Purified water, typically produced by advanced filtration methods like reverse osmosis or distillation, is stripped of contaminants but also nearly all naturally occurring minerals. This results in water with extremely low Total Dissolved Solids (TDS). The concern that purified water can be detrimental to health stems from this removal of dissolved solids, as exclusive, long-term consumption can affect the body’s mineral balance.
Mechanisms of Water Purification
Two primary methods result in highly demineralized water: reverse osmosis (RO) and distillation. RO systems force water under pressure through a semi-permeable membrane, blocking larger particles, including salts, heavy metals, and dissolved minerals. Distillation involves heating water to create steam, leaving non-volatile substances behind; the steam is then cooled and condensed back into liquid water. Both processes effectively remove contaminants like bacteria and chemicals, but they also remove beneficial compounds, resulting in water with a Total Dissolved Solids level often below 10 mg/L.
Essential Minerals Removed During Purification
Purification significantly reduces the concentration of minerals essential for human health, primarily calcium and magnesium. These minerals are naturally found in most untreated water sources and provide a supplemental source to dietary intake. Calcium is necessary for maintaining bone density, nerve signaling, and muscle contraction. Magnesium supports muscle relaxation, energy production, and cardiovascular function, being involved in over 300 enzymatic reactions. When these elements are absent from drinking water, the body loses a regular contribution, which is relevant for individuals with borderline deficient diets.
Physiological Effects of Consuming Demineralized Water
The primary concern with exclusive, long-term consumption of demineralized water relates to osmosis. Water lacking dissolved solids (a hypotonic solution) attempts to achieve equilibrium by drawing solutes from areas of higher concentration. When consumed, this water can trigger a “leaching effect,” pulling essential electrolytes and minerals out of the body’s tissues and cells. This results in an electrolyte imbalance, manifesting acutely as tiredness, weakness, and muscle cramps. Sustained mineral loss over time can contribute to reduced bone mineral density and is associated with an increased risk of cardiovascular disease mortality.
Context, Frequency, and Remineralization
The risks associated with purified water depend on the frequency and duration of use. Occasional consumption is not a health risk; the concern arises when it is the exclusive source of hydration over many months or years, leading to a cumulative mineral deficit. Many manufacturers address this through remineralization, adding controlled amounts of beneficial minerals, typically calcium and magnesium, back into the water. Consumers using home reverse osmosis systems often install a remineralization cartridge to introduce a healthy balance of dissolved solids. While a well-balanced diet can help compensate, relying solely on diet may not be sufficient to offset the loss of minerals.