Mineral water is a type of bottled water distinguished by its stable concentration of mineral salts and trace elements, which originates from a protected underground source. Unlike purified or tap water, mineral water is not typically treated or disinfected. This means its unique chemical profile, including its calcium content, is naturally occurring and consistent. The amount of calcium found in these waters varies widely, and understanding this variation is key to assessing its potential contribution to daily nutrition.
The Origin of Calcium in Mineral Water
The presence of calcium in mineral water is a result of a natural geological filtration process. As rainwater seeps through the earth, it travels through different layers of subterranean rock, such as limestone, gypsum, and dolomite. The slightly acidic water dissolves minerals from these rocks, which are primarily composed of calcium carbonate, picking up various mineral ions along the way.
The water’s ultimate mineral composition, including its specific calcium concentration, is directly determined by the type of rock it passes through and the length of time it remains underground. Water sourced from aquifers surrounded by calcium-rich rock will naturally have higher levels of the mineral.
Measured Calcium Content in Common Brands
Calcium content in commercial mineral waters demonstrates a large range of concentrations, illustrating the wide variability between sources. Some brands contain less than 20 milligrams of calcium per liter (mg/L), while others can exceed 300 mg/L, and in some cases, even 500 mg/L. Mineral waters generally show a higher average calcium concentration, around 208 mg/L, compared to spring waters, which average about 21.8 mg/L.
A brand like Evian contains approximately 78 mg/L of calcium, placing it in the moderate range, while a brand such as Gerolsteiner contains a significantly higher concentration, around 348 mg/L. Consumers must always check the product’s label, specifically the “mineral analysis” or “total dissolved solids” (TDS) section, to find the precise calcium figure for that particular water source.
Bioavailability and Contribution to Daily Intake
The calcium found dissolved in mineral water is highly bioavailable, meaning the body can absorb and utilize it efficiently. Studies have shown that the bioavailability of calcium from mineral water is often comparable to, or even better than, the calcium found in dairy products like milk. This dissolved form of calcium, often present as calcium bicarbonate, is readily absorbed through the digestive tract.
The Recommended Dietary Intake (RDI) for most adults is 1,000 milligrams (mg) per day. Drinking just one liter of a high-calcium mineral water containing 348 mg/L can provide over one-third of the RDI for many adults. This makes high-calcium mineral water a calorie-free option for individuals, such as those who are lactose intolerant or who choose not to consume dairy, to help meet their overall calcium requirements.
Important Consumption Considerations
While the calcium in mineral water is beneficial, consumers should be aware of consumption considerations, particularly regarding very high intake. Excessive intake of calcium from all sources, including water, may lead to a condition known as hypercalcemia, although this is rare from water consumption alone. Symptoms of excessive calcium intake can include gastrointestinal issues like constipation or nausea.
The term “hard water” refers to water with a high concentration of dissolved minerals, predominantly calcium and magnesium. For most healthy people, drinking hard water is not harmful. However, for those with a history of kidney stones, high calcium levels from any source may be a concern, and moderation is advisable. Additionally, the high mineral content of some waters can potentially interact with certain medications, such as thyroid hormones or some antibiotics. The timing of mineral intake must be separated from the drug’s administration to ensure proper absorption.