Carbonation itself does not appear to harm your kidneys. The bubbles in sparkling water are carbon dioxide dissolved under pressure, and research consistently points away from the fizz and toward other ingredients as the real concern. The clearest evidence separates cola drinks from other carbonated beverages: in a large epidemiological study, people who drank two or more colas per day had roughly double the odds of developing chronic kidney disease, while noncola carbonated drinks carried no increased risk at all. That distinction tells you that the problem is not the carbonation but what rides along with it, including sugar, phosphoric acid, and artificial sweeteners.
Cola Stands Apart from Other Fizzy Drinks
The single most important study to understand here tracked thousands of participants and found that drinking two or more colas daily was associated with about 2.3 times the odds of chronic kidney disease compared with people who drank fewer. Both regular colas and artificially sweetened colas showed a similar pattern of elevated risk. But noncola carbonated beverages, things like lemon-lime sodas, ginger ale, and sparkling water, showed essentially no increase in kidney disease risk at all.1Lippincott Williams & Wilkins. Carbonated Beverages and Chronic Kidney Disease
That finding reframes the question entirely. If carbonation were the culprit, every fizzy drink would carry risk. Instead, something specific to colas drives the association. The leading candidate is phosphoric acid, the ingredient that gives cola its tangy bite. Phosphoric acid is rarely used in noncola soft drinks, which tend to rely on citric acid instead. High dietary phosphate loads force the kidneys to work harder to maintain phosphorus balance, and over years, that extra burden may contribute to the kind of gradual damage that leads to chronic kidney disease. The cola-specific finding is the strongest piece of evidence that plain sparkling water and citrus-flavored carbonated drinks are not in the same category as cola.
Sugar-Sweetened Beverages and the Kidneys
Setting cola aside, sugar-sweetened beverages of all types appear to carry kidney risk that scales with how much you drink. A large study using UK Biobank data, which followed hundreds of thousands of participants, found that people consuming more than one serving per day of sugar-sweetened beverages had about a 19% higher risk of developing chronic kidney disease compared with non-drinkers, and the association followed a dose-response pattern, meaning that more daily servings meant progressively higher risk.2JAMA Network Open. Sweetened Beverage Intake and Incident Chronic Kidney Disease in the UK Biobank Study
One of the earlier warning signs that sugar-sweetened drinks affect the kidneys comes from data on albuminuria, which is when small amounts of protein leak into your urine as a signal that the kidney’s filters are under stress. An analysis of national survey data in the United States found that people drinking two or more sugary sodas per day had about 40% higher odds of having albuminuria compared with those who didn’t drink sugary soda. Interestingly, diet soda was not associated with albuminuria in that same analysis.3PubMed Central. Sugary Soda Consumption and Albuminuria: Results from the National Health and Nutrition Examination Survey, 1999–2004
Why would sugar damage the kidneys? Fructose, which makes up about half the sugar in regular soda (whether from sucrose or high-fructose corn syrup), is metabolized in ways that raise uric acid levels in the blood. Over time, elevated uric acid is linked to insulin resistance, higher blood pressure, and a cascade of metabolic problems that collectively stress the kidneys. The connection between fructose, uric acid, and kidney disease has been documented across age groups, with evidence that these metabolic pathways begin causing harm well before anyone gets a clinical diagnosis.4Europe PMC. Fructose and Uric Acid: Major Mediators of Cardiovascular Disease Risk Starting at Pediatric Age
Diet Soda Is Not a Free Pass
Switching to artificially sweetened drinks does not eliminate the kidney concern, even though it removes the sugar and its fructose-driven metabolic effects. A study of women in the Nurses’ Health Study found that consuming two or more servings per day of diet soda was associated with roughly double the odds of a meaningful decline in kidney function, specifically a drop of 30% or more in the estimated filtration rate. Women who drank fewer than two servings per day didn’t show the same elevated risk.5Europe PMC. Associations of sugar and artificially sweetened soda with albuminuria and kidney function decline in women
The dose-response pattern held up in a separate study that looked at the most severe outcome: end-stage kidney disease requiring dialysis or transplant. Compared with people who drank less than one glass of diet soda per week, those drinking five to seven glasses a week had about a third higher risk of progressing to end-stage disease, and those consuming more than seven glasses per week had about 83% higher risk. The trend was statistically significant even after adjusting for diabetes, blood pressure, body weight, and baseline kidney function.6Europe PMC. Diet Soda Consumption and Risk of Incident End Stage Renal Disease
The mechanism behind diet soda’s kidney risk is still debated. Some researchers suspect that artificial sweeteners alter the gut microbiome or affect insulin signaling in ways that indirectly burden the kidneys. Others point out that people who drink large quantities of diet soda often have pre-existing metabolic conditions that make them vulnerable. And as noted earlier, cola-based diet drinks still contain phosphoric acid, which means that the phosphate concern applies regardless of whether the drink contains sugar or an artificial sweetener. The evidence is strong enough to say that heavy diet soda consumption is not the safe alternative it is often assumed to be.
