For most people, plain water is better.
Bottled water sold as alkaline water is subject to regulation by the U.S. Food and Drug Administration. Alkaline water sometimes has nutrients added to it to achieve an alkaline pH.
Scientists use pH to describe how acidic a substance is on a scale of 0 to 14. By definition, a substance is alkaline if it has a pH of over 7.
Because alkaline water has a higher pH level than does plain tap water, proponents say that it can neutralize acid in your bloodstream. However, research suggests that alkaline water is unlikely to significantly change blood pH.
Some studies suggest that alkaline water might help slow bone loss, but it's not clear if the benefit is maintained over the long term.
Some say that alkaline water can help prevent disease, such as cancer and heart disease. However, there's little credible evidence to support such claims.