Reference values of elements in human hair: A systematic review

Abstract Background The lack of systematic review on reference values of elements in human hair with the consideration of methodological approach. The absence of worldwide accepted and implemented universal reference ranges causes that hair mineral analysis has not become yet a reliable and useful method of assessment of nutritional status and exposure of individuals. Objectives Systematic review of reference values of elements in human hair. Data sources PubMed, ISI Web of Knowledge, Scopus. Study eligibility criteria Humans, hair mineral analysis, elements or minerals, reference values, original studies. Results The number of studies screened and assessed for eligibility was 52. Eventually, included in the review were 5 papers. The studies report reference ranges for the content of elements in hair: macroelements, microelements, toxic elements and other elements. Reference ranges were elaborated for different populations in the years 2000–2012. The analytical methodology differed, in particular sample preparation, digestion and analysis (ICP-AES, ICP-MS). Consequently, the levels of hair minerals reported as reference values varied. Conclusions It is necessary to elaborate the standard procedures and furtherly validate hair mineral analysis and deliver detailed methodology. Only then it would be possible to provide meaningful reference ranges and take advantage of the potential that lies in Hair Mineral Analysis as a medical diagnostic technique.