Reverse osmosis is a type of water filtration that removes potentially harmful compounds from drinking water. Many bottled water companies use reverse osmosis to purify their products. Drinking reverse-osmosis water offers some health benefits -- and a few potential disadvantages.
Reverse osmosis, commonly abbreviated as RO, was first introduced in North America through home purification systems in the 1970s. This purification method uses a semipermeable membrane, which filters out water contaminants and various compounds. If the particle is larger in size than water molecules, it’s trapped by the membrane. Conversely, particles smaller than water molecules typically remain in the drinking water, so RO systems effectively remove harmful contaminants such as lead, arsenic and nitrates. They also remove a high percentage of added fluoride, which has become a controversial issue. Fluoride is added to many municipal water systems in the United States to deter cavities, although too much of it is toxic and leads to a variety of side effects.
Compared to unfiltered tap water, RO water is likely to contain fewer contaminants. Lead is a relatively common contaminant in tap water, especially in areas where the water pipes and infrastructure are old and in need of repair. Too much lead in your body results in increased blood pressure, reduced fertility and nerve damage. Lead toxicity can also cause brain damage and anemia in children. An RO system is also great for filtering out parasites such as cryptosporidium, which is a common contaminant in lakes and rivers. Cryptosporidium infection leads to stomach cramps, fever and diarrhea.
Taste is obviously very subjective, but RO water is usually rated as better tasting than tap water by people who directly compare the two in blind taste tests, according to the National Rural Water Association. Lead, iron, nitrates, sulfur-based compounds and various chemical residues often make tap water unpalatable. The removal of these substances by reverse osmosis can give drinking water a cleaner or fresher taste. By contrast, fresh spring water naturally high in minerals is often rated as better tasting than RO water. It depends on where you live and the primary source of your drinking water.
Reverse osmosis removes the vast majority of natural minerals and salts. For example, calcium, magnesium and potassium are trapped by RO membranes. Minerals are important for bone health and the transmission of electrical signals from your brain. They are also important for fluid balance in your body and the taste of the water. A lack of minerals in drinking water also reduces the pH levels, which means it becomes a little more acidic. Acidity in the body seems to promote degenerative diseases such as arthritis and osteoporosis.
Cleansing your drinking water with a reverse-osmosis system may save you money compared to buying bottled water because bottled water is expensive. However, to offset any potential health hazards, consider adding some pre-dissolved minerals, called ionic, and a little pinch of sea salt. Your RO water will taste better and contain trace amounts of healthy nutrients.
- Public Health Nutrition: From Principles to Practice; Mark Lawrence and Tony Worsley
- Contemporary Nutrition: Functional Approach; Gordon M. Wardlaw et al.
- Textbook of Functional Medicine; David S. Jones
Sirah Dubois is currently a PhD student in food science after having completed her master's degree in nutrition at the University of Alberta. She has worked in private practice as a dietitian in Edmonton, Canada and her nutrition-related articles have appeared in The Edmonton Journal newspaper.