The subject application provides a method of identifying or screening compounds or compositions suitable for reducing the production of reactive oxygen species (ROS) comprising: a) feeding (or orally administering) compositions comprising dietary material containing dietary calcium (or dietary calcium) to at least one subject; b) measuring intracellular concentrations of calcium in cells of said at least one subject, wherein a decrease of intracellular calcium concentration in said cells of said at least one test subject as compared to the intracellular concentrations of calcium in the cells of at least one control subject is indicative of a compound, composition, combination of compounds or combination of compositions suitable for use in reducing the production of ROS in a subject. Methods of treating ROS-related diseases comprising the oral administration of dietary material containing dietary calcium (or dietary calcium) are also provided.