Traditional coca chewing and cortisol modulation in Andean miners: A pilot quasi-experimental repeated-measures study on stress physiology at high altitude.

Ethnopharmacological relevance: Traditional coca leaf chewing (Erythroxylum Coca Lam.) remains a widespread cultural practice in the Andean highlands, particularly among miners exposed to high-altitude and high-strain working conditions. While coca's ethnopharmacological significance is well documented, its physiological effects on stress-related biomarkers, such as cortisol, remain underexplored.

Aim of the study: We investigated whether habitual coca chewing during work shifts was associated with different serum cortisol concentrations in Peruvian miners working day and night shifts at high altitudes.

Materials and methods: A quasi-experimental design with repeated measures at two time points was implemented at a mining site located 4000 m above sea level. A group of male local miners (n = 20) was purposively sampled and stratified into habitual coca chewers (CC, n = 10) and non-chewers (NC, n = 10), with each group subdivided by work shift (day vs. night). Serum cortisol was measured at 8:00 a.m. and 4:00 p.m. using radioimmunoassay, and group status was confirmed via urinary benzoylecgonine testing. Two-way ANOVA, post-hoc Tukey tests, and effect sizes were calculated.

Results: Coca-chewers exhibited significantly lower cortisol levels than non-chewers at both time points. The most pronounced difference was observed at 8:00 a.m. among night-shift workers (17.17 μg/dL vs. 8.90 μg/dL, p < 0.001, d = 4.67). Group × shift interaction effects were significant at 8:00 a.m. (p = 0.0415), but not at 4:00 p.m.

Conclusions: These findings suggest that traditional coca chewing shows a cortisol pattern consistent with lower HPA axis activity under occupational stress, particularly during circadian disruptions. Interpretation, however, is constrained by the small sample size (n = 20) and should be considered exploratory. Further research is warranted to examine the long-term effects and underlying mechanisms through biocultural and molecular approaches.