A scoping review of turmeric adulteration based on data from six continents

Turmeric (Curcuma longa) is widely used as a spice and in dietary/food supplements and herbal medicines. Reports assessing the authenticity of commercial products have shown that the ingredient is subject to adulteration with, among others, artificial dyes, undeclared diluents, and synthetic curcumin.

This scoping review summarizes published data on adulteration of turmeric products sold as spice and dietary or food supplements to estimate the prevalence of non-authentic turmeric on the market.

This scoping review was based on a literature analysis from Google Scholar, PubMed, ScienceDirect, Scopus, and Web of Science databases, covering publications from 2000 to 2025. Article selection was performed according to PRISMA-ScR guidelines. After the initial search, specific countries were added to refine the search. Of the 375 publications retrieved, 347 were eliminated as duplicates or because they lacked information on turmeric adulteration, adulteration of commercial products, or did not provide the number of adulterated samples. An additional 19 papers were found searching the citations, or by using Google Search with the keywords "Curcuma longa", "turmeric", "government report", and "adulteration". One more report from the CVUA Stuttgart was found using the keywords "Kurkuma", "Verfälschung", and "Report". In total, 48 papers were included in the review.

A total of 48 publications representing 2235 commercial turmeric samples were included in the study. The overall adulteration rate was 20.0%, with spice samples having a slightly lower percentage of adulterated samples (20.4%) than dietary and food supplements (22.0%).

Adulteration of turmeric remains a concern on markets worldwide.