Carbonated drinks are made by dissolving carbon dioxide gas in a liquid under pressure, a simple process that creates the familiar fizzy sensation. When people ask if carbonation is bad for the liver, they are often concerned about the physical effect of the bubbles themselves. The truth is that the carbonation process is generally not the source of any risk to your liver. The potential for harm lies almost entirely in the ingredients that are often added to these beverages, such as high amounts of sugar or artificial sweeteners.
Carbon Dioxide: No Direct Harm to the Liver
The carbon dioxide (CO2) used to carbonate drinks is not metabolized by the liver and does not directly cause liver damage. When consumed, a portion of the dissolved CO2 is released in the stomach, often causing burping, while the remainder is rapidly absorbed into the bloodstream. Once in the blood, this extra CO2 is efficiently handled by the body’s natural system for waste gas removal. The lungs regulate CO2 levels, quickly transporting the gas there to be exhaled with every breath. This process prevents CO2 accumulation and places no metabolic strain on the liver.
In unflavored sparkling water, the only components are water and CO2, making the drink as hydrating and safe for the liver as plain water. Some animal studies suggest the gas may increase levels of the hunger hormone ghrelin, potentially leading to increased food intake and subsequent weight gain. However, this is a secondary concern compared to the metabolic effects of added sugars. The consensus is that carbonation poses no significant threat to the liver’s function or structure.
The True Liver Risk: Fructose and Added Sugars
The greatest threat to liver health from carbonated drinks comes from the high concentration of added sugars, particularly fructose, found in regular sodas and many sweetened beverages. Fructose is metabolized differently than glucose, and the liver is the primary organ responsible for processing it. Unlike glucose, which can be used for energy by nearly every cell, fructose bypasses a major regulatory step in metabolism, leading to its rapid and unregulated entry into liver cells (hepatocytes).
This influx of fructose, especially the large amounts found in a single sugary drink, overwhelms the liver’s processing capacity. The liver converts the excess fructose into fatty acids, a process known as de novo lipogenesis (DNL). These fatty acids are then packaged and stored as triglycerides within the liver cells.
Over time, this continuous fat accumulation leads to Non-Alcoholic Fatty Liver Disease (NAFLD), now often referred to as Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD). This condition is characterized by the buildup of fat in the liver not caused by alcohol consumption. This accumulation can trigger an inflammatory cascade and oxidative stress, potentially leading to a more severe condition known as non-alcoholic steatohepatitis (NASH). Regular consumption of sugary soft drinks has been shown to increase liver fat and inflammation, significantly raising the risk for these liver diseases.
Evaluating Common Carbonated Drinks
The potential risk of a carbonated drink to the liver is determined entirely by its non-carbonated components. Plain sparkling water or seltzer, which contains only CO2 and water, carries a very low risk to the liver. This makes unflavored carbonated water a safe and hydrating alternative to still water.
Regular sugar-sweetened sodas and fruit-flavored carbonated beverages represent the highest risk category due to their substantial fructose load. Daily consumption of these drinks is strongly associated with an increased risk of developing MASLD because of the direct metabolic pathway that converts excess fructose into liver fat. The combination of rapid fructose delivery and high quantity places a significant, direct burden on liver function.
Diet sodas and zero-sugar carbonated drinks, which use artificial sweeteners like sucralose or aspartame, present a different concern. While they eliminate the high-fructose risk, some studies suggest that artificial sweeteners may still be linked to an increased risk of MASLD and liver-related mortality. Proposed mechanisms include alterations to the gut microbiota, which can indirectly affect liver metabolism, or interference with the liver’s detoxification processes. Therefore, while not as directly damaging as sugary sodas, replacing any soda with plain water or unflavored seltzer remains the healthiest choice.