A Canadian health law and policy expert says he’s not surprised by a new study that suggests herbal products often contain fillers or substitute ingredients not listed on the label.

University of Guelph scientists studied the DNA of various herbal products and found that some of them contained unlisted ingredients that could lead to allergic reactions or other unexpected outcomes.

“I wasn’t that surprised by it,” said Timothy Caulfield, an author and professor of law and science policy at the University of Alberta.

The production, sale and marketing of herbal products is a “massive” industry and people often forget that, Caulfield told CTV’s Canada AM Friday.

“There’s a lot of money to be made in it,” he said. “I do hope this is sort of a wake-up call for people who use supplements.”

The latest study, which will appear in the BMC Medicine journal, tested 44 products sold by 12 different companies (no brand names were revealed).

The study found that nearly 60 per cent of those products contained DNA from at least one plant species that wasn’t listed on the product label. More than 20 per cent of the products contained unlisted fillers, including rice, soybeans and wheat.

About a third of the products involved product substitution, the study’s authors said. For instance, a bottle of “gingko biloba” may not contain any gingko DNA at all.

Steve Newmaster, the first author of the study and a professor of integrative biology at the University of Guelph, told The Canadian Press that alfalfa can be sold as gingko because the two substances are indistinguishable in powder form.

Newmaster, who is also the botanical director of the Biodiversity Institute of Ontario, said the product substitution may not be deliberate among manufacturers or distributors. When he and his colleagues showed their finding to some herbal product companies, they were surprised to find out which ingredients were really in the bottles.

The problem is that some active ingredients can cause adverse reactions in people who have certain medical conditions, or are taking pharmaceuticals that don’t interact well with those substances, Caulfield said.

Fillers like wheat, for example, could cause problems for those who are gluten intolerant.

Many people believe that herbal supplements are “all-natural” and therefore “inherently good for you,” Caulfield said. But sticking to a healthy diet should provide all the necessary nutrients for the average person, he said.

“In general, you don’t turn to supplements to live a healthy life.”

With files from The Canadian Press