To find out whether different types of selenium have different chemopreventive properties, the researchers studied how two forms -- SeMet and MeSeCys -- are processed in human lung cancer cells.

To find out whether different types of selenium have different chemopreventive properties, the researchers studied how two forms—SeMet and MeSeCys—are processed in human lung cancer cells.

For one, he said, there are multiple different types of selenium, which may have different effects -- and supplements contain only a single type.