[Purpose]To investigate the potential causal relationships between serum levels of trace elements and head and neck cancers.[Methods]Single nucleotide polymorphism(SNP)of oral cancer,oropharyngeal cancer,laryngeal cancer and thyroid cancer,associated with calcium,copper,iron,magnesium,zinc,were obtained from genome-wide association studies(GWAS).A two-sample bidirectional Mendelian randomization(MR)analysis was performed using the inverse variance weighting(IVW)method by calculating odds ratio(OR)and 95％confidence interval(CI).Pleiotropy was assessed using MR-PRESSO and MR-Egger regression,and sensitivity analysis was conducted via the"leave-one-out"method.[Results]IVW analysis revealed a causal association between serum magnesium levels and the incidence of oral cancer(OR=0.976,95％CI:0.956～0.997,P=0.025),also between thyroid cancer and serum calcium levels(OR=1.008,95％CI:1.001～1.015,P=0.023).No significant causal associations were observed between other trace ele-ments and head and neck cancers(all P＞0.05).[Conclusion]This MR study suggests that serum magnesium levels serve as a protective factor against oral cancer,while thyroid cancer leads to el-evated serum calcium levels.

[Purpose]To investigate the potential causal relationships between serum levels of trace elements and head and neck cancers.[Methods]Single nucleotide polymorphism(SNP)of oral cancer,oropharyngeal cancer,laryngeal cancer and thyroid cancer,associated with calcium,copper,iron,magnesium,zinc,were obtained from genome-wide association studies(GWAS).A two-sample bidirectional Mendelian randomization(MR)analysis was performed using the inverse variance weighting(IVW)method by calculating odds ratio(OR)and 95％confidence interval(CI).Pleiotropy was assessed using MR-PRESSO and MR-Egger regression,and sensitivity analysis was conducted via the"leave-one-out"method.[Results]IVW analysis revealed a causal association between serum magnesium levels and the incidence of oral cancer(OR=0.976,95％CI:0.956～0.997,P=0.025),also between thyroid cancer and serum calcium levels(OR=1.008,95％CI:1.001～1.015,P=0.023).No significant causal associations were observed between other trace ele-ments and head and neck cancers(all P＞0.05).[Conclusion]This MR study suggests that serum magnesium levels serve as a protective factor against oral cancer,while thyroid cancer leads to el-evated serum calcium levels.