Plain seltzer water, which is simply water infused with carbon dioxide gas, has no demonstrated ability to harm a healthy liver. The only randomized controlled trial that directly measured liver markers in people drinking carbonated water over several months found the opposite of damage: liver enzyme levels actually dropped. The concern tends to arise from conflating plain seltzer with sweetened or artificially flavored soft drinks, which have their own metabolic baggage, and from a widely shared animal study whose conditions bear little resemblance to how people actually drink sparkling water.
The Clinical Trial That Tested This Directly
In a 2025 randomized trial, healthy Japanese adults drank either carbonated water or non-carbonated placebo water daily for 12 weeks. At the end of the study, two standard markers of liver cell stress, AST and ALT, fell in the carbonated water group compared to placebo. AST dropped by about 4 units per liter and ALT dropped by roughly 9.5 units per liter, both statistically meaningful changes.1Scientific Reports. Randomized trial of carbonated water consumption on snacking behavior, alcohol intake, and health indices in healthy Japanese adults These are not large shifts in absolute terms, but they go in the direction of better liver health, not worse. Nobody in the carbonated water arm showed any liver-related harm.
This is, to date, the most direct human evidence we have. It was a single trial in a healthy population, so it would be premature to claim that seltzer water actively protects the liver. But it firmly undermines the idea that carbonation itself is doing damage. The researchers were actually studying whether carbonated water changed snacking and alcohol intake, and the liver enzyme findings were secondary. Still, the results are reassuring for anyone who enjoys sparkling water as their main beverage.
Where the Fear of Liver Harm Comes From
Much of the worry traces back to a 2008 animal experiment conducted in Brazil. Researchers gave rats carbonated water under conditions designed to distend their stomachs substantially, then measured liver enzymes afterward. They found increases in ALT, alkaline phosphatase, and a trend toward higher AST, which they attributed to the swollen stomach physically compressing blood vessels around the liver and causing congestion in the hepatic circulation.2Acta Cirúrgica Brasileira. The effect of gastric dilatation in rats submitted to gasified water ingestion under the hepatic metabolic function
This study gets cited in online discussions as evidence that carbonated water harms the liver, but the context makes it a poor basis for human dietary advice. The gastric dilatation in these rats was extreme and designed to test a very specific mechanical hypothesis about pressure on abdominal organs. People sipping a can of seltzer throughout the day are not inflating their stomachs to the point of compressing their portal circulation. The study is interesting as a physiological curiosity, and the mechanism it describes is real in the narrow scenario it tested. It just does not translate to what happens when you drink a glass of sparkling water with dinner.
The Crucial Difference Between Plain Seltzer and Sweetened Drinks
A lot of the confusion around seltzer and liver health stems from treating all carbonated beverages as interchangeable. They are not. A can of plain seltzer contains water and carbon dioxide. A can of regular soda contains water, carbon dioxide, and roughly 40 grams of sugar. A can of diet soda replaces the sugar with artificial sweeteners and often adds caramel color, phosphoric acid, and other additives. These are fundamentally different products that happen to share fizz.
Sugar-sweetened beverages are among the best-documented dietary drivers of fatty liver disease. The fructose in soda is metabolized almost exclusively by the liver, and chronic overconsumption promotes fat accumulation in liver cells. This is well-established enough that it does not need belaboring here. The relevant point is that none of this applies to plain seltzer water, which contains no sugar at all.
Diet soft drinks sit in a murkier middle ground. A large cross-sectional analysis using U.S. national health survey data found that frequent diet soft drink consumption was associated with roughly double the odds of metabolic dysfunction-associated steatotic liver disease, the current term for fatty liver related to metabolic problems.3PubMed Central. Association between diet soft drink consumption and metabolic dysfunction-associated steatotic liver disease: findings from the NHANES But the same analysis estimated that about 85% of that association was explained by body mass index alone. In other words, people who drank the most diet soda also tended to weigh more, and weight is itself a powerful predictor of fatty liver. The diet soda may be a marker of broader metabolic patterns rather than a direct cause of liver fat.
Meanwhile, a small randomized trial that switched overweight adults from sugar-sweetened beverages to artificially sweetened ones found that liver fat actually decreased to about 74% of initial values after the swap.4PubMed. Sugar- and artificially sweetened beverages and intrahepatic fat: A randomized controlled trial The reduction was most pronounced in people who started with higher levels of liver fat. This does not mean artificially sweetened beverages are a health food, but it does show that replacing sugar with a non-caloric alternative, even an artificial one, moves the liver in the right direction. Plain seltzer would logically do the same or better, since it does not carry even the questionable ingredients that come with diet sodas.