The Metabolic Middleman
One reason the link between sweetened drinks and kidney disease is so persistent is that the connection runs partly through metabolic syndrome, the cluster of conditions that includes abdominal obesity, high blood sugar, high blood pressure, and abnormal cholesterol levels. A mediation analysis found that metabolic syndrome accounted for roughly 12–18% of the observed association between both sugar-sweetened and artificially sweetened beverages and chronic kidney disease. Among the individual components of metabolic syndrome, central obesity was the single biggest mediator, explaining up to 27% of the association for people drinking more than one daily serving of artificially sweetened drinks.7Frontiers in Nutrition. Sugary beverages intake and risk of chronic kidney disease: the mediating role of metabolic syndrome
This means a substantial portion of the kidney harm attributed to sweetened drinks actually flows through weight gain and metabolic disruption. But it also means that 80% or more of the risk is not explained by metabolic syndrome alone, so the drinks appear to carry some direct or additional indirect harm beyond just making people gain weight. The practical takeaway is that staying at a healthy weight partially offsets the risk but does not eliminate it entirely.
Kidney Stones Tell a Slightly Different Story
Chronic kidney disease and kidney stones are distinct problems, and the beverages that contribute to each don’t line up perfectly. A large prospective study found that sugar-sweetened colas raised kidney stone risk by about 23%, while sugar-sweetened noncola sodas actually carried an even higher risk, about 33%. There was also a marginally significant increase in stone risk from artificially sweetened noncola drinks.8Europe PMC. Soda and other beverages and the risk of kidney stones
The sugar in these drinks appears to be the dominant factor for stone formation. Sugar drives up calcium excretion in the urine and can reduce citrate levels, both of which favor crystal growth. Citrate is one of the body’s natural defenses against stones, binding to calcium so it doesn’t form crystals. This is why some citrate-rich beverages may actually reduce stone risk. A clinical trial found that a high-citrate drink increased 24-hour urinary citrate, raised urine pH, and decreased the supersaturation of calcium oxalate, the most common type of stone, compared with an equal volume of plain water.9SpringerLink. Effect of a high-citrate beverage on urine chemistry in patients with calcium kidney stones
What about plain diet sodas? A controlled crossover study found no increased stone risk from consuming a caffeine-free diet cola or a citrus-flavored diet soda compared with bottled water.10PubMed Central. Effect of soda consumption on urinary stone risk parameters That lines up with the broader pattern: sugar is the main stone-promoting ingredient in soda, not carbonation or artificial sweeteners. If you’re prone to kidney stones, the worst choices are sugary sodas of any flavor. Citrate-containing beverages, including some citrus-flavored sparkling waters, may actually be mildly protective.
Caffeine Complicates Things
Many carbonated drinks contain caffeine, and caffeine itself has a nuanced relationship with the kidneys. A large genetic analysis (a Mendelian randomization study, which uses genetic variants to approximate what would happen in a randomized trial) found a paradox: higher genetically predicted caffeine intake was associated with a lower risk of chronic kidney disease, roughly a 16% reduction. But higher genetically predicted plasma caffeine levels, meaning more caffeine circulating in the blood at a given time, were associated with slightly worse kidney filtration markers.11PubMed Central. Caffeine Intake, Plasma Caffeine Level, and Kidney Function: A Mendelian Randomization Study
That distinction matters because people who habitually drink caffeine develop tolerance: they consume more, but their bodies metabolize it faster, so plasma levels don’t stay high. The findings suggest that habitual moderate caffeine consumption may be neutral or even mildly protective for the kidneys, while acute spikes in blood caffeine could temporarily stress kidney function. In older adults with conditions like high blood pressure or metabolic syndrome, caffeinated beverages may cause short-lived increases in blood pressure and glomerular hyperfiltration, a state where the kidneys filter too aggressively, which over time can contribute to damage.12Nature / Scientific Reports. Consumption of caffeinated beverages and kidney function decline in an elderly Mediterranean population with metabolic syndrome
For most people with healthy kidneys, the caffeine in a few sodas or cups of coffee per day is unlikely to be a meaningful contributor to kidney problems. The concern grows for people who already have high blood pressure, early kidney disease, or who consume very large quantities of caffeinated drinks daily.
