Hair for a long-term biological indicator tissue for assessing the strontium nutritional status of men and women.

Strontium (Sr) is a trace element that closely resembles calcium metabolism. At the present time there is no available long-term biological indicator tissue for assessing the human Sr nutritional status. Here we have presented a novel concept on how to assess the Sr nutritional status by studying the frequency distribution properties of hair Sr (H) concentration. In this prospective, observational, cross-sectional, and exploratory epidemiological study, we analyzed H in 311 apparently healthy adult Croatians (123 men, 188 women). Hair strontium was analyzed by the ICP-MS. The natural frequency distribution of H followed the Power law, so that the data were analyzed by fitting the logistic bioassay sigmoid curve (ogive) of median derivatives. Women tend to accumulate three and a half time more H than men (median men 867ngg vs. median women 3120ngg). The normal (adequate) linear physiological response range of the sigmoid curve was 351-3489ngg for men and 846-8457ngg for women. Values below that linear range are considered to indicate deficient Sr nutritional status, whereas values above that linear range indicate excessive strontium exposure. Hair, as a long-term, and whole blood as a short-term biological indicator tissues were not commensurable entities. Similarly, H accumulation was not age dependent in either men or women. Hair strontium is a reliable long-term biological indicator tissue for assessing the strontium nutritional status.