Making sense of the hair zinc literature: where do we go from here?

The authors make a critical review on the hair zinc literature, discussing the main contributions in this field. Certain explanations, as well as some solutions aimed to put an end to the confusion which exists on this matter are suggested. As a first step, it is recommended that only endogenous zinc in hair be reliably measured. Therefore, the zinc metabolic status should be operationally defined in function of the zinc detected in hair. Each one of the variables should thus be identified, quantified and controlled. It must be added that these variables would have to include differences in zinc metabolism. Only then would it be possible to see the real baseline reference value of hair zinc. At present researchers should begin looking for a functional relation and not just a statistical significant association between hair zinc concentration and zinc metabolic status. At the same time, it would be necessary to ratify and prove findings of the great number of studies reported in the paper, through the replication of studies with experimental animals.