Are the UV based and RO water purifiers effective?

Q: I would like to know whether UV based water purifiers (like Aquaguard) and RO water purifiers are effective in removing harmful viruses and bacteria, and if so, which one is better? I have heard that it is not advisable to use RO systems because they remove beneficial minerals from the water, apart from the harmful substances too - is this true?

A:I do not have specific information on the effectiveness of various types of water filters. Presumably the safest water is that which has been boiled, whereas the purest water is that which has been distilled. The latter tastes flat , and its use may result in a reduction of daily mineral intake. However, the latter is unlikely to be a problem if food intake is appropriately balanced in a typical adequate normal diet. In food deprived populations, iodine deficiency can occur when this element is absent from drinking water and salt in the diet.