Inorganic elements (such as iron or zinc) that come from the earth, soil, and water and are absorbed by plants. Animals and humans absorb these minerals from the plants they eat. Like vitamins, these naturally occurring micronutrients are essential for a healthy life. Over twenty dietary elements are necessary for mammals and several more for various other types of life. Seven are major dietary elements: calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium. Other "trace" or minor dietary elements are also necessary for human and animal life including iron, cobalt, copper, zinc, molybdenum, iodine, and selenium. Ultra-trace amounts of some elements (e.g., boron and chromium) are also known to have a role in health.