Consumers should be careful of natural health products, as the majority of herbal products on the market contain ingredients not listed on the label.
Most companies substitute cheaper alternatives and use fillers, according to new research from the University of Guelph.
The study used DNA barcoding technology to test 44 herbal products sold by 12 companies.
Only two of the companies provided authentic products without substitutions, contaminants or fillers.
Overall, nearly 60 percent of the herbal products contained plant species not listed on the label.
Researchers detected product substitution in 32 percent of the samples.
More than 20 per cent of the products included fillers such as rice, soybeans and wheat not listed on the label.
"Contamination and substitution in herbal products present considerable health risks for consumers," lead author Steven Newmaster, an integrative biology professor and botanical director of the Guelph-based Biodiversity Institute of Ontario (BIO), home of the Canadian Centre for DNA Barcoding, said.
"We found contamination in several products with plants that have known toxicity, side effects and/or negatively interact with other herbs, supplements and medications," he said.
The study is published in the open access journal BMC Medicine.