Sodium in Sparkling Water and Why It Matters for Cirrhosis
Plain seltzer water is essentially sodium-free. Club soda, on the other hand, has added sodium bicarbonate and sometimes potassium sulfate, and many European-style mineral sparkling waters naturally contain meaningful amounts of sodium. The labels look similar on the shelf, but the sodium content can differ by an order of magnitude. For most people, this distinction is trivial. For someone with liver cirrhosis, it is not.
In cirrhosis, the liver’s structural damage leads to elevated pressure in the portal vein system. The body responds by retaining sodium and fluid through hormonal pathways, which can lead to ascites, the accumulation of fluid in the abdomen. For this reason, patients with cirrhosis are typically advised to monitor their sodium intake.5PubMed Central. Dietary salt in liver cirrhosis: With a pinch of salt! The picture is actually more nuanced than a blanket “eat less salt” message. Recent randomized trials in cirrhosis patients found that overly strict sodium restriction sometimes led to worse outcomes, including a higher risk of low sodium levels in the blood, reduced calorie intake, and even greater mortality.5PubMed Central. Dietary salt in liver cirrhosis: With a pinch of salt!
The practical takeaway for someone with existing liver disease is straightforward: plain seltzer is fine from a sodium perspective, but check the label if you are choosing club soda or mineral water. Some sparkling mineral waters contain over 100 milligrams of sodium per serving, which adds up if you are drinking several bottles a day and already watching your sodium budget. This is not a reason to avoid sparkling water; it is a reason to know what kind you are buying.
Sparkling Mineral Water and Gallbladder Function
The liver produces bile, stores it in the gallbladder, and releases it during digestion. A handful of studies have looked at whether mineral sparkling water changes how the gallbladder contracts, with somewhat mixed findings that reveal an interesting wrinkle.
One randomized crossover trial tested a sodium-bicarbonate mineral water alongside a standard meal and found that the mineral water slowed gallbladder emptying. Participants who drank the mineral water with food had higher gallbladder volumes at 30, 60, and 120 minutes after eating, and a lower gallbladder ejection fraction, meaning the gallbladder squeezed out less bile per contraction. They also had lower blood levels of the hormone that triggers gallbladder contraction, and their post-meal blood fat levels were lower at the 30- and 60-minute marks.6PubMed. A sodium-bicarbonated mineral water reduces gallbladder emptying and postprandial lipaemia: a randomised four-way crossover study
An earlier study found a somewhat different pattern: an alkaline bicarbonate mineral water actually prompted gallbladder contraction, reducing gallbladder volume at 15, 30, 45, and 60 minutes after drinking, while a saline control did not trigger emptying at all. The researchers suggested this type of water could help people with sluggish gallbladder motility.7Minerva Medica. Gallbladder motility following intake of mineral bicarbonate-alkaline water. Ultrasonographic assessment
The apparent contradiction probably comes down to the specific mineral composition of each water tested, whether the water was consumed with a meal or on its own, and the timing of measurements. Bicarbonate content, calcium levels, and magnesium all vary widely across mineral water brands and can each influence bile dynamics independently. None of these studies suggest harm to the liver itself. They show that mineral-rich sparkling waters interact with the digestive system in ways that plain tap water does not, which is not surprising. If you have gallstones or a gallbladder condition, the mineral profile of your sparkling water could theoretically matter, but this is a niche concern far removed from the question of liver toxicity.
Does the Container Matter More Than the Water?
If there is a legitimate concern about seltzer and organ health, it may have less to do with what is in the water and more to do with what is around it. Most seltzer comes in aluminum cans or plastic bottles, both of which have their own baggage.
A review of 21 studies on microplastics in drinking water found that bottled water consistently contained more microplastic particles than tap water. Among bottled products, reusable PET bottles and, surprisingly, glass bottles showed higher contamination than other packaging types. Particle counts increased as researchers looked for smaller and smaller particles, suggesting that much of the contamination is at sizes not easily filtered out.8PubMed Central. Occurrence of Microplastics in Tap and Bottled Water: Current Knowledge What microplastics do inside the human body over decades is still an open question, and the liver, as the body’s primary detoxification organ, is one of the places researchers are watching most closely. But the evidence so far is not specific to seltzer. Any bottled beverage carries the same exposure.
