Water left out overnight often tastes different in the morning. This common experience prompts questions about changes in the water and our bodies, influencing this altered perception.
Water’s Overnight Transformation
Water left in an open container overnight undergoes several changes. As the water adjusts to room temperature, its taste profile can shift; cold water masks flavors, while warmer water amplifies them, making dissolved minerals more noticeable. This temperature change alters the sensory experience.
Another factor is the absorption of gases from the air. Carbon dioxide (CO2) dissolves into the water, forming carbonic acid. This process slightly lowers the water’s pH, making it more acidic, which can impart a flat, sour, or bitter taste.
For tap water, chlorine dissipation is another change. Chlorine, added to municipal water for disinfection, off-gasses over several hours, altering its flavor. Container material also plays a role; some plastics may leach compounds, and uncovered water can collect airborne dust or debris, subtly impacting taste.
Our Morning Taste Perception
Our physiological state in the morning also influences how water tastes. Overnight, the body can experience dehydration, which reduces saliva and dries the mouth. This altered oral environment affects taste bud sensitivity and flavor perception.
During sleep, bacteria accumulate in the mouth. These microorganisms break down organic matter, releasing volatile sulfur compounds (VSCs). VSCs cause “morning breath” and are detectable in small amounts, strongly influencing taste and odor.
The VSCs and bacterial activity create an oral environment that alters water taste. This combination of dry mouth and bacterial byproducts leaves a residual taste, affecting initial water perception. Heightened taste receptor sensitivity in this environment makes subtle water changes more pronounced.
Safety and Solutions for Better Taste
Despite altered taste, water left out overnight is safe to drink, especially if from a clean source and covered. Water lacks sugars, fats, or proteins that spoil like food. While some bacterial growth can occur, particularly from backwash, these are typically mouth bacteria and unlikely to cause harm. However, prolonged exposure (several days) or external contamination could introduce issues.
For a more pleasant morning hydration experience, several solutions exist. A water filter pitcher improves taste by removing chlorine and impurities. Storing water in a sealed glass bottle in the refrigerator keeps it cool and prevents gas absorption and airborne particles.
Pouring fresh water from the tap or a filtered source each morning is another approach. Rinsing your mouth with water before drinking helps clear overnight bacterial byproducts, improving taste. Infusing water with fruit, vegetables, or herbs adds refreshing flavor.