The acidity of beverages is measured using the pH scale, which ranges from 0 to 14. A pH below 7 indicates acidity, a pH above 7 indicates alkalinity, and 7 is neutral. Seltzer water, also known as plain carbonated water, is water into which carbon dioxide gas has been dissolved under pressure, without added sugars or flavorings. This carbonation process causes the drink’s slight acidity, leading to questions about its potential effects on the body.
The Chemistry Behind Seltzer Water’s Acidity
The effervescence and tangy taste of seltzer water result from a simple chemical reaction. When carbon dioxide gas is injected into water under pressure, a small fraction reacts to form carbonic acid. This weak acid lowers the liquid’s pH from neutral (7.0) to an acidic range.
Plain seltzer water typically has a pH between 3.0 and 4.5. This range classifies it as mildly acidic, similar to black coffee or some fruit juices. It is significantly less acidic than most sodas, which often have a pH closer to 2.5. The resulting carbonic acid partially dissociates, releasing hydrogen ions into the solution, which determines the final, lower pH.
Impact on Dental Enamel
The primary health concern regarding seltzer water’s mild acidity involves its potential effect on tooth enamel. Enamel, the hardest substance in the human body, is primarily composed of a mineral called hydroxyapatite, which can dissolve when exposed to acid. This process, known as demineralization, begins when the environment’s pH drops below the critical pH of approximately 5.5.
Since seltzer water’s pH (3.0 to 4.5) is below this threshold, there is a theoretical risk of erosion with frequent or prolonged exposure. However, the erosive potential of plain seltzer water is substantially lower than that of sugary soft drinks or fruit juices, which often contain additional acids like citric or phosphoric acid. Saliva acts as a natural buffer, neutralizing acids in the mouth and helping remineralize the enamel after an acid attack.
Mitigation Strategies
Dental experts suggest consuming seltzer water quickly rather than sipping it over long periods. Drinking carbonated water with meals also helps, as increased saliva production provides a greater protective buffer. Using a straw can further reduce contact time between the acidic liquid and the tooth surface. Note that flavored seltzers containing added acids, such as lemon or lime juice, may have a lower pH and a greater potential for erosion.
Systemic pH Regulation and Digestive Effects
Despite its mild acidity, seltzer water does not affect the body’s overall systemic acid-base balance. The human body has highly efficient, multilayered buffering systems designed to maintain blood pH within a very narrow range of 7.35 to 7.45. The most powerful of these is the bicarbonate buffer system, which constantly regulates the levels of carbon dioxide and bicarbonate ions in the blood.
The lungs and kidneys work constantly to quickly eliminate any excess acid or base, ensuring that the blood’s pH remains stable. Therefore, the small amount of carbonic acid introduced by drinking seltzer water is easily neutralized and poses no risk to systemic health.
Regarding digestion, the stomach is naturally a highly acidic environment, typically maintaining a pH between 1.5 and 3.5 to break down food. The mild acidity of seltzer water is negligible compared to the stomach’s existing acid levels and will not disrupt the digestive process. A common side effect is a temporary increase in burping or bloating, which is simply due to the release of the dissolved carbon dioxide gas in the digestive tract.