I was told that Reverse Osmosis (RO) units remove minerals. Is that true?

It’s true that RO units remove some minerals but that isn’t really the whole story. The mineral issue is probably the most controversial question in drinking water purification. “Experts” on both sides of the issue speak convincingly.
The amount of minerals from water is very little comparing with food. No matter the water is filtered or not, you need to drink a huge amount of water in order to get enough mineral for daily consumption. Therefore, we recommend getting minerals from your daily diet. Moreover, the cleanness of water should be the most concerned refer than mineral content.