Carbonation itself, the dissolved carbon dioxide that gives sparkling water its fizz, does not appear to harm your liver. The one randomized trial that directly tested plain carbonated water against still water in healthy adults actually found a small improvement in liver enzyme levels after twelve weeks. The liver problems commonly linked to “carbonated drinks” trace back to what else is in the bottle: added sugars, high-fructose corn syrup, energy-drink additives, or alcohol paired with a fizzy mixer. Separating the bubbles from the baggage they travel with reveals a more interesting picture than a simple yes or no.
The Only Direct Trial on Carbonated Water and the Liver
Surprisingly few studies have tested whether carbonated water on its own does anything to liver function. The best available evidence comes from a 2025 randomized trial that assigned healthy Japanese adults to drink either plain carbonated water or still water for twelve weeks. At the end of the study, the carbonated water group showed lower levels of two key liver enzymes compared to the control group. AST dropped by about 4 units per liter, and ALT dropped by roughly 9.5 units per liter, both statistically significant changes.1Scientific Reports. Randomized trial of carbonated water consumption on snacking behavior, alcohol intake, and health indices in healthy Japanese adults Those enzymes are standard markers that clinicians use to gauge liver stress. Lower values suggest less inflammation or cell damage, not more.
This is one study, and it measured healthy adults over a relatively short period. It does not prove that sparkling water actively protects the liver. But it does undercut the idea that bubbles themselves cause harm. The researchers speculated that carbonated water may have displaced other, less healthy beverages, which could partly explain the enzyme improvements. Either way, the CO2 in your seltzer was not the villain.
Why Sugary Soda Gets Confused with Carbonation
When people worry that carbonation hurts the liver, they are usually thinking about soda, not sparkling water. And soda does have a well-documented link to liver trouble. A systematic review and meta-analysis found that higher intake of sugar-sweetened beverages was associated with about a 40% increase in the odds of developing non-alcoholic fatty liver disease compared to the lowest intake levels.2PubMed. Association of sugar sweetened beverages consumption with non-alcoholic fatty liver disease: a systematic review and meta-analysis A large study from the Framingham Heart Study cohorts found a similar dose-response pattern: people who drank the most sugar-sweetened beverages had about 60% higher odds of fatty liver disease after adjusting for body weight, diet, alcohol, and other factors.3PubMed Central. Sugar-sweetened beverage, diet soda, and fatty liver disease in the Framingham Heart Study cohorts
A smaller study of patients with fatty liver disease found that 80% of them consumed large amounts of soft drinks, compared to 20% of healthy controls. When the researchers controlled for overall diet and physical activity, soft drink consumption was the only independent predictor of fatty liver disease in their model.4PubMed Central. Soft drink consumption linked with fatty liver in the absence of traditional risk factors The pattern is consistent: the more sugary soda people drink, the more fat tends to accumulate in the liver. But the mechanism behind that fat accumulation has everything to do with what the sugar does once it arrives in your liver, and nothing to do with whether the drink was fizzy.
Fructose Is the Ingredient That Actually Drives Liver Fat
The sugar in most regular sodas is either sucrose (table sugar) or high-fructose corn syrup, both of which deliver a substantial dose of fructose. Your liver processes fructose very differently from glucose. While glucose enters general circulation and gets used throughout the body, fructose is metabolized almost entirely in the liver, where excess amounts get converted into fat through a process called de novo lipogenesis. A review in Nutrients noted that intervention studies in both animals and humans show large doses of fructose to be especially effective at promoting this liver fat production.5PubMed Central. The role of dietary sugars and de novo lipogenesis in non-alcoholic fatty liver disease
A controlled trial published in the Journal of Hepatology put numbers on this. Participants who drank beverages sweetened with fructose or sucrose daily saw roughly a twofold increase in liver fat production rates compared to controls. Glucose-sweetened beverages at the same dose did not change liver fat production at all.6PubMed. Fructose- and sucrose- but not glucose-sweetened beverages promote hepatic de novo lipogenesis: A randomized controlled trial That finding makes the distinction crystal clear: the liver responds to the fructose load, not the carbonation. A flat fruit juice with the same fructose content would pose the same problem. A fizzy sparkling water with no sugar would not.
This also explains why fatty liver rates have climbed in parallel with sugar-sweetened beverage consumption, not with carbonated-water consumption. Researchers have pointed out that the primary mechanism by which regular soft drinks promote liver fat accumulation is fructose-driven lipogenesis.7PubMed Central. Soft drinks consumption and nonalcoholic fatty liver disease Strip out the fructose, and the carbonation is physiologically unremarkable.
