Carbonated water is water infused with carbon dioxide gas under pressure, creating effervescence. Consumers often question whether the bubbles negatively affect hydration compared to still water. Research confirms that plain carbonated water hydrates the body just as well as non-carbonated water. This perception that it is less hydrating is largely a misconception stemming from the unique sensory experience of drinking a bubbly beverage.
The Hydration Verdict
Studies show that plain carbonated water and still water have the same hydration effectiveness. Researchers use the Beverage Hydration Index (BHI) to measure a drink’s ability to promote fluid retention, using still water as the baseline (BHI of 1.0). Plain sparkling water consistently scores identically to still water on this index. This means the body does not lose more fluid or absorb less water due to the carbonation.
The body processes the water content identically regardless of the dissolved carbon dioxide. A glass of carbonated water contributes the same amount of fluid toward daily hydration goals as a glass of plain tap water.
The Physiology of Absorption
The reason carbonated water hydrates effectively lies in the fate of the carbon dioxide gas after ingestion. Upon drinking, the dissolved CO2 quickly separates from the water, primarily in the stomach. A significant portion of this gas is immediately expelled through burping.
Any remaining carbon dioxide is rapidly absorbed into the bloodstream across the stomach and intestinal walls. Once in the blood, the respiratory system takes over. The lungs exhale this excess CO2 as part of the normal breathing process, regulating carbon dioxide levels.
The presence of the gas does not impede the absorption of water molecules by the intestines. However, the feeling of fullness or bloating caused by gas expanding in the stomach can be a psychological factor. This sensation often leads people to stop drinking sooner, inadvertently reducing overall fluid intake.
Non-Hydration Health Considerations
While carbonated water is equally hydrating, its chemical nature introduces other health considerations unrelated to fluid balance. Carbonation occurs when carbon dioxide reacts with water to form carbonic acid, making the water slightly acidic. The pH of plain carbonated water typically ranges from 5 to 6, which is below the enamel’s critical pH of 5.5, where demineralization can begin.
Regular, frequent consumption may pose a mild risk of dental erosion over time. This effect is dramatically less severe than with sodas or flavored sparkling waters containing citric acid. To minimize this erosive potential, dental professionals suggest drinking carbonated water with meals or using a straw to limit contact with the teeth.
The physical presence of the gas can also affect digestive comfort for some individuals. The carbon dioxide bubbles can cause temporary bloating and abdominal distension. This gaseous pressure can exacerbate symptoms in people with pre-existing gastrointestinal conditions, such as Irritable Bowel Syndrome (IBS) or Gastroesophageal Reflux Disease (GERD). The discomfort is a matter of personal tolerance, not a sign of impaired hydration.