The spice, used in cooking and in Ayurvedic medicine in India for centuries, has been touted for its supposed health benefits, leading to a rise in people interested in using it as a supplement.
Google dubbed turmeric a “rising star” in a Food Trends report after searches for the spice increased by 56 per cent in a few months at the end of 2015.
Turmeric, the study says, can show effects where there are none.
Turmeric has been associated with many health claims and heralded for supposed anti-inflammatory properties and curcumin, an active compound in the spice, has been touted for cancer treatment, diabetes, weight loss, and dermatitis.
Extensive studies of the compound have been conducted but a new review in the Journal of Medicinal Chemistry says the compound is unstable, unreliable and can give false results.
In the most comprehensive study of the spice, the paper’s authors concluded there was no evidence of any therapeutic benefits, the journal Nature reports.
The article said common drug screening techniques test whether a compound, at a molecular level, binds to a disease-causing chemical.
If binding occurs, then it paves the way for further investigation.
But some compounds and chemicals provide false “hits”, mimicking binding and giving false signals. There is an entire discipline within chemistry exploring these false hits of compounds with the technical name “pan-assay interference compounds” (PAINS).
Curcumin is one such “chemical con artist”, according to the paper, The Essential Medicinal Chemistry of Curcumin.
The journal article said the “likely false activity” of the compound had led to more than 120 clinical trials targeting several diseases.
“No double-blinded, placebo controlled clinical trial of curcumin has been successful. This reviews the essential medicinal chemistry of curcumin and provides evidence that curcumin is an unstable, reactive, nonbioavailable compound and, therefore, a highly improbable lead.”
One of the chemists told Nature that curcumin had been proposed as a treatment for erectile dysfunction, baldness, and Alzheimer’s disease but it has never yielded a proven treatment.
Other researchers have said there is some evidence the compound does have a biological effect worthy of further study.
However, University of North Carolina chemical biologist Bill Zuercher said:
“It may very well be the case that curcumin or turmeric extracts do have beneficial effects, but getting to the bottom of that is complex and might be impossible.”
University of Minnesota medicinal chemist Michael Walters said the study of turmeric was a cautionary tale for science and he was not confident the review would stop muddled research.
“The people who should be reading this probably won’t,” he told Nature.
There have been some studies backing up claims of health benefits but the research, in many cases, now appears questionable.