Zinc nutrition among ancient Andeans in Northern Chile: determination of hair zinc concentrations using LA-ICP-MS

Zinc (Zn) is an essential trace metal in the human body, a critical structural and functional component of many proteins, and it regulates enzyme catalytic activity. Very little information is available about Zn nutrition among ancient Andeans in Northern Chile. This study reports an analytical approach developed to determine hair-Zn concentrations of Andean mummies across different cultural periods from three burial sites in Northern Chile using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The laser ablation operating parameters were optimized, and 1000 μm ablations along the axis of each hair strand were performed at the root, mid, and distal regions. Analytical signals for 66 Zn, 13 C, and 34 S isotopes were measured, and 13 C was used as an internal standard. The LA-ICP-MS instrument system was calibrated using the CRM GBW 07601 human hair standard, and very good recoveries were obtained for Zn. The Zn spatial distribution plots in the mid and distal regions demonstrate that they are free from external Zn contamination. The average hair-Zn concentration across all Andean mummies tested (n = 76) was 80.5 μg/g (median = 78.1 μg/g; range: 34.6-155.4 μg/g), indicative of low Zn status. Overall, these hair-Zn concentrations among pre-Columbian Andeans in northern Chile indicated Zn deficiency. Even though they had access to Zn-rich marine and animal foods, the authors posit steady consumption of phytate-rich cereals such as maize reduced zinc bioabsorption, as well as poor plant-available soil Zn in the region, resulting in Zn deficiency, especially during the Late and Late Intermediate periods.