The American Herbal Products Association (AHPA) has voiced its opposition to the findings of a recently published case report concluding a kelp supplement could cause arsenic poisoning.
The University of California Davis risk assessment, published in this month's journal of Environmental Health Perspectives, posited from the outset that dietary herbal supplements can cause inadvertent arsenic toxicosis. This was based on the case of a 54-year-old woman who was found to have a higher than normal arsenic intake, which UC Davis attributed to her kelp supplements.
In a letter to the journal, AHPA stated:
"The authors fail to report that the product was used at two - to 'at least' four - times the suggested amount, of potential significance due to the naturally occurring presence of iodine in kelp."
The trade association said that while each tablet of the product was labeled to contain 225 mcg of iodine, federal regulations limit daily ingestion of kelp to an amount that provides no more than 225 mcg of iodine.
The UC Davis researchers tested samples from three different batches of the nine supplements selected from local health food outlets. They determined the arsenic content by means of inductively coupled argon plasma (ICP) using the identical hydride vapour generation method.
According to the report, the arsenic content found in the supplements ranged from 1.59ppm to 65.5ppm by dry weight, and the median value was set at 10.23ppm.
"Given the numerous studies demonstrating unsafe levels of heavy metals in dietary herbal preparations, the growing number of case reports connecting heavy metal toxicities to ingestion of herbal dietary supplements, and the growing popularity of herbal remedies for self-mediation in the general public, it is prudent that companies demonstrate safety and efficacy before their products are placed on the market," concluded the risk assessment.
AHPA posits that woman's symptoms are also those associated with iodine toxicity - something the organization said should be considered.
"We agree with the authors, that marketers have a responsibility to control the level of potentially harmful contaminants in herbal products," continued AHPA in its letter. "However, inaccurate reporting and speculative science should not be part of evaluating case reports associated with supplements."