But there are numerous exceptions. In another case, the California Department of Health Services found combinations with drug components and potentially toxic heavy metals in at least 83 of 260 imported traditional Chinese remedies. Other reports involved side effects ranging from lead poisoning from an herbal remedy for diabetes, cognitive impairment and vomiting resulting from a body building supplement, and estrogen-like side effects from a remedy used to treat prostate cancer. While purchasing herbal products from reputable companies may minimize the risk of contamination, there is no guarantee, since manufacturing standards for herbal remedies and most other dietary supplements are not yet in place. And there is still the risk of adverse effects that are not due to contaminants.
Botanicals are difficult to standardize because of the innate biological variability of plants.
We also are learning that complexities and variables are introduced in their collection, storage and transport. While there has not been much published on herbal drug interactions, they can and do occur. Additionally, there is increasing concern that environmental pollution may contaminate herbs that were once pure and natural. Compounding the confusion and the hyperbole is the odd regulatory niche into which herbs fall. The federal government classifies many herbal remedies as dietary supplements, even though consumers use them as medicine.