Arsenic in Herbal Kelp Supplements: Concentration, Regulations, and Labeling

“Case Report: Potential Arsenic Toxicosis Secondary to Herbal Kelp Supplement” by Amster et al. (2007) is fundamentally flawed, both scientifically and with regard to the regulation of dietary supplements. Amster et al. (2007) claimed to have found “detectable levels of arsenic in eight of the nine kelp herbal supplements, ranging from 1.59 ppm to 65.5 ppm by dry weight (1.59, 2.28, 9.55, 9.97, 10.5, 24.1, 34.8, and 65.5 ppm),” with a median of 10.23 ppm. In this instance, concentrations are irrelevant without disclosing the mass of the capsules. This would allow for calculation of the potential exposure to arsenic; any valid scientific argument on toxicity has to be based on exposure levels and daily intake, not on concentration. For example, if we applied a 50-mg mass as the capsule mass, this would equate to arsenic concentrations of 0.0795, 0.114, 0.478, 0.499, 0.525, 1.21, 1.74, and 3.275 μg/capsule, respectively. With a serving of one capsule per day, this is well below the normal daily intake cited by Amster et al. (2007):