Reverse osmosis water filters remove the large majority of minerals in the water. The low level mineral concentration in water produced by reverse osmosis filtration systems is a major point of controversy. However valid the point may be that the human body requires salts, calcium, magnesium and other minerals found in unpurified water, the body does not need the contaminants and microbes that are also found there. It can be argued that although water that has passed through a reverse osmosis filter is lacking in healthy minerals, it is also purified of dangerous substances and toxins. It is not recommended that a person drink contaminated water just to acquire necessary minerals and salts that are not found in water from a reverse osmosis filtration system. These things can be obtained through a healthy diet. Calcium, for example, is better acquired through a glass of milk.