This 15-year study found that the risk of cognitive decline and dementia was higher for people who consumed large amounts of aluminum in their drinking water. 

Additionally, it discovered that waters containing Silica had the beneficial effect of neutralizing Aluminum.

Silica and Alzheimer's
Magnesium and Calcium in drinking water

Magnesium and Calcium are essential for the human body to function properly. 

The absence of these important minerals in demineralized drinking water can result in serious health problems.

cardiovascular disease and magnesium levels in water

Correlation between cardiovascular disease and drinking water magnesium levels, based on German (Teitge, 1990), Swedish (Rylander et al, 1991)

This Texas and Iowa study used data from the National Birth Defects Prevention Study. It found that higher water nitrate intake was associated with several birth defects.

Nitrate intake and birth defects