Taking a high dose of a single mineral is dangerous because IT CAN LEAD TO ADVERSE SIDE EFFECTS AND HEALTH CONSEQUENCES.
The side effects that will result depend on the type of mineral that is taken in excess. For instance, when zinc is taken in excess, it has been found to suppress immune functions. It does this by interfering with copper absorption leading to copper deficiency, anemia and change in white and red blood cells and generally lowered level of immunity.