Colloidal Gold Atoms, are trace minerals that the body will absorb just like any other vitamin or nutriend.
What can damage the kidney and much worse than that is the Gold Chlorides in most Colloidal Gold supplments.
Many use Gold Chloride and if you know anything about gold chloride it will immediately kill the skin cells on contact and turn them black.
Its best to avoid any Colloidal Gold that has color to it.
Even though the Ruby Red solutions are appealing to the eye, they are caused by peroxides, chlorides, and quite frankly every color under the moon can be made depend on the chemicals used and depending on the quantities that are added in the productio process.
If you are going to buy Colloidal Gold , look for Colloidal Gold Atoms, or atomic size particle colloidal gold.