Genetics and Individual Susceptibility
Not everyone’s kidneys respond the same way to the same drinks. Genetic variation in the SLC2A9 gene, which encodes a transporter that exchanges uric acid for glucose and fructose, may help explain why some people develop problems like gout or elevated uric acid from sugar-sweetened beverages while others do not. Researchers have tested whether SLC2A9 genotype interacts with sugar-sweetened beverage consumption to determine gout risk, finding evidence that certain genetic backgrounds amplify the harmful effects of sugary drinks on uric acid handling.13PubMed Central. Sugar-sweetened beverage consumption: a risk factor for prevalent gout with SLC2A9 genotype-specific effects on serum urate and risk of gout
Gout and chronic kidney disease are intertwined: chronically elevated uric acid damages kidney blood vessels and contributes to inflammation that accelerates kidney decline. If your genetics make you an inefficient processor of the fructose-uric acid pathway, your kidneys bear more of the burden when you drink sugary sodas. You might not know your genotype, but a family history of gout or early kidney problems could be a clue that your body handles these drinks less gracefully than average.
What About Aluminum from Cans
A concern that gets less attention is what the packaging itself contributes. A recent study examining soft drinks in aluminum cans found a clear and significant rise in aluminum content in all canned beverages over time. The beverages became slightly more acidic during prolonged storage, which appeared to accelerate the migration of aluminum from the can lining into the drink.14ScienceDirect (Food Packaging and Shelf Life). Metal content in soft drinks depending on packaging and storage time
Healthy kidneys are the body’s primary route for excreting aluminum, so for people with normal kidney function, the aluminum absorbed from a few canned drinks is unlikely to accumulate to harmful levels. But for anyone with reduced kidney function, aluminum clearance is impaired, and even modest chronic exposure can build up. This is one of those risks that is negligible for most people but worth knowing about if you already have kidney disease and regularly drink canned beverages. Choosing glass-bottled or freshly dispensed drinks removes this concern entirely.
A Practical Guide to What Actually Matters
If you take one thing from the research, it should be that the type of carbonated drink matters far more than the carbonation. Here is a rough hierarchy of kidney-related concern based on the available evidence:
- Highest concern: Regular cola, consumed daily in quantities of two or more servings. Combines sugar, phosphoric acid, and often caffeine. Associated with elevated chronic kidney disease risk, kidney stone risk, and albuminuria.
- Significant concern: Other sugar-sweetened sodas, consumed daily. Lower phosphate load than cola but still contribute to metabolic disruption, elevated uric acid, and higher kidney stone risk.
- Moderate concern: Diet cola and other artificially sweetened sodas, consumed heavily. The phosphoric acid in diet cola and potential metabolic effects of artificial sweeteners at high doses are associated with kidney function decline and higher end-stage disease risk, though the mechanisms remain less clear than for sugary drinks.
- Minimal concern: Sparkling water, seltzer, and citrus-flavored carbonated waters without added sugar. No evidence links these to kidney harm, and citrate-containing varieties may modestly help prevent kidney stones.
This hierarchy is not meant to label any single drink as dangerous in small amounts. The studies that consistently find harm involve daily consumption of two or more servings. An occasional cola at a cookout is not the same exposure as a two-liter-a-day habit. And because metabolic syndrome mediates a meaningful fraction of the risk, anything you do to manage weight, blood pressure, and blood sugar partially buffers the kidney impact of the sodas you do drink.
When Your Kidneys Are Already Compromised
Everything discussed so far applies mainly to people with generally healthy kidneys. If you already have diagnosed chronic kidney disease, even at an early stage, the considerations become stricter. Phosphorus management is often a central part of treatment for kidney patients, and cola’s phosphoric acid is an easily avoidable source of added phosphate. High-fructose beverages raise uric acid, which further accelerates kidney decline in people whose kidneys are already struggling to keep up with waste clearance. Aluminum from cans, as noted, becomes a more meaningful concern when kidney filtration is reduced.
Most nephrologists advise patients with chronic kidney disease to eliminate regular soda and cola entirely and to limit diet soda to occasional use at most. Plain water remains the safest choice for hydration in this population, though unflavored sparkling water is generally considered acceptable. If you have kidney disease and find plain water unappealing, citrate-rich sparkling waters can satisfy the craving for fizz while potentially offering a small benefit against stone formation. The key is to read labels carefully, since some flavored sparkling waters contain added sugar, phosphates, or sodium that undercut the advantage of having skipped the soda.