Bisphenol A, or BPA, is another container-related concern. A review of the factors that drive BPA leaching from food and beverage packaging found that higher temperatures, higher pH, repeated use of containers, and prolonged storage all increase BPA release into the contents.9PubMed Central. Bisphenol A release from food and beverage containers – A review Carbonated water has a slightly lower pH than still water because dissolved carbon dioxide forms a weak acid, which would theoretically work in seltzer’s favor when it comes to BPA leaching compared to an alkaline beverage. Aluminum cans are typically lined with a resin that historically contained BPA, though many manufacturers have switched to BPA-free linings in recent years. Again, this is a packaging issue rather than a carbonation issue, and it applies equally to canned sparkling water, canned beer, and canned soup.
When Seltzer Could Plausibly Interact With Liver Conditions
For the vast majority of people, drinking plain seltzer is metabolically identical to drinking still water, plus some carbon dioxide that you belch out. But there are a few edge cases where someone with an existing liver condition should think about their sparkling water habits, not because carbonation is toxic, but because of the details.
- Ascites management: If you have cirrhosis with fluid retention, the carbonation itself is not the problem, but the sodium in club soda or mineral water can contribute to fluid buildup. Stick to plain seltzer and read labels.
- Medication timing: Some liver medications are sensitive to stomach pH. Carbonated water is mildly acidic, and drinking a large amount right before taking medication could theoretically affect absorption. This is the kind of question worth raising with a pharmacist, though it applies to all carbonated beverages, not just seltzer.
- Gastroesophageal issues in liver disease: People with advanced liver disease sometimes develop varices, which are enlarged veins in the esophagus. Carbonation causes belching, and forceful belching could theoretically aggravate esophageal irritation, though there is no published evidence specifically linking seltzer consumption to variceal complications.
These scenarios are narrow enough that they should not worry anyone with a healthy liver. They come up because liver disease changes how the body handles fluid, pressure, and digestion in ways that make otherwise trivial factors occasionally relevant.
Why This Question Keeps Circulating
Seltzer water occupies an unusual cultural space. It is marketed as a health-conscious alternative to soda, which invites scrutiny from people looking for a hidden catch. The internet is full of claims that carbonation leaches calcium from bones, erodes tooth enamel, and damages internal organs. Most of these claims are either wrong or wildly overstated. The bone claim has been debunked repeatedly. The tooth enamel concern is technically real but practically minor compared to citrus juice or soda. And the liver claim, as we have seen, rests on a rat study with extreme gastric distension and a general confusion between seltzer and soft drinks.
There is also a tendency to assume that anything you consume in large quantities must eventually harm something. People who drink four or five cans of seltzer a day sometimes worry they are overdoing it. In terms of liver impact, there is nothing in the evidence to support that concern. The human trial that found improved liver enzymes involved daily carbonated water consumption over three months.1Scientific Reports. Randomized trial of carbonated water consumption on snacking behavior, alcohol intake, and health indices in healthy Japanese adults The realistic downsides of heavy seltzer consumption are bloating, gas, and possibly some dental wear from the mild acidity if you are sipping all day. The liver simply does not appear to be involved.
How Seltzer Compares to Other Things People Worry About
Putting seltzer in context helps. The liver processes alcohol, medications, excess sugar, and environmental toxins on a daily basis. A single night of heavy drinking produces far more measurable liver stress than a lifetime of seltzer ever could. A daily habit of sugar-sweetened soda carries a well-documented risk of fatty liver disease over time. Even fruit juice, which carries a health halo, delivers a substantial fructose load that the liver must process.
Plain seltzer gives the liver essentially nothing to do. There is no sugar to metabolize, no alcohol to detoxify, no novel chemical compounds to break down. The carbon dioxide dissolves in the stomach, some of it gets absorbed into the blood, and the lungs exhale it. The liver is largely a bystander in this process. If you are looking for dietary changes that actually move the needle on liver health, the evidence points toward reducing sugar-sweetened beverage intake, moderating alcohol, maintaining a healthy weight, and eating enough fiber and whole foods. Swapping soda for seltzer is, if anything, one of the easier steps in the right direction, and the liver enzyme data from the Japanese trial, limited as it is, suggests the trade is a good one.1Scientific Reports. Randomized trial of carbonated water consumption on snacking behavior, alcohol intake, and health indices in healthy Japanese adults