Yuan S, Mason AM, Carter P, et al. - A Mendelian randomization study was conducted to investigate how selenium levels are associated with 22 site-specific cancers and any cancer.

• Instrumental variables used were single nucleotide polymorphisms strongly linked with toenail and blood (TAB) and blood selenium levels in mild linkage disequilibrium (r2<0.3).

• The UK Biobank, including a total of 59,647 cancer cases and 307,914 controls, was used to obtain genetic associations of selenium-associated single nucleotide polymorphisms with cancer.

• In the FinnGen consortium comprising more than 180,000 individuals, researchers tested associations with p < 0.1 in UK Biobank for replication.

• There appeared no association of genetically-predicted TAB selenium levels with the risk of the 22 site-specific cancers or any cancer (all 22 site-specific cancers).

• Similarly, no strong correlation was recorded for genetically-predicted blood selenium levels.

• However, associations were suggested between genetically-predicted blood selenium levels with risk of kidney cancer and multiple myeloma.

• FinnGen showed the same direction of association for kidney cancer but not for multiple myeloma.

• Overall findings suggest no preventive effect of high selenium status against cancer development.