While highly purified water lacks the minerals found in typical drinking water, the human body has mechanisms to adapt to varying water compositions. This article clarifies the scientific understanding of “pure” water and its interaction with the body, addressing common misconceptions.
Defining “Pure” Water
“Pure” water, in the context of drinking, refers to water from which nearly all dissolved solids, minerals, and other contaminants have been removed. This differs from standard tap or bottled mineral water, which naturally contain varying levels of these substances. Methods used to achieve this high level of purity include distillation, deionization, and reverse osmosis.
Distillation involves boiling water and then condensing the steam, leaving impurities behind. Deionization uses ion exchange resins to remove charged mineral particles. Reverse osmosis pushes water through a semi-permeable membrane, filtering out contaminants. These processes remove minerals like calcium, magnesium, and sodium that are naturally present in water.
How Water Interacts with Your Body
The human body is approximately 60% water, and maintaining its fluid balance is a finely tuned process. This balance relies on electrolytes, which are minerals like sodium, potassium, and chloride that carry an electrical charge when dissolved in water. Electrolytes are essential for nerve and muscle activity, and for regulating the amount of water inside and outside cells.
Water movement across cell membranes occurs through a process called osmosis. Cells function optimally when there is a balanced concentration of solutes, including electrolytes, both inside and outside their membranes. If a person consumes a large quantity of water with a very low concentration of solutes, like highly purified water, it can create an osmotic imbalance. Water tends to move from an area of low solute concentration (the pure water) to an area of higher solute concentration (inside the body’s cells) to balance the concentration, causing cells to swell. This swelling, particularly of brain cells, can lead to a serious condition called hyponatremia, where blood sodium levels become dangerously low.
Is It a Realistic Danger?
While the theoretical risk of drinking pure water exists, it is not a common danger for the average person. The human body has robust regulatory mechanisms, such as thirst and the kidneys’ ability to excrete excess water, which typically prevent such an extreme imbalance under normal circumstances. Consuming small amounts of purified water occasionally is not harmful.
The danger primarily arises from consuming extremely large quantities of water, whether purified or not, over a short period, especially without adequate electrolyte replenishment. This can lead to water intoxication or dilutional hyponatremia. Such scenarios are rare and are more often seen in specific situations, such as endurance athletes over-hydrating during prolonged events without replacing electrolytes, or individuals with certain medical conditions that impair fluid regulation. Symptoms of hyponatremia can include nausea, headache, bloating, and in severe cases, confusion, seizures, or coma.
Choosing Your Daily Hydration
For most individuals, common tap water, if safe and treated, filtered water, or standard bottled water are adequate sources of hydration. These water sources contain varying amounts of naturally occurring minerals like calcium, magnesium, and sodium, which contribute to overall health. While pure water purification processes remove these minerals, the primary source of essential minerals for the body comes from a balanced diet, not drinking water.
Staying adequately hydrated is important for overall health, and listening to the body’s thirst signals is a reliable guide for most people. The recommended daily fluid intake varies by individual factors like activity level, health, and environment, but generally falls within a range of 2.7 to 3.7 liters per day for adults, including fluids from food. Focusing on consistent, moderate water intake from typical sources supports the body’s natural fluid balance without concerns about water purity.