Disclosed are methods for treating a disease or condition associated with abnormal glucose metabolism. In another aspect, the disclosure relates to a method for reducing incidence or progression of insulin-dependent diabetes mellitus. The methods include orally administering to a mammal in need thereof an effective amount of a composition, which includes a naturally occurring material derived from eggshell, eggshell membrane, or a combination thereof. Particularly disclosed is treating diabetes mellitus with a composition that comprises powdered eggshell membrane in insulin-dependant diabetic mammals.
