Excessive heat could cause stainless steel to warp. Also, foods are more likely to stick, scorch, or burn. Cooking with high heat can also cause food to shrink, become dry and could deplete nutritional value. It's okay to bring large amounts of liquid to a boil over medium-high heat, for when you need to boil water for dry goods like rice, pasta or beans, but reduce the heat to low after the boiling point has been reached.