Minerals and Trace Elements
Oxygen, carbon, hydrogen and nitrogen are the most common elements that make up 96% of the total weight of a mammal. The next most abundant elements are calcium, phosphorus, potassium, sulphur, sodium, chlorine and magnesium. These make up nearly the remaining 4%.
Fifteen additional elements are required but their total combined amount in mammalian body is less than 0.01% of the body weight. Of the known 90 naturally occurring elements how many are essential for life? This is not known for many animals. In humans 26 elements are known to be necessary.