Clarifications regarding purification methods

In the purification methods like RO, UV we know that all the impurities are very well eliminated but what about the essential minerals? Are they eliminated through this process and how they are retained by the well known brands, eg. Eurekha Forbes, Purit Aquaguard, etc. How safe is drinking the water filtered through these methods and if not could you please suggest any other way of filtration of drinking water?