Reference values of elements in human hair: A systematic review

• We performed a systematic search of articles which provide intervals for the level of minerals in hair.
• We have prepared a systematic review.
• We reported values of reference intervals for macroelements, microelements, toxic elements and other.
• Elaboration of standard laboratory procedures for hair mineral analysis will enable validation of the method.

BackgroundThe 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.ObjectivesSystematic review of reference values of elements in human hair.Data sourcesPubMed, ISI Web of Knowledge, Scopus.Study eligibility criteriaHumans, hair mineral analysis, elements or minerals, reference values, original studies.ResultsThe 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.ConclusionsIt 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.