Fluoride helps to prevent tooth decay. If your main source of drinking water is bottled water, you may be missing out on the decay preventing benefits of fluoride. This according to the American Dental Association (ADA). Most bottled waters do not contain optimal levels of fluoride and some do not contain any at all. If you just prefer drinking bottled water, consider using tap water in other ways, such as when preparing meals and for mixing juices and powdered drinks.