It is moderately toxic, but the FDA considers it safe when used within their guidelines. Flavor Enhancers - These chemical compounds intensify desireable flavors in meats, fish, poultry, vegetables, fruits, cakes, breads, and beverages. They can also mask undesireable flavors. There are several others, and they will have entries as well. There is constant debate on whether or not this is safe and whether or not it is actually beneficial to our teeth.
Most sources of information contradict themselves at best.
It is also a by-product of the aluminum industry. Its greatest concentrations in the body are in the teeth, bones, and vital organs. I have yet to find studies or tests that prove conclusively that it is beneficial to our health when supplemented. Most sources state that it is readily available in our food. Good sources being organ meats, gelatin, saltwater fish, and tea.