Tap water can contain more minerals than filtered water, with the mineral content in tap water varying by city and source. Drinking tap water from mineral-rich sources can help you meet a fraction of the dietary reference intake for important minerals like calcium and magnesium. Filtering water removes the majority of these minerals.
You may not think of tap water as being a good source of calcium, but it can be if you drink enough of it. According to the "Journal of General Internal Medicine," a study published by researchers at McGill University in March 2001 affirmed that drinking 2 liters of tap water in some cities can fulfill between 6 percent and 18 percent of your recommended daily allowance of calcium. Furthermore, according to a study published by a French research team in "Osteoporosis International" in 2002, the calcium in water can be as readily absorbed in the body as calcium from dairy foods. In comparison, filtered water contains much less calcium -- from 6 to 18 mg per liter of calcium.
Tap water can also be a clinically significant source of magnesium, another mineral essential to the human body. Magnesium supports blood cell turnover and the immune system. According to the study published in 2002 in the "Journal of General Internal Medicine" drinking 2 liters of tap water provides between 16 percent and 31 phttp://write.demandstudios.com/edit.php?articleid=3668336ercent of the recommended daily allowance of magnesium. The same study found that filtered water provides much less magnesium, from 3 to 8 mg per liter of magnesium.
Your cardiac and nervous systems need sodium to function properly, but too much sodium can be detrimental to your health, leading to hypertension. The U.S. Department of Agriculture Dietary Guidelines for Americans states that normal, healthy adults need from 2,400 to 3,000 mg of sodium daily. Tap water can be a very modest source of sodium, with North American tap water having in the range of 18 to 41 mg per liter of sodium. In comparison, filtered bottled water contains sodium in the range of 4 to 8 mg per liter.
Filtered water is a big industry, with sales in the billions of dollars annually. According to a study by English researchers at the University of Anglia, published in 2006 in the "Journal of Water Health," consumers prefer bottled water because of health concerns and because of dissatisfaction with the taste of tap water. Preference for tap water also varies by demographics, perceived quality of the tap water, and trust in tap water companies. Reusable water filters make it possible for households to filter their own tap water at home without purchasing commercial bottled water.
Minerals are removed from commercially sold purified waters by one of several processes, including distillation, reverse-osmosis and deionization. Purified water is also known as "demineralized water," "deionized water," "distilled water," and "reverse osmosis water."
Mineral-Rich Bottled Water
The FDA distinguishes among five types of bottled water: artesian water, spring water, mineral water, sparking mineral water and purified water. Bottled water labeled "mineral water" must contain no less than 250 parts per million of dissolved solids, and cannot have added minerals. Some mineral waters, especially European varieties, have higher concentrations of calcium, magnesium, and sodium. Check the nutrition label to verify the mineral content.
- Osteoporosis International; Consumption of a High-Calcium Mineral Water Lowers Biochemical Indices of Bone Remodeling in Postmenopausal women With Low Calcium Intake; 2000
- "Journal of General Internal Medicine"; Comparison of the Mineral Content of Tap Water and Bottled Waters; 2001
- "Journal of Water Health"; Bottled Water Versus Tap Water: Understanding Consumers Preferences; 2006