Reverse osmosis (RO) is a highly effective water purification technology that uses a semi-permeable membrane to remove contaminants from water. Water is forced under pressure through an extremely fine filter, blocking molecules larger than water itself. While this process results in exceptionally clean water, it also strips out nearly all dissolved solids, including naturally occurring minerals. This creates highly purified, yet demineralized, water, raising the question of whether beneficial minerals should be reintroduced for long-term drinking suitability.
The Composition of Reverse Osmosis Water
Reverse osmosis systems achieve a high level of purification by forcing water through a membrane with pores as small as 0.0001 microns. This mechanism separates water molecules from larger substances, including chemical contaminants, heavy metals, and microorganisms. The resulting product, known as permeate, has a dramatically reduced concentration of dissolved materials.
These dissolved substances are quantified as Total Dissolved Solids (TDS), measured in parts per million (ppm). Standard municipal water often ranges from 100 to 500 ppm, but RO filtration reduces this level below 50 ppm, often close to zero. This aggressive filtration removes virtually all ions, including those that make water “hard,” such as calcium and magnesium.
Water extremely low in TDS is chemically described as “soft” or “aggressive.” This means the water has a high capacity to dissolve substances, having been stripped of its own dissolved solids. While beneficial for preventing scale buildup, this characteristic confirms the water lacks the mineral content found in natural sources.
Nutritional Necessity of Remineralization
The necessity of remineralization centers on the contribution of waterborne minerals to human health. Drinking water naturally contains minerals, primarily calcium and magnesium, which are absorbed by the body. Water provides a measurable supplement to overall dietary intake, even though the majority of these minerals come from food.
Magnesium supports muscle and nerve function, participating in over 300 enzymatic reactions, while calcium is known for its role in bone strength. Research suggests health benefits are associated with minimum concentrations in drinking water: 20 to 30 milligrams per liter (mg/L) for calcium and 10 mg/L for magnesium. Consuming severely demineralized water over an extended period does not provide this supplemental intake.
The World Health Organization (WHO) suggests a minimum TDS level of 100 mg/L in drinking water, primarily for taste and to discourage consuming water that is too aggressive. Water below 50 mg/L TDS is often described as tasteless or “flat.” Long-term consumption of water lacking dissolved salts may potentially lead to an electrolyte imbalance or increased loss of essential minerals from the body.
The body must expend energy to maintain its internal mineral balance when consuming nearly pure water. For individuals whose diet is marginal in calcium and magnesium, the contribution from mineralized water becomes more important. Reintroducing these specific compounds ensures the water is not only clean but also contributes to general hydration and mineral intake.
Methods for Reintroducing Minerals
Several practical methods are available for restoring beneficial minerals and a balanced taste to RO water. The most common solution involves installing a post-filtration system, often called a remineralization or alkaline cartridge. These cartridges are installed as the final stage of an existing RO system, automatically reintroducing minerals like calcium and magnesium as the purified water flows through.
An inline cartridge provides a consistent, hands-off approach to achieving specific mineral concentrations directly from the tap. These systems typically use natural mineral media, such as calcite or corosex, to dissolve trace amounts of minerals back into the water stream. This method addresses nutritional concerns and often raises the water’s pH.
For a more manual approach, mineral drops or liquid concentrates offer a simple alternative. These concentrated blends contain measured amounts of calcium, magnesium, and other trace electrolytes. They are added directly to a glass or pitcher of RO water, allowing the user to precisely control the mineral level based on personal preference.
Another technique is the addition of mineral-rich substances, such as a small pinch of high-quality sea salt or Himalayan salt. Beyond the physiological benefits, reintroducing a balanced mineral profile restores a more natural and palatable flavor to water that many find noticeably “flat.”