Utilization of human nails as a trace-element monitor in epidemiologic studies

The utilization of human nails as a monitor for dietary intake of minerals, and especially trace elements, has been under investigation in the authors laboratories using neutron activation analysis. Rationale for the choice of the toenail is two-fold. First, experience has demonstrated that a high percentage of subjects will cooperate by furnishing nail samples when requested. These samples are easily transferred and can be conveniently catalogued and stored. Second, the elemental content of a nail sample was deposited prior to its being sampled. In the case of the nail sample from the great toe, this time differential can be approximately one year. This allows case control studies of human disease to be designed where there is less chance that the disease has caused substantial changes in diet or metabolism. Even so, epidemiologists prefer to design and conduct prospective case control studies if possible. Due to their ease of collection, transfer, and storage, nails can potentially make a greater number of such studies feasible. Toenails are currently being analyzed in their laboratory via instrumental neutron activation analysis in two case-control, cancer studies. Results for selenium, magnesium, calcium, and sulfur will be discussed with respect to the evaluation of the toenail as a dietary monitor for these elements