves, producing positive results that are artefacts of the measurement. Medicinal chemists now use it as the standard example of the problem. Thousands of papers and no approved drug.
The absorption problem then produced the safety problem. Formulations were developed to force more of it into the bloodstream, usually with piperine from black pepper, and liver injury reports climbed alongside. Making an inert compound bioavailable does not make it work; it makes it a drug with unknown effects.
Nomenclature verified against GBIF backbone taxonomy.