Professor Garland along with his colleagues investigated 903 healthy volunteers of average age of 74. In 1997-1999, during the study, when these volunteers underwent examination and answered questionnaires, none of them were diagnosed with diabetes or prediabetes.
During the study visits, their blood samples were also tested for the level of vitamin 25(OH)D and some other markers.
Over a study duration that completed in 2009, the volunteers collectively developed 47 cases related to type 2 diabetes and 337 cases related to prediabetes, a disease where the levels of blood Sugar are higher than the normal levels, but not high enough to be called as diabetic.