What About Diet Soda
If sugar is the problem, does switching to diet soda protect the liver? The Framingham study looked at this directly and found no significant association between diet soda intake and fatty liver disease.3PubMed Central. Sugar-sweetened beverage, diet soda, and fatty liver disease in the Framingham Heart Study cohorts That is consistent with the fructose-centered explanation: no sugar means no fructose load, which means no extra liver fat through that pathway.
There is a rat study that found liver tissue changes in animals gavaged daily with both regular and zero-calorie carbonated drinks at a dose of 10 milliliters per kilogram of body weight for three weeks.8Journal of Rawalpindi Medical College. Hepatic Damage Induced By Fructose And Aspartame In Carbonated Drinks: Morphological And Histological Analysis In Adult Male Albino Rats Animal gavage studies (where liquid is pumped directly into the stomach) are useful for spotting potential hazards, but the doses and delivery method make them hard to translate directly to human drinking habits. The study itself pointed to fructose and aspartame as the likely culprits, not the CO2. No comparable findings have emerged from human observational data on diet soda and the liver.
Carbonation Can Speed Up Alcohol Absorption
Here is where carbonation does enter the liver conversation in a roundabout way, though not by causing direct damage. If you drink alcohol mixed with a carbonated mixer rather than a flat one, the alcohol may reach your bloodstream faster. A study of 21 participants found that two-thirds of them absorbed alcohol faster when it was mixed with a carbonated drink, and the average absorption rate with the fizzy mixer was significantly higher than with the still mixer.9PubMed. Alcohol concentration and carbonation of drinks: the effect on blood alcohol levels
The mechanism likely involves carbonation’s effect on the stomach. While carbonated water does not change how quickly the stomach empties overall, it does shift where food and liquid sit within the stomach, concentrating more material in the upper portion.10PubMed. Effect of carbonated water on gastric emptying and intragastric meal distribution That redistribution may expose alcohol to a larger absorptive surface area sooner. A separate study found that gastric emptying was faster with artificially sweetened (diet) mixers compared to sugar-containing mixers, leading to higher peak blood alcohol levels with diet drinks.11PubMed. Artificially sweetened versus regular mixers increase gastric emptying and alcohol absorption
So a vodka-soda may get alcohol into your system faster than a vodka mixed with flat water. The carbonation itself is not damaging the liver, but it may be amplifying the liver’s exposure to alcohol, and alcohol is a well-established liver toxin. For anyone who already drinks moderately, the practical difference is small. For someone drinking heavily, the faster absorption means the liver faces a sharper spike in alcohol concentration. A study comparing different beers (all carbonated) found that gastric emptying times were similar regardless of carbohydrate or alcohol content, suggesting that carbonation’s effect is modest compared to the alcohol load itself.12PubMed Central. Comparative effects of low-carbohydrate, full-strength and low-alcohol beer on gastric emptying, alcohol absorption, glycaemia and insulinaemia in health
Energy Drinks Are a Different Animal
Carbonated energy drinks have been linked to liver damage in multiple case reports, but the concern is their cocktail of additives, not the fizz. A case published in the ACG Case Reports Journal described acute liver failure in a man who drank three cans of a sugar-free energy drink daily for a year. The researchers focused on niacin (vitamin B3) as the likely cause. Each can contained 40 milligrams, bringing his daily intake to 120 milligrams. While that is lower than the doses typically associated with liver toxicity, the authors suggested a possible cumulative effect, compounded by the patient’s history of binge alcohol use.13PubMed Central. Acute Liver Failure Following One Year of Daily Consumption of a Sugar-Free Energy Drink
Another case report documented simultaneous acute kidney injury and acute hepatitis linked to energy drink consumption.14PubMed Central. Acute kidney injury and hepatitis associated with energy drink consumption: a case report The literature includes several similar reports, and the suspected agents are consistently things like niacin at high cumulative doses, excessive caffeine, taurine, or herbal additives, not carbon dioxide. An energy drink in a flat formulation would carry the same risks from those ingredients. The carbonation is incidental.
Plastic Bottles, Microplastics, and the Liver
A less obvious way that any bottled drink, carbonated or not, might affect the liver involves microplastics leached from packaging. A 2025 study published in Scientific Reports detected microplastics in various beverages and noted that these particles can be transported to organs including the liver, potentially altering metabolic pathways.15Scientific Reports. Occurrence and health risk assessment of microplastics in beverages and ice packs
A study in Environmental Science & Technology went further using a zebrafish model. Researchers found that microplastics from PET bottles that had been stored at elevated temperatures for a week caused liver damage and fat accumulation in the zebrafish after 80 days of chronic exposure. The same type of pristine PET microplastics stored at room temperature did not cause those effects.16Environmental Science & Technology. Suboptimal Thermal Storage Facilitates Aging of Bottle-Sourced Polyethylene Terephthalate Microplastics Fueling Hepatic Steatosis through Gut-Liver Axis Disruption The implication is that how a bottle is stored, particularly exposure to heat, matters more than whether the drink inside is sparkling or flat. Carbonation does create slightly higher internal pressure in a bottle, which could theoretically accelerate leaching, but the research to date has focused on temperature and time rather than CO2 pressure specifically. This is an active area of investigation, not a settled concern.
