What each mineral in water does

These are the values on a bottled water label. Amounts in water are usually small compared with food, so we show the FDA Daily Value where one exists, for scale.

Calcium (Ca)

The body needs calcium to build and maintain bones and teeth, and for muscles, nerves and blood vessels.^[7] The FDA Daily Value is 1,300 mg.^[6] On UK/EU natural mineral water labels, "contains calcium" means more than 150 mg/L.^[2]

Magnesium (Mg)

Magnesium helps regulate muscle and nerve function, blood sugar and blood pressure, and is needed to make protein, bone and DNA.^[8] FDA Daily Value: 420 mg.^[6] "Contains magnesium" on a UK/EU label means more than 50 mg/L.^[2]

Sodium (Na)

The FDA Daily Value for sodium is less than 2,300 mg per day.^[6] On UK/EU natural mineral water labels, "suitable for a low-sodium diet" requires less than 20 mg/L, and "contains sodium" means more than 200 mg/L.^[2]

Potassium (K)

Potassium is needed for the kidneys, heart, muscles and nerves to work properly.^[9] FDA Daily Value: 4,700 mg.^[6] Bottled waters usually contain only a few mg/L.

Bicarbonate (HCO₃)

Bicarbonate is the main contributor to a water's alkalinity, its ability to buffer acids. "Contains bicarbonate" on a UK/EU label means more than 600 mg/L.^[2] US reports often give "alkalinity as CaCO₃" instead of bicarbonate; these are different units, so we do not convert one to the other.

Nitrate (NO₃)

WHO's guideline value for nitrate in drinking water is 50 mg/L as nitrate, set to protect bottle-fed infants.^[4] The FDA limit for bottled water is 10 mg/L as nitrogen.^[1] European labels give nitrate as NO₃ while US reports usually give nitrate-N, so the two are not directly comparable. We show each as published.

Silica (SiO₂)

Silica is dissolved from the rock the water passes through, and values vary widely: FIJI reports 86 mg/L and Volvic 32 mg/L, while Acqua Panna reports 7.1 mg/L. The FDA has no Daily Value for silica, and we make no health claims about it.

Sulfate (SO₄) and chloride (Cl)

Both affect taste. The FDA bottled water limit for each is 250 mg/L, but mineral water is exempt.^[1] The EPA tap water guideline is also 250 mg/L for each, set for taste.^[5] On UK/EU labels, "contains sulphate" and "contains chloride" each mean more than 200 mg/L.^[2]