With regard to diseases leading to mineral toxicity, about one person in ten in the United States has the genetic mutation that can lead to hemochromatosis; however, not everyone with this mutation necessarily develops the disease.
For example, a disorder known as hemochromatosis leads to iron toxicity, while Wilson's disease results in copper toxicity.
Vitamin C is necessary to help the body absorb iron, and among people with a disease called hemochromatosis, or at very high doses, too much vitamin C can lead to excessive iron in the body.