Does Carbonation Affect How Much You Eat or Drink
Some researchers have explored whether carbonation changes appetite in ways that could indirectly affect the liver over time, for example by encouraging overeating that leads to fatty liver. The evidence here is genuinely mixed and hard to interpret. One study found that carbonated beverages increased levels of ghrelin, a hunger hormone, in both rats and a small group of 20 healthy men.17PubMed. Carbon dioxide in carbonated beverages induces ghrelin release and increased food consumption in male rats: Implications on the onset of obesity That might suggest carbonation makes you hungrier.
But another human study found the opposite result under certain conditions: when participants drank a carbonated beverage before a small meal, their ghrelin levels were actually lower than with still water or a non-carbonated drink.18PubMed Central. The role of a pre-load beverage on gastric volume and food intake: comparison between non-caloric carbonated and non-carbonated beverage The randomized trial from Japan that found improved liver enzymes also examined snacking behavior, and the carbonated water group did not show increased food intake over twelve weeks.1Scientific Reports. Randomized trial of carbonated water consumption on snacking behavior, alcohol intake, and health indices in healthy Japanese adults The appetite effects of carbonation, if any, seem to be small and inconsistent, and there is no clear pathway from fizzy water to liver damage through overeating.
Hydration and the Liver
Adequate hydration supports liver function, and some people wonder whether carbonated water hydrates as well as still water. The answer is straightforward: it does. A review of the Beverage Hydration Index, which measures how well different drinks maintain fluid balance compared to plain water, found that sparkling water, sugar-free carbonated drinks, and sugary carbonated drinks all hydrated at essentially the same level as still water.19Journal of Renal Nutrition and Metabolism. Beverage Hydration Index You are not shortchanging your liver’s hydration needs by choosing sparkling water over tap.
Gastric Effects That Sometimes Get Misattributed to the Liver
Bloating, a sensation of fullness, and upper abdominal discomfort after drinking something fizzy are real. People sometimes interpret these symptoms as a sign that something is wrong with their liver, especially if they have heard warnings about carbonation. In reality, the discomfort comes from the stomach stretching as CO2 gas is released. Carbonated water shifts where food and liquid sit in the stomach, concentrating more in the upper portion, which can make the fullness feel more pronounced.10PubMed. Effect of carbonated water on gastric emptying and intragastric meal distribution But the overall rate at which the stomach empties is not affected. One study during exercise confirmed that carbonation had no effect on gastric emptying rates.20PubMed. Effects of drink carbonation on the gastric emptying characteristics of water and flavored water
The liver sits in the upper right abdomen, not far from the stomach, so discomfort from gastric distension can feel like it is coming from the liver area. This anatomical proximity probably contributes to the misconception. If carbonated water consistently causes you upper abdominal pain, it is worth mentioning to a doctor, but the explanation is far more likely to be gastric or esophageal than hepatic.
Who Should Actually Be Cautious
For most people, plain carbonated water is a neutral choice for the liver. But a few groups have legitimate reasons to think twice about carbonated drinks more broadly:
- Heavy drinkers: If you regularly drink alcohol with carbonated mixers, you may be absorbing alcohol faster, which increases the burden on your liver during each drinking session.
- People consuming multiple energy drinks daily: The additive load, especially niacin and caffeine in large cumulative doses, poses a real hepatic risk that has nothing to do with carbonation.
- Regular soda drinkers: Several servings of sugar-sweetened soda per day delivers enough fructose to measurably promote liver fat accumulation over time. Switching to sparkling water removes the fructose while keeping the fizz.
- People with existing liver disease: If you have cirrhosis or another serious liver condition, talk to your hepatologist about your overall diet rather than fixating on carbonation. The disease affects how your body handles everything from sodium to protein, and a single ingredient like CO2 is not the priority.
For everyone else, the bubbles are not the issue. The decades of research linking carbonated drinks to liver disease are really decades of research linking sugar, alcohol, and energy-drink additives to liver disease. When those substances are stripped away, what remains is water with dissolved gas, and the limited evidence available suggests it is benign for the liver or, in one trial, mildly favorable.