Their sample, they note, comprises only those patients who took proprietary products processed into pills or other finished doses — not the considerable number who consumed whole, unprocessed plant or animal materials.
After testing 487 products handed over by sick patients, Dr. Mak and his colleagues discovered 1,234 hidden ingredients, including both approved and banned Western drugs, drug analogues and animal thyroid tissue.
Sibutramine, an appetite suppressant taken off the market after it was linked to cardiovascular problems, was the most commonly identified adulterant, found in 155 products.
Health supplements containing undeclared ingredients are illegal in Hong Kong, Dr. Mak said, but residents may purchase them in unscrupulous local shops, on the internet, or while visiting mainland China or abroad.
It is impossible to say how prevalent these contaminated supplements are in Hong Kong, Dr. Mak said. He only tests samples from patients whose adverse reactions are severe enough to require medical attention.
Many more may not seek help, or may not experience any side effects at all. “In China, we have so many products around and we take them all the time,” Dr. Mak said. “I do not know the denominator here.”
Chinese medicinal remedies are gaining popularity worldwide thanks to a perception that they are “natural and safe,” Dr. Mak said. A study of 2,600 proprietary Chinese medicine products in Taiwan found that a quarter were contaminated with synthetic drugs.
In the United States, the Food and Drug Administration has identified more than 800 adulterated dietary supplements